EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Transparent Conductors Materials (TCM) are of great technological importance for many devices and applications in the renewable energy production field. Tin-doped indium oxide (ITO) is the most used transparent conductive oxide (TCO) due to its high transparency in the VIS region (~ 80%) and low resistivity (10^(-2)-10^(-3) Ωcm). However, its large-scale usage faces the issue of scarcity, price and toxicity of In, so promoting new materials with superior properties in terms of sustainability or, at least, in terms of performances. Doping indium oxide with transition metal (Mo, Zr, Hf, Ta) as dopant has been proposed as potential strategy to improve conductivity and transparency in ultra-thin films. In this work we show a further approach to improve ITO properties by using Mo co-doping (ITMO). Thin films (~75nm) of ITMO with Mo concentrations of about 1-2% were deposited by RF magnetron co-sputtering from ITO and Mo targets. Thermal annealings, up to 400°C, were also performed to improve optical and electrical properties of the as deposited films. Samples have been characterized by UV-VIS-NIR spectrophotometry, 4-points electrical probe, XPS and RBS. Although a high doping efficiency is measured already in the as deposited ITMO films, a drastic improvement in both electrical and optical properties has been observed for thermal annealing at about 300 °C, probably due to the annealing of structural defects limiting the carrier mobility. The XPS analysis, in particular, helps to understand the role of the Mo oxides in the ITMO matrix.