Inert interlayers and evaporation techniques for high-quality BaSi₂ heterostructures

Abstract BaSi 2 has suitable optoelectronic properties for solar cells, with a limiting efficiency of over 30% under one sun condition. However, its high reactivity often hinders heterojunction or heterostructure formation with other materials for property analysis and device fabrication. Here, we demonstrate the effectiveness of MgO and Sm 2 O 3 interlayers by synthesizing BaSi 2 films on fused silica substrates using two evaporation-based techniques: machine learning-assisted thermal evaporation and close-spaced evaporation. The BaSi 2 films were deposited at 450–500 °C and 800 ∘ C, respectively. High-temperature depositions did not produce secondary phases, except for surface oxidation-induced Si segregation after long in situ annealing at 500 ∘ C for 30 min. These results highlight the effectiveness of the interlayers and machine learning-assisted thermal evaporation. Investigations on close-spaced evaporation on Si layers revealed the benefits of excess Ba deposition for BaSi 2 synthesis and challenges like exfoliation and cracking. These findings are crucial for fabricating BaSi 2 -based heterostructures via evaporation-based techniques.