Bandgap of Epitaxial Single-Crystal BiFeMnO Films Grown Directly on SrTiO/Si(001).

We report the growth and optical characterization of single-crystal BiFeMnO thin films directly on SrTiO/Si(001) substrates using molecular beam epitaxy. X-ray diffraction confirmed epitaxial growth, film crystallinity, and sharp interface quality. Scanning electron microscopy and energy dispersive X-ray spectroscopy verified uniform film morphology and successful Mn incorporation. Spectroscopic ellipsometry revealed a systematic bandgap reduction with increasing Mn concentration, from 2.7 eV in BiFeO to 2.58 eV in BiFeMnO, consistent with previous reports on Mn-doped BiFeO. These findings highlight the potential of BiFe₋MnO films for bandgap engineering, advancing their integration into silicon-compatible multifunctional optoelectronic and photovoltaic applications.