X-ray photoelectron spectroscopic studies of sellinite and eulytite BGO and BSO crystals

Abstract

Single crystals of Bi₁₂GeO₂₀, Bi₁₂SiO₂₀, Bi₄Ge₃O₁₂, and Bi₄Si₃O₁₂ are grown by Floating zone and Czochralski techniques. The X-ray photoelectron spectroscopic (XPS) studies have been carried out on BSO and BGO crystals. XPS is employed to characterise the surface quality and bulk nature of the crystals. The surface contamination on both types of crystals are identified. In addition to the contamination, some amount of Bi atoms are observed with Bi ions on sellinite. It is demonstrated that the eulytite crystals are chemically more robust to degradation than the sellinite crystals. The predominant covalent and ionic character of Bi₄Ge₃O₁₂ and Bi₄Si₃O₁₂ respectively is explained from their oxygen 1s core level spectra.