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  • Physics  (41)
  • 1
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    Springer
    Applied physics 59 (1994), S. 579-582 
    ISSN: 1432-0630
    Keywords: 42.65 ; 42.70 ; 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Two-beam coupling gain and speed of a Cr-doped strontium-barium niobate single crystal at 514.5 nm and 632.8 nm are measured to compare photorefractive origins and responses. The same single deep center and single carriers are found to be responsible for the observed photorefractivities at both wavelengths. Self-pumped phase-conjugate reflectivities are also measured at both wavelengths.
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  • 2
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    Applied physics 58 (1994), S. 87-90 
    ISSN: 1432-0630
    Keywords: 72.40 ; 73.60 ; 81.15
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Recombination and transport parameters were determined in Schottky diodes made of thin TiO2 solgel films with particle size around 50 nm. Effective recombination times are typically in the range, 10 μs〈τ〈1 ms, depending on injection level. The lifetimes are found to decrease at higher current levels, indicating bimolecular recombination kinetics due to a progressive increase in trap occupation. The mobility-lifetime product is estimated to be ≈5×10−11 cm2/V and is independent of current level.
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  • 3
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    Applied physics 59 (1994), S. 563-567 
    ISSN: 1432-0630
    Keywords: 61.70 ; 72.40 ; 78.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Photoconductivities and photovoltaic currents of ruthenium-doped KNbO3 are orders of magnitude larger than that of undoped and ion-doped crystals. KNbO3:Ru is very sensitive for holographic recording with red light and the photovoltaic current increases sublinearly with light intensity.
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  • 4
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    Applied physics 57 (1993), S. 437-440 
    ISSN: 1432-0630
    Keywords: 78.20 ; 61.70 ; 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Holograms recorded under suitable conditions in photorefractive BaTiO3 exhibit an unusual dark build-up. The diffraction efficiency increases by some orders of magnitude after the recording beams are switched off, and then steadily decreases afterwards. An interpretation of this effect in terms of a two-center charge transport model is given.
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  • 5
    ISSN: 1432-0630
    Keywords: 42.80 ; 72.40 ; 68.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Pb1−x−y Sn x Ge y Te:In epitaxial films are examined in a wide temperature interval and at various background fluxes. These films have high sensitivity to infrared radiation in the spectral range λ〈20μm. The lifetime depends exponentially on temperature and varies from several seconds at T=10 K to 10−2 s at T=20 K. The two-electron model of Jahn-Teller centers is proposed to explain the results. Multielement photoresistors based on these films are fabricated and D*=1.7×1013 cm Hz1/2 W−1 at T=25 K is achieved. Noise of the photoresistors is independent of background flux when it varies from 1012 cm−2 s−1 to 1018 cm−2 s−1. As compared with Si:Ga and Ge:Hg photoresistors, the responsitivity is several orders larger at the operating temperature 25–30 K.
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  • 6
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    Applied physics 57 (1993), S. 427-430 
    ISSN: 1432-0630
    Keywords: 71.55 ; 72.20.Jv ; 72.40 ; 72.80.Ey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Time-resolved photoconductivity measurements have been used to characterize electron traps in wide-gap n-HgO0.3Cd0.7Te for the first time. The characterization was made possible by combining the time-resolved photoconductive data with the analytical method conventionally used in DLTS spectroscopy. Two electron traps were found in the band gap with 61 meV and 79 meV below the conduction band edge, their concentrations are 1.1×1013 cm−3 and 5.8×1011 cm−3, respectively. Compared with DLTS spectroscopy, this characterization method markedly simplifies sample preparation and experimental procedure.
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  • 7
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    Applied physics 56 (1993), S. 335-341 
    ISSN: 1432-0630
    Keywords: 72.40 ; 85.30 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The effect of signal-modulated optical radiation on the characteristics of a GaAlAs/GaAs MODFET has been studied analytically. It is found that the offset voltage increases with modulation frequency and the effect of frequency is negligible above 5 MHz. The drain-source current decreases with increase in signal frequency at a constant radiation flux density, doping concentration and drain-source voltage. Studies on sheet concentration and transconductance also show that the signal frequency has a significant effect upto a certain modulation frequency (≲5 MHz) above which the effect of frequency is insignificant.
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  • 8
    ISSN: 1432-0630
    Keywords: 42.65 ; 42.70 ; 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We present new results on the growth of semi-insulating vanadium-doped cadmium telluride crystals and their characterization by different optical techniques such as photoinduced current transient spectroscopy, absorption, photoconductivity spectra, and photorefractive wave mixing. Our joint research program aims at developing optimized crystals for efficient optical processing in the near infrared through the photorefractive effect.
