Ge Sb Se Research Articles

Optical absorption of glassy semiconductors of the GeSbSe system

The optical transmittance of chalcogenide glasses Ge 2SbSe 7 (I), Ge 3SbSe 6 (II), GeSb 2Se 7 (III) and GeSbSe 3 (IV) was studied in the near infrared spectral region, 0.7–25 μm. The longwavelength tail of the absorption edge can be described by Urbach's rule. At higher absorption levels the absorption coefficient K depends quadratically on the energy of incident radiation. The temperature dependence of the absorption edge is discussed and the optical gaps 1.77 eV (I), 1.67 eV (II), 1.66 eV (III), 1.57 eV (IV) together with the corresponding temperature coefficients are also determined. The studied glasses are quite transparent in the 600–5000 cm −1 wavenumber range.

Electrical conductivity of melts and their ability to form glasses: I. The GeSbSe system

The electrical conductivity of melts in the glass forming system GeSbSe was measured as a function of temperature to greater than 1000°C by a new electrodes method. Compositions inside the glass forming region show typical semiconducting behavior, with energy gaps in the range 1–2 eV, up to several hundred degrees above the softening point; at still higher temperatures the conductivities increase more rapidly with temperature. This sharp increase in conductivity probably results from a change in short-range order wherby average coordination numbers larger than the valencies of the elements are reached. In compositions well outside the glass forming region, i.e., with large Sb- and Ge-contents, the melts show metallic conductivity. In the transition region in which glasses are only obtained by very rapidly quenching small samples in water, a relatively high, but not metallic, conductivity was found. It is thought that these essentially glassy melts contain micro regions of a second, highly conducting phase. The elements Ge and Sb, with their tendency to form directed (sp)-hybrid bonds, promote the formation of well developed spatial networks. When the Ge- and Sb-content is high, the atoms can become mobile in the melt only if the bonding goes over to a mesomeric pσ-system, as has been found in the melting of elemental Ge. This leads to a closer packing (CN = 6) and metallic-like conductivity. The conductivity measurements revealed two-phase melts over part of the GeGeSe system. Liquid immiscibility was also confirmed in the SbSe system, but over a slightly different composition range than previously reported. The critical temperature for mixing is around 1000°C.

Electrical Conductivity and Formation of Chalcogenide Glasses in Ge–As–Se and Ge–Sb–Se Melts

Electrical Conductivity and Formation of Chalcogenide Glasses in Ge–As–Se and Ge–Sb–Se Melts