Growth and characterization of β-FeSi2 thin films prepared by laser ablation method

Under ultra high vacuum, β-FeSi2 thin films were formed by laser ablation method using poly crystal β-FeSi2 as target material that was prepared by horizontal gradient freeze method. In order to compare the physical properties of thin films prepared by laser ablation with those of bulk crystal, β-FeSi2 single crystal was prepared by chemical vapor transport method. The β-FeSi2 plate-like and needle-like crystals were formed at 7 mg and 1 .0 g of iodine quantity, respectively. To check a crystal symmetry and orientation, Laue transmission patterns were taken. Anisotropic Raman signals were observed from polarized Raman scattering measurements. Further, electron spin resonance measurement was carried out to examine the residual impurities and to determine g values. From β-FeSi2 films during laser ablation growth, streaky signals were obtained in the RHEED observation. Highly oriented (202)/(220) β-FeSi2 films were predominantly identified in XRD measurements. Raman scattering and optical absorption measurements for these layers revealed that the grown samples are nearly epitaxially-like and have ∼0.85 eV as its direct optical band-gap.