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  • 9
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    Applied physics 55 (1992), S. 61-64 
    ISSN: 1432-0630
    Keywords: 42.65 ; 42.70 ; 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We report on the photorefractive properties of a Cr-doped (K1−x Na x )2A−2 (Sr y Ba1−y )2−A Nb10O30 (x=0.586, y=0.659, A=1.12) single crystal in the near-infrared spectrum. The sample exhibits photorefractivity for wavelengths up to at least 840 nm where the steady-state two-beam coupling gain is found to be larger than 2 cm−1. Photorefractive gain and decay rate are measured as a function of wavelength, grating spacing and intensity. The wavelength dependence of gain fluctuations in two-beam coupling are also measured.
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  • 10
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    Applied physics 55 (1992), S. 49-54 
    ISSN: 1432-0630
    Keywords: 42.40 ; 72.40 ; 78.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We report the presence of quasipermanent effects of photochromic and hole-photorefractive nature in Bi12TiO20 (BTO) at low irradiance at 514.5 nm. A new selective two-wave mixing (S2WM) detection technique was used that allows to separately detect phase and amplitude gratings. S2WM is used in this work for operating a self-stabilized recording setup which allows to produce unusually large quasipermanent effects. We also show that stabilized recording is necessary to obtain reliable information from hologram erasure experiments. Results reported in this paper show the complex nature of recording in BTO and the capabilities of stabilized recording and S2WM for fundamental and applied research on photorefractive crystals.
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  • 11
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    Applied physics 54 (1992), S. 68-71 
    ISSN: 1432-0630
    Keywords: 7340L ; 72.40 ; 72.20J ; 72.80E
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In the present work the photoconductive response of low resistivity, n-type GaAs epitaxial layers is studied by experimentally monitoring the dependence of the photoconductive gain (PG) optoelectronic parameter upon incident photon flux and temperature. The characterized samples fall into three major categories: ion implanted (II) GaAs epilayers formed within undoped, semi-insulating GaAs substrates; GaAs epitaxial layers grown by liquid phase epitaxy (LPE) on Cr-doped, semi-insulating GaAs substrates; and ungated GaAs MESFETs.
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  • 12
    ISSN: 1432-0630
    Keywords: 71.55 ; 72.40 ; 76.30.Da ; 78.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract On the basis of a previous identification of paramagnetic defects in nominally undoped as grown BaTiO3 single crystals, we have investigated the changes of the concentrations of these centers and their optical absorptions under illumination with light of varying wavelengths. The most pronounced charge transfers occur by hole ionization of Fe4+ and — to a lesser extent — of Cr5+ and Cr4+. At low temperatures the created holes are trapped in the form of O−-ions next to Al3+ or unknown acceptor defects. Corresponding Fe4+ and O− absorptions have been identified.
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  • 13
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    Applied physics 55 (1992), S. 30-32 
    ISSN: 1432-0630
    Keywords: 42.65 ; 42.40 ; 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Using a ps-transient grating technique the contribution of the ps-photorefractive effect to the first-order probe-beam diffraction signal has been studied in CdTe at 1 μm investigating diffraction kinetics at different sample orientations in the thin grating regime. A fast photorefractive grating formation time during the pump pulses and a characteristic decay time of 600 ps, shorter than the free-carrier lifetime, have been observed.
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  • 14
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    Applied physics 53 (1991), S. 194-197 
    ISSN: 1432-0630
    Keywords: 72.40 ; 72.20 ; 85.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A transient negative photoconductivity phenomenon observed in silicon doped with gold atoms has been investigated. On the basis of the trapping of photo-excited carriers into two deep levels of gold atoms, a model for the occurrence of transient negative photoconductivity is proposed and related qualitatively to some experimental results.
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  • 15
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    Applied physics 53 (1991), S. 81-86 
    ISSN: 1432-0630
    Keywords: 61.70 ; 72.40 ; 78.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Measurements of photoconductivity and light-induced absorption in KNbO3: Fe are performed at different light intensities and crystal temperatures. The results are interpreted in terms of a two-center charge transport model. Different model parameters may be evaluated from the experimental data. A complete set of parameters is suggested explaining the dependences of photoconductivity and light-induced absorption on light intensity and temperature for the KNbO3: Fe crystal investigated.
