Modification Of Metal Insulator Transition In Ultrathin Vo2 Films Via Ultra Violet Radiation

Open Access
Author:
Guo, Lu
Graduate Program:
Materials Science and Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 06, 2014
Committee Members:
  • Venkatraman Gopalan, Thesis Advisor
Keywords:
  • Vanadium dioxide
  • thin Film
  • UV Irradiation
Abstract:
VO2 exhibits metal-insulating transition as a function of temperature, which makes it one of the prototypical strongly correlated materials. External factors such as pressure, strain and electrical field can trigger this first order phase transition. The dramatic property changes as well as the fast transition time make VO2 a promising candidate for switching devices. In our study, we point out a new way to not only take advantage of the MIT in VO2 but also to manipulate it. We demonstrate light-induced modification of the metal-insulator transition in single crystalline VO2 ultrathin films (10 nm) grown on (001) TiO2 substrates. Exposure to 365 nm UV light at 0.19 W/cm2 in non-oxidizing atmosphere caused the films to remain metallic even when temperatures were below transition temperature. Post-annealing in oxidizing atmosphere successfully recovered the MIT transition. Oxygen vacancies formation is proposed to be the mechanism for this MIT suppression. The ability to eliminate and recover the MIT of VO2 film presents a flexible way to build electronic circuits using correlated oxides.