Observation of the crystalline orientation dependence of the semiconductor–metal transition for thermal oxidation induced VO2 films over amorphous quartz glasses.

Polycrystalline VO2 films were obtained through a vacuum annealing of sputtered V-rich films over quartz substrates and were characterized with x-ray diffraction, field-emission scanning electron microscopy, and x-ray photoelectron spectroscopy, respectively. The semiconductor–metal transition (SMT) was studied with the temperature-variable electric resistances. It was seen that the VO2 film crystalline orientation changes with the O2 partial pressure during the vacuum annealing. We observed a relation between the thermal hysteresis of the SMT and the crystalline orientation of the monoclinic VO2 films. The (011) oriented monoclinic film presents a narrower thermal hysteresis and a larger transition amplitude as compared to the (200) orientated films. In addition, a transition shoulder appears in the thermal hysteresis of the SMT for the (200) oriented VO2 films during the cooling process and becomes absent for the (011) orientated VO2 films. [ABSTRACT FROM AUTHOR]