Changes in Lattice Parameters of VO_2 Films Grown on c-Plane Al_2O_3 Substrates across Metal-Insulator Transition

摘要

We demonstrated lattice parameters of vanadium dioxide (VO_2) films grown on AI_2O_3(001) substrates across metal-insulator transition using temperature-controlled X-ray diffraction measurements. Changes in lattice length for both the monoclinic and tetragonal phases were shown against temperature. Films prepared by pulsed laser deposition (PLD) and reactive sputtering were examined to discuss the dependence of the transition properties on lattice parameters. The expansion of c_m sin β due to smaller angle β was revealed to be a characteristic in the low-temperature monoclinic phase and to be transformed to a larger in-plane a_t length in the high-temperature tetragonal phase. We discussed the dependence of transition temperature on c_t length in the tetragonal phase in relation to the a_m length in the monoclinic phase across metal-insulator transition.