Surface topographic study of chalcogenide thin films of GexSb(As)₄₀-xS₅₀Te₁₀ glasses.
The surface topography and fractal properties of GexSb(As)40-xS50Te10 (x=10, 20, 27 at.%) films, evaporated onto glass substrates, have been studied by atomic force microscopic imaging at different scales. The surface of the chalcogenide films is smooth (<5 nm roughness), isotropic and having some particular differences in texture. All films are self-similar with Mean Fractal Dimension in the range of 2.25-2.63. The films with GexSb40-xS50Te10 composition are more uniform in terms of surface morphology (grains structure) than those with GexAs40-xS50Te10 composition for which the film surface exhibits a superimposed structure of large particles at x=10 and 20 at.%.
DC electrical conductivity in glasses and thin films
DC electrical conductivity for bulk and thin-film samples of the Sb chalcogenide glass system was measured in the temperature range 293-430 K. The activation energy and the pre-exponential factor have been determined. Values of suggest different mechanisms of conductivity in bulk glasses and in thin films. For all compositional dependences a peculiarity was observed in the region with an average coordination number which can be associated with a topological phase transition from a 2D to a 3D structure.
GeSx glass for Pr3+-doped fiber amplifiers at 1.3 μm
Germanium sulfide glass is investigated as host glass material for pr3+-doped fiber amplifiers in the 1.3 I~m telecommunications window. The solubility limit for Pr in GeS x glass is low. Only around 400 ppm Pr are soluble in GeS 2 and 200 ppm in GeSz. 5 and GeS 3. At higher dopant levels, phase separation of a secondary crystalline (GeS2)3(Pr2S3) 2 phase in the amorphous glass matrix produces a glass-ceramic material. The Pr 3+ IGn-3H 5 photoluminescence spectrum of Pr-doped GeS x glass is located at 1.340 Ixm with a full-width at half-maximum of 0.11 Ixm. The emission lifetime of the Pr 3÷ 1G 4 state at room temperature is 360 I~s in (hydroxyl-free) GeS x glass. At a temperature of 10 K, the lower multiphonon relaxation rate of the non-radiative 1G4-3F 4 transition increases the emission lifetime to 400 Ixs and it is shown that this lifetime can be considered to be the radiative lifetime of the Pr 3+ 1G 4 state in GeS x glass. The quantum efficiency is 0.9 in this glass at room temperature. Impurity hydroxyl, identified in some of the glasses by infrared spectroscopy, is shown to reduce the emission lifetime by non-radiative energy transfer from excited Pr to OH vibrations; OH is a serious Pr luminescence quencher in GeSx glass.