A Fabrication Method For Type-Ii Ge Clathrate Film By Annealing Of Ge Film Covered With Na Layer

A simplistic and improved technique was employed for type-II Ge clathrate film fabrication on the sapphire substrate. This method involves the deposition of metal Na layer onto amorphous Ge film and subsequent annealing for several hours by an infrared lamp heater under high vacuum in the same chamber. X-ray diffraction and Raman measurements confirmed the synthesis of type II Ge clathrate film and the crystallographic parameters were refined by Rietveld analysis. Scanning electron micrographs revealed the sample to be 1.2 mu m thick and granular film with a lot of cracks. Nevertheless, the sample appeared homogeneous and uniform with the naked eye and the optical transmission spectrum indicated periodic fluctuation due to the light interference.