Influence of compositional variation on the optical and morphological properties of Ge Sb Se films for optoelectronics application
2018; Elsevier BV; Volume: 93; Linguagem: Inglês
10.1016/j.infrared.2018.08.008
ISSN1879-0275
AutoresNicoleta Nedelcu, M. Gärtner, Mihai Anastasescu, Mihai Stoica, M. Nicolescu, Hermine Stroescu, Irina Atkinson, Veronica Brătan, Ioana Stănculescu, A. Szekeres, Penka Terziyska, Margit Fábián,
Tópico(s)Chalcogenide Semiconductor Thin Films
ResumoThin films of GexSb40-xSe60 (x = 15, 20, 25, 27, 32 and 35 at.%) were deposited on quartz by vacuum thermal evaporation of the pre-synthesized parental glasses powders. By spectroscopic ellipsometry the complex refractive index values are determined in the 0.20–33 μm spectral range. The optical band gap and single oscillator energies are established as a function of the Ge content and average coordination number Z. In the (0.85–3.5) μm spectral range the GexSb40-xSe60 films possess about 80% transmission. Infrared ellipsometric and Raman studies identified SeSe and GeGe homopolar bonds, oxygen and hydrogen related impurity bonds and heteropolar GeSe and SbSe chemical bonds. Neutron- and X-ray Diffraction data coupled with Reverse Monte Carlo simulations support the optical results reproducing the GeSe and SbSe cell units and cross-linked GeGe bonds. Atomic force microscopic imaging confirmed smooth surfaces with low RMS roughness values (<2.3 nm) and continuous structure of grains of (16–22) nm diameters. All the considered material parameters show peculiarities in the compositional dependences around 27 at.% Ge, corresponding to average coordination number Z = 2.67, testifying structural phase transition at high Ge content in the GexSb40-xSe60 films.
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