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  • porous silicon  (61)
  • Springer  (61)
  • 2015-2019
  • 2000-2004  (61)
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  • Springer  (61)
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  • 1
    Electronic Resource
    Electronic Resource
    Porosified Silicon Wafer Structures Impregnated With Platinum Anti-Tumor Compounds: Fabrication, Characterization, and Diffusion Studies (2000)
    Springer
    Biomedical microdevices 2 (2000), S. 265-272 
    Details
    ISSN: 1572-8781
    Keywords: porous silicon ; cis-platin ; drug delivery ; calcium phosphate ; carbo-platin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract In this work, the incorporation and characterization of cis-platin (cis-diammine dichloroplatinum(II)), carbo-platin [cis-diammine(cyclobutane-1,1-dicarboxylato] platinum(II)), and Pt(en)Cl2 (ethylenediamminedichloro platinum(II)) within layers of calcium phosphate on porous Si/Si substrates are described. These materials have been characterized by scanning electron microscopy, secondary ion mass spectrometry, and X-ray energy dispersive spectroscopy. The diffusion of platinum species from the doped calcium phosphate layers has also been investigated by UV-visible absorption spectrometry and inductively-coupled plasma spectroscopy. The influence of initial platinum concentration, the impact of thermal annealing of the calcium phosphate/porous Si/Si matrix, as well as the effect of varying the ligand coordination sphere of the Pt complex on its ability to be delivered to the surroundings have also been analyzed. For the case of cis-platin, it is found that increasing the concentration of platinum complex in the electrolyte during cathodic growth of calcium phosphate results in a relatively greater concentration of Pt incorporated into the calcium phosphate layers and a larger amount of Pt which subsequently can be delivered to the surrounding medium upon exposure to solvent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009951121205
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  • 2
    Electronic Resource
    Electronic Resource
    Electrical Characterisation of Photovoltaic Porous Si (2000)
    Springer
    Journal of porous materials 7 (2000), S. 295-298 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; photo-voltage ; d.c. conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this study n-type and p-type PV devices have been fabricated by anodising Si wafers with various resistivities in aqueous ethanoic HF solution followed by deposition of semitransparent contacts. semitransparent deposition onto the porous layers. Various methods have been used for the optimisation of problematic contact to nanoporous layers. The measurements of importance are current-voltage (I-V) characteristics, the photovoltaic (PV) decay time spectrum, and the PV response as a function of excitation energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009600619044
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  • 3
    Electronic Resource
    Electronic Resource
    Laser Induced Degradation of Photoluminescence Intensity of Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 307-310 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; photoluminescence ; degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The evolution, under vacuum, of the photoluminescence (PL) intensity of porous silicon (PS) has been studied as function of anodisation conditions, laser line and post-anodisation treatments. It was shown that the degradation of the PL intensity depends on the internal structure of PS. In particular, the degradation is important for PS layers formed essentially by crystallites having small size or where amorphous phase exists. The experimental results have been interpreted using a theoretical model, which takes into account the variation with time of the local concentration of the luminescent centers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009613004932
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  • 4
    Electronic Resource
    Electronic Resource
    Stress Measurement Technique to Monitor Porous Silicon Processing (2000)
    Springer
    Journal of porous materials 7 (2000), S. 319-321 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; stress measurements ; thermal annealing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Macroscopic stress measurements are used to monitor Porous Silicon processing. Silicon wafer of 1Ω cm resistivity, n-type and 〈1 0 0〉 orientation were used as starting material. Porous Silicon layers with a porosity of 57% and a thickness of 85 μm, fabricated by electrochemical anodisation, were differently dried, then the evolution of the wafer deflection has been followed with storage time in air. Thermal treatments both in inert and oxidant atmosphere have been performed up to 1000°C. The stress behaviour vs. temperature allows to estimate the hydrogen desorption activation energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009621206749
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  • 5
    Electronic Resource
    Electronic Resource
    Superlattices as Characterisation Tool for the Beginning of PS Formation (2000)
    Springer
    Journal of porous materials 7 (2000), S. 373-376 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; superlattices ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Initial stage of porous silicon (PS) formation has been studied in an original way. Multilayer structures constituting of very thin layers of low porosity and thick layers of high porosity have been fabricated and characterised by optical tools and electron microscopy. The non linear behaviour resulting in a change in the dissolution velocity has been quantified by using a stack layer structure. Finally using thermal oxidation it has been shown that, due to the selective oxidation as a function of the porosity, porous silicon can be used to produce a Si/SiO2 like structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009618517652
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  • 6
    Electronic Resource
    Electronic Resource
    Laplacian Growth Models for Porous Silicon Formation—Stability Analysis (2000)
    Springer
    Journal of porous materials 7 (2000), S. 345-348 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; interface growth ; Laplacian growth ; linear stability analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We develop a Laplacian model of interface growth which includes basic features of the anodisation of silicon in hydrofluoric acid. Our aim is to find mechanisms for the characteristic properties of porous silicon formation, such as the transition from electropolishing to pore formation and the typical pore distance. The local etching rate of the interface between the semiconductor and the electrolyte is determined by the local current density. We model the diffusive transport of charge carriers in the semiconductor and of reactants in the electrolyte including the basic features of the electrochemical reaction at the interface. A linear stability analysis of a flat and planar interface is performed in order to study the initial state of pore formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009630920378
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  • 7
    Electronic Resource
    Electronic Resource
    Orientation Effect of the Wafer on the Structural Properties of P+ Type Porous Silicon Layers (2000)
    Springer
    Journal of porous materials 7 (2000), S. 357-361 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; X-ray diffraction ; differential scanning calorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The structural properties of (111) oriented p+ type Porous Silicon (PS) samples are investigated using various X-ray diffraction techniques and compared to (001) p+ type PS layer structure. High resolution X-ray diffractometry was used to record rocking curves and reciprocal space maps, giving indications about the crystalline quality of the PS samples as well as about the pore orientation. X-ray diffraction and reflectivity performed on thin PS layers allow to estimate the layer thickness, porosity and roughness of the PS/substrate interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009691122195
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  • 8
    Electronic Resource
    Electronic Resource
    AC Conductivity of Porous Silicon from Monte Carlo Simulations (2000)
    Springer
    Journal of porous materials 7 (2000), S. 107-110 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; conductivity ; percolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The AC conductivity of a percolation model with local energetical disorder for porous Silicon in three dimensions, σ(ω), is studied by Monte Carlo simulations. The model includes both diffusion and recombination processes and σ(ω) is obtained by a Fourier transform of the mean-square displacement of the carriers, where hopping diffusion of a single type of carrier (either an electron or an exciton) and two types of carriers (an electron and a hole) are considered. It is found that at low temperatures, the behavior of σ(ω) depends sensitively on the type of carrier considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009678502689
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  • 9
    Electronic Resource
