Preparation of TaO₂ thin films using NbO₂ template layers by a pulsed laser deposition technique

TaO₂ thin films were prepared using rutile-type NbO₂ template layers on Al₂O₃(0001) substrates by a pulsed laser deposition technique. The structural and electronic properties of the films were characterized by performing four-circle X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS) measurements. Four-circle XRD measurements revealed the formation and epitaxial growth of (100)-oriented tetragonal TaO₂ on the NbO₂ template layers. On the other hand, XPS measurements showed two kinds of valence states, namely Ta^{4 +} and Ta^{5 +} in the surface region of the film. The results from the XRD and XPS measurements suggest that the film is composed of epitaxially grown TaO₂ with an amorphous Ta₂O₅ surface layer. It is found from control experiments that the NbO₂ template layers play an important role in inducing the crystallization of the TaO₂ films and promoting the formation of Ta^{4 +} in the films deposited thereon. The results indicate the effectiveness of the NbO₂ template layers for the formation of TaO₂ thin films. Our work presents a promising method for the preparation of TaO₂ thin films and provides a starting point for further research on TaO₂.