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This paper describes the successful preparation of high quality (104) oriented Al2O3:Cr2O3 (1:1) thin film with rhombohedral phase and bone like surface morphology by RF magnetron sputtering technique. Compositional purity and its corresponding chemical states of the elements (Al3+ and Cr3+) present in the deposited films were ascertained by EDX and XPS analyses, respectively. In particular, the film deposited with 300 W RF power not only possess unique morphology (bone like morphology), but also exhibits superior gas sensing performance towards NH3 at room temperature due to its very high surface-to-volume ratio, which provide a more reaction site for NH3 gas molecules. Due to this unique morphological feature, the 1000 °C annealed Al2O3:Cr2O3 (1:1) film exhibited the good selectivity, long-term stability, high sensitivity (sensitivity = 4.14), excellent sensor response (SR = 99.7% for 100 ppm) for diverse range of ammonia concentrations and the film has an ability to respond even at very low concentration (1 ppm level) at room temperature. The probable gas sensing mechanism was also discussed.

In the present study, we report the high visible to near infrared (NIR) transparent Al2O3:CuO thin films prepared using homemade high purity sputtering target by radio frequency magnetron sputtering technique with sputtering powers of 100, 200 and 300 W at room temperature and the prepared films were annealed at 300, 600 and 1000 °C for 1 h. X-ray diffraction analysis confirmed the amorphous formation of the deposited films. The obtained X-ray profiles of the sputtering target are refined using Rietveld refinement technique through the program package of general structure analysis system with EXPGUI interface. Optical study showed the sputtering power and annealing temperature persuaded red shift in absorption edge and as a consequence the shrinkage in optical band gap was observed. The obtained high average transparency of 87–96% in the wavelength range 400–1100 nm validates the transmittance of as-deposited and annealed Al2O3:CuO thin films is well extended into the near infrared region. The obtained optical transmittance and absorbance data were utilized to calculate various optical parameters.

This article describes a facile fabrication of spinel structured n-type CuAl2O4 thin film with nano-grass like morphological feature by radio frequency (RF) magnetron sputtering technique and the direct realization of this structure as room temperature NH3 gas sensor. X-ray diffraction (XRD) study confirmed the predominant presence of cubic phase CuAl2O4 in the homemade sputtering target and also in the fabricated films. X-ray photoelectron spectroscopic (XPS) investigation confirms the formation of Al3+ and Cu2+ chemical states in the films. Purity and stoichiometry of the deposited films were further confirmed by energy dispersive X-ray spectroscopy (EDX). A randomly aligned nano-grass like morphology with diameters of 25–100 nm and lengths in the range of 0.5 to 2 μm was observed for the film deposited with 300 W sputtering power on quartz substrate by FESEM study, which provides more reaction sites for gas molecules due to their high aspect ratios (length/diameter). The gas sensing measurements revealed that the prepared n-type CuAl2O4 thin films exhibited superior sensing performance towards ammonia gas in terms of high sensor response, quick response time and recovery time, high sensitivity, long stability, and good reproducibility even at room temperature operation condition. Therefore, we believe that the prepared n-type CuAl2O4 thin films have potential for the detection of ammonia gas leaks in chemical industries.

In the present investigation, for the first time, we report the room temperature gas sensing characteristics of Cr2O3:CuO (50:50) thin films prepared by RF magnetron sputtering technique. The X-ray diffraction data show that the prepared Cr2O3:CuO (50:50) films are amorphous nature. The X-ray photoelectron spectroscopic study confirmed the formation of Cr3+ and Cu2+ states in the films. The growth conditions induce the change in morphology of Cr2O3:CuO (50:50) films from cauliflower like structure to single nanoplate like structure, which may be due to the change in nucleation. The FTIR spectra of Cr2O3:CuO (50:50) thin films exhibit peaks between 431 cm−1 and 774 cm−1 which correspond to the characteristic stretching vibrations of Cu O and Cr O bonds in the films. Optical study showed the RF power induced red shift in absorption edge, which revealed the systematic reduction in optical energy band gap of the films. The activation energy (ΔE) of Cr2O3:CuO (50:50) thin films estimated from the Arrhenius plot are varied between 0.369 and 0.504 eV. The respective response and recovery times of Cr2O3:CuO (50:50) thin film sensor exposed in 25 ppm of ammonia gas are about 11 and 14 s, while that in 100 ppm, are about 51 and 53 s. The maximum sensor response of 98% was observed for 100 ppm of NH3 gas at room temperature. The present report suggests that the RF magnetron sputtered Cr2O3:CuO (50:50) thin films can perform efficiently as a ammonia gas sensor at room temperature.

In this work, we report on RF sputtering power and substrate temperature induced changes in the optical properties of Al2O3:Cr2O3 thin films deposited on glass substrates by radio frequency (RF) magnetron sputtering technique. The films were deposited with the RF powers of 100 and 150 W and the substrate temperatures of room temperature and 200°C. The optical properties of the films were characterized by UV-Vis-NIR spectrophotometer. It is observed that the transmittance of prepared films decreased with increasing RF power and substrate temperature. From the optical transmittance data, various optical parameters like absorption coefficient, refractive index, extinction coefficient, dielectric constants (real and imaginary parts) and optical conductivity of the deposited films were calculated and their variations with the RF powers and substrate temperatures are discussed.

Zinc oxide (ZnO) and tin oxide (SnO2) thin films have attracted significant interest recently for use in optoelectronic application such as solar cells, flat panel displays, photonic devices, laser diodes and gas sensors because of their desirable electrical and optical properties and wide band gap. In the present study, thin films of ZnO:SnO2 (50:50) were deposited on pre-cleaned microscopic glass substrate by RF magnetron sputtering technique. The substrate temperature and RF power induced changes in structural, surface morphological, compositional and optical properties of the films have been studied.

Aluminium oxide (Al2O3) and chromium oxide (Cr2O3) thin films have received great attention of researchers because of their unique properties of corrosion/oxidation resistance and high dielectric constant. In addition, chromium aluminium oxide has been considered as a best candidate for deep-ultraviolet optical masks. In the present work, thin films of Al2O3:Cr2O3 (50:50) were deposited on pre-cleaned microscopic glass substrate by RF magnetron sputtering technique. The substrate temperature and RF power induced changes in structural, surface morphological, compositional and optical properties of the films have been studied.