    Electronic Resource
    Porous Semiconductor Micropatterns Formed on Focussed Ion Beam Implants (2000)
    Springer
    Journal of porous materials 7 (2000), S. 233-237 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; integrated optics ; wave guides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this work we report a principle that allows one to write visible light emitting silicon patterns of arbitrary shape down to the sub-micrometer scale. We demonstrate that porous Si growth can electrochemically be initiated preferentially at surface defects created in an n-type Si substrate by Si++ ion bombardment. Using a focused ion beam (FIB) as a source of ions, arbitrary defect patterns can be written into a substrate. The growth of light emitting porous silicon is then selectively achieved by an electrochemical treatment which triggers Si dissolution only at these defect sites. The selectivity of the electrochemical dissolution reaction can be attributed to a facilitated Schottky barrier breakdown at the implanted surface defects which leads to the desired pore formation in confined surface areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009655324979
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  • 10
    Electronic Resource
    Electronic Resource
    Electroluminescence from Porous Silicon Studied Experimentally (2000)
    Springer
    Journal of porous materials 7 (2000), S. 267-270 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; photoluminescence ; electroluminescence ; band structure ; experimental
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electroluminescence, photoluminescence, and current-voltage measurements have been carried out on a series of samples consisting of porous silicon on top of crystalline silicon. The electroluminescence spectral distributions are markedly shifted towards long wavelengths in comparison to those seen with photoluminescence. The results are discussed and explained in terms of the energy-band structure of porous silicon. The problem of injecting electrons as well as holes into the porous silicon layer is pointed out and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009675829522
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  • 11
    Electronic Resource
    Electronic Resource
    Self-consistent Recombination Scheme in Porous Silicon Under Intense Laser Excitation (2000)
    Springer
    Journal of porous materials 7 (2000), S. 315-318 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; nonradiative ; radiative recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental investigation of the general characteristics of nonradiative and radiative recombination of charge carriers in strongly excited porous silicon is presented. It is shown that photoconductivity, photomagnetoelectric effect, quantum yield, and intensity of visible radiation of porous silicon demonstrates strong nonlinearities against laser excitation intensity. It is suggested that the band-to-band Auger recombination is dominant similar to that in crystalline silicon, whereas the visible luminescence is determined by the bimolecular process. The nonequilibrium density of charge carriers Δn ≈ 1019 cm−3, and the bimolecular radiative recombination coefficient Brad ≤ 9 × 10−14 cm3/s have been found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009669122679
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  • 12
    Electronic Resource
    Electronic Resource
    Structural Changes of Porous Silicon Surface with Thermal Annealing Studied by 29Si Nuclear Magnetic Resonance Spectroscopy and Fourier Transform Infrared Spectroscopy (2000)
    Springer
    Journal of porous materials 7 (2000), S. 327-330 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; thermal annealing ; nuclear magnetic resonance spectroscopy ; infrared spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract 29Si nuclear magnetic resonance (NMR) spectra and infrared spectra were measured for as-prepared and annealed porous silicon (PS) samples to characterize the change of PS structure. Annealing changed the infrared spectra remarkably: after 4-h annealing, the signals due to SiH2 disappeared and the intensity of the signals due to SiH decreased. On the other hand, the 29Si NMR spectra with magic-angle spinning (MAS) were not much affected by the annealing. The linewidth of spectra without MAS, however, increased with annealing time with the peak location unchanged. Annealing caused hydrogen on the PS surface to be desorbed, especially in the case of SiH2 species, and (SiH)2 dimer structure was produced during the annealing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009677332673
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  • 13
    Electronic Resource
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    Investigations of Activation Energy of Porous Silicon Oxidation Using Calorimetric Methods (2000)
    Springer
    Journal of porous materials 7 (2000), S. 335-338 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; oxidation ; calorimeter ; desorption ; activation energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of porous silicon has been studied using differential scanning calorimeter. The oxidation was found to consist of two parts with different activation energies. This indicates the existence of two different reaction mechanism. The results from the hydrogen desorption measurements have been used to study the different oxidation behaviour of the n- and p+-type porous silicon. The results show that the dihydride structure dominates on the surface of the n-type porous silicon, contrary to p+-type porous silicon, where the monohydride is the major structure. Explanations of these features are discussed. Using the activation energy, the surface termination effects are investigated. The best improvement in the activation energy was observed in the sample, whose surface was partially stabilized by ammonium groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009674702631
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  • 14
    Electronic Resource
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    Effect of Light Exposure and Ultrasound on the Formation of Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 381-383 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; microstructure ; infrared spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We have investigated the effect of light exposure and ultrasonic (US) treatment on the formation of porous Si layers grown by electroless stain-etching technique. It was shown that; the He-Ne laser exposure resultedin a considerable increase in both the hydrogenation and the oxidation amounts in n-type Si, but a decrease in p-type wafers. The effect is attributable to effective change in the concentration of free hole carriers. The UV light exposure has led to the shift at the peak positions, indicating probably a change in bonding configuration, and increase in oxidation. Also, a correlation was established between the ultrasonic treatment and the microstructure. The US treated samples exhibit a decrease in hydrogenation and oxidation. UV exposure together with the US has led to a further decrease in both hydrogen and oxygen amounts, which was rather indicative of an excessive surface etching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009687021287
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  • 15
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    Photoluminescence Decay and Hydrogen Desorption of n-Type Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 385-388 
    Details
    ISSN: 1573-4854
    Keywords: hydrogen desorption ; photoluminescence decay ; porous silicon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The decay under illumination of the photoluminescence (PL) intensity ofn-type porous silicon (PS) samples prepared by electrochemical etching has been investigated. We have found that the PL evolution with illumination time presents two different stages: an initial very fast decay which lasts ∼300 s, followedby a second one, much slower, which extends for times longer than 104 s. Thisevolution suggests that two different mechanisms could be responsible for the PLintensity decay. Samples subjected to different illumination times were studied byThermal Desorption Spectroscopy (TDS). The desorption rate of H2 and SiHx species was monitored during linear heating of the samples. A qualitative correlationbetween the decay of the PL intensity under illumination and the amount of H2 and SiHx species evolved from the illuminated samples has been observed. Experimentaldata suggest that H2 could be desorbed from the sample during the illuminationtime through a photoinduced H2 desorption process, inducing the decrease of the PLintensity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009647307174
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  • 16
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    An Investigation of Porous Silicon by Means of Positron Annihilation (2000)
    Springer
    Journal of porous materials 7 (2000), S. 323-326 
    Details
    ISSN: 1573-4854
