Crystal Structure Analysis of Metalorganic Chemical Vapor Deposition-β-FeSi₂ Thin Film by X-ray Diffraction Measurement

A crystal structure was analyzed for (101)- and (110)-oriented epitaxial β-FeSi₂ films grown on (111)Si substrate by using high-resolution X-ray diffraction (XRD). Three interaxial angles and three-lattice parameters of (101)- and (110)-oriented variants can be individually decided by selecting the appropriate diffraction peaks taking account of the peