title: Photoheat-induced Schottky nanojunction and indirect Mott transition in VO₂: photocurrent analysis.
abstract: In order to elucidate a mechanism of the insulator-to-metal transition (IMT) for a Mott insulator VO2 (3d(1)), we present Schottky nanojunctions and the structural phase transition (SPT) by simultaneous nanolevel measurements of photocurrent and Raman scattering in microlevel devices. The Schottky nanojunction with the monoclinic metallic phase between the monoclinic insulating phases is formed by the photoheat-induced IMT not accompanied with the SPT. The temperature dependence of the Schottky junction reveals that the Mott insulator has an electronic structure of an indirect subband between the main Hubbard d bands. The IMT as reverse process of the Mott transition occurs by temperature-induced excitation of bound charges in the indirect semiconductor band, most likely formed by impurities such as oxygen deficiency. The metal band (3d(1)) for the Mott insulator is screened (trapped) by the indirect band (impurities).
authors.affiliation: Metal-Insulator-Transition Center, Electronics & Telecommunications Research Institute, Daejeon 305-700, Korea. School of Advanced Device Technology, Korea University of Science and Technology, Daejeon 305-333, Korea.
authors.forename: Hyun-Tak
authors.initials: HT
authors.lastname: Kim
authors.forename: Minjung
authors.initials: M
authors.lastname: Kim
authors.forename: Ahrum
authors.initials: A
authors.lastname: Sohn
authors.forename: Tetiana
authors.initials: T
authors.lastname: Slusar
authors.forename: Giwan
authors.initials: G
authors.lastname: Seo
authors.forename: Hyeonsik
authors.initials: H
authors.lastname: Cheong
authors.forename: Dong-Wook
authors.initials: DW
authors.lastname: Kim