Impact of Mo+2 addition and thermal annealing on the surface morphology, electrical transport properties and Mott's parameters of WO3 films for potential photonic devices

Abstract

This work investigates the compositional dependence and thermal annealing of the morphological properties, electrical conductivity mechanisms and Mott's parameters of sprayed MoxW1-xO3 (x = 0, 0.05, 0.10 and 0,20) thin films. The prepared thin films were examined using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX) and Fourier transform infrared spectroscopy (FTIR) techniques. In addition, the two-point probe method was used to calculate the electrical properties of MoxW1-xO3 thin films. The FTIR results revealed that; the tungsten hydroxyl bond (W-OH) and the surface hydroxyl group vibrated within the ranges of 1558.62–1645.56 cm−1 and, 3296.76 and 3424.34 cm−1, respectively. Furthermore, a prominent band in the spectrum spanning from 850 to 650 cm−1 represents the W-O-W bridge mode. The FE-SEM investigations found that the molybdenum (Mo) dopant caused significant changes in the surface morphology of the films. The EDX results showed that the percentages of the isotropic elements MoxW1-xO3 agreed well with those obtained by atomic weight. Studies of the conduction mechanism indicate that the transition temperature was approximately 393K. Corresponding to Mott's model, the conduction mechanism below this temperature was across the variable hopping conduction band near the Fermi level. The mechanism exhibited a cycle of localised states through activated thermionic emission above 393K. Mott parameters were also estimated in addition to barrier potential energies, trapping state energies, local state densities, and other variables. The results revealed that both temperature areas had a rise in ρo and ρ1 values during and after annealing. The ΔEo and ΔE1 values in each temperature area decreased as the Mo-ion concentration increased. Furthermore, the conversion temperature gradually reduced as Mo was added. Based on these properties, the study's overall findings indicate that MoxW1-xO3 is suitable for future photonic devices and optoelectronic applications.

Keywords

• Conductivity mechanisms
• Mott's parameters
• Thin solid films
• Metal transition oxides