Optical Characterization of Boron Doped In2O3 Thin Films

Indium oxide (In2O3) thin films are valuable materials for optoelectronic applications owing to their wide band gap, high transparency, and modifiable electrical properties. This study focuses on the comprehensive optical characterization of undoped and boron-doped In2O3 thin films with various boron concentrations (0.02, 0.03, 0.06, and 0.09 M) prepared by spray pyrolysis. Systematic analysis of transmittance and reflection spectra measured using a JASCO spectrophotometer (300–2000 nm range, 2 nm pitch) resulted in the determination of various fundamental optical parameters such as absorbance, absorption coefficient, optical band gap, refractive index, extinction coefficient, dielectric constants, and optical conductivity. The undoped In₂O₃ film was found to have a direct band gap of 3.37 eV with the sharp absorption edge located in the UV region (300–400 nm) and an average refractive index of 2.31. Also, the film exhibited moderate optical transmittance in the visible range (400–700 nm) with transmittance values generally below % 70. It was observed that the calculated optical properties changed systematically with the addition of boron. For example, band gaps ranged from 2.88 eV (0.06 M) to 3.46 eV (0.09 M), while refractive indices ranged from 2.34 (0.09 M) to 2.58 (0.03 M). The results show that the addition of boron will be an effective method for controlling optical properties and that boron-doped indium oxide films will be an important material for transparent conductive oxide applications and thin-film transistor technologies. This study focuses on a comprehensive analysis of the optical parameters of In2O3:B films. The scope of the study is limited to optical characterization, and the results are supported by correlation with the author's previous structural and electrical studies. This approach reveals the relationship between optical changes and crystal structure and carrier mechanisms.