IR photoresponsive VO2 thin films and electrically assisted transition prepared by single-step chemical vapor deposition

Abstract

Photodetection based on active materials such as VO₂ is less complex and less expensive. Usually such a detector's performance depends on the properties of active materials like the absorption coefficient, structural morphology and band gap width. Herein, we report the photoresponse of high quality VO₂ thin films synthesized by a single-step chemical vapor deposition. The phase was identified by X-ray diffraction and confirmed by Raman spectroscopic studies. Morphological studies by atomic force microscopy and scanning electron microscopy revealed uniform well packed grains in the thin films with a surface roughness of 54 ± 0.9 nm. Temperature variable I–V analysis of the thin films exhibited a first order transition with changes in resistance of 3 orders of magnitude and a temperature coefficient of resistance of −1.25% K⁻¹ at 30 °C. The infrared photodetector fabricated with synthesized VO₂ thin films showed good photoresponse properties with excellent stability and reproducibility at room temperature giving responsivity, sensitivity, quantum efficiency and detectivity of 7.13 × 10⁻² mA W⁻¹, 1272.7%, 5.71 × 10⁻³% and 1.06 × 10¹¹ Jones respectively after exposing the films to a 1550 nm laser at a power density of 250 mW cm⁻² and 10 V bias. We also demonstrated a field assisted thermally induced phase transition by out of plane electrical and piezoforce microscopy measurements on the films.