Optical Absorption Properties of BaSi₂ Epitaxial Films Grown on a Transparent Silicon-on-Insulator Substrate Using Molecular Beam Epitaxy

We have grown 100-nm-thick BaSi 2 films on transparent silicon-on-insulator (SOI) substrates using molecular beam epitaxy, for optical absorption measurements. The SOI substrate has a 0.7-µm-thick (111)-oriented Si layer on top of a fused silica substrate. Reflection high-energy electron diffraction and θ–2θ X-ray diffraction patterns showed that a -axis-oriented BaSi 2 layers were grown epitaxially. The absorption spectrum of the film measured in a transmission configuration at room temperature revealed that BaSi 2 has a large absorption coefficient of 3 ×10 4 cm -1 at 1.5 eV and an indirect optical absorption edge of 1.34 eV.