Si/Fe flux ratio influence on growth and physical properties of polycrystalline β-FeSi2 thin films on Si(100) surface

[摘要] This work investigates the Si/Fe flux ratio (2 and 0.34) influence on the growth of beta-FeSi2 polycrystalline thin films on Si(100) substrate at 630 degrees C. Lattice deformations for the films obtained are confirmed by X-ray diffraction analysis (XRD). The volume unit cell deviation from that of beta-FeSi2 single crystal are 1.99% and 1.1% for Si/Fe = 2 and Si/Fe = 0.34, respectively. Absorption measurements show that the indirect transition (similar to 0.704 eV) of the Si/Fe = 0.34 sample changes to the direct transition with a bandgap value of similar to 0.816 eV for the sample prepared at Si/Fe = 2. The absorption spectrum of the Si/Fe = 0.34 sample exhibits an additional peak located below the bandgap energy value with the absorption maximum of similar to 0.36 eV. Surface magneto-optic Kerr effect (SMOKE) measurements detect the ferromagnetic behavior of the beta-FeSi2 polycrystalline films grown at Si/Fe = 0.34 at T = 10 K, but no ferromagnetism was observed in the samples grown at Si/Fe = 2. Theoretical calculations refute that the cell deformation can cause the emergence of magnetization and argue that the origin of the ferromagnetism, as well as the lower absorption peak, is beta-FeSi2 stoichiometry deviations. Raman spectroscopy measurements evidence that the film obtained at Si/Fe flux ratio equal to 0.34 has the better crystallinity than the Si/Fe = 2 sample.

[发布日期] 2017-10-15

[效力级别]  Proceedings Paper

[关键词] beta-FeSi2 iron disilicide;Optical properties;Reflection high-energy electron diffraction;Raman spectroscopy;ab initio calculation