Abstract
In this work, vanadium pentoxide (V2O5) thin films were prepared using rf magnetron sputtering on silicon wafer and glass substrates from V2O5 target at 200 °C substrate temperature, followed by annealing at 400 and 500 °C in air for 2 h. The prepared thin films were examined by X-ray diffraction (XRD), forier transform infra-red spectroscopy (FTIR), UV-visible absorbance, and direct current coductivity to study the effects of annealing temperature on their structural and optical properties. The XRD analysis exhibited that the annealing promoted the highly crystallized V2O5 phase that is highly orientated along the c direction. The crystalline size increased from 22.5 nm to 35.4 nm with increasing the annealing temperature to 500 °C. The FTIR spectroscopy showed the enhancement of the characteristics band for the V2O5 with increasing annealing temperature to 500 °C. The optical study showed that the energy gap for the sample deposited on glass slides decreased from 2.85 eV, for as deposited sample, to 2.6 eV upon annealing the sample to 500 °C. There was a linear dependence between sensitivity and relative humidity (RH) at the range from 25% to 70%, while the behavior was exponential at high RH range.
Highlights
The humidity affects all environmental biological and chemical processes
The effects of annealing temperature on the structural and optical properties of V2O5 thin films was studied by using radio frequency sputtering technique on Si and glass substrates
The crystalline film appeared with high orientation along the (001) direction, which agrees with the results reported by Raman et al, [12]
Summary
The humidity affects all environmental biological and chemical processes. It negatively affects various industrial-manufacturing methods if proper steps are not taken [1]. The deposition technique and the precipitation parameters, such as deposition rate, substrate temperature, sputtering power, and pressure, determine the thin film properties. The effects of annealing temperature on the structural and optical properties of V2O5 thin films was studied by using radio frequency sputtering technique on Si and glass substrates. We employed the deposited V2O5 thin film in the development of resistive type humidity sensors by studying the variation in sample resistance versus relative humidity. Optical measurements of thin films were performed by UV-Visible spectrometer (UV-vis Shimadzu 1700) for samples deposited on glass slide. The humidity sensor, based on resistance variation, was built using V2O5 thin film deposited on Si substrate and annealed at 500 °C. Silver paste was used to deposit mesh electrodes on the surface of V2O5 by print screen and dried in an oven at 70 °C. The RH varied from approximately 25 to 90 %, using moisture generator
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