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Amorphous Ge x Se 1− x compounds have been prepared and carefully characterized in the range 0 ⩽ x ⩽ 0.43 (density and micro-hardness measurements and DTA experiments). By heating samples from the amorphous phase, the crystallization process has been investigated for 0.15 ⩽ x ⩽ 0.30. An immiscibility gap in the vitreous region is determined by optical microscopy, from phase-separation observations; moreover, a new metastable crystalline phase appearing as an intermediate step between phase separation and stable GeSe 2 is described.

The recrystallization of amorphous cellulose at various relative humidities was studied to clarify the relation between the amount of adsorbed water in cellulose and the molecular motion by the DSC method. The initial recrystallization kinetics of amorphous cellulose at various relative humidities were observed on the basis of the exothermic peak between 380° and 470°K in a DSC curve. The recrystallization occurred easily by conditioning at higher than 80per thousand R.H., but hardly by conditioning at lower than 65per thousand R.H. These facts suggest that the conformation of cellulose seems to be easily changeable if cellulose has a moisture regain which is approximately comparable to capillary water. When the Avrami equation was applied to the slope of calorific value versus conditioning time at higher than 80per thousand R.H., it also appeared that the mode of recrystallization growth of amorphous cellulose exposed to water vapor is one-dimensional.

Thin films of Sn with additives are prepared by quench condensation. The annealing behaviour of the electrical resistivity and the transition to the superconducting state of these films are investigated in relation to the dependence of composition and film thickness. The data indicate, whether the films are in an amorphous state or not. It appears that the films become amorphous, if the addition has an atomic radius less than Sn and if the mean valence electron concentration is less than 3.7. With further reduction of the valence electron concentration the amorphous films become more stable and the temperature of transformation from the amorphous state to the crystalline state rises. The thickness dependence of the transformation temperature can be explained with a simple further assumption.

The fluorescence emission spectra and fluorescence decay times of amorphous films prepared by evaporation of a number of aromatic hydrocarbons on to a substrate cooled with liquid nitrogen were measured. The fluorescence of such films appears to originate from sites where the interaction between neighbouring molecules is of the same kind as that present in the well-known excimer state. The density of such sites is found to be so high as effectively to prevent energy migration. Some interesting exceptions to this behaviour are noted and comparisons drawn with experimental data reported for excimer formation in solution and in the crystalline phase.

Magnetic susceptibility measurements of Cu-Mn type ailoys have revealed the same type of behaviour in both crystalline and amorphous substrates, i.e. the susceptibility is Curie or Curie-Weiss in the high-temperature limit, and curves towards a maximum at low temperatures. It is therefore proposed that the susceptibilities of crystalline and amorphous solutions be explained on the same basis. The low-temperature magnetic susceptibility of amorphous Ag-Mn is calculated within the framework of partial paramagnetic response, by extending an approach that has been adopted previously for crystalline alloys.

The article gives a review of the current state of the theory of bremsstrahlung by electrons of ultrahigh energy and pair production by photons of ultrahigh energy in condensed matter in the case in which the effective coherence length of the processes discussed is so large that the effect of competing processes is possible. Qualitative reasoning is considered which permits correct estimation of the effects, and the results of a quantitative discussion are presented.

Photoluminescence excitation spectra in chalcogenide glasses show a rapid fall-off in efficiency at high photon energies, which some authors attribute to surface recombination. This feature is discussed in the light of new experimental data, including luminescence in selenium. It is shown that surface recombination is an unlikely explanation and an excitation-energy dependent quantum efficiency must be assumed. The relationship between photoluminescence and photoconductivity is examined and an earlier model is developed in which the excitation spectrum is explained in terms of enhanced absorption near recombination centres.

Melt-spun fibers of isotactic polypropylene have been formed using specific combinations of shearing and elongational flow. Such rheological conditions were achieved with a take-up device capable of subjecting molten polymer filaments continuously to various combinations of torsional and elongational strains. Relationships were determined between mechanical properties of the resulting fibers and their molecular organizations. The results obtained indicated that these flow fields would produce fibers whose mean-preferred-chain-orientation directions ranged between being tilted radially from a direction parallel with the fiber axis (no torsional shear strain imposed) and having some additional tilt that is tangential with respect to the fiber circumference (some torsional shear strain imposed). It is not possible to resolve the observed helical chain tilts into contributions from crystalline and amorphous regions, respectively.

