Bandgap widening of β-FeSi2 deposited by RF-sputtering method using a Si-rich FeSi4 target

β-FeSi₂ films were deposited on silicon substrates by RF-sputtering method with a Si-rich FeSi₄ target and optical absorption properties of the films were investigated. Direct bandgap of the β-FeSi₂ films deposited using an FeSi₄ target was larger than that using an FeSi₃ target because Si crystals were formed in the films deposited using a Si-rich FeSi₄ target.