作者：
JERZAK, SFUJIMOTO, MUiv of Guelph
Guelph-Waterloo Program for Graduate Work in Physics Guelph Ont Can Uiv of Guelph Guelph-Waterloo Program for Graduate Work in Physics Guelph Ont Can
A comparative EPR study with various paramagnetic probes of iron-group elements has been carried out on the ferroelectric phase transition in tris-sarcosine calcium chloride (TSCC) crystals. These ions have yielded co...
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A comparative EPR study with various paramagnetic probes of iron-group elements has been carried out on the ferroelectric phase transition in tris-sarcosine calcium chloride (TSCC) crystals. These ions have yielded complementary results, and one probe was found to be insufficient to obtain necessary information about the transition mechanism. While the soft-mode vector is inferred from the VO++] spectra, either Cr+++] or Fe+++] ions are best suited to observe the critical phenomena near the transition temperature (Tc ~ 130 K). A critical broadening above Tc and an asymmetrical splitting below Tc are observed in the Cr+++] and Fe+++] spectra. The Mn++] spectra are unique in that the order–parameter fluctuation appears only slightly in the line widths above Tc, while the critical region below Tc is characterized by the coexistence of para- and ferroelectric phases. The critical slowing-down effect in the EPR line widths is found to be consistent with that observed in dielectric measurements, suggesting that sarcosine dipoles in TSCC crystals are associated with the elementary dipole for spontaneous polarization.
作者：
DAMASKINOS, SDIXON, AEUniv of Waterloo
Guelph-Waterloo Program for Graduate Work in Physics Waterloo Ont Can Univ of Waterloo Guelph-Waterloo Program for Graduate Work in Physics Waterloo Ont Can
A scanning laser microscope was used to study the electronic and recombination properties at grain boundaries of bothn- andp-type Wacker polycrystalline silicon in a spatially resolved photoconductivity experiment. Th...
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A scanning laser microscope was used to study the electronic and recombination properties at grain boundaries of bothn- andp-type Wacker polycrystalline silicon in a spatially resolved photoconductivity experiment. The light energy falling on the samples was varied over five orders of magnitude from 10−1to 10−6 mW. Forp-type material the measuredLdecreased with beam intensity from 150 to 60 μm, reaching a constant value at very low beam intensities. The small focal spot of the microscope allowed the measurements to be extended to includen-type samples. Forthese samplesLwas found to change from 90 to 18 μm with decreasing beam intensity. The surface recombination velocitySGBwas evaluated for both samples. Forp-type samples it decreased from 25 000 to 6000 cm/s and forn-type samples from 21 000 to 3000 cm/s with decreasing beam intensity. The quasi-Fermi level separation was determined as a function of the excess minority-carrier-concentration density at the grain boundary and found to increase linearly with beam intensity.
Thin films of a-Si:C have been prepared by thermal evaporation from resistive- and rf-induction-heated carbon crucibles. Samples were prepared with and without electron-beam irradiation of the substrate during deposit...
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Thin films of a-Si:C have been prepared by thermal evaporation from resistive- and rf-induction-heated carbon crucibles. Samples were prepared with and without electron-beam irradiation of the substrate during deposition, and the resulting film properties (electrical and optical) were measured. Reference samples prepared with substrate temperatures from 150 to 250 °C and annealing temperatures from 200 to 250 °C had very similar film properties. The use of vitreous carbon instead of compressed carbon for the crucibles reduced the carbon content by about 30% and the oxygen content of the films by more than a factor of four. Electron-beam irradiation of the purer films produced a tenfold decrease in the conductivity at room temperature and an increase of the high-temperature activation energies compared with the reference samples.
A simple force constant model is developed and applied to the vibrations of the chorine, bromine, and iodine crystals. Fundamental frequencies are calculated and compared to those observed by infrared absorption, Rama...
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A simple force constant model is developed and applied to the vibrations of the chorine, bromine, and iodine crystals. Fundamental frequencies are calculated and compared to those observed by infrared absorption, Raman scattering, and inelastic neutron scattering. The dependence of the halogen–halogen force constants on atomic separation is investigated. Ein einfaches Kraftkonstantenmodell wird entwickelt und auf die Schwingungen der Chlor-, Brom- und Jodkristalle angewendet. Die Fundamentalfrequenzen werden berechnet und mit denen verglichen, die mittels Infrarotabsorption, Ramanstreuung und inelastischer Neutronenstreuung beobachtet werden. Die Abhängigkeit der Halogen–Halogen-Kraftkonstanten vom Atomabstand wird untersucht.
作者：
VONSACKEN, UBRODIE, DEUniv of Waterloo
Guelph-Waterloo Program for Graduate Work in Physics Waterloo Ont Can Univ of Waterloo Guelph-Waterloo Program for Graduate Work in Physics Waterloo Ont Can
Vacuum-deposited Zn3P2films, prepared with and without low-energy electron bombardment during the deposition process, have been characterized both structurally and electronically. Zinc phosphide was chosen for this st...
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Vacuum-deposited Zn3P2films, prepared with and without low-energy electron bombardment during the deposition process, have been characterized both structurally and electronically. Zinc phosphide was chosen for this study because it is a promising material for the absorbing layer in a low-cost thin-film solar cell. The structure of the films has been studied using glancing-angle X-ray diffraction and transmission electron microscopy. Electron bombardment can be used to modify the properties of zinc-phosphide films. The e-beam parameters used in this study increased the degree of preferred orientation and altered the nature of the glass–Zn3P2interface.
