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Low-cost VO₂(M1) thin films synthesized by ultrasonic nebulized spray pyrolysis of an aqueous combustion mixture for IR photodetection

Author:
Tadeo, Inyalot Jude, Mukhokosi, Emma P., Krupanidhi, Saluru B., Umarji, Arun M.
Source:
RSC advances 2019 v.9 no.18 pp. 9983-9992
ISSN:
2046-2069
Subject:
Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, ambient temperature, atomization, combustion, cost effectiveness, electric potential difference, lighting, phase transition, pyrolysis, reflectance, ultrasonics, ultraviolet-visible spectroscopy
Abstract:
We report detailed structural, electrical transport and IR photoresponse properties of large area VO₂(M1) thin films deposited by a simple cost-effective two-step technique. Phase purity was confirmed by XRD and Raman spectroscopy studies. The high quality of the films was further established by a phase change from low temperature monoclinic phase to high temperature tetragonal rutile phase at 68 °C from temperature dependent Raman studies. An optical band gap of 0.75 eV was estimated from UV-visible spectroscopy. FTIR studies showed 60% reflectance change at λ = 7.7 μm from low reflectivity at low temperature to high reflectivity at high temperature in a transition temperature of 68 °C. Electrical characterization showed a first order transition of the films with a resistance change of four orders of magnitude and TCR of −3.3% K⁻¹ at 30 °C. Hall-effect measurements revealed the n-type nature of VO₂ thin films with room temperature Hall mobility, μₑ of 0.097 cm² V⁻¹ s⁻¹, conductivity, σ of 0.102 Ω⁻¹ cm⁻¹ and carrier concentration, nₑ = 5.36 × 10¹⁷ cm⁻³. In addition, we fabricated a high photoresponsive IR photodetector based on VO₂(M1) thin films with excellent stability and reproducibility in ambient conditions using a low-cost method. The VO₂(M1) photodetector exhibited high sensitivity, responsivity, quantum efficiency, detectivity and photoconductive gain of 5.18%, 1.54 mA W⁻¹, 0.18%, 3.53 × 10¹⁰ jones and 9.99 × 10³ respectively upon illumination with a 1064 nm laser at a power density of 200 mW cm⁻² and 10 V bias voltage at room temperature.
Agid:
6363401