    Keywords: positron annihilation ; porous silicon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Positron lifetime spectroscopy has been used to investigate a porous silicon film subjected to heat treatments up to 1170°C. Annealings between 300 and 500°C resulted in a 17% mass increase of the film due to oxygen uptake following the effusion of hydrogen. The positron data also indicate that vacancy clusters are formed in the silicon oxide layer or the silicon oxide—silicon interface surrounding the nanocrystallites as oxygen replaces the effusing hydrogen. The vacancy cluster concentration, which may have a bearing on the photoluminescent properties, increased by a factor of three with heating to 500°C and then decreased to one-third the original value at higher temperatures. Above 900°C vacancy migration and clustering occurred, accompanied by visible deterioration of the film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009625307658
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  • 17
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    Study on the Si–Si Vibrational States of the Near Surface Region of Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 339-343 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; infrared spectroscopy ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The Si–Si vibrational states near the surface region of porous silicon has been characterized using Fourier Transform Infrared Spectroscopy (FTIR) due to its enlarged surface area. By means of anodic etch and oxidization experiments, two Si–Si vibration modes of porous silicon have been identified as near the surface regions and in the bulk, respectively. The intensity of absorption peak at 620 cm−1, which originates from the Si–Si bonds vibrations on the surface and near surface regions of porous silicon, is found to vary depending on the length of etch and degree of oxidation of porous silicon, which exists before etching and is recovered again after fully oxidation. The peak of 610 cm−1 doesn't change throughout the oxidation experiment, and to be assigned for Si–Si bond vibrations in the bulk. With an extra irradiation of Nd:Yag laser on the PS sample the Raman and FTIR spectra reveal a red shift. These results can give an interpretation to explain the different phenomenon of Si–Si vibrations of Raman and FTIR spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009622601723
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  • 18
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    Laser Structuring of Luminescent Porous Silicon During Etching (2000)
    Springer
    Journal of porous materials 7 (2000), S. 367-371 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; luminescence ; light assisted chemical etching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new approach to the problem of preparation of laterally structured luminescent porous silicon is proposed. The effect is based on the photosensitivity of chemical etching of silicon. Contrary to the other technique recently reported where the porous layer was modified with light assisted chemical dissolution, a one stage anodisation-free process is used. Any desired lateral structure can be produced, depending on the illumination pattern, which is defined by optical imaging. A 2D micro-array was prepared as an example of this fast mask-free technology with an accuracy of 5 μm. Samples have a broadband visible photoluminescence centred at 680 nm when illuminated with UV or blue light. The results are analysed to determine the possible achievable accuracy of the technique and to improve our understanding of the mechanism of light assisted etching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009695223104
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  • 19
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    Raman Scattering from Metal-Deposited Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 397-400 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; Raman spectroscopy ; immersion plating ; silver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Raman scattering from porous silicon layer into which silver is immersion-plated was studied. Ag-deposited samples show extra Raman bands. Heat treatment of the Ag-deposited samples results in a great decrease in such Raman bands. Also dipping in hydrofluoric acid solution causes a spectral change. Some comments on the assignment of the Raman peaks of the Ag-deposited porous silicon are given, and the structure of porous silicon on which metal is immersion-plated is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009603524921
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  • 20
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    A Systematic Study of Synchrotron Light Induced Luminescence from Porous Silicon: Implications to Morphology and Chemical Effect Dependent Electronic Behaviour (2000)
    Springer
    Journal of porous materials 7 (2000), S. 165-168 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; photoluminescence ; synchrotron radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Using synchrotron as a tunable excitation source, we have carried out a study on the photoluminescence systematics from a series of porous silicon samples prepared under different conditions, Luminescence spectra were recorded with excitation photon energies tuned to the Si L3,2 absorption edge (∼100 eV). The luminescence yield was in turn used to monitor the Si L3,2-edge absorption characteristics of porous silicon. A trend of luminescence wavelength and intensity as a function of preparation conditions emerges. Other related observations are also noted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009618216802
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  • 21
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    Nature of the Silicon-Animal Cell Interface (2000)
    Springer
    Journal of porous materials 7 (2000), S. 191-195 
    Details
    ISSN: 1573-4854
    Keywords: cell growth ; porous silicon ; cytotoxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The paper reports the results of the study of cell culture growth at the surface of porous silicon. They show that porous and poly(nano)crystalline Si offer significant advantages over bulk Si surfaces for cell adherence and viability: these materials do not require coating with substances such as polylysine to support cell growth; porous Si is light-addressable because of photoluminescence and photovoltaic effects noted [Unal and Bayliss, J. Appl. Phys. 80, 3532 (1996)], allowing the potential for optical data transfer and less susceptibility to interference from external electronic equipment; finally nanostructured coatings can be applied to most object shapes, giving flexibility in their application.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009686704506
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  • 22
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    Light Emission from Highly Reflective Porous Silicon Multilayer Structures (2000)
    Springer
    Journal of porous materials 7 (2000), S. 209-213 
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    ISSN: 1573-4854
    Keywords: porous silicon ; superlattices ; photoluminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Porous silicon photoluminescence and electroluminescence can be controlled by periodically modulating the material porosity to form high quality multilayer stacks and microcavities. Important issues not yet fully addressed are (a) the precise role played by this microstructuring, given that the luminescence is distributed throughout the entire structure and that the low porosity layers are highly absorbing at short wavelengths, and (b) whether the quality of such microcavities could be sufficient to support lasing. Using both experimental and theoretical techniques, the emission and reflection properties of different porous silicon single and multilayer structures have been investigated in order to understand further and exploit the nature of light propagation within them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009694906324
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  • 23
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    Formation of Porous Silicon Filter Structures with Different Properties on Small Areas (2000)
    Springer
    Journal of porous materials 7 (2000), S. 223-225 
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    ISSN: 1573-4854
    Keywords: porous silicon ; patterning ; photolythography dielectric filters ; reactive ion etching (RIE) ; microoptics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Porous silicon (PS) layer systems have a broad range of possible applications. An advantage is the good control of the refractive index and the etch rate of the layers by the applied current density and the time respectively. For micro-optical devices you need patterned PS. For some optical devices it is not sufficient to have only one filter but it is necessary to form filters with different properties on a small area. We applied a method (M. Frank, U.B. Schallenberg, N. Kaiser, and W. Buß, in Conference on Miniaturized Systems with Microoptics and Micromechanics, edited by M.E. Moamedi, L.J. Hornbeck, and K.S.J. Pister (SPIE, San Jose, 1997), SPIE Proceedings Series 3008, p. 265) to PS which fits this goal by the following steps: fabrication of the desired reflectors below each other and partial removal of upper reflectors with reactive ion etching (RIE). The technological aspects of patterning PS after the fabrication are an important topic of this work. Problems are discussed in detail and solutions are given.