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  • 16
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    Applied physics 51 (1990), S. 13-17 
    ISSN: 1432-0630
    Keywords: 61.70 ; 72.40 ; 78.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A charge transport model including deep and shallow traps explains both the nonlinear relation between photoconductivity and light intensity and the light-induced absorption in BaTiO3. A correlation between measurements of photoconductivity and light-induced absorption as a function of temperature yields parameters for the shallow center, among them thermal activation energy and generation rate.
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  • 17
    ISSN: 1432-0630
    Keywords: 61.70 ; 78.30 ; 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Shallow thermal donors are electrically active oxygen-related thermally formed defects observed in oxygen-rich silicon annealed between 300 ° and 600 ° C. Seven donors have been identified with an average central-cell correction of only 5 meV. In view of their molecule-like nature this close agreement to the effective mass theory prediction for a hydrogen-like donor in silicon is of interest. It is shown that these centres are not correlated to the residual impurities phosphorus and boron but rather to the presence of nitrogen. Nitrogen-doped oxygen-rich samples show increased shallow thermal donor growth and a reduction in the growth of other oxygen-related donors in comparison to normally nitrogen-undoped oxygen-rich samples. A reduction in shallow thermal donor concentration at high nitrogen concentrations is reported.
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  • 18
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    Applied physics 48 (1989), S. 237-240 
    ISSN: 1432-0630
    Keywords: 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This study presents a simulation that is used to determine the sensitivity of the phase shift analysis of the modulated photocurrent method to the differences in the fine scale structures in the density of states (DOS) distributions. Four DOS distributions are considered and the expected data are obtained. The results show that the modulated photocurrent method is very sensitive to such fine features in the DOS distributions. A comparison is also made with the sensitivity of other techniques commonly used in the determination of the DOS profiles.
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  • 19
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    Applied physics 49 (1989), S. 165-169 
    ISSN: 1432-0630
    Keywords: 72.20 ; 72.40 ; 73.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper is concerned with the optimization of growth conditions for a-Si1-x Ge x :H alloys. It is shown that H-dilution of source gases selectively improves the band transport of electrons without significantly affecting the recombination center density or the band transport of holes. It is further shown that the beneficial effects of H-dilution are most pronounced in alloys with comparable densities of Si and Ge.
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  • 20
    ISSN: 1432-0630
    Keywords: 72.20 ; 72.40 ; 72.80J ; 77.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract ac measurements (1 Hz–10 kHz) have been carried out on a Pb2CrO5 ceramic sample (with surface electrodes) at room temperature as a function of voltage and intensity of visible light illuminating the sample. Cole-Cole complex impedance plots show that the electrical behaviour of Pb2CrO5 is strongly modified when the sample is illuminated. The bulk conductance of the sample is found to increase with increasing light intensity indicating that this dielectric material becomes semiconducting due to the photogeneration of free charge carriers in the conduction band. The dielectric constant of the sample is enhanced by illumination probably due to light-dependent space charge effects in a manner where the dielectric's relaxation time (τ=RC=0.7 ms) remains constant with light intensity. On the other hand, both the bulk conductance and geometrical capacitance of the sample have been found to be almost independent of the applied voltage.
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  • 21
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    Applied physics 48 (1989), S. 517-520 
    ISSN: 1432-0630
    Keywords: 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract One of the major problems of the method of phase shift analysis of modulated photocurrent for studying the density of states in the energy gap of amorphous semiconductors has been the determination of the energy scale corresponding to this DOS profile. This study presents a new way of dealing with this problem. This new method is especially useful in the case where the DOS profile lacks a characteristic peak. A computer analysis is used to confirm the validity of this method and to demonstrate how it can be used.
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  • 22
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    Applied physics 45 (1988), S. 221-224 
    ISSN: 1432-0630
    Keywords: 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract For the determination of the density of states in the mobility gap of amorphous semiconductors using the “phase shift analysis of modulated photocurrent,” this paper suggests that making use of the magnitude of the induced photocurrent helps to remove arbitrariness in the energy scale. The working equations for the density of states and the corresponding energy position are expressed in terms of the intensity of the photocurrent. A simulation is made for a specific distribution, to investigate the validity of the procedure. The results show that the profile of the energetic distribution of localized states and the exact energy position of each state are consistent with the original distribution considered.
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  • 23
    ISSN: 1432-0630
    Keywords: 72.40 ; 73.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Excess charge carrier kinetics in moderately doped pSi wafers were investigated with a contactless transient photoconductivity method, i.e. the time-resolved microwave conductivity (TRMC) method. The surface structure of the wafers was changed by etching and polishing, the volume structure by irradiation with high-energy electrons. Comparison of the photoconductivity decay after excitation by strongly absorbed light and by weakly absorbed light was used to distinguish between surface and volume decay processes. The experimental results deviate from predictions based on a linear surface decay rate. These results are discussed and suggestions are made for the use of transient photoconductivity measurements to characterize semiconductor wafers.
