Optimization of synthesis condition of type II Ge clathrate film

Abstract Type II Ge clathrate has been investigated by many researchers in powder and film forms; however, it lacks an extensive investigation of basic properties such as optical and electrical properties and application to practical devices. The main reason points to the difficulties in achieving a good quality film with minimal defects. In the present work, an experimental approach was investigated to establish the key synthesis parameters, actively affecting the type II Ge clathrate film quality. The main parameters which were investigated include temperature profile and duration, amount of guest atom (Na) evaporated during the synthesis steps, etc. As-prepared films were investigated by X-ray diffraction, Rietveld analysis, Raman spectroscopy for the structural characterization; scanning electron microscope for morphological studies, and UV–vis-NIR and FTIR spectroscopy measurements for optical properties. Optimization of the synthesis condition resulted in good-quality film in comparison to the previously reported results.