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    URL: http://dx.doi.org/10.1023/A:1009651224071
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    Probing Carrier Transport in Porous Silicon with Synchrotron Radiation (2000)
    Springer
    Journal of porous materials 7 (2000), S. 115-118 
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    ISSN: 1573-4854
    Keywords: porous silicon ; synchrotron radiation ; coulomb blocade
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper we demonstrate that photo-electron emission excited by X-UV synchrotron radiation can be used as a “contactless” probe of the gross conduction processes in porous silicon. Moreover we demonstrate that this approach reveals the underlying conduction geometry. We show that conduction in porous silicon is to some degree controlled by percolation phenomena and finally present data which support the notion that the fundamental blocking process may be Coulomb Blockade [P.A. Lee, Physica B 189, 1–5 (1993); D. Ali and H. Ahmed, Appl. Phys. Lett. 64, 2119–2120 (1994)].
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    URL: http://dx.doi.org/10.1023/A:1009667627705
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    Porous Silicon Studied with Time-Resolved Photoluminescence (2000)
    Springer
    Journal of porous materials 7 (2000), S. 263-266 
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    ISSN: 1573-4854
    Keywords: porous silicon ; time-resolved photoluminescence ; decays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Porous silicon has been studied with time-resolved photoluminescence, and growth as well as decay curves have been measured at several detection energies, with sample temperatures between 10 and 300 K. In the decay curves, three components are mainly observed, a small one which is very fast, with time scales of the order of nanoseconds or faster, the main component having time scales of the order of milliseconds, and a very small, very slow component, with time scales of the order of seconds. The main components can in most—but not all—cases be fitted well with stretched exponentials containing two fitting parameters. Of these, it comes out that the parameter accounting for disorder or the like depends only little upon detection energy and temperature, whereas the parameter accouting for the development in time decreases substantially for increasing temperature. The results are discussed.
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    Optical Absorption in Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 279-282 
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    ISSN: 1573-4854
    Keywords: porous silicon ; optical absorption ; theoretical modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The optical properties of porous silicon (p-Si) are calculated from the electronic band structure obtained by means of an sp3s* tight-binding Hamiltonian and a supercell model, in which the pores are columns detched in crystalline silicon (c-Si). The disorder in the pore sizes and the undulation of the silicon wires are considered by the existence of arandom perturbative potential, which produces non-vertical interband transitions, otherwise forbidden. A typical interval around each k-vector (optical window), where non-vertical transitions make an important contribution, depends on the value of the disorder and its order of magnitude is given by l−1, where l is the localization length. The calculated absorption spectra are compared with experiments, showing good agreement.
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    Cathodoluminescence from Implanted and Anodized Polycrystalline Silicon Films (2000)
    Springer
    Journal of porous materials 7 (2000), S. 291-294 
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    ISSN: 1573-4854
    Keywords: nanocrystalline silicon ; porous silicon ; cathodoluminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Luminescence emission of LPCVD polycrystalline silicon films has been studied by cathodoluminescence (CL) in the scanning electron microscope. As-deposited films show visible luminescence with dominant blue band. The relative intensity of blue emission is enhanced by implantation and by slight anodization treatments. Our investigations are consistent with previous PL results and indicate that the origin of blue emission is related to quantum confinement effects. On the other hand, the effect of annealing in these samples is a reduction of the CL signal that could be related to the increase of the nanocrystals size.
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    The Energy-Band Structure of Porous Silicon Studied with Photoluminescence Excitation and Photoacoustic Spectroscopy (2000)
    Springer
    Journal of porous materials 7 (2000), S. 173-176 
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    ISSN: 1573-4854
    Keywords: porous silicon ; photoacoustic spectroscopy ; energy band
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Porous silicon has been studied with photoluminescence, photoluminescence excitation, and photoacoustic spectroscopy. From the luminescence data, an energy-level diagram related to the luminescence is constructed. The diagram is confirmed in detail by the photoacoustic spectra. The results are discussed with the conclusion that they are in good agreement with the surface-band oxyhydride-like emitter, which recently has been established as the source for the photoluminescence from porous silicon.
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    Raman Light Scattering in System of Oriented Wires in Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 275-278 
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    ISSN: 1573-4854
    Keywords: porous silicon ; Raman spectroscopy ; morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Raman-light scattering in porous silicon samples with oriented quantum wires was studied. It was shown, that the experimental data depends on the type of organization of wire system. The explanation of observed effect is discussed.
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    URL: http://dx.doi.org/10.1023/A:1009632114501
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    Sensitivity of Porous Silicon Photoluminescence to Low Concentrations of CH4 and CO (2000)
    Springer
    Journal of porous materials 7 (2000), S. 287-290 
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    ISSN: 1573-4854
    Keywords: porous silicon ; sensors ; gas absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper we report the sensitivity of porous silicon photoluminescence (PL) to diluted mixtures of methane and carbon monoxide in synthetic air. We also investigate the separate effect of synthetic air, purified nitrogen and relative humidity on both photoluminescence and conductance (G). Porous silicon samples have been prepared from n-type silicon substrates. We find that PL intensity and G decrease in synthetic air with respect to their values in N2. Presence of carbon monoxide reduces the PL intensity while methane provokes the opposite behaviour. The dependence of the PL spectra on methane and carbon monoxide concentrations has been investigated. The observed effects can be related to gas induced modifications in porous surface and suggest that porous silicon can be employed in gas sensor technology.
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    URL: http://dx.doi.org/10.1023/A:1009640316318
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    Studies on Gold/Porous Silicon/Crystalline Silicon Junctions (2000)
    Springer
    Journal of porous materials 7 (2000), S. 299-301 
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    ISSN: 1573-4854
    Keywords: porous silicon ; Schottky emission ; photoluminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electrical transport in Gold/porous silicon/crystalline silicon junctions has been studied. The junctions are found to improve when the porous silicon is exposed to a hydrogen plasma before depositing the top metal. The hydrogen passivated junctions exhibited higher current levels and emitted light at lower voltages as compared to the unhydrogenated ones. Internal photoemission measurements were carried out to investigate the gold/porous silicon barrier. The barrier height determined from the Fowler plot is independent of the top material. The temperature dependence of the barrier height is similar to that of the crystalline silicon energy gap.
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    URL: http://dx.doi.org/10.1023/A:1009604703115
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    Electrochemical Aspects of Porous Silicon Formation (2000)
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    Journal of porous materials 7 (2000), S. 11-16 
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    ISSN: 1573-4854
    Keywords: porous silicon ; kinetics electrochemistry ; etching ; surface analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The electrochemistry of porous silicon formation has been investigated by different electrochemical as well as surface analytical methods. The kinetics of pore nucleation was observed as small steps in fast current and potential pulse transients. Oxidic intermediates were identified by ex-situ XPS. Cyclic voltammetry in solutions of different HF concentration was correlated with the etching rate of silicon dioxide. On the basis of these experimental data, an electrochemical model for the porous silicon formation is presented.
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    URL: http://dx.doi.org/10.1023/A:1009667411891
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    Contactless Characterization of Porous Silicon Structures by Four-Wave Mixing and Microwave Techniques (2000)
    Springer
    Journal of porous materials 7 (2000), S. 303-306 
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    ISSN: 1573-4854
    Keywords: porous silicon ; four-wave mixing ; microwave harmonics generation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We apply optical contactless techniques, namely the four-wave-mixing and microwave harmonics generation for the characterization of nanocrystalline free-standing films and platelets of microcrystalline porous silicon. We observe (i) full carrier localization and significant lifetime shortening in free-standing films, which is thought to be a manifestation of their low-dimensional confinement, (ii) increased carrier lifetime in microcrystalline porous silicon, presumably originating from passivated surface states at the surface of pores.
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    URL: http://dx.doi.org/10.1023/A:1009660820862
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    Towards the Morphology Control of Stain Etched Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 407-410 
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    ISSN: 1573-4854
    Keywords: porous silicon ; stain etching ; morphology ; HREM ; reflectance spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Porous silicon films, nearly 100 nm thick, were produced by stain etching of n+-type silicon substrates. The films were studied by a non-destructive technique: dielectric function profiles were deduced by spectral reflectance via a finite difference model, and porosity was computed by the Effective Medium Approximation. The obtained information, combined with High Resolution Electron Microscopy observations,provided a deeper insight on the relations among technological process, morphology and reflective properties. Our preliminary results outline the possibility to control the porosity profile as well the reflectance of the porous films via the oxidising species concentration in the stain etching solution.
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    URL: http://dx.doi.org/10.1023/A:1009607725830
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    In-Situ Surface-Roughness Measurements during the Preparation of Chemically Etched Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 47-49 
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    ISSN: 1573-4854
    Keywords: stain etching ; porous silicon ; neutron reflection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We have monitored the stain-etching of silicon in real time using neutron reflection. The etching process does not occur uniformly with time and possible dynamics of the process is under consideration. Distinct irregularities are produced on the PS surface and some gas bubbling from the cell is observed.
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    URL: http://dx.doi.org/10.1023/A:1009638504564
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    Localized Photo-Assisted Electro-Deposition of Zinc Selenide into p-Type Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 77-80 
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    ISSN: 1573-4854
    Keywords: porous silicon ; ZnSe ; electrochemical deposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electroplating of II-VI semiconductors like ZnSe into porous silicon can be an efficient and low cost method to fill the porous volume with a transparent and conductive material. With n-type porous layers, ZnSe impregnation is more effective near the sample surface because of reaction rate limitations due to diffusion in the electrolyte. In this paper, it is shown that the deposition of ZnSe into p-type porous silicon can be localized in the lower part of the porous layer if the reduction reaction rate is monitored by limiting the charge carrier supply. This can be done by controlling the power of the laser beam which photo-generates the carriers at the bottom of the pores. Studying the porous layer chemical composition by Auger electron spectroscopy confirms that the deposit is localized at the pore bottom, whereas the changes in the chemical composition of the porous silicon surface are analyzed by infra-red spectroscopy.
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    URL: http://dx.doi.org/10.1023/A:1009611225946
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    AC Impedance Study of Porous Silicon Aging in HF Solution (2000)
    Springer
    Journal of porous materials 7 (2000), S. 97-101 
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    ISSN: 1573-4854
    Keywords: AC impedance ; porous silicon ; residual moisture ; aging effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The present work aims to study the AC impedance of porous silicon films left in the contact with the anodizing bath after their growth is over. It is shown that the layers grown at p-type silicon experience noticeable changes of their impedance behavior resulting in the gradual growth of electrical resistance of the p-PS layer. This change is assumed to be related with the deposition of a passive layer at the pore bottoms associated with reabsorption of dissolved Si-containing material from the electrolyte. The layers formed at n-Si also show changes of the electrical impedance, although they are much more complicated than in the previous case (dependence of the kinetics of changes on the polarization current and polarization time, presence of the inductive loops at the impedance spectra, etc.
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    URL: http://dx.doi.org/10.1023/A:1009619415893
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    New EXAFS Measurements by XEOL and TEY on Porous Silicon (2000)
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    Journal of porous materials 7 (2000), S. 169-172 
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    ISSN: 1573-4854
    Keywords: EXAFS ; XEOL ; porous silicon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Results of an EXAFS investigation on porous Silicon carried out by X-ray Excited Optical Luminescence (XEOL) and Total Electron Yield (TEY) techniques, at the Si K absorption edge, are reported. For the first time XEOL spectra of porous silicon have been recorded in a wide energy range (1800–2500 eV) and EXAFS signals have been singled out from them. Simultaneous TEY and XEOL measurements yield to different results: in particular TEY-EXAFS is sensitive up to the third coordination shell of Si, while XEOL-EXAFS reveals only the contributions of the first two coordination shells; moreover they show a different dependence on changes of the etching parameters. This evidences the sensitivity of XEOL technique to the local structure of the quantum confined luminescent sites. The dependence of the light emission properties on the main preparation parameters and their influence on the short-range structure of red and yellow porous silicon samples are also investigated.
