Properties of reduced graphene oxide doped tin oxide thin films deposited by thermionic vacuum arc plasma

Nowadays, two-dimensional (2D) nanomaterials are widely used as doping material due to their potential to enhance the electrical, optical, and structural properties of the semiconductor material. In the thesis, tin oxide (SnO₂) thin films, an n-type semiconductor, were modified with reduced graphene oxide (rGO) and then an annealing process was applied to investigate the effects of temperature on the films. The literature frequently emphasizes that rGO, can affect the carrier mobility and tunable electronic band properties of the semiconductor. Thin film deposition was carried out using the Thermionic Vacuum Arc (TVA) plasma technique; rGO-doped SnO₂ films were deposited under stable plasma conditions in a high vacuum environment and then annealed at 400 °C investigate the annealing effect on semiconductor material. Surface morphology and composition of the thin films were analyzed using field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM) devices. A theoretical reflection model was developed using the Quadoa Optical CAD software and was compared with experimental reflection data. According to EDS results, the films contained carbon and tin in weight ratios of 35% and 65%, respectively; AFM analysis revealed a homogeneous surface distribution. Optical properties were investigated using an UV-Vis spectrophotometry, and the optical band gap was calculated to be 3.50 eV and the value was reduced to 3.00 eV after the annealing process. It was observed that the absorbance and transmittance values were not significantly affected by the annealing process. Furthermore, reflection and refractive index measurements were performed using a Filmetrics F20 instrument, reflection values ranged between 6% and 14%, and the refractive index at 630 nm was determined to be 1.89. Finally, it was observed that the rGO-doped SnO₂ thin films maintained their structural integrity at elevated temperatures compared to similar semiconductor structures operating at room temperature, suggesting that such nanocomposites may be suitable candidates for optoelectronic applications needing to require high-temperature stability.