Structural defects and electronic structure of N-ion implanted TiO2: bulk versus thin film

TL;DR

This study investigates how nitrogen implantation affects the atomic and electronic structure of TiO2 in bulk and thin film forms, revealing substitutional and molecular-like defect formations that influence band gap properties.

Contribution

It provides a comparative analysis of N-ion implantation effects in bulk versus thin film TiO2 using experimental XPS data and first-principles DFT calculations, highlighting defect formation mechanisms.

Findings

N substitutes O in bulk TiO2.

Molecular N2 and NO structures form in thin films.

Oxygen vacancies significantly reduce the band gap.

Abstract

Systematic investigation of atomic structure of N-ion implanted TiO2 (thin films and bulk ceramics) was performed by XPS measurements (core levels and valence bands) and first-principles density functional theory (DFT) calculations. In bulk samples experiment and theory demonstrate anion N->O substitution. For the thin films case experiments evidence valuable contributions from N2 and NO molecule-like structures and theoretical modeling reveals a possibility of formation of these species as result of the appearance of interstitial nitrogen defects on the various surfaces of TiO2. Energetics of formation of oxygen vacancies and its key role for band gap reduction is also discussed.