Characteristics of phase transition of VO_2 films grown on TiO_2 substrates with different crystal orientations

摘要

Vanadium dioxide (VO_2) films were synthesized on two-side polished titanium dioxide (TiO_2) substrates of five different crystal orientations, (001), (100), (101), (110), and (111), through pulsed laser deposition. X-ray diffraction measurements suggested that epitaxial VO_2 films with good crystallinity were grown on TiO_2. Transmission electron microscopy measurements showed the thickness of VO_2 films to be about 50 nm and revealed the presence of an inter-mixing layer of ～10 nm thickness at the interface between VO_2 and TiO_2. A metal-insulator transition (MIT) showing a change in resistance of 3-4 orders of magnitude was observed in all samples. The MIT temperature (T_(MI)) showed a significant variation with crystal orientation: the highest value of T_(MI) was 350 K in VO_2/TiO_2(001) and the lowest value was 310 K in VO_2/TiO_2(110), and VO_2 films for the (111), (101), and (10 0) orientations exhibited T_(MI)～315K, 330 K, and 340 K, respectively. For infrared light, the change in the optical transmittance by the MIT was about 60%.