Modulating the metal-insulator transition in VO2/Al2O3 (001) thin films by grain size and lattice strain

摘要

A series of high quality VO2/Al2O3 thin films were prepared by DC sputtering, and the effects of surface topology change on their metal-insulator transition (MIT) behaviors have been discussion in this paper. A similar to 103 nm-thick VO2/Al2O3 thin film shows extremely large order of magnitude change (similar to 4.2) and low T-MIT (56 degrees C), and both grain size and lattice strain have been determined as the main causes responsible for the improvement of metal-insulator transition. Specifically, the increase of crystalline size that results in enlarging the grain size, has been identified significantly improves the sheet conductivity of VO2 thin films in rutile phase, which indeed also implements large change in order of magnitude. Besides, the lattice strain has been proven strongly affects the electronic orbitals (pi* and d(parallel to)) occupancy in rutile phase, which has been identified as the one of significant signatures in indicating T-MIT change, and thus the increase of lattice strain is believed efficient to modulate T-MIT. The close relationships between the surface grain size, lattice strain, T-MIT and sheet conductivity in this study for sure will open the door to the fabrication and research on highly quality VO2/Al2O3 thin films. (C) 2021 Elsevier B.V. All rights reserved.