Mg/Si interface reaction: How and why. Towards rational technologies of Mg2Si film growth for energy conversion

• Published in: Vacuum 2022-02, Vol.196, p.110798, Article 110798
• Main Authors: Gouralnik, Alexander S., Luniakov, Yuri V.
• Format: Article
• Language: English
• Subjects: Ab initio calculations; Energy conversion materials; Interface reaction mechanism; Metastable phases; Mg2Si; Solar cells
• ISSN: 0042-207X; 1879-2715
• DOI: 10.1016/j.vacuum.2021.110798

Ab initio calculations were used to study the mechanisms of the processes of Mg–Si solid state intermixing and silicide formation. An evolutionary algorithm was used to search for MgαSi(1-α) structures with lowest formation energies, Ef; the composition parameter α was varied over the range 0–1. New structures with negative formation energies have been found for α > 0.67. Tentatively, the obtained structure Mg3Si, has been observed in experiments. Besides the minimum at α = 0.67 corresponding to Mg2Si, the dependence of Ef(α) has two positive maxima: near low and high α. This dependence indicates that certain energy barriers prevent the initiation of Mg–Si intermixing. High temperatures and abundance of both Mg and Si atoms at the interface are required for initiation of the intermixing and silicide formation processes. Practical implications of this conclusion for routine and new methods of Mg2Si growth in vacuum are analyzed. Some characteristic experimental data are explained. Rational methods of fabrication of cheap and environmentally-friendly Mg2Si and related compounds for applications in solar cells and thermoelectric devices are indicated. •Calculations with USPEX code were used to study the reaction at Mg/Si interface.•The shape of the MgαSi1-α alloy formation energy dependence on α was analyzed.•Some energy barriers block the initiation of Mg/Si intermixing.•High T and abundance of both Mg and Si are necessary for intermixing initiation.•The calculated structure Mg3Si (tentatively) has been observed in experiments.