Ge Te System Research Articles

The excess enthalpies of liquid GaGeTe and GaSnTe alloys

The excess enthalpies of the liquid alloys GaGeTe and GaSnTe were measured in a heat-flow calorimeter at 1203 K. The enthalpy surface in the ternary space in both systems is characterized by a valley stretching from the exothermic minimum in the GaTe system to the minima of the GeTe and SnTe systems. The minima in the ternary systems were found in this valley, i.e. on the sections Ga 2Te 3-GeTe and Ga 2Te 3-SnTe. A comparison of the experimental data with those calculated from the excess enthalpies of the constituent binaries with the aid of the Bonnier model, reveals only small deviations. A preliminary investigation was made into the ternary phase diagram of GaSnTe. This system contains the two quasibinary sections Ga 2Te 3-SnTe, GaTe-SnTe and the ternary compound Ga 6SnTe 10. The previously reported compounds Ga 2SnTe 3 and GaSnTe 2 do not exist.

Système AsGeTe: II. Diagramme de phase du système ternaire AsGeTe

The AsGeTe system is formed by three independent triangles, corresponding to the two quasibinary systems GeAsGeTe and As 2Te 3GeTe. The presence of four phases As 2Ge n Te 3+ n ( n = 1 to 4) having peritectic decomposition introduces eight ternary peritectic invariants, whose temperatures and compositions are described. The three ternary eutectics have the following characters: E 1, As 19Ge 52Te 29 (662°C); E 2, As 42Ge 5Te 53 (368°C); E 3, As 22Ge 5Te 73 (350°C).

Non-linear transport properties of the PbTeGeTe system

The dependence of the resistivity on temperature for PbTe crystals alloyed with <10% GeTe shows a smooth resistivity hump at low temperatures, which indicates a phase transition. Below the resistivity hump the behaviour of the system is non-ohmic. The I–V characteristics at these low temperatures are S shaped. At a critical current density the system oscillates. The resistivity anomaly and the critical temperature at which this anomaly occurs was found to depend on the current density.

ChemInform Abstract: Structural Description and Thermal Behaviour of a Family of As2GenTe3+n Compounds in the As2Te3 ‐ GeTe System.

AbstractThe As2Te3 ‐ GeTe system is essentially characterized by the existence of a novel family of crystalline phases with the general formula As2Ge"Te3+".

Evidence for a new metastable crystalline compound in GeTe system

Pressure dependence of the electrical resistivity of bulk, melt quenched Ge xTe 100−x glasses (15 ⩽ x ⩽ 28) has been studied up to 8GPa pressure. All the glasses exhibit a sharp, discontinuous glass to crystal transition under pressure. The high pressure crystalline phases are identified to have a face centered cubic structure. The value of the cell constant is 0.779nm for 15 ⩽ x ⩽ 17, 0.642nm for x=20 and 0.55lnm for 22 ≤ x ≤ 28 samples respectively. The cell constants of the high pressure crystalline phases suggest the possible existance of a new metastable crystalline compound in the GeTe system with F.C.C. structure and cell constant equal to 1.109nm as reported by Moore et al.

Laser-induced Effects in Te-Ge Multilayer Thin Films

Experiments on the interaction of an excimer and argon lasers with multilayer configurations in the Ge-Te system are performed. The use of similar laser energy densities with very different irradiation pulse lengths and areas induces widely differing damage effects.

Chalcogenide thin films for laser-beam recordings by thermal creation of holes

The shapes of holes thermally created by a laser beam in thin films of wide range of materials are studied. The most cleanly shaped holes, which measure up to recent requirements for direct-read-after-write video recordings by submicron dots, are obtained in some compositions of amorphous chalcogenide thin films such as As-Te system, Ge-Te system, As-Se system, Ge-Se system, and Sb-S system thin films. The experiments clarify several important conditions helpful in obtaining cleanly shaped holes. The most important condition is that the viscosity of the material in liquid or softened state should be high. The required incident laser-beam power for recording in an As-Te system thin film on a polymethyl methacrylate substrate rotating at 1800 min−1 is about 10 mW. Addition of Se to the As-Te system thin films greatly increases film stability. A signal-to-noise ratio of about 45 dB is obtained in reproduced color video signals.

