Simple Vacuum Evaporation Route to BaSi2 Thin Films for Solar Cell Applications

The BaSi2 semiconductor has excellent optoelectronic properties for solar cell applications and consists of earth-abundant elements. In this study, we have investigated the thin film growth of BaSi2 by a simple vacuum evaporation technique. It is shown by X-ray diffraction that single-phase BaSi2 films can be formed at high substrate temperatures of 500 and 600 ˚C on either Si(111) or EAGLE XG glass substrate. The film growth mechanism is discussed on the basis of the transmission electron microscopy observation and energy-dispersive X-ray spectra of the film and the residue of evaporation source. It is concluded that high substrate temperatures are needed to remove excess Ba atoms and to eliminate a composition gradient. In addition, suitable optical properties for solar cell applications are revealed by analyzing the transmittance and reflectance spectra.