Concentration-dependent study of Ga₂O₃/FTO bilayers: structural, optical, and morphological tuning for optoelectronic applications

Abstract

This study systematically investigates the structural, morphological, elemental, and optical properties of Ga₂O₃/FTO bilayer thin films deposited with varying Ga₂O₃ precursor concentrations (0.1, 0.2, and 0.4 M) for optoelectronic applications. Comprehensive characterization using X-ray diffraction (XRD) reveals the dominant (200) plane in both FTO and bilayer structures, while energy-dispersive X-ray spectroscopy (EDS) confirms uniform bilayers with Ga content varying from 11.73 wt% (0.1 M) to 21.9 wt% (0.4 M). Scanning electron microscopy (SEM) demonstrates that higher precursor concentrations yield smoother Ga₂O₃ layers (12.04 nm particles at 0.4 M) with thicknesses up to 2.74 μm, though Urbach energy analysis indicates increased disorder (0.63–0.91 eV). Optical studies show strong UV absorption below 360 nm, with tunable transmittance (60–85 % in visible range) and consistent band gaps (∼4.55 eV) across all concentrations. The bilayer's combination of FTO's conductivity and Ga₂O₃’s UV sensitivity, coupled with its structural stability, makes it particularly suitable for UV photodetectors and transparent electrodes in harsh environments. These findings provide critical insights for optimizing Ga₂O₃/FTO bilayers for next-generation optoelectronic devices.