Far-IR transmittance and metal–insulator phase transition properties of VO2 films using Al2O3 as buffer layer

Abstract

Owing to its outstanding metal–insulator transition, vanadium dioxide is considered as an attractive material used for optical modulation devices at far-IR bands. In this work, vanadium dioxide films were successfully prepared on (111) directional silicon substrates using Al2O3 as buffer layer by direct current magnetron sputtering. It is worth noting that, Al2O3 buffer layer significantly enhances the amplitude modulation at far-IR bands. Particularly, when Al2O3 buffer layer’s thickness increases to ~ 40 nm and VO2 film is ~ 300 nm, the amplitude modulation is largely increased from 51.2 to 71.3% at 395 cm−1 and from 18.0 to 40.2% at 280 cm−1. According to XRD, XPS and SEM tests, it can be found that Al2O3 buffer layer affects the composition, crystal structure and metal–insulator transition properties of the films. Moreover, compared with VO2 films deposited on silicon substrates, VO2 films using Al2O3 as buffer layer exhibit better metal–insulator phase transition properties with narrower hysteresis width (11.8 °C, 6.7 °C narrower than former films). Such excellent metal–insulator transition properties indicate that VO2 films using Al2O3 as buffer layer have great potential for far-IR bands modulation applications.