Investigation on the valence state of Te ions in the Bi_6Ti_5TeO_(22) thin film using X-ray photoelectron spectroscopy

摘要

Bi_6Ti_5TeO_(22) (BTT) thin films were grown on a Pt/Ti/SiO_2/Si(1 0 0) substrate under various conditions and the valence state of the Te ion was investigated. For the BTT firms grown at 300 deg C, most of the Te ions existed as Te~(4+) ions. However, for the 10 mol percent Mn-added BTT films grown at 300 deg C, Te~(6+) 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 Mn~(2+) ions, which assisted the transition of Te~(4+) ions to Te~(6+) ions in order to maintain the charge balance of the Ti~(4+) sites. Furthermore, in the films grown at 300 deg C under a high OPP of 80.0 Pa and subsequently annealed at 600 deg C under a high oxygen pressure of 101 kPa, most of the Te ions existed as Te~(6+) ions. However, for the film grown at 300 deg C under low OPP, even though the film was annealed under a high oxygen pressure of 101 kPa, only a few of Te~(6+) ions were formed, whereas most of Te ions remained as the Te~(4+) ions.