Study of epsilon-near-zero response in Al substituted titanium oxynitride thin films using computational and experimental investigations

[Display omitted] •DFT calculations of Al substituted titanium oxynitride compositions.•Phase pure growth of thin films.•Band gap of Tatania reduced with the increment of dopant contents.•A significant variation was observed in thermoelectric and optical properties.•Epsilon near zero response was achieved in highly doped composition. Titanium oxide (TiO2) is considered as an important semiconductor material due to having promising tuneable optoelectronic, thermoelectric, and photovoltaic applications. First-principles calculations based on the density functional theory were used to elucidate the effect of dopant on various properties. Thin films have been fabricated using a reactive magnetron sputtering. X-ray diffraction analysis displayed the formation of the rutile phase of Titania in thin films. Atomic force and scanning electron microscopy revealed the growth of uniform, smooth, and well distributed granular thin films. Photoluminescence intensity was observed to decrease with an increase in dopant concentration. Experimentally obtained energy bandgap of the un-doped and doped TiO2 thin film samples was found to decrease and observed as 2.90 eV for pure Titania and 0.85 eV for maximum dopant contents. The present study exhibited that prepared oxynitrides thin films with epsilon near zero response are suitable candidate for enhanced optoelectronic and thermoelectric applications.