The electrical transport properties of three vinyl carbazole polymers have been examined to determine if the observed variations in NMR chemical shifts resulting from inter−ring shielding effects could be correlated with carrier mobilities in the polymers. Drift mobilities were measured in films of the polymers overcoated with thin layers of amorphous Se using a xerographic discharge technique. Under the conditions for observing trap free space charge limited currents the hole mobilities were calculated from Child’s law. The three polymers exhibited mobilities varying as the square of the electric field over the range of fields examined. P2VK which showed the overall largest upfield shift of the aromatic protons exhibited a mobility of 1.4×10−6 cm2/V⋅sec at a field of 4×105 V/cm. PVK which exhibit an intermediate degree of shielding had a mobility of 1.4×10−7 cm2/V⋅sec and P3VK which exhibits the smallest shielding effect had a mobility of 2.4×10−8 cm2/V⋅sec both at equivalent fields. Although P2VK showed...

Reswelling processes of drawn nylon-6 and poly(ethylene terephthalate) in tetrachloroethylene, water, and DMF were investigated. Starting specimen containing some voids was prepared by the heat treatment of drawn nylon-6 and drawn poly (ethylene terephthalate) in benzyl alcohol and DMF respectively. Structural change on swelling was studied by the small-angle X-ray scattering method. The following results were obtained.1. Substantially tetrachloroethylene did not penetrate into the amorphous region of drawn nylon-6, while it could fill the voids, On the other hand, water could penetrate into both the amorphous region and voids.2. Degree of swelling of nylon-6 in water was higher than that in tetrachloroethylene.3. Swelling of nylon-6 in water attains equilibrium within a few minutes, though the time taken to reach swelling equilibrium in tetrachloroethylene is about 20 hours.These differences in swelling behaviors of nylon-6 in tetrachloroethylene and water may be interpreted on the basis of differences in molecular sizes of solvents and the differences in interaction between solvents and nylon-6.4. Tetrachloroethylene and DMF could penetrate into the voids and the amorphous region of drawn poly (ethylene terephthalate).

(1975). A new type of junction: Amorphous/crystalline. C R C Critical Reviews in Solid State Sciences: Vol. 5, No. 4, pp. 591-595.

The residual disorder caused by different implanted ions after annealing at elevated temperatures (850−1150 °C) is dependent upon the ion species. The gettering of Au by damaged layers produced by Ar, O, P, Si, As, and B has been quantitatively compared to gettering by phosphorus diffusion. Each individual comparison was made between opposite surfaces of a Si sample by use of Rutherford backscattering. The damage disorder was quantitatively measured by backscattering and structurally studied using electron microscopy. Typically, an ion dose of 1016/cm2 and ion energy of 200 keV were used for implantations. The Au was present in the Si at ’’moderate’’ levels so that solubility in the phosphorus diffused layers was not exceeded. Ar ion−damaged layers were more effective for gettering Au than were phosphorus−diffused layers below ∼1000 °C and equally effective up to 1150 °C. The relative gettering efficiency of the damage produced by other ions studied was less than that of phosphorus diffusion at 1000 °C and was ranked in the order Ar≳O≳P≳Si≳As≳B. In general, the relative gettering efficiency of ion−damaged layers was related to the amount and type disorder after annealing. The initial disorder was of an amorphous nature for 1016 heavy ions/cm2 (As, Si, P, Ar, or O), and the final disorder state was different for different implanted ions after annealing. It is suggested that the disorder (and gettering efficiency) was influenced by size effects of the implanted ion during annealing.

The work required to move a charge between different sites in a lattice subject to an electric field is treated in detail. It includes a local-field contribution when the sites are inequivalent and in non-centrosymmetric crystals also when the sites are equivalent (except for special field directions). The effect on carrier hopping mobilities is discussed, ignoring dynamical and polaron effects. In most cases of interest, the local field does not affect low-field mobilities significantly, but it can affect high-field mobilities. For amorphous materials, this effect is probably less important than fluctuations in the barriers to hopping.

