Effect of solution flow rate on the physical properties of spray pyrolyzed MoO3 thin films as silicon-based heterojunction device

Abstract

Molybdenum trioxide (MoO3) films were synthesized on n-type silicon via spray pyrolysis technique. In this study, the influence of arriving aerosol on the silicon substrate was controlled by varying the solution flow rate (ranged from 3.0 to 1.5 ​ml/min) at substrate temperature of 300 ​± ​5 ​°C. The X-ray diffraction (XRD) analysis indicates the co-existence of orthorhombic (α-MoO3) and hexagonal (h-MoO3) crystal phases. As the flow rate decreases, the peaks correspond to the hexagonal phases were disappeared. Meanwhile, the Raman spectral analysis showed peaks mode of unshared oxygen at 979 ​cm−1. Moreover, a morphological study using Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscope (AFM) demonstrated the reducing grains size with decreasing flow rate, which promotes the homogeneity and smoothness of the film. The basic diode parameters: ideality factor (n) and barrier height (ΦB), were effectively determined and analyzed by the thermionic emission (TE) theory. It has been observed that the ideality factor reduced while the barrier height broadened by lowering the solution flow rate. Moreover, when the diode exposes to light illumination, both the barrier heights and ideality factors decrease. The obtained results signify that the solution flow rate is a crucial parameter affecting the MoO3 film growth and its selective carrier properties.