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  • 1
    Electronic Resource
    Electronic Resource
    Observations on the surface and bulk luminescence of porous silicon (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6335-6340 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using the x-ray excited optical luminescence technique, we have investigated the soft x-ray induced photoluminescence of porous silicon in the optical region (200–900 nm) and the Si K-edge x-ray absorption fine structures of porous silicon in the near edge region. It is found that while porous silicon prepared at low current density (20 mA/cm2 for 20 min) exhibits a single broad luminescence band, porous silicon prepared at high current density (200 mA/cm2 for 20 min) exhibits three optical luminescence channels; i.e., in addition to the broad peak characteristic of all porous silicon, there are at least two additional optical luminescence channels at shorter wavelengths, one with modest intensity at ∼460 nm and the other a weak and very broad peak at ∼350 nm. These optical channels have been used to monitor the Si K-edge absorption of porous silicon in the near edge structure region. Analysis of the data shows that while the band at ∼627.5 nm corresponds to the bulk emission, the other channels are of a surface origin. These observations and their implications are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355156
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  • 2
    Electronic Resource
    Electronic Resource
    Transport property in narrow barrier GaAs/AlAs superlattice under hydrostatic pressure (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4259-4261 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The current–voltage (I–V) characteristics of a doped weakly coupled GaAs/AlAs superlattice (SL) with narrow barriers are measured under hydrostatic pressure from 1 bar to 13.5 kbar at both 77 and 300 K. The experimental results show that, contrary to the results in SL with wide barriers, the plateau in the I–V curve at 77 K does not shrink with increasing pressure, and becomes wider after 10.5 kbar. It is explained by the fact that the EΓ1–EΓ1 resonance peak is higher than the EΓ1–EX1 resonance peak. At 300 K, however, because of the more important contribution of the nonresonant component to the current, the plateau shrinks with increasing pressure. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370340
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  • 3
    Electronic Resource
    Electronic Resource
    Rotating garnets (1999)
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 17 (1999), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The origin of snowball and sigmoidal inclusion patterns in porphyroblasts is discussed. Snowball garnets are peculiar to shear zones whereas sigmoidal patterns occur in porphyroblasts both in shear zones and on the limbs of folds. There are currently two models for the development of snowball garnets and these have been discussed extensively in the literature. We show that although the typical two-dimensional snowball pattern can be produced by either model, the three-dimensional inclusion patterns are model-specific thus providing a distinguishing criterion. We have applied this criterion to all the available data and find that the classical model, which is dependent on the rotation of garnet relative to a single foliation, is applicable in all cases. Syn-kinematic porphyroblasts on the limbs of horizontal normal folds generally show little rotation relative to geographical coordinates. What rotation they do show generally has the same sense as that of the host limb, but is less in magnitude. This has been used as evidence that the porphyroblasts have remained irrotational while the rocks deformed around them; the implication being that they were unaffected by vorticity associated with folding. This has been explained by claiming that the porphyroblasts are restricted in distribution to small domains of coaxial deformation path. We show that for reasonable deformation models of horizontal normal folds, porphyroblasts affected by vorticity will rotate little with respect to geographical coordinates and our results predict the commonly observed natural patterns. We conclude therefore that lack of rotation relative to geographical coordinates cannot be used to demonstrate that porphyroblasts have grown only in coaxially deforming domains; much less restrictive and more reasonable interpretations are possible. Consequently, the lack of rotation relative to geographical coordinates is more significant for fold modelling than it is for the garnet controversy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1525-1314.1999.00203.x
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  • 4
    Electronic Resource
    Electronic Resource
    Formation of a nickel carbonyl cation containing a cyclophosphenium ligand by hydride abstraction (1987)
    s.l. : American Chemical Society
    Inorganic chemistry 26 (1987), S. 1629-1631 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00257a032
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of secondary electron emission on sheath potential in an electron cyclotron resonance plasma (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2119-2123 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The sheath potential φM is calculated from the difference between the plasma potential and the floating potential. The plasma potential has been measured by using a retarding field analyzer with an entrance slit located in front of it. The electron temperature Te and ion temperature Ti are also measured with the same analyzer in an electron cyclotron resonance plasma. Comparing the normalized sheath potential, −eφM/kTe, with the different theoretical values, it is found that the secondary electron emission could not be neglected in our experiment and is noncritical. The critical emission corresponds to zero electric field at the emitter. The various calculations have shown that the thermionic electron emission need not be required to be taken into consideration. The total energy transmission factors δT(=W/FTe, where W is the energy flux from the plasma, F is the ion flux, and Te is the electron temperature at the sheath edge) for hydrogen, nitrogen, and argon plasmas are calculated from the estimated secondary electron emission coefficient and the sheath potential, respectively. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364264
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  • 6
    Electronic Resource
    Electronic Resource
    Temperature dependence of photoluminescence from GaAs single and multiple quantum-well heterostructures grown by molecular-beam epitaxy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1371-1377 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoluminescence (PL) from GaAs/AlxGa1−xAs single and multiple quantum well (QW) heterostructures grown by molecular-beam epitaxy (MBE) has been studied in the temperature range 10〈T〈300 K. The temperature dependence of the PL peak energy and of the integrated intensity observed under both direct and indirect excitation of the GaAs QWs provides insight into the capture mechanism of photoexcited carriers. The temperature dependence of the QW emission energy follows the band-gap shrinkage of bulk GaAs. Deviations from this behavior are caused by lateral monolayer thickness fluctuations of the GaAs quantum well. Under direct excitation the QW luminescence intensity decreases with increasing temperature first due to a partial dissociation of excitons and finally due to thermally activated nonradiative centers. Free carriers generated in the AlxGa1−xAs barrier layers under indirect excitation diffuse rapidly into the GaAs well where they recombine radiatively. This diffusion is enhanced with the increase of temperature. A simple model allows the quantitative description of this diffusion process and of the quantum efficiency of the GaAs quantum well as a function of temperature. In the calculation of the temperature dependence of the luminescence intensity under indirect excitation we use a temperature-independent radiative recombination term and a temperature-dependent nonradiative recombination term to interpret the experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341862
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  • 7
    Electronic Resource
    Electronic Resource
    Luminescence properties of (GaAs)l(AlAs)m superlattices with (l,m) ranging from 1 to 73 (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 845-852 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a systematic investigation of (GaAs)l(AlAs)m (l(approximately-equal-to)m) superlattices by photoluminescence excitation at T=2 K in the energy range of 1.52–2.42 eV. The luminescence spectra of the superlattice samples differ strongly from the spectra of the ternary Al0.5Ga0.5As alloy. The luminescence peak energy is largest for l,m=3 and decreases when l,m〈3. The superlattices with l,m≤15 show sidebands of low intensity. The excitation spectra for superlattices with l,m≤8 show threshold energies but no discrete states corresponding to light-hole related transitions. Superlattices with l,m〉15 display a splitting of light- and heavy-hole states. The optical measurements confirm that this new material has properties which are very different from the ternary Al0.5Ga0.5As alloy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340079
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  • 8
    Electronic Resource
    Electronic Resource
    Angular scanning stage for glancing-incidence surface EXAFS (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 60-63 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this paper a simple and inexpensive angular positioning apparatus is described which can be applied to measurements of x-ray reflectivity and extended x-ray absorption fine structure (EXAFS) at glancing angles of incidence. An efficient interactive alignment procedure is discussed and the performance of the device is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139966
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  • 9
    Electronic Resource
    Electronic Resource
    Photovoltaic effect and its polarity in Si doping superlattices (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1777-1779 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the photovoltaic effects in Si doping superlattices (nipi) under different excitation conditions with and without additional cw optical biasing using a He-Ne laser. On the basis of the photovoltaic theory of carrier spatial separation in superlattices, we propose the concept of spatial fixity of the photovoltage polarity in type-II superlattices and examine the experimental results. The photovoltaic effect in Si nipi is found mainly from the direct transitions related with shallow impurities in real space, not the electron-hole band-to-band process as in GaAs nipi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110659
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  • 10
    Electronic Resource
    Electronic Resource
    SiO2/Si(100) interface studied by Al Kα x-ray and synchrotron radiation photoelectron spectroscopy (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2941-2943 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Both synchrotron radiation photoemission spectroscopy (PES) and Al Kα photoelectron spectroscopy (XPS) are used to determine the suboxide distribution at SiO2/Si (100) interfaces. High resolution PES measurements clearly resolved various suboxides with chemical shifts of 0.97, 1.80, and 2.60 eV for Si+1, Si+2, and Si+3, respectively. A total of 9.3×1014 atoms cm−2 of suboxide is found by PES measurements while only 4.2×1014 atoms cm−2 is measured by XPS on the same sample. This discrepancy is neither caused, as previously believed, by a difference in SiO2/Si (100) quality nor by a difference in methodology in data analysis. The possible factors, e.g., electron mean-free path and photoionization cross section, which contribute to the difference between PES and XPS data, are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110279
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