In situ electronic structural study of VO₂ thin film across the metal–insulator transition

【摘要】 The in situ valence band photoemission spectrum(PES) and X-ray absorption spectrum(XAS) at V LII LIIIedges of the VO2 thin film, which is prepared by pulsed laser deposition, are measured across the metal–insulator transition(MIT) temperature(TMIT= 67°C). The spectra show evidence for changes in the electronic structure depending on temperature. Across the TMIT, pure V 3d characteristic d and O 2p-V 3d hybridization characteristic πpd, σpdbands vary in binding energy position and density of state distributions. The XAS reveals a temperature-dependent reversible energy shift at the V LIII-edge. The PES and XAS results imply a synergetic energy position shift of occupied valence bands and unoccupied conduction band states across the phase transition. A joint inspection of the PES and XAS results shows that the MIT is not a one-step process, instead it is a process in which a semiconductor phase appears as an intermediate state. The final metallic phase from insulating state is reached through insulator–semiconductor, semiconductor–metal processes, and vice versa. The conventional MIT at around the TMIT= 67°C is actually a semiconductor–insulator transformation point.更多还原

【Abstract】 The in situ valence band photoemission spectrum(PES) and X-ray absorption spectrum(XAS) at V LII LIIIedges of the VO2 thin film, which is prepared by pulsed laser deposition, are measured across the metal–insulator transition(MIT) temperature(TMIT= 67°C). The spectra show evidence for changes in the electronic structure depending on temperature. Across the TMIT, pure V 3d characteristic d and O 2p-V 3d hybridization characteristic πpd, σpdbands vary in binding energy position and density of state distributions. The XAS reveals a temperature-dependent reversible energy shift at the V LIII-edge. The PES and XAS results imply a synergetic energy position shift of occupied valence bands and unoccupied conduction band states across the phase transition. A joint inspection of the PES and XAS results shows that the MIT is not a one-step process, instead it is a process in which a semiconductor phase appears as an intermediate state. The final metallic phase from insulating state is reached through insulator–semiconductor, semiconductor–metal processes, and vice versa. The conventional MIT at around the TMIT= 67°C is actually a semiconductor–insulator transformation point.更多还原