Die Absorptionskante der Selen–Tellur‐Mischkristallreihe

Abstract

70,BSowohl dieser Verlauf als auch die sehr stmke Konzentrationsabhangigkeit des Bandabstandes fur kleine Tellurgehalte in Selen geht parallel mit der Variation des Bindungswinkels der Atome in der Mischkristallreihe. Der spektrale Verlauf der Absorptionskonstanten in der Kante entspricht der Theorie fur indirekte ubergange.Solid solutions of selenium and tellurium with a composition varying in steps of 10 atyo were prepared by the Bridgman procedure. The edge absorption of these crystals was investigated with light polarized parallel and perpendicular to the c-axis. The band gap varies continuously from pure selenium to pure tellurium with a break at 20% tellurium in selenium. In the range of 20 to 100 atyo tellurium the dependence of the band gap on the tellurium concentration is given by an exponential relation : E, = 1.29 exp -~ ( 7 t B ) e V . This dependence and also the strong variation of the band gap for small tellurium admixtures to selenium go parallel to the variation of the bond angle in the solid solution series. The spectral dependence of the absorption constant a t the edge follows the theory for indirect transitions. Einf iihrung

Conductivity and thermoelectric power of trigonal SexTe1−x single crystals

“…The fact that near this composition the character of the band gap changes is also shown by optical results. According t o the measurements of Sutter [25], the absorption coefficient at the edge differs appreciably for both polarizations of light for mixtures up to 40% Se content as observed for Te, whereas for higher Se concentrations the difference is much less like for Se. Measurements of the magnetic susceptibility of mixed crystals also indicate that a t about 40% Se content a change in the character of the band gap occurs [261.…”

Optical, thermal and phase transition studies in Sn1-x Ge x Te

“…Particularly between the concentrations 0⋅02 and 0⋅2, the variation in the thermal diffusivity is not monotonic whereas there are two maxima. For Sn 1-x Ge x Te such studies are not reported, even though electrical and optical studies are available (Nussbaum 1954;Rosenman 1963;Lanyon 1964;Beyer et al 1969;Sutter 1969;Kessler and Sutter 1971;Dawar et al 1981).…”