We investigate the complex relationship between the growth conditions and the structural and transport properties of TixOy thin films grown by molecular beam epitaxy. Transport properties ranging from metallicity to superconductivity and insulating states are stabilized by effectively tuning the O/Ti ratio via the Ti flux rate and the O partial pressure, POx, for films grown on (0001)-Al2O3 substrates at 850∘ C. A cubic c−TiO1±δ buffer layer is formed for low O/Ti ratios while a corundum cr-Ti2O3 layer is formed under higher oxidizing conditions. Metallicity is observed for c-TiO1−δ buffer layers. The superconducting γ−Ti3O5 Magn\'eli phase is found to nucleate on a c-TiO1−δ buffer for intermediate POx conditions and an insulator-superconducting transition is observed at 4.5 K (TConset=6K) for 85 nm thick films. Strain relaxation of the γ−Ti3O5 occurs with increasing film thickness and correlates with a thickness-dependent increase in TC observed for TixOy thin films.
@article{arxiv.2203.01405,
title = {Superconducting Phase of $\mathrm{Ti_xO_y}$ Thin Films Grown by Molecular Beam Epitaxy},
author = {Yasemin Ozbek and Cooper Brooks and Athby Al-Tawhid and Xuanyi Zhang and Vladmir Stoica and Zhan Zhang and Divine P. Kumah},
journal= {arXiv preprint arXiv:2203.01405},
year = {2022}
}