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THE PRESSURE VARIATION OF THE GLASS-TRANSITION TEMPERATURE IN ATACTIC POLYSTYRENE

JOURNAL OF CHEMICAL physics 1986年第2期84卷 1006-1014页

作者： STEVENS, JR COAKLEY, RW CHAU, KW HUNT, JL Guelph‐Waterloo Program for Graduate Work in Physics University of Guelph Campus Guelph Ontario Canada N1G 2W1

Brillouin frequency shifts from light scattering are used to measure the variation with pressure of the zero‐frequency glass transition temperature T g in atactic polystyrene (PS) at pressures up to 3 kbar. These r... 详细信息

Brillouin frequency shifts from light scattering are used to measure the variation with pressure of the zero‐frequency glass transition temperature T _g in atactic polystyrene (PS) at pressures up to 3 kbar. These results are extrapolated to high pressures and compared with theoretical predictions. Experimentally it is found that T _g asymptotically approaches a critical value at high pressures. The equilibrium lattice model of DiMarzio, Gibbs, Fleming, and Sanchez which approximates the residual entropy of a polymeric glass correctly predicts the experimentally observed trends. The molecular theory of Bengtzelius, G?tze, and Sj?lander is also qualitatively correct at high pressures even though it deals with the glass transition of a classical monatomic fluid. Neither theory is quantitatively in agreement with our results.

关键词： Glass transitions High pressure Polymers Atomic and molecular physics Brillouin scattering

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SPATIALLY RESOLVED LIFETIME MEASUREMENTS IN NEUTRON-TRANSMUTATION-DOPED POLYCRYSTALLINE SILICON

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JOURNAL OF APPLIED physics 1986年第5期60卷 1681-1688页

作者： DAMASKINOS, S DIXON, AE ROBERTS, GD DAGG, IR Guelph‐Waterloo Program for Graduate Work in Physics Waterloo Campus University of Waterloo Waterloo Ontario N2L 3G1 Canada

Spatially resolved carrier lifetimes have been measured at the same grain boundary using a series of adjacent samples doped to different levels by neutron transmutation. The samples had dopant concentration levels between 10¹ ³ and 10¹ ⁷ atoms/cm³. The carrier lifetime was measured using a contactless microwave absorption technique to monitor the decay of photoconductivity which allowed us to perform either isothermal or isochronal annealing to remove the damage caused by irradiation. An optimum anneal of 30 min at 700?°C resulted in almost full recovery to the lifetime before irradiation. A short laser pulse of wavelength 900 nm was focused to a 0.3‐mm‐diam spot on the samples. Lifetimes of two different sets of carriers were measured, the bulk carrier lifetime at the center of a grain and the carrier lifetime at a grain boundary. This latter carrier lifetime involves both fast and slow recombination mechanisms. The slow decay mechanism is due to interface states at the grain boundary. The fast recombination lifetime was found to be of the same order as the bulk recombination lifetime (of the order of 1 μs) and the slow one was of the order of 1 ms. Doping levels up to 10¹ ⁶ atoms/cm³ show no significant effect on the measured bulk carrier lifetime.

关键词： Carrier lifetimes Doping Grain boundaries Annealing Laser beam effects

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Mn++EPR studies on the ferroelasticity in tris-sarcosine calcium chloride crystals

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Philosophical Magazine B 1986年第6期53卷

作者： M. Fujimoto S. Jerzak Guelph-Waterloo Program for Graduate Work in Physics University of Guelph Ontario Canada N1G 2W1 Guelph-Waterloo Program for Graduate Work in Physics University of Guelph Ontario Canada N1G 2W1 Physics Department Academy of Agriculture Poznan Poland

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.

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CRITICAL ANOMALIES IN ELECTRON-PARAMAGNETIC-RES SPECTRA NEAR THE FERROELECTRIC PHASE-TRANSITION IN TRIS-SARCOSINE CALCIUM-CHLORIDE CRYSTALS

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CANADIAN JOURNAL OF physics 1985年第3期63卷 377-386页

作者： JERZAK, S FUJIMOTO, M Uiv 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 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.

关键词： FERROELECTRIC MATERIALS

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SCANNING-LASER-MICROSCOPE MEASUREMENTS OF MINORITY-CARRIER DIFFUSION LENGTH AND SURFACE RECOMBINATION VELOCITY IN POLYCRYSTALLINE SILICON

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CANADIAN JOURNAL OF physics 1985年第6期63卷 870-875页

作者： DAMASKINOS, S DIXON, AE Univ 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. 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.

关键词： Semiconducting silicon

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EFFECTS OF ELECTRON-BEAM IRRADIATION AND SUBSTRATE-TEMPERATURE ON THE PHYSICAL-PROPERTIES OF EVAPORATED A-SI-C THIN-FILMS

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CANADIAN JOURNAL OF physics 1985年第6期63卷 838-841页

作者： AUDAS, RD MOORE, CJL STURTEVANT, TEW JOHNSON, GW LESLIE, JD BRODIE, DE Univ 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

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.

关键词： Silicon carbide

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EFFECTS OF ELECTRON-BOMBARDMENT DURING VACUUM DEPOSITION OF ZN3P2 FILMS

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CANADIAN JOURNAL OF physics 1985年第6期63卷 757-761页

作者： VONSACKEN, U BRODIE, DE Univ 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 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.

关键词： Semiconducting zinc compounds

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SIMPLE DYNAMICAL MODEL FOR THE VIBRATIONS OF THE HALOGEN CRYSTALS

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PHYSICA STATUS SOLIDI B-BASIC RESEARCH 1985年第2期129卷 569-576页

作者： HIGGS, JF ANDERSON, A Guelph-Waterloo Program for Graduate Work in Physics Waterloo Campus University of Waterloo

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.

关键词： CHLORINE

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EFFECT OF ELECTRON-BOMBARDMENT DURING DEPOSITION OF CADMIUM-SULFIDE FILMS USING A HOT-WALL TECHNIQUE

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CANADIAN JOURNAL OF physics 1985年第6期63卷 712-715页

作者： HAQUE, A DIXON, AE BRODIE, DE Univ 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 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.

关键词： Semiconducting cadmium compounds

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INFRARED-ABSORPTION BY LOCALIZED-ELECTRONS IN SOLID DEUTERIUM

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CANADIAN JOURNAL OF physics 1985年第8期63卷 1105-1109页

作者： BOSE, SK POLL, JD Univ 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 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.

关键词： DEUTERIUM

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