Identification of an adsorption-controlled growth window for new Ge-based oxide films by MBE: Sr₃GeO and Sr₂MnGe­₂O₇

The advancement of the electronic industry is powered by new materials and new physics. In this work, we report the results of combining density functional theory (DFT) and CALculation of PHAse Diagrams (CALPHAD) to obtain temperature-pressure conditions of thermodynamic stability for Sr₂MnGe₂O₇, a quaternary oxide with the melilite structure, and Sr₃GeO, an antiperovskite, to aid in the synthesis of thin films by molecular beam epitaxy (MBE). The former material has recently been proposed to be a Weyl semimetal,¹ and has been previously synthesized in powder form,² while the latter is a narrow bandgap semiconductor.³ However, neither material has been stabilized as an epitaxial thin film.

A thermodynamic database is built by incorporating thermochemical data through DFT calculations to the existing Gibbs energy database (SSUB6) and is then used for the identification of adsorption-controlled growth windows for both materials. Results from thin films grown under the identified synthetic conditions will be presented.

References

1. Gao, J. et al. Sci. Bull. 66, 667–675 (2021).

2. Endo, T., Doi, Y., Hinatsu, Y. & Ohoyama, K. Inorg. Chem. 51, 3572–3578 (2012).

3. Ohashi, N. et al. Inorg. Chem. 59, 18305–18313 (2020).