We report the film growth of distorted rutile-type NbO 2 (4d 1 system), MoO 2 (4d 2 ), and WO 2 (5d 2 ) by radio-frequency (RF) magnetron reactive sputtering. Through optimization of growth conditions for the three oxides on Al 2 O 3 (0001), we found that the increase/decrease in the RF power had an equivalent role to that of the decrease/increase in the oxygen ratio in the Ar-O 2 sputtering gas. X-ray photoelectron spectroscopy supported the d 1 electronic configuration of NbO 2 and d 2 electronic configurations of MoO 2 and WO 2 . An electrical transport measurement confirmed that NbO 2 was insulating, while MoO 2 and WO 2 were metallic, consistent with the d-electron filling in the molecular orbital bonding band. The growth scheme presented in this study will be useful for valence control in various oxide thin films with a simple sputtering technique.
ASJC Scopus subject areas
- Physics and Astronomy(all)