Zero added oxygen for high quality sputtered ITO: A data science investigation of reduced Sn-content and added Zr

The authors demonstrate mobilities of >45 cm²/V s for sputtered tin-doped indium oxide (ITO) films at zero added oxygen. All films were deposited with 5 wt. % SnO₂, instead of the more conventional 8–10 wt. %, and had varying ZrO₂ content from 0 to 3 wt. %, with a subsequent reduction in In₂O₃ content. These films were deposited by radio-frequency magnetron sputtering from nominally stoichiometric targets with varying oxygen partial pressure in the sputter ambient. Anomalous behavior was discovered for films with no Zr-added, where a bimodality of high and low mobilities was discovered for nominally similar growth conditions. However, all films showed the lowest resistivity and highest mobilities when the oxygen partial pressure in the sputter ambient was zero. This result is contrasted with several other reports of ITO transport performance having a maximum for small but nonzero oxygen partial pressure. This result is attributed to the reduced concentration of SnO₂. The addition of ZrO₂ yielded the highest mobilities at >55 cm²/V s and the films showed a modest increase in optical transmission with increasing Zr-content