Abstract
This work reports on the characteristics of the insulator-to-metal transition (IMT) of reactive pulsed laser deposited vanadium dioxide (VO2) films in the terahertz (THz) frequency range, namely the transition temperature T-IMT, the amplitude contrast of the THz transmission over the IMT Delta A, the transition sharpness Delta T and the hysteresis width Delta H. XRD analysis shows the sole formation of VO2 monoclinic structure with an enhancement of (011) preferential orientation when varying the O-2 pressure (P-O2) during the deposition process from 2 to 25 mTorr. THz transmission measurements as a function of temperature reveal that VO2 films obtained at low P-O2 exhibit low T-IMT, large Delta A, and narrow Delta H. Increasing P-O2 results in VO2 films with higher T-IMT, smaller Delta A, broader Delta H and asymmetric hysteresis loop. The good control of the VO2 IMT features in the THz domain could be further exploited for the development of advanced smart devices, such as ultrafast switches, modulators, memories and sensors. (C) 2016 Published by Elsevier B.V.