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    URL: http://dx.doi.org/10.1023/A:1009622417710
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    An Investigation into Silane Evolution from Porous Silicon by Temperature Programmed Desorption Method (2000)
    Springer
    Journal of porous materials 7 (2000), S. 187-190 
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    ISSN: 1573-4854
    Keywords: porous silicon ; temperature programmed desorption ; FTIR ; silane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The gaseous species desorbed from porous silicon (PS) were investigated using the method of temperature programmed desorption (TPD) and fourier transform infrared spectroscopy (FTIR). Silicon wafers (25–50 Ω cm, p−, FZ) were anodised in 40% HF and HF/C2H5OH electrolytes. The PS samples were linearly heated at 1.5 K s−1 using a custom built heating unit in a oil-free pump backed vacuum chamber at a base pressure of 〈10−8 torr. A quadrupole mass spectrometer, which was used as the detector, was fitted in line of sight of the sample at a distance of about 6 mm. It was observed that silane was liberated during the heating of porous silicon samples produced from both electrolytes. The peak temperature at which this occurred was at 570 ± 10 K. This temperature coincides with the temperature of silicon-silicon bond breakage in ≡Si–SiH3 groups on the pore walls, as shown by the FTIR results. It is proposed that silane formation involves the reaction of the Si-silyl group with moisture: ≡Si–SiH3 + H2O → ≡Si–OH + SiH4.
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    Electrical Control of the Reflectance of Porous Silicon Layers (2000)
    Springer
    Journal of porous materials 7 (2000), S. 205-208 
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    ISSN: 1573-4854
    Keywords: porous silicon ; oxidation ; liquid crystal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper we demonstrate the filling of porous silicon (PS) layers with liquid crystals (LC's) in order to control the reflectance electrically. The preparation of PS and the choice of the right group of LC's will be presented. Especially an oxidation of PS is necessary so that the methods and parameters of oxidation will also be discussed. As a first result the increasing and decreasing of the thickness oscillations in the reflectance as a function of the applied voltage can be observed.
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    Porous Silicon Micromachining to Position Optical Fibres in Silicon Integrated Optical Circuits (2000)
    Springer
    Journal of porous materials 7 (2000), S. 227-231 
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    ISSN: 1573-4854
    Keywords: porous silicon ; micromachining ; localised anodisation ; fibre positioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Low-loss optical fibre connections require deep grooves etched in silicon substrate for accurate fibre positioning. As shown in this paper these grooves can be obtained by using localised formation of porous silicon on patterned substrates. Cr-Au masking layer with a duration in HF solution longer than 30 min is used to fabricate grooves with a depth higher than 75 μm. N+-type silicon provides grooves with a pseudo-V shape which is compatible with accurate fibre alignment. By using this technology, arrays of optical fibres are positioned with an accuracy higher than 1 μm.
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    URL: http://dx.doi.org/10.1023/A:1009603308141
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    Optical Waveguides Fabricated from Oxidised Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 243-246 
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    ISSN: 1573-4854
    Keywords: porous silicon ; oxidation ; refractive index ; optical waveguide ; optical losses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Further results on the optical properties of oxidised porous silicon as a function of porosity and oxidation conditions are presented in this paper. The refractive index varies logarithmically with the oxidation time irrespective of the porosity of the sample and the oxidation temperature. Burried waveguides have been realised from as-prepared and oxidised porous silicon. Optical losses of 18 dB cm−1 at λ = 1.3 μm have been obtained after oxidation at 800°C for 35 min.
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    URL: http://dx.doi.org/10.1023/A:1009659409958
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    Novel Structures for Porous Silicon Light-Emitting Diodes (2000)
    Springer
    Journal of porous materials 7 (2000), S. 119-123 
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    ISSN: 1573-4854
    Keywords: porous silicon ; light-emitting diode ; series resistance ; external quantum efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper, two novel structures of porous silicon (PS) light-emitting diodes (LEDs) are proposed aiming at the reduction of series resistance, Rs. The basic idea of the novel structures is to suppress the excessive growth of nanoporous silicon (nano-PS) layer that is electroluminescence- (EL-) active but highly resistive. The initial wafer of the first structure consists of a lightly-doped layer stacked on a highly-doped substrate. As a consequence of anodization, nano-PS layer is formed only in the lightly-doped layer, while meso-PS layer with moderate resistivity is formed in the highly-doped substrate. The second structure consists of alternately stacked nano- and meso-PS layers, since it is expected that multiple thin nano-PS layers connected in series are less resistive than a single thick nano-PS layer. Preliminary experimental results proved the effectiveness of these novel structures on the reduction of Rs.
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    URL: http://dx.doi.org/10.1023/A:1009671728614
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    The Electrical Band-Gap Energy of Porous Silicon Measured Versus Sample Temperature (2000)
    Springer
    Journal of porous materials 7 (2000), S. 271-273 
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    ISSN: 1573-4854
    Keywords: porous silicon ; photoconductivity ; energy band gap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Photocurrent measurements have been carried out on a series of samples consisting of porous silicon on top of crystalline silicon, in the temperature range 10–300 K. From the experimental data set, the electrical band-gap energy of porous silicon is deduced to be (1.80 ± 0.01) eV, independent of sample temperature. The results are discussed with the conclusion that for the samples studied here, the electrical bandgap in porous silicon is of molecular nature and cannot be related to quantum-confinement properties of nanocrystals of elemental silicon.
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    URL: http://dx.doi.org/10.1023/A:1009679930431
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    Blue Photoluminescence of Oxidized Films of Porous Silicon (2000)
    Springer
    Journal of applied spectroscopy 67 (2000), S. 852-856 
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    ISSN: 1573-8647
    Keywords: porous silicon ; photoluminescence spectrum ; photoexcitation spectrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is found that the films of n +-type porous silicon of low (10–50%) porosity exhibit photoluminescence in the region 400–500 nm after a 5-month storage in an air atmosphere. The spectrum of blue photoluminescence of the least porous but strongly oxidized films has maxima at 417, 435, and 465 nm. The same spectrum structure manifests itself upon the introduction of an Er3+- and Yb3+-containing complex. The mechanisms of blue photoluminesence are discussed.
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    Improvement of Porous Si Luminescence Intensity Durability by Nitrogen Ion Irradiation Using an ECR Ion Source (2000)
    Springer
    Journal of porous materials 7 (2000), S. 73-76 
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    ISSN: 1573-4854
    Keywords: porous silicon ; passivation ; photoluminescence intensity stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We have investigated the effects of the porous Si surface passivation by oxygen or nitrogen ion processing on the photoluminescence (PL) intensity and its stability using an electron cyclotron resonance ion source. The results indicate that an anneal before exposure to ion beam causes a PL intensity enhancement upon exposure to oxygen or nitrogen ion beam. A combination of an anneal and a passivation by exposure to nitrogen ion beam enhances the PL intensity by a factor of ∼2.5 compared to the intensity of the initial as-anodized PS and the enhanced intensity is stabilized for more than 180 min under Ar+-laser illumination while oxygen-ion-exposed PS exhibits an enhancement in PL intensity only by ∼1.4 and a decay in PL intensity by ∼20% after 180 min Ar+-laser illumination. The results suggest that the reaction of nitrogen with a PS surface plays a key role for the PL intensity enhancement and stability.
