Incorporation of N in the TiO2 Lattice Versus Oxidation of TiN: Influence of the Deposition Method on the Energy Gap of N-Doped TiO2 Deposited by Reactive Magnetron Sputtering

Diego Alexandre Duarte,Marcos Massi

doi:10.1590/1980-5373-mr-2016-0303

Diego Alexandre Duarte, Marcos Massi

Open Access

https://doi.org/10.1590/1980-5373-mr-2016-0303

Copy DOI

Abstract

N-doped TiO2 can be deposited by reactive magnetron sputtering by two methods: incorporation of nitrogen particles in the TiO2 lattice or incorporation of oxygen particles in the TiN lattice (oxidation). This paper investigates both procedures by experimental and numerical methods in order to establish the best way for incorporation of substitutional nitrogen in the TiO2 lattice. Films were deposited with different oxygen and nitrogen flow rates for fixed values of argon flow rate, working pressure, DC power, film thickness and target-to-substrate distance. After deposition, samples were characterized by optical spectrophotometry to calculate the energy gaps. The mechanism for incorporation of substitutional nitrogen was investigated by a numerical model based on Berg model, where data were faced to experimental data in order to validate the growing mechanism. Results indicate that the deposition with oxygen flow rates lower than that set for nitrogen decreases the energy gap due to the incorporation of substitutional nitrogen in the film lattice and depositions with high oxygen flow rates decrease the amount of nitrogen in the film lattice due to the fast oxidation of the nitride layers caused by the high sticking coefficient of the oxygen particles.

Highlights

Titanium dioxide is a functional semiconductor used in several technological applications due to its chemical and physical characteristics[1,2,3,4,5,6,7]
Based on papers published in the past, films of N-doped TiO2 is commonly deposited by sputtering of a metallic titanium target with the reactive gas mixture composed by argon, nitrogen and oxygen, where the amount
The two latter films are crystalline, according to results show in ref.[11]; among these three conditions, the oxygen flow rate of 0.6 sccm was the best condition for deposition of crystalline N-doped TiO2

Summary

Introduction

Titanium dioxide is a functional semiconductor used in several technological applications due to its chemical and physical characteristics[1,2,3,4,5,6,7]. Among the alternatives for improving the catalytic and photovoltaic properties of this material, doping and self-doping are the most suggested[8,9] Both procedures incorporate mid-gap states in the film lattice that are responsible by absorption of visible and near-infrared radiation. Based on papers published in the past, films of N-doped TiO2 is commonly deposited by sputtering of a metallic titanium target with the reactive gas mixture composed by argon, nitrogen and oxygen, where the amount. Besides the oxidation of TiN layers, nitrogen can be embedded in the pre-deposited TiO2 film; this method requires high energy procedures, such as, ion implantation[24] or nitridation of the TiO2 under oxygen-free conditions[25].

Experimental

Results and Discussions

Conclusions