Substitution of vanadium by chromium in thallium pentavandium octasulfide. Part II. Electronic structure. an XPS and UPS study

Abstract

UPS investigations reveal that the metallic character within the substitution series TIV 5−yCr yS 8 decreases with increasing Cr content. The Cr richest sample is a poor metal or a semiconductor. The emission just below the Fermi level is mainly due to metallic states. This emission shifts to lower binding energies with increasing substitution of Cr for V. The different core levels exhibit only small chemical shifts and are indicative of low formal charges on the different atoms. The shape of the emission lines as well as the occurence and intensity of shake-up peaks are sensitive to the composition and suggest a variation of the covalency within the series. The Cr 3s core level exhibits a multiplet splitting. The intensity of the satellite increases with rising Cr content. The asymmetry of the Tl 5d shallow core level is more pronounced in the V-rich samples than in the Cr-rich compounds and can be regarded as an evidence for the stronger ionic character of Tl in the Cr-rich compounds.