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    URL: http://dx.doi.org/10.1023/A:1009659109107
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    Near-Field Electron Energy Loss Spectroscopy in Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 159-163 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; EELS ; NFEELS ; SiO2 layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract First results of an Electron Energy Loss Spectroscopy in the Near Field (NFEELS) mode of n+ porous silicon are described here. Sequences of EELS spectra in the low loss energy range (0–30 eV) were recorded, using a scanning transmission electron microscope, as the e-beam was scanned across a nano-hole surrounded by Si platelets. This technique is shown to be very sensitive to spectral and spatial changes in the electromagnetic field distribution outside the surface of nanoparticles, governed by their local nature and shape.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009666132731
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    Processing of Infrared Spectroscopy Data on Thin Porous Films Using Software “Prospect” (2000)
    Springer
    Journal of porous materials 7 (2000), S. 239-242 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; interference fringes ; infrared-spectroscoy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Here we present the software utility “ProSpect” which allows to process and interpret the data of infrared spectrophotometry studies of thin porous films. These spectra are often complicated by the presence of interference fringes. The program allows to remove fringes and thus enhance the intensity of useful IR bands as well as calculate optical parameters of the films (medium thickness value, refractive index, deviation of the thickness from medium value). Application of ProSpect in analysis of the FT-IR spectra of non-uniform porous silicon films is illustrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009607409050
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  • 49
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    Electro-, Photo- and Scanning Tunneling—Luminescence Studies of Efficient Light-Emitting Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 125-130 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; photoluminescence ; electroluminescence ; scanning tunneling microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Porous silicon films as used in efficient blue-green electroluminescent devices (internal efficiency about 0.1%) were studied by scanning tunneling microscopy light emission spectroscopy (STMLES) as well as photoluminescence (PL) and electroluminescence (EL) spectroscopy. Areas of the n-type porous Si surfaces with small particles of about 5 nm dimensions gave STMLE, but areas with larger structures gave no emission. Clear STMLE spectra gave a peak at 630 nm, quite different from the EL peak at 500 nm. Whereas the PL peak at 700 nm was consistent with the STM indication of quantised entities, the EL seemed more readily explicable in terms of defects at the metal contact barrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009627913593
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    Deposition of Erbium Containing Film in Porous Silicon from Ethanol Solution of Erbium Salt (2000)
    Springer
    Journal of porous materials 7 (2000), S. 37-40 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; erbium containing films ; electrochemical cathode treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electrochemical treatment of porous silicon (PS) in ethanol solution of Er(NO3)3 was investigated to obtain material suitable for optoelectronic application. The voltammograms of n+-type and p-type PS vs. an Ag/AgCl reference electrode were examined and compared with these of a Pt electrode. The basic cathode reactions were marked out the voltammograms: (i) the formation and the adsorption of atomic hydrogen; (ii) the formation of molecular hydrogen; (iii) the electrolysis of water and ethanol. No zones relating to on electrochemical transitions of Er ions were revealed on the voltammograms. Nevertheless, with the cathode polarization, the formation of an Er-containing deposit was observed at the surface of the cathode. The IR and SIMS analysis were used to study the composition of the deposits. The scheme of the electrochemical and chemical reactions at the cathode is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009647903656
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    Oxidation of Porous Silicon in Dry and Wet Environments under Mild Temperature Conditions (2000)
    Springer
    Journal of porous materials 7 (2000), S. 63-66 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; oxidation ; IR spectroscopy ; vibrational analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Oxidation behavior of porous silicon under various environments of dry and wet air, and solution with and without appropriate oxidant at mild temperatures has been investigated. The progress of oxidation was followed by infrared spectroscopy. The presence of water vapor greatly accelerates the oxidation rate in comparison with the rate in dry air. The oxidized states are clarified with the help of oxidation experiments of partially hydrogen-desorbed porous silicon, which does not contain SiH2 and SiH3 as the hydride species. An oxidation mechanism is proposed to explain that oxidation is accelerated in the presence of water vapor and at the partially hydrogen-desorbed porous silicon. Further, oxidation behavior of porous silicon in solution containing appropriate oxidant is also investigated. The rate is very rapid and the oxidation does not produce the back-bond oxidized state of OySiHx in contrast to the oxidation in air.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009694608199
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    Pore Propagation Directions in P+ Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 57-61 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; pore propagation ; orientation dependence ; RBS ; EPR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A comparative study is presented on the pore propagation directions of porous silicon layers (PSL) formed on p+-type substrates of different orientations. PSLs were formed on plain (0 0 1) and (1 1 1) silicon wafers as well as on structured (0 0 1) wafers containing facets of various orientations. During anodization, regular pores follow the 〈0 0 1〉 direction on the (0 0 1) planes. While on the (1 1 1) planes fewer regular pores develop and seemingly propagate closely to the 〈1 1 1〉 direction. These results indicate that the pores propagate perpendicular to the surface i.e. along the field lines when the surface orientation is either (0 0 1) or (1 1 1). When the silicon surface provided (1 1 0) orientation (Chuang, Collins, and Smith, 1989), or its position is in between the (0 0 1) and (1 1 1) planes then the pores do not propagate perpendicular to the surface but along the 〈0 0 1〉 direction. All the phenomena exhibited might be explained by presuming that during formation, the pores propagate along the 〈1 0 0〉 directions, and that those 〈1 0 0〉 directions are preferred which are closely to the field lines. In PSLs formed on (0 0 1) surfaces the field lines and the 〈0 0 1〉 crystallographic direction are coincident. However, in the (1 1 1) oriented wafer where three equally probable 〈1 0 0〉 directions exist around the field lines, more irregular structure of PSLs will develop.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009642605473
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    Correlation of Photoluminescence and Bandgap Energies with Nanocrystal Sizes in Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 81-84 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; photoluminescence ; bandgap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We have measured the crystallite sizes, the bandgap energies, and the photoluminescence (PL) energies in porous silicon (PSi) samples having a wide range of porosities and kept in different ambient conditions. The dependence of the bandgap energy on the crystallite size agrees with theory. For PSi samples exposed to air and containing crystallites smaller than 5 nm, the PL intensity increases by several orders of magnitude and the PL peak energy shifts from the near infrared to the red, in agreement with the quantum confinement model for the PL. For crystallites smaller than 3 nm, there is a Stokes shift between the excitonic bandgap and PL energies, which increases to several hundreds of meV for sizes ∼2 nm, indicating that, in PSi exposed to air, the PL is not due to free excitons. Before exposure to air, very high porosity PSi samples emit at shorter wavelengths than after exposure to air, suggesting that the Stokes shift depends on the surface chemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009663210016
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    Electronic Structure and PL Spectrum of the Diffusion-Limited Model for Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 93-96 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; diffusion-limited model ; electronic structure ; photoluminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We present the results of theoretical calculations for electronic structures and photoluminescence (PL) spectrum of porous silicon whose morphology is generated through the diffusion limited aggregation process of pores in a two-dimensional honeycomb lattice. We have found that due to irregularity of the structure most of its eigenstates near band gap are localized while some of them are relatively delocalized. The localization of the eigenstates near band gap causes band-gap narrowing analogous to the quantum confinement effect. Solving the time-dependent equations for the occupation numbers of the eigenstates, we show that the present model reproduces the stretched exponential decay of PL intensity observed in the experiments.
