TY - JOUR
T1 - Formation of distorted rutile-type NbO 2 , MoO 2 , and WO 2 films by reactive sputtering
AU - Fujiwara, Kohei
AU - Tsukazaki, Atsushi
N1 - Funding Information:
The authors thank K. Omura for the XPS measurement. K.F. acknowledges S. Nakao for his insightful advice. This study was performed under the Inter-University Cooperative Research Program of the Institute for Materials Research, Tohoku University (Proposal Nos. 17G0417 and 18G0406). This study was partly supported by JSPS KAKENHI (No. JP15K13949), Nippon Sheet Glass Foundation for Materials Science and Engineering, and Mazda Foundation.
Publisher Copyright:
© 2019 Author(s).
PY - 2019/2/28
Y1 - 2019/2/28
N2 - 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.
AB - 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.
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U2 - 10.1063/1.5079719
DO - 10.1063/1.5079719
M3 - Article
AN - SCOPUS:85062173281
SN - 0021-8979
VL - 125
JO - Journal of Applied Physics
JF - Journal of Applied Physics
IS - 8
M1 - 085301
ER -