Effect of SiO2 buffer layer on phase transition properties of VO2 films fabricated by low-pressure chemical vapor deposition

Vanadium dioxide (VO2) is a promising material with semiconductor-metal phase transition for novel electronic and optic applications. One of the most widely used substrates for VO2 films is silicon (Si) covered with a silicon dioxide (SiO2) buffer layer because such a substrate is compatible with standard silicon technology. However, little attention has been paid to the effect of SiO2 buffer layer preparation and properties of the VO2/SiO2 interface to the VO2 phase-transition parameters. In the present paper, we investigate the phase-transition properties of VO2 films grown by low-pressure chemical vapor deposition on dry and wet thermally grown SiO2 buffer layers. The x-ray diffraction technique, scanning electron microscopy, and temperature-dependent resistance measurements showed a high crystal quality of the grown VO2 films. We identified the synthesis conditions for obtaining a sharp reversible semiconductor-metal phase transition in VO2 films on both SiO2 buffer layers. It was found that the resistance jump due to phase transition in VO2 films grown on dry and wet SiO2 was 6.5 × 103 and 5.6 × 103 with the hysteresis widths being equal to 2 and 3 °C, respectively. The calculated average size of VO2 crystallites on the dry SiO2 buffer layer proved to be 1.5–2 times larger than that on the wet SiO2 buffer layer. The field-effect measurements showed that the electric-current modulation in VO2 films synthesized on dry SiO2 is almost ten times higher than on wet SiO2 due to different interface layer properties. For 250 nm VO2 film on dry SiO2, the current modulation value reached 0.6%. The results of this work may be useful for the fabrication of new VO2-based functional devices compatible with standard silicon technology.