This paper describes experimental studies of the multiple scattering of a number of different ions with $1l{Z}_{1}l18$ and 500 keV incident energy, transmitted through thin films of Se, Pd, Ag, Te, ${\mathrm{Ta}}_{2}$${\mathrm{O}}_{5}$, and Bi, and foils consisting of a mixture of C and Au atoms. We found that the targets fell into two groups with respect to structure. The first group, in which the targets were amorphous or had very small crystallites, showed multiple-scattering distributions of heavy ions, in agreement with current theory. In the second group, where the targets had grain sizes larger than approximately 100 \AA{}, the distributions were consistently narrower than those predicted theoretically. Possible mechanisms responsible for the deviations were investigated.

The tunnelling-states model is applied to the thermal conductivity of non-crystalline materials. It is shown that the presence of a quadratic term in the energy dependence of the density of tunneling states, as implied by specific heat and ultrasonic measurements, can give rise near 10 K to the plateau in the thermal conductivity which is characteristic of amorphous solids.

A simple method is outlined for the calculation of the paramagnetic spin susceptibility χs appropriate t o a random spatial distribution of antiferromagnetically coupled spins. This method considers the microscopic sample to be a collection of decoupled clusters each containing three spins. It is specifically applied t o the n-type silicon system with donor impurity concentrations in the range 1017 donors,/cm3 ≦ ND, ≦ 4 × 1018 donors/cm3. The resulting theoretical susceptibilities were of the Curie-Weiss form for temperatures T > 5 K, but exhibited steepening of the xs−1 vs. T curves a t low temperatures and high concentrations. Both of these features have been observed in amorphous antiferromagnetic systems. On decrit une methode simple pour calcule la susceptibilite paramagnetique d'une distribution sans ordre spatial de spins dont l'interaction d'hchange est negative. Cette methode considere l'echantillon comme une collection de faisceaux decouples, chacun avec trois spins. On l'applique speifiquement au systeme de n-type silicon avec la concentration de donneurs dans la gamme 1017 donneurs cm−3 ≦ ND, ≦ 4 × 1018 donors/cm3 donneurs cm−3. Les susceptibilites theoriques qui se produisent obeissent a la loi Curie-Weiss pour les temphaperes T > 5 K, maisles courbes de xs−1 vs. T se redressent plus rapidement pour les tempkra tures inferieures et les concentrations superieures. On a observe ces deux traits dans les solides amorphes antiferromagnetiques.

Dc transport and optical measurements have been made on amorphous gallium arsenide and gallium-magnesium-arsenide alloy thin films vacuum deposited by coevaporation of the elements at a substrate temperature of 150°C. The transport properties have been measured on over 40 films over the temperature range 77 \leq T \leq 450 K and for dc fields up to 106V/cm. For dc fields less than 2 X 104V/cm conduction in the GaAs films is Ohmic and bulk-limited. The dc activation energy is 0.50 eV at 300 K which is about half the optical band gap. At high fields and low temperatures the dc current is proportional to exp(V1/2) and is in good agreement with Poole-Frenkel theory. The thermoelectric power is n-type and relatively temperature independent over the temperature range 300 \leq T \leq 420 K. The addition of magnesium, a p-type dopant in crystalline GaAs, to the amorphous GaAs thin films has no measured effect on the electrical properties of the films in the lowconcentration regime (less than 2 atomic % Mg). At higher magnesium concentrations there is a shift in the optical absorption edge to higher energy, a decreased dc conductivity and an increased activation energy, and a shift in the thermoelectric power toward p-type conduction.

X-ray phtoemission spectra of palladium prepared by vacuum evaporation and by argon ion sputtering are compared. The former show a close correlation with calculated band structures but the latter exhibit much less detail, strongly suggesting that the sputtered surface is amorphous. The narrow core lines of the evaporated samples show the asymmetry predicted to arise from the hole-conduction electron interaction.

Effective-field theories of disordered and amorphous magnets are discussed from a unified point of view, including the first-order approximation of the structure fluctuation and also the coherent potential approximation. The theories are applied to dilute magnets and crystalline magnets disordered by thermal motion.

