X-ray photoelectron spectroscopy analysis of Ge–Sb–Se pulsed laser deposited thin films

Pulsed laser deposition was used to prepare amorphous thin films from (GeSe2)(100-x)(Sb2Se3)(x) system (x=0, 5, 10, 20, 30, 40, 50, and 60). From a wide variety of chalcogenide glass-forming systems, Ge-Sb-Se one, especially in thin films form, already proved to offer a great potential for photonic devices such as chemical sensors. This system has a large glass-forming region which gives the possibility to adjust the chemical composition of the glasses according to required physical characteristics. The chemical composition of fabricated thin films was analyzed via X-ray photoelectron spectroscopy (XPS) and compared to energy dispersive spectroscopy (EDS) data. The results of both techniques agree well: a small deficiency in chalcogen element and an excess of antimony was found. The structure of as-deposited thin films has been investigated by XPS. The presence of the two main structural units, [GeSe4] and [SbSe3] proposed by Raman scattering spectroscopy data analysis, was confirmed by XPS. Moreover, XPS core level spectra analysis revealed the presence of M-M bonds (M=Ge, Sb) in (Ge,Sb)-Ge-(Se)(3) and (Ge,Sb)-Sb-(Se)(2) entities that could correspond to Ge-based tetrahedra and Sb-based pyramids where one of its Se atoms at corners is substituted by Ge or Sb ones. The content of depicted M-M bonds tends to increase with introduction of antimony in the amorphous network of as-deposited thin films from x=0 to x=40 and then it decreases. XPS analysis of as-deposited thin films shows also the presence of the (Ge,Sb)-Se-(Ge,Sb) and Se-Se-(Ge,Sb) entities.