The role of pseudosymmetry for the spontaneous strain in tris-sarcosine calcium chloride (TSCC) crystals has been investigated through Mn++EPR spectra as a function of temperature and externally applied uniaxial stres...
The role of pseudosymmetry for the spontaneous strain in tris-sarcosine calcium chloride (TSCC) crystals has been investigated through Mn++EPR spectra as a function of temperature and externally applied uniaxial stress. The on-axis fine-structure splittings are a sensitive measure of the pseudosymmetry, and the spontaneous strain in improper ferroelastic TSCC crystals can be attributed to the anisotropic expansion or compression of the lattice. Although macroscopically insignificant, the off-axis splittings yielded evidence for a collective molecular mechanism to become significant toward higher temperatures. An anomaly was observed atTo≃ 10°C, indicating the lock-in transition of the modulated structure above this temperature. However, the lattice remained as paraelectric and ferroelastic throughout from the ferroelectric transition up to the decomposition temperature.
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.
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.
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：
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.
作者：
BOSE, SKPOLL, JDUniv of Guelph Campus
Guelph-Waterloo Program for Graduate Work in Physics Guelph Ont Can Univ of Guelph Campus Guelph-Waterloo Program for Graduate Work in Physics Guelph Ont Can
A broad absorption in the spectral region 4000–7500 cm−1] has been observed in tritiated as well as proton-irradiated samples of solid deuterium. To explain this absorption we investigate two different types of local...
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A broad absorption in the spectral region 4000–7500 cm−1] has been observed in tritiated as well as proton-irradiated samples of solid deuterium. To explain this absorption we investigate two different types of localized electronic states in the solid. It is shown that the absorption can be interpreted as being due to the lowest energy bound-state transitions of electrons localized in nonspherical cavities of two different average radii. The localization is assumed to be initiated by vacancies. The shape of the absorption line is calculated by estimating the cavity size and the frequency of the breathing-mode oscillation of these cavities.
Different roles for internal standards in PIXE analysis of fluid residues are discussed. The efficacy of internal standards is predicated on having homogeneous targets of uniform thickness; the use of lecithin additiv...
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Different roles for internal standards in PIXE analysis of fluid residues are discussed. The efficacy of internal standards is predicated on having homogeneous targets of uniform thickness; the use of lecithin additives to achieve this is described and data are presented to illustrate the dependence of analytical precision on the mode of specimen preparation. Determination of actual thickness via measurement of the energy loss of transmitted protons is demonstrated; this provides a means of correcting for departures from the much-quoted “thin target” criterion.
Monoenergetic X-ray lines produced by diffraction from a curved crystal monochromator have been used to test the applicability of the Hypermet function for Si(Li) detectors. Excellent fits are achieved; the function&#...
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Monoenergetic X-ray lines produced by diffraction from a curved crystal monochromator have been used to test the applicability of the Hypermet function for Si(Li) detectors. Excellent fits are achieved; the function's parameters vary smoothly with energy, and the intensity of the non-Gaussian peak components correlates with the thickness of the frontal dead layer where charge collection is incomplete. Accurate silicon escape peak intensities are presented and the contribution to the lineshape from Compton-scattered events is discussed qualitatively.
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