A series of amorphous calcium phosphate and hydroxyapatite samples synthesized under different preparative conditions were studied by the x-ray radial distribution method. The results indicate that amorphous calcium phosphate has a reproducible structure independent of a wide variety of preparation conditions. Detail in the RDF of amorphous calcium phosphate diminishes rapidly for atomic separations greater than 9.5 A, suggesting ordered domains or clusters of about this size. It is proposed that amorphous calcium phosphate is an amorphous cluster or microcrystallite material rather than a random network structure. Small-angle x-ray scattering and dehydration studies indicate that the ACP water of constitution is interstitial to the domains. Finally, hydroxyapatite prepared at 25°C has lower perfection of atomic order than material prepared at 100°C.

Very-high-quality Al/SUB 2/O/SUB 3/ films have been grown by anodizing aluminum films in a bath of tartaric acid, buffered with NH/SUB 4/OH and diluted with propylene glycol. Several thousand films were evaluated to demonstrate high resistivities and breakdown voltages, as well as dielectric properties stable with respect to film thickness, frequency, and applied voltage. It is shown that an optimum solution, an optimum buffer, an optimum pH, and an optimum anodization time exist.

Atactic polystyrene was subjected to an elevated pressure–temperature cycle with the resulting densification, mechanical properties, and thermal scanning behavior observed. Most densifications were carried out with the PST as a viscous liquid. In this manner, ambient residual compactions greater than 2% were produced. Pressures up to 90,000 psi and temperatures to 320°C were employed. The technique used for vitrification from the high pressure–temperature region was found to drastically affect the mechanical behavior. If the polystyrene was vitrified from the treatment region by lowering the temperature, the material exhibited enhanced yield strength, by up to 40%. If the polystyrene was quenched by raising the pressure, the samples exhibited much lower mechanical strength. While the mechanical behavior of temperature-vitrified samples is enhanced compared to the pressure-vitrified materials, their densities are comparable. The compaction achieved is primarily determined by the pressure applied as the polymer vitrifies. Thermal scanning behavior of the pressure-vitrified materials show endothermic and exothermic responses below Tg, while the temperature-vitrified materials do not. Annealing the compacted polystyrene at room temperature caused little change in density. However, at temperatures above 60°C, the density relaxed rapidly. Samples which had been temperature vitrified and annealed such that the compaction completely relaxed, still maintained the enhanced mechanical properties of the densified materials.

The author has studied the optical properties of crystalline and amorphous bismuth films. The spectrum of crystalline bismuth is discussed on the basis of a pseudopotential band structure calculation by Golin (1968). The shift of the main absorption peak with temperature is discussed in terms of a pseudopotential calculation. The spectrum of amorphous bismuth could be described well by the Drude equations and the plasmon frequency and electron lifetime thus obtained were similar to those found in liquid bismuth.

It is shown that the pair breaking parameter of the Maki-Thompson contributions to the fluctuation conductivity above the superconducting transition temperature has the same thickness dependence as the transition temperature depression in very thin amorphous Be-Al films. Both can be ascribed to an extremely thin surface sheath with suppressed superconductivity.

Through the use of differential scanning calorimetry, the heat capacity and crystallization parameters of amorphous As 2 Se 3 have been studied. It is found that the heat capacity above the glass transition temperature ( T g ) exceeds, by a factor of 1.6, the Dulong-Petit limiting value found below T g . The crystallization process is found to obey first-order kinetics with an activation enthalpy of 1.24 eV and an enthalpy of crystallization of 0.36 eV · molecule −1 . The effect of sample age on the rate constant is also reported.

Thin metal films are evaporated onto a cooled Be-foil at 15–19 K in high vacuum. The specific heat is measured in the temperature range from 2.5–5 K after condensation and after annealing. The specific heat of disordered Pb- and In-films is about 1.5 times larger than that of annealed films. The additional contribution to the specific heat of amorphous Pb-, Bi- and Tl-films increases with decreasing temperature.

The far-infrared transmission spectrum of amorphous selenium has been measured for different temperatures of quenching. The spectrum shows that the weight fraction of Se8-ring decreases and that of the polymeric chain increases if the temperature just before quenching, Tbq, increases above the melting point of 217°C. The thermal crystallization process of selenium samples with different values of Tbq has been studied by differential scanning calorimetery (DSC), The result may be explained by a phenomenological model that the crystallization of amorphous selenium develops from nuclei with the Maxwellian velocity of the crystallization front with the activation energy, E=0.85 eV for Tbq

The use of Rutherford backscattering for the investigation of monocrystals overlaid with thin amorphous layers is briefly described. Using silicon crystals covered with silicon nitride and aluminium layers, methods are exhibited, which provide special informations about surface layers (mass and area concentration of the layer atoms, composition of the layers and density and thickness, respectively).