作者：
HAQUE, ADIXON, AEBRODIE, DEUniv of Waterloo
Guelph-Waterloo Program for Graduate Work in Physics Waterloo Ont Can Univ of Waterloo Guelph-Waterloo Program for Graduate Work in Physics Waterloo Ont Can
The use of electron-beam irradiation combined with a hot-wall technique during deposition of CdS films is described. CdS films 2–10 μm thick were thermally deposited with and without electron bombardment on glass su...
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The use of electron-beam irradiation combined with a hot-wall technique during deposition of CdS films is described. CdS films 2–10 μm thick were thermally deposited with and without electron bombardment on glass substrates using a hot-wall technique under a pressure greater than 1 × 10−6] Torr (1 Torr = 133.3 Pa). Film properties were studied using low-angle X-ray diffraction, scanning electron microscopy, optical microscopy using a chemical decoration technique, Hall-effect measurements, and temperature-dependent dark conductivity. The surface grain size varied from 2 to 5 μm and films were brownish orange with a smoky appearance.
A simple force constant model is used to calculate the normal mode frequencies and eigenvectors of the carbon disulphide crystal. By adjustment of three intramolecular and four intermolecular parameters, good agreemen...
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A simple force constant model is used to calculate the normal mode frequencies and eigenvectors of the carbon disulphide crystal. By adjustment of three intramolecular and four intermolecular parameters, good agreement with spectroscopic data is obtained for the lattice mode frequencies and for the crystal field splittings of the molecular modes. Es wird ein einfaches Kraftkonstantenmodell benutzt, um die Normalmodenfrequenzen und Eigenvektoren des Kohlenstoffdisulfidkristalls zu berechnen. Durch Anpassung von drei intramolekularen und vier intermolekularen Parametern wird gute Übereinstimmung mit spektroskopischen Werten für die Gittermodenfrequenzen und für die Kristallfeldaufspaltungen der Molekülmoden erhalten.
A detailed analysis is reported examining the local magnetic susceptibility chi(r), in relation to the correlation function GIR) and correlation length xi, of a spherical model ferromagnet confined to geometry Omega =...
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A detailed analysis is reported examining the local magnetic susceptibility chi(r), in relation to the correlation function GIR) and correlation length xi, of a spherical model ferromagnet confined to geometry Omega = L(d-d') x infinity(d') (d' less than or equal to 2, d > 2) under a continuous set of twisted boundary conditions. The ''twist'' parameter ($) under bar tau in this problem may be interpreted as a measure of the geometry-dependent doping level of interfacial impurities (or antiferromagnetic seams) in the extended system at various temperatures. For tau(j) --> 0, For All j is an element of d-d', no seams are present except at infinity, whereas if tau(j) = 1/2, impurity saturation occurs. For 0 < tau(j) < 1/2 the physical domain Omega(phys) = D-d-d' x infinity(d') (D > L), defining the region between seams containing the origin, depends on temperature above a certain threshold (T > T-0). Below that temperature (T < T-0), seams are frozen at the same position (D approximate to L/2 tau, d-d' = 1), revealing a smoothly varying large-scale structural phase transition.
The problem of localized single-particle excitations and the density of states (DOS) for an inhomogeneous system consisting of a spherical superconductor (with radius a and order parameter Δ1) embedded in another sup...
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The problem of localized single-particle excitations and the density of states (DOS) for an inhomogeneous system consisting of a spherical superconductor (with radius a and order parameter Δ1) embedded in another superconductor (order parameter Δ2) of infinite size is considered. With the assumption of constant values of Δ1and Δ2, the Bogoliubov equations are solved for general values of l (the orbital angular momentum quantum number). For a fixed value of Δ1/Δ2and different values of Δ2/EF, the dependence of the excitation energy ε(l=0)/Δ2on the particle sizekFa is shown(kFis the Fermi wave vector andEFis the Fermi energy). ForkFa=300, 450, and 800 and a fixed value of Δ2/EF, the variations in the DOS by changing Δ1/Δ2are
The critical curve of a transition of the second kind in an antiferromagnetic superconductor (AFS) with nonmagnetic impurities has been studied. The AFS is described by using the mean-field model given by Nass, Levin,...
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The critical curve of a transition of the second kind in an antiferromagnetic superconductor (AFS) with nonmagnetic impurities has been studied. The AFS is described by using the mean-field model given by Nass, Levin, and Grest and assuming a one-dimensional electron band. We find that the points on the critical curve satisfy the thermodynamic stability condition for 0≤α1τ/Δ0≤5.04 and 0.49≤HQτ/Δ0≤***α1is the inverse lifetime of a conduction electron for nonmagnetic impurity scattering,HQis the antiferromagnetic molecular field, Δ0is the zero-temperature order parameter of a superconductor in the absence ofHQand impurities. Further, α1τand HQτdenote the values of these quantities for points on the critical curve. For α1τ/Δ0>5.04 and HQτ/Δ0>1.64, the phase transition from the superconducting to the normal state is always of the second kind. Some thermal properties of the system near the critical curve have also been investigated and we find that these depends dramatically on the
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