Formation of Ge and GeSi nanocrystals in GeOx/SiO2 multilayers

Abstract

Amorphous GeOx films and GeOx/SiO2 multilayers were deposited by evaporations of GeO2 and SiO2 powders onto Si substrates maintained at 100 °C. The GeOx layer thickness in multilayer structures was varied from 4 to 1 nm, the thickness of SiO2 layers was 4 nm, all samples contain 10 periods. Evolution of structure and optical properties of the samples was investigated by Raman spectroscopy, infrared (IR)-absorption spectroscopy and ellipsometry for annealing temperatures up to 800 °C. Decomposition of the GeOx and appearance of amorphous Ge nanoclusters, Ge and GeSi nanocrystals (NCs) were observed. Correlations between the GeOx layer thicknesses and the structure of Ge and GeSi NCs were studied. The comparative analysis of evolution of the photoluminescence with the structure of the nanostructured GeOx layers and GeOx/SiO2 multilayers was carried out.