A method for the calculation of vacancy concentrations, induced by ion implantation, is presented which is based on the change of the parameters in the curve of radial distribution of the atomic density (CRD) after irradiation. It is shown that the lowering of the crystallization temperature of amorphous films after ion bombardment can be explained with a decrease of the self-diffusion activation energy by the change of interatomic distances. Using the change of parameters in CRD with irradiation the degree of the lowering of the crystallization temperature is calculated. Agreement with experimental values of SiO2 is obtained. [Russian Text Ignored]

The influence of substrate temperature, evaporation rate, and gas ambient on thermoelectric power and conductivity of amorphous Ge and Si layers was investigated. A continuous variation of the high temperature thermoelectric power from positive values for high evaporation rates to negative ones for low rates is found. Simultaneously the hopping conductivity decreases and the small hopping thermoelectric power shows a complementary sign reversal for amorphous Si and a tendency to this reversal for amorphous Ge. From the influence of substrate temperature and gas ambient it is concluded that at high rates the defects produced during the evaporation process determine the electrical properties, whereas at low rates the incorporation of impurity atoms into the layers and the resulting saturation of dangling bonds, particularly by oxygen, predominates. Both the conductivity and thermoelectric power features can be explained by a simple model of the density of states distribution in the forbidden gap. Der Einflus von Substrattemperatur, Aufdampfrate und Restgasdruck auf Thermokraft und Leitfahigkeit von amorphen Ge- und Si-Schichten wurde untersucht. Fur die Thermokraft bei hohen Temperaturen ergibt sich ein kontinuierlicher Ubergang von positiven Werten fur hohe Aufdampfraten zu negativen Werten fur niedrige Raten. Gleichzeitig sinkt die Hopping-Leitfahigkeit ab und die kleine Hopping-Thermokraft zeigt einen Vorzeichenwechsel von negativen zu positiven Werten fur amorphes Si und eine Tendenz dazu fur amorphes Ge. Aus dem Einflus von Substrattemperatur und Restgasdruck wird geschlossen. das fur hohe Aufdampfraten Defekte, die beim Herstellungsprozes erzeugt werden, die elektrischen Eigenschaften bestimmen, wahrend bei kleinen Raten insbesondere Sauerstoff in die Schichten eingebaut wird und dort freie Bindungen absattigt. Leitfahigkeits- wie Thermokraftverhalten konnen durch ein einfaches Modell der Zustandsdichte-Verteilung in der verbotenen Zone erklart werden.

The anisotropic mechanical behaviour of oriented polymers at low strains is discussed. In the case of amorphous polymers and polymers of low crystallinity, attempts to interpret the anisotropy in terms of an aggregate model are reviewed. This is followed by an account of recent work on the measurement of all the elastic constants for polymer films of orthorhombic symmetry. After a brief discussion of cold drawn crystalline polymers, where very high Young's moduli can be obtained, the behaviour of annealed oriented polymers is considered. It appears that the latter can be understood in terms of a composite solid model, combining the early notions of Takayanagi with more recent ideas of interlamellar shear.

Both direct and indirect evidence has suggested that low−density a−Ge films grown at substrate temperatures Ts

A dense random packing of 888 hard spheres has been relaxed with respect to a realistic interatomic potential. The result is compared to the experimental pair distribution function of amorphous Co and an amorphous Ni76P24 alloy. The positions of the maxima of the pair distribution function of Co are accurately reproduced. The differences between Co and Ni76P24 are discussed.

A detailed examination by transmission electron microscopy and selected−area diffraction revealed that the thin−film intergranular phase in a highly non−Ohmic multicomponent metal oxide varistor system based on ZnO with small additions of antimony, bismuth, cobalt, manganese, and tin oxides is amorphous and is chemically related to a Bi2O3−rich pyrochlore coexisting in the ceramic.