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Tungsten trioxide (WO 3 ) thin films have been prepared via sol-gel spin-coating technique for different concentrations of Al (0, 3, 6, 9 and 12 wt.%) and investigated them by structural, optical, dc electrical and Al:WO 3 /p-Si heterojunction diodes. The XRD analysis reveals that the trivalent impurity of Al effectively influences the WO 3 . The UV–vis analysis shows an increase in the Al dopant that caused the band gap energy (E g ) to decrease. The SEM analysis shows that the size of the plate-like grains has reduced the Al:WO 3 thin films. The composition ratio of W, O and Al elements has been confirmed by EDX spectrum. The dc electrical conductivity analysis has identified that Mott’s 3D variable hopping (VRH) mechanism influences the Al:WO 3 thin films. The Al:WO 3 /p-Si p - n heterojunction diode parameters of ideality factor (n), barrier height (Φ B ) and series resistance (R s ) have been calculated using the J-V method. From the current density-voltage-temperature (J-V-T) analysis, the inhomogeneity of barrier heights was extracted using the thermionic emission mechanism with Gaussian distribution (GD) function. As a result, the 9 wt.% of Al:WO 3 /p-Si diode gives better results compared to the other Al:WO 3 /p-Si diodes. [ABSTRACT FROM AUTHOR]

The ln(J)-V-T characteristics of the p-Si/n-WO 3-x /Ag junction diode have been analyzed by thermionic emission (TE) mechanism with Gaussian distribution (GD) of the barrier heights. The ultra-fine homologous phases of tungsten oxide (WO 3-x ) thin films on the glass substrate can be prepared simply via sol-gel spin coating method. The oxygen reduction of the tungsten trioxide (WO 3 ) thin films was experimentally controlled by various organic acid additives. The organic acid-treated films have hexagonal and monoclinic crystallographic Magneli phases of W n O 3n-2 series (WO 2.92 , WO 2.9 and WO 2.89 ). The morphological changes in the plate-like structure under the strong influence of the organic acids were observed from SEM analysis. In the temperature dependent dc electrical conductivity, the charge transport mechanism of the WO 3-x thin films was analyzed by Arrhenius, Mott’s variable hopping, small polaron mechanisms. From the J-V-T characteristics of the p-Si/n-WO 3-x /Ag diode, the increasing of barrier height (Φ B ) and decreasing of ideality factor (n) reveal that barrier inhomogeneities at the interface, which is assumed by Gaussian distribution. The mean barrier height ( Φ B ) , the standard deviation (σ 0 2 ) and Richardson constant (A*) values were investigated in the temperature range 303−423 K. The better diode performance was acquired to the Si/WO 2.89 /Ag device with the experimentally intended A* value of 34.81 A/cm 2 /K 2 which is near to the well-known value of 32 A/cm 2 /K 2 for p-type Si. [ABSTRACT FROM AUTHOR]

Molybdenum trioxide (MoO 3 ) thin films were prepared at room temperature (RT) and at different annealing temperatures of 250, 350, 450 and 550 °C. We also prepared MoO 3 films using additives of water-soluble and water-insoluble organic acids. The thin films were coated using the spin coating technique and annealed at 350 °C temperature. The effects of different annealing temperatures and different organic acid additives on MoO 3 films were characterized by structural and optical studies. From the XRD pattern, the structure of the MoO 3 films is found to vary with respect to increase in the annealing temperature. For RT and 250 °C, the hexagonal structure was observed and for 350, 450 and 550 °C, the orthorhombic structure was observed. The XRD pattern for all the organic acid additive used MoO 3 films exposed the orthorhombic structure. SEM images show hasty variations in the surface morphology for different annealed MoO 3 films and different additive used MoO 3 films. The EDX analysis confirmed the presence of Mo and O elements for all the films. The UV–vis results show the absorbance and transmittance values. The band gap energy was found to be around 3.8 eV for all the MoO 3 films. [ABSTRACT FROM AUTHOR]