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  • 24
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    Applied physics 47 (1988), S. 193-197 
    ISSN: 1432-0630
    Keywords: 68.55 ; 72.40 ; 81.15
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Hydrogenated amorphous silicon films have been prepared by primary ion beam deposition with a new electrodeless rf ion source. The design of the ion source is described. The composition of the a-Si:H films has been determined by Rutherford backscattering, and the photoconductivity by the constant photocurrent method (CPM). The best a-Si:H films show photoconductivities of 5×10−5 (Ω cm)−1. The deposition rates were between 0.7 and 1.2 nm s−1.
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  • 25
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    Applied physics 43 (1987), S. 205-208 
    ISSN: 1432-0630
    Keywords: 72.40 ; 72.20 ; 85.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A transient negative photoconductivity phenomenon observed in silicon doped with gold atoms by an appropriate diffusion condition has been investigated. The transient negative photoconductivity could be observed with a diode doped with gold atoms under intrinsic light-pulse illumination. In the recovery process of the transient negative photoconductivity to a steady-state dark level, two kind of time constants were observed, which may be related with the emission of electrons from gold level. A dependence of the magnitude of the peak value on the ambient temperature was observed; a qualitative explanation is given.
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  • 26
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    Applied physics 42 (1987), S. 173-177 
    ISSN: 1432-0630
    Keywords: 72.15 ; 72.40 ; 78.55 ; 79.20 ; 85.40 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A superlattice avalanche photodiode using III–V materials is expected to be used in long-distance fiberoptic communication systems in the 1.3 to 1.55 μm wavelength range. Theoretical studies have been made on the effective ionization rates of electrons and holes of the device, I–V characteristic and the frequency response characteristic of the Al x Ga1−x As/GaAs superlattice p+-i-n+ structure. It is observed that theα/β ratio of the device increases with the field and the bandwidth of the response curve increases with decrease in the dc multiplication gain.
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  • 27
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    Applied physics 42 (1987), S. 311-315 
    ISSN: 1432-0630
    Keywords: 70.20 ; 72.40 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Avalanche photodetectors are very important solid-state detectors currently used in long-distance and wide-band optical communication systems, due to their faster speed of response compared to other solid-state photodiodes. Furthermore, it has been found that by using heterostructures one can improve both multiplication gain and quantum efficiency of such a device. DOVATT is a heterojunction impatt device in which there is one avalanche zone followed by two drift zones at different scattering limited velocities. The device is very useful for generation of high power in the X-band. The present paper examines the effect of optical radiation on such a device. Studies have been made on the frequency-response characteristics of the device. The results show that the device has the potentiality of becoming a powerful photodetector in optical communication systems.
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  • 28
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    Applied physics 44 (1987), S. 245-247 
    ISSN: 1432-0630
    Keywords: 61.70T ; 71.55F ; 72.40 ; 78.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Photoionization of the DX center in Si-doped A10.33Ga0.67As has been studied by means of photoconductivity. The optical cross-sectionσ nd 0 shows a threshold atħω=200 meV and relative maxima (shoulders) around 400, 600, 950, and 1700 meV. The results throw doubt on the validity of the large lattice relaxation model, generally accepted for this class of centers. They can be well accounted for by the small relaxation model, recently proposed by the authors.
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  • 29
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    Applied physics 44 (1987), S. 361-364 
    ISSN: 1432-0630
    Keywords: 72.40 ; 78.55 ; 85.30 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Carrier frequency-dependent intrinsic parameters of an ion-implanted silicon photo-MESFET have been analysed theoretically. The internal gate source capacitanceC gs is found to increase with increasing carrier frequency under the normally OFF condition and the change is small under the normally ON condition. Also, the internal drain-source resistanceR ds increases with frequency at a fixed flux density and wavelength of operation. The ion-implanted photo-MESFET could become useful as optically controlled switching device in digital circuits.
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  • 30
    ISSN: 1432-0630
    Keywords: 77.40 ; 72.40 ; 77.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The electrical and dielectric properties of mercuric iodide were studied at room temperature under various intensities and colours of light in the frequency range 1 Hz–10 kHz. In the high-frequency region (〉40 Hz), the real part of the dielectric constant (ɛ′) is almost constant with frequency (f), colour and intensity of light. At lower frequencies,ɛ′ varies nearly as 1/f and monotonically increases with intensity (I) of the yellow (or green) light, whereas it is almost constant with red light intensity. This behaviour is discussed in the view of the different polarization contributions. The imaginary part of the dielectric constant (ɛ″) was found to vary as 1/f over the frequency range studied. This behaviour was observed whether the crystal was in dark or illuminated implying that the roomtemperature ac dark- or photo-conductivity (σ) is independent of frequency. The observed variation ofσ with intensity of yellow (or green) light was found to follow anI 1/2 dependence and a weaker dependence for the red light. the red light. The conductivity behaviour is discussed in the view of the current theories.