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    URL: http://dx.doi.org/10.1023/A:1009667310925
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    Conduction and Luminescent Properties of Wet Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 103-106 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; photoluminescence ; electroluminescence ; quenching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Carrier transport and photoluminescence-quenching mechanisms in reverse-biased p-type porous silicon in contact with an aqueous electrolyte are investigated. Concerning transport mechanisms investigation, experiments are based on the study of the photo-induced current as a function of the porous layer thickness. The liquid-impregnated porous silicon skeleton is found under equipotential conditions. Transport of electrons (supplied by the substrate) in porous silicon is shown to be dominated by a diffusion process. Photoluminescence-quenching is investigated by using a reverse-biased p-type porous silicon illuminated at 365 and 809 nm simultaneoulsy. The first illumination generate photoluminescence and the second supplies carriers in the substrate. A progressive photoluminescence-quenching has been observed, under a constant applied voltage, by increasing progressively the electron concentration in the porous layer. This original experiment allows to reject the hypothesis of an electric-field-induced separation of carriers as the photoluminescence-quenching mechanism in wet porous silicon, while it strongly supports the mechanism based on Auger recombination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009670300872
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    Monitoring Anodic Silicon Dissolution in Acidic Fluoride Electrolyte by the Mirage Effect (2000)
    Springer
    Journal of porous materials 7 (2000), S. 17-22 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; electropolishing ; anodic silicon dissolution ; probe beam deflection technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Probe beam deflection (PBD) technique was used for the in-situ characterization of p-Si anodic dissolution in fluoride containing acidic media in the regimes of porous Si formation, electropolishing and sustained electrochemical oscillations. When trends in deflectometric signal differed from those of current density, PBD could provide complementary informations on the occurrence of chemical reactions at the electrode. A model is proposed for the estimation of oxide thickness based on the instantaneous formation and dissolution rates in galvanostatic conditions. Results point to the existence of different oxide phases at the p-Si/electrolyte interface.
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    URL: http://dx.doi.org/10.1023/A:1009675328730
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    Investigation of Morphology of Porous Silicon Formed on N+ Type Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 23-26 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; morphology ; mechanism of growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The properties of porous silicon (PS) are closely connected to its morphology, much investigation has been done in order to correlate the morphological characteristics of PS with the anodisation parameters. In this paper the results of morphological analysis of PS formed on N+type substrates of 〈1 0 0〉 and 〈1 1 1〉 orientation are presented. The dependences of the porosity, thickness of PS, density of pores and of the effective surface on the current density are obtained. Interpretation of these results in terms of diffusion layer and energy levels is given, with special attention given to the low current density case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009627412800
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    Correlation of Photoluminescence and Optical Absorption Spectra of Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 311-314 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; photoluminescence ; optical absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Using a quantum confinement based-PL model, PS was modelled as a mixture of Quantum Dots (QDs) and Quantum Wires (QWs) having different concentrations and sizes. It was shown that in the optical absorption edge the PL peak energy and the Optical Absorption (OA) exhibit the same trend, depending on preparation conditions. The spectral behaviours of PL and OA are analysed and correlated throughout the shapes and the size distribution of the nanocrystallites forming PS. Using the quantum confinement formalism, the value of the effective band-gap energy determined from the lowest PL energy almost corresponds to that estimated from the optical absorption coefficient. These results suggest that the lowest radiative transition between the valence band and the conduction band corresponds to the largest luminescent wires, and that the radiative recombination process leading to the PL emission occurs in the c-Si crystallite core.
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    URL: http://dx.doi.org/10.1023/A:1009665021770
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    Pulsed Anodic Anodisation of Porous Silicon Films (2000)
    Springer
    Journal of porous materials 7 (2000), S. 377-379 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; photoluminescence ; pulse anodizing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Porous Silicon is conventionally made by dc anodisation of silicon. In this paper we have studied the luminescence of porous silicon made by pulsed anodisation as a function of duty cycle and HF concentration. Specifically we show for the first time that the luminescence can be tuned over a wide range in energy.
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    URL: http://dx.doi.org/10.1023/A:1009678819470
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    Analysis of Publications on Porous Silicon: From Photoluminescence to Biology (2000)
    Springer
    Journal of porous materials 7 (2000), S. 363-366 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; publications ; bibliographic analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The issue of porous silicon has attracted much research during last seven years due to perspectives of the formation of all-silicon optoelectronic devices (first of all—LEDs). The work presents a bibliographic analysis of publications made during the period from 1990 (when red-light photoluminescence from porous silicon was first reported by Dr. L. Canham) to the present time in order to reveal the existing tendencies of the researches (what particular field attracts the most research, who is the most fruitful in publishing articles related to porous silicon, etc.). The contributions of different research centres and countries are also evaluated. Personal contributions of leading researchers are disclosed and their citation ranking is given. It is concluded that emerging applications of porous silicon in micro-machining, chemical and biological monitoring will stimulate further activities in studying the mechanism of porous silicon growth and its physical and chemical properties.
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    URL: http://dx.doi.org/10.1023/A:1009643206266
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    Electrical and Optical Properties of Conducting Polymer/Porous Silicon Structures (2000)
    Springer
    Journal of porous materials 7 (2000), S. 393-396 
    Details
    ISSN: 1573-4854
    Keywords: porous silicon ; phenylene vinylene oligomer ; photoluminescence ; electrical conduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electrical and optical properties of diode structures based on porous silicon (PS) and thin films of phenylene vinylene oligomer (PVO) have been studied. Steady-state photoluminescence spectroscopy show that the structure of the luminescence band depends on the PS morphology. We assign the observed effect to the morphology-dependent penetration of PVO material into the pores. Current-voltage characteristics of the PVO/PS diodes are studied and interpreted assuming Schottky emission and hopping transport of carriers aspossible mechanisms of d.c. electrical conduction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009651408083
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