We report the film growth of distorted rutile-type NbO2 (4d1 system), MoO2 (4d2), and WO2 (5d2) by radio-frequency (RF) magnetron reactive sputtering. Through optimization of growth conditions for the three oxides on Al2O3(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–O2 sputtering gas. X-ray photoelectron spectroscopy supported the d1 electronic configuration of NbO2 and d2 electronic configurations of MoO2 and WO2. An electrical transport measurement confirmed that NbO2 was insulating, while MoO2 and WO2 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.

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