Study of structural properties and J-V voltametric cyclic of MoTe2 binary thin films: Phase transition from MoO3-TeO2 to 2H-MoTe2

Abstract

The structural phase transition and ionic exchange in two-dimensional transition metals oxides have very important effect on their physical properties. The MoO3-TeO2 binary compounds can be used to improve these properties. In binary compounds, this exchange occurs easily due to the formation of an oxygen vacancy. In this paper, the MoO3 - TeO2 binary compounds thin films have been deposited by spray pyrolysis technique at Ts = 400 °C and structural phase transition from MoO3-TeO2 to 2H-MoTe2 has been investigated. The molar concentration of [MoO3 - TeO2] in initial solution was changed at molar ratios (a) MoO3 (0.05 M) - TeO2 (0.15 M), (b) MoO3 (0.1 M) -TeO2 (0.1 M) and (c) MoO3 (0.15 M) - TeO2 (0.05 M). The structural and electrochromic properties of MoO3 - TeO2 thin films have been studied before and after annealing at T = 500 °C. The X-ray diffraction results of the films showed that, before annealing, the amorphous phase and after annealing at T = 500 °C, the MoO2, Te2O5, H6TeO6 and MoTe2 phases were formed. The FE-SEM images after annealing showed that, the morphology of films including nanoparticles which are almost uniformly distributed, is polygon structures. The electrochromic results showed that higher number of particles and holes in the surface of the electrochromic layers lead to the higher charge exchange rate and then the coloration. Also, in the hysteresis curve of J-V voltametric cyclic, MoO3-TeO2 compound with molar concentration of (a) MoO3 (0.05 M) - TeO2 (0.15 M) has higher area than other compounds and the diffusion coefficient of this sample has been studied before and after annealing at T = 500 °C.