Investigation on the valence state of Te ions in the Bi6Ti5TeO22 thin film using X-ray photoelectron spectroscopy

Abstract

Bi6Ti5TeO22 (BTT) thin films were grown on a Pt/Ti/SiO2/Si(1 0 0) substrate under various conditions and the valence state of the Te ion was investigated. For the BTT films grown at 300 degrees C, most of the Te ions existed as Te4+ ions. However, for the 10 mol% Mn-added BTT films grown at 300 degrees C, Te6+ ions were found even in the film grown under low oxygen partial pressure (OPP) and their number increased with increasing OPP. This increase was attributed to the presence of Mn2+ ions, which assisted the transition of Te4+ ions to Te6+ ions in order to maintain the charge balance of the Ti4+ sites. Furthermore, in the films grown at 300 degrees C under a high OPP of 80.0 Pa and subsequently annealed at 600 degrees C under a high oxygen pressure of 101 kPa, most of the Te ions existed as Te6+ ions. However, for the film grown at 300 degrees C under low OPP, even though the film was annealed under a high oxygen pressure of 101 kPa, only a few of Te6+ ions were formed, whereas most of Te ions remained as the Te4+ ions. (C) 2009 Elsevier Ltd. All rights reserved.