Magnetic Susceptibilities of Liquid IVb-Te Alloys

The magnetic susceptibilities of molten Ge-Te and Sn-Te alloys have been measured as a function of concentration and temperature. Curves of the isothermal susceptibilities for Sn-Te system show a large deviation from the linearly interpolated ones at the composition near Sn 50 Te 50 . On the contrary for molten Ge-Te system a rather small deviation is found around 45 at% of Te. From these results, the electronic state and chemical bonding in liquid IV-Te system are discussed in comparison with those in liquid IIIb-Te system.

A new compound in the Ge-Te system

A new compound in the Ge-Te system

Optical properties and energy gap of GeTe from reflectance studies

AbstractThe reflectance spectra of bulk samples of the germanium telluride (GeTe) system have been measured in the wavelength range 13 to 0.2 μm. The principal optical constants of the system have been obtained by inverting the spectra using the Kramers‐Kronig technique. Two distinct types of behavior were encountered depending on whether or not a sample exhibited a free carrier absorption peak. Samples rich in germanium lacked such a peak and had optical properties very similar to amorphous GeTe films. Tellurium rich samples always showed a large free carrier peak and from analysis of their optical Constants the effective mass and optical energy gap of the system was obtained. The variation of the effective mass and energy gap with composition (i.e., hole carrier density) is consistent with the existence of two sets of valence‐conduction bands in the system. A multiple band model based on experimental and theoretical data is outlined and its parameters are found to be in good agreement with published work.

Chemical aspects of glass formation in telluride systems

The compositional dependence of the electrical activation energy, the optical absorption and the glass transition temperature in typical binary, pseudo-binary and ternary glass forming telluride systems has been measured in an effort to correlate chemical binding with physical properties. A modification of the valency satisfaction model to include chemical ordering effects is required to account for the property singularities observed in the GeTe system at the composition GeTe 2. The ordering effects in Te-based alloys containing Ge are further verified by an endothermic disordering reaction in these liquids peaking between 400–475°C depending on composition.

Structural differences among different non-crystalline GeTe phases

Structural differences among non-crystalline phases of the same composition in the GeTe system prepared by various methods have been shown to exist using their crystallization behavior as a probe. An extreme example occurs in pure Ge where two different films may be obtained depending only on substrate position during sputtering. One of these forms crystallizes in milliseconds at room temperature.

Thermal behavior of noncrystalline sputtered films in the system GeTe

As part of a systematic study of vapor deposited noncrystalline solid (VDNCS) sputtered films in the GeTe system, this paper reports on the thermal behavior of these films. Heating experiments were conducted on samples of various compositions throughout the NCS forming region which extends from pure Ge to at least 95 at.% Te. The crystallization temperatures of the films have been shown to be highly reproducible and sensitive to the particular NCS structure. At compositions from 70 to 95 at. % Te and at 30 at. % Te two stage crystallization was observed, in which the Te phase and Ge phase, respectively, crystallized first, followed in both cases, by crystallization of GeTe. All other compositions showed single stage crystallization in which the two phases, either GeTe + Te or GeTe + Ge, crystallized simultaneously. The possible existence of non-uniform structure in the films is indicated in the data on two stage crystallization. The relation between the crystallization temperature and the degree of disorder, or structure, of the VDNCS films is discussed with emphasis on both the composition and conditions of preparation of the films. The relevance of the current results to memory switch device research is noted.

Ultra-violet band systems of GeSe and GeTe, and their relations to those of similar molecules

The production of ultra-violet band systems of two of the three group-IV(b)+group-VI(b) molecules which remained to complete the authors' investigations in this series, viz., GeSe and GeTe, is described. They are obtained in emission in silica discharge tubes of the type successfully used in previous work. The bands are degraded to the red, and show strong vibrational isotope effect. About 24 band heads have been measured and assigned to a GeSe system lying in the region λ3170-λ3570, while a number of weakly developed bands in the region λ3060-λ2660 which may belong to a second GeSe system have been measured, but not analysed. 29 bands lying between λ3380 and λ3830 are assigned to the GeTe system. Band heads of the systems are represented by the equations (i) GeSe. νhead = 30431.9 + (272.4u' - 1.05u'2) - (406.8u - 1.2u2), (ii) GeSe. νhead = 27969.5 + (219.4u' - 1.3u'2) - (323.4u - 1.0u2), where u = ν + ½. As a result of this work, ground-state data are available for 19 of the 20 molecules of the group, and a fairly complete discussion of the behaviour of the vibrational constants is made possible. The vibrational frequencies, force constants, energies of dissociation and internuclear distances are considered in turn, and the homogeneity of the group is established to a remarkable degree. Unfortunately the same cannot be said of the upper states of these molecules, data on which are still inadequate in many directions.