Orbital change manipulation metal-insulator transition temperature in W-doped VO2

• Published in: Physical chemistry chemical physics : PCCP Vol. 17; no. 17; pp. 11638 - 11646
• Main Authors: He, Xinfeng, Zeng, Yijie, Xu, Xiaofeng, Gu, Congcong, Chen, Fei, Wu, Binhe, Wang, Chunrui, Xing, Huaizhong, Chen, Xiaoshuang, Chu, Junhao
• Format: Journal Article
• Language: English
• Published: England 07.05.2015
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c4cp04889j

A series of epitaxial V 1− x W x O 2 (0 ≤ x ≤ 0.76%) nanocrystalline films on c -plane sapphire substrates have been successfully synthesized. Orbital structures of V 1− x W x O 2 films with monoclinic and rutile states have been investigated by ultraviolet-infrared spectroscopy combined with first principles calculations. Experimental and calculated results show that the overlap of π* and d orbitals increases with increasing W doping content for the rutile state. Meanwhile, in the monoclinic state, the optical band gap decreases from 0.65 to 0.54 eV with increasing W doping concentration. Clear evidence is found that the V 1− x W x O 2 thin film phase transition temperature change comes from orbital structure variations. This shows that, with increasing W doping concentration, the decrease of rutile d orbital occupancy can reduce the strength of V-V interactions, which finally results in phase transition temperature decrease. The experimental results reveal that the d orbital is very important for the VO 2 phase transition process. Our findings open a possibility to tune VO 2 phase transition temperature through orbital engineering. Using ultraviolet-infrared spectroscopy and first principles calculations, it is revealed that changes in the orbital structure can regulate the W-doped VO 2 phase transition temperature.