Unraveling the Growth Dynamics of Rutile SnGeO Using Theory and Experiment.

Rutile GeO and related materials are attracting interest due to their ultrawide band gaps and potential for ambipolar doping in high-power electronic applications. This study examines the growth of rutile SnGeO films through oxygen-plasma-assisted hybrid molecular beam epitaxy (hMBE). The film composition and thickness are evaluated across a range of growth conditions, with the outcomes rationalized by using density functional theory calculations. We find that up to 34% Ge can be successfully incorporated into SnGeO/r-AlO ( ≤ 0.34) at 600 °C. Our phase diagram calculations suggest that spinodal decomposition occurs at Ge concentrations exceeding 34%. However, the formation of a Ge-rich rutile phase is inhibited by amorphization of the Ge-rich film and volatility of GeO. We therefore speculate that maximizing the Ge content requires higher Ge flux and more oxidizing environments, providing insights into the growth mechanism of SnGeO and paving the way toward the synthesis of pure rutile GeO films.