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  • 31
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    Applied physics 39 (1986), S. 291-296 
    ISSN: 1432-0630
    Keywords: 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract p-Type Ge is investigated as a photon-drag detector for high-power pulsed CO2 laser, using 3-samples of different dimensions and resistivities. Nonlinear behaviour of the photon-drag effect is observed. This phenomena could be accounted for by taking into consideration the decrease of absorption and the increase of resistivity instantaneously at the moment of interaction, rather than the effect of multireflection. The observed saturation at intensities higher than 30 MW/cm2 could be due to multireflection since its role increases at high intensities. Using the quantum mechanical model with the above considerations it was possible to obtain good agreement to the measured results.
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  • 32
    ISSN: 1432-0630
    Keywords: 86.30 ; 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have made theoretical studies on the limitation of the open-circuit voltageV oc of a hydrogenated amorphous silicon (a-Si:H) p-i-n type solar cell. The effects of the tail states in the a-Si:H i layer and of the interface recombination are discussed in detail. The opencircuit voltage increases when the distribution of the tail states is sharp and/or the capture cross sections of these states are small. This is because the recombination rate of photogenerated carriers and/or the density of space charge due to trapped carriers in these states become low in these conditions. These effects of the tail states on the value ofV oc become pronounced when the built-in potential of the p-i-n junction is high. The decrease in the effective recombination velocity of carriers at the p/i and n/i interfaces results in an increase ofV oc. This increase becomes remarkable when the effects of the tail states on the value ofV oc are small. Both the sharp distribution of tail states and the small value of the interface recombination velocity are necessary to increase considerably the value ofV oc. We show the conditions of the material parameters necessary to obtain an open-circuit voltage of 1.0 V.
    Type of Medium: Electronic Resource
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  • 33
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 37 (1985), S. 153-164 
    ISSN: 1432-0630
    Keywords: 86.30 ; 72.40 ; 73.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have made theoretical studies on the trapping and recombination of photogenerated carriers in hydrogenated amorphous silicon (a-Si∶H) p-i-n solar cells. We discuss in detail the following points: 1) The limitations of the assumptions in the previous analysis. It has been clarified that the single-level Shockley-Read-Hall model for carrier recombination and the treatment of trap occupation in terms of quasi-Fermi levels are inadequate for exact analysis. 2) The superlinear dependence of carrier recombination rate on the free-carrier density which can explain the enhancement of photo-induced changes ina-Si∶H under high intensity light. 3) The estimation of capture cross section of the tail states ina-Si∶H. We show that the charged and neutral tail states have rather small capture cross sections of less than 10−16 cm2 and of less than 10−19 cm2, respectively. 4) The effect of the recombination of photogenerated (PG) carriers at the p/i and the n/i interfaces. We estimate the recombination velocityS of PG carriers at these interfaces to be about 103 cm/s. It has been also clarified that the decrease inS is effective to improve the cell performance, especially the open circuit voltage.
    Type of Medium: Electronic Resource
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  • 34
    ISSN: 1432-0630
    Keywords: 73.60 ; 72.40 ; 78.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Amorphous Si1−xCx: H thin films were prepared by the rf magnetron sputtering method using a composite target of silicon and graphite. The dependence of the optical, structural, electrical, and optoelectronic properties on the carbon contentx was investigated, by measuring the optical absorption spectra, ir spectra, dark conductivity, photoconductivity and ESCA spectra. The optical gap was found to be unchanged with increasingx below about 0.6, in spite of the increase in the amount of the SiC bond. This is considered to be due to the formation of the carbon clusters. It is found that the photosensitivity shows a maximum at aboutx = 0.2, and is about one order of magnitude larger than the film withx = 0. This is related to the decrease in the dark conductivity, which is ascribed both to the formation of the SiC bond and to the reorganization of the defect-rich structure of sputter-deposited amorphous Si by the addition of about 20% carbon. The photoconductive effect was gradually lost in the range ofx above 0.6. In this range, the optical gap increases rapidly owing to the rapid increase of the SiC bond.
    Type of Medium: Electronic Resource
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