A facile synthesis of shell-shaped GeOx (x≤2) islands by metal-assisted chemical etching of Ge and their optoelectronic properties

Abstract

Here we report a facile synthesis of GeOx islands on Ge substrates, having a unique shell-shaped microstructure, and investigate its optoelectronic properties. In this study, Ge substrates are subjected to metal-assisted chemical etching (MaCE) method, leading to the formation of GeOx islands. Interestingly, dimension of the GeOx islands and their coverage on Ge substrates can be tuned by various etching parameters. Formation of hexagonal phase of crystalline GeOx islands is confirmed by x-ray diffraction studies. We also observe an increasing trend in the band-gap values with higher coverage of GeOx islands on Ge substrates. While scanning electron microscopy and atomic force microscopy measurements reveal the formation of shell-shaped microstructure of GeOx islands, x-ray photoelectron spectroscopy, micro-Raman, and energy dispersive x-ray spectroscopic data confirm the occurrence of GeOx islands during the MaCE processing of Ge substrates. The specular reflectance data of GeOx-decorated Ge surface show up to ∼28% reduction in the optical reflectance value compared to the pristine one. Due to their improved light trapping capacity, GeOx-decorated Ge surfaces can therefore be used as an anti-reflecting layer suitable for optoelectronic applications.