Electronic, Optical, and Epsilon Near-Zero Response in Magnetron-Sputtered Tantalum Oxynitride Thin Films

Tantalum oxide and tantalum oxynitride structures were examined through density functional theory using the trans-blaha-modified Becke–Johnson approximation and an experimental approach for the prediction of electronic, thermoelectric, and optical properties. Pure Ta₂O₅ and Ta₂O_5-xN_x thin films were prepared using the well-known DC magnetron sputtering for comparative computational and experimental investigations. The thermoelectric properties were evaluated, and a considerable improvement in parameters was observed with an increase in dopant concentration. Phase identification and structural analysis of the thin films were performed using x-ray diffraction analysis. The optical band gap measured by the Tauc relationship showed a decrease in the band gap from 2.57 to 2.05 eV with the increase in nitrogen content which followed the simulation trend. The experimental investigation of the optical parameters of pure and N-doped Ta₂O₅ thin films was carried out. The simulation and experimental results depicted an epsilon near-zero response with maximum N doping (Ta₂O_1.25N_3.75) in the visible and near-infrared regimes. The theoretical and experimental results showed nearly identical correlations. These thin films are considered suitable potential candidates for thermoelectric and optoelectronic applications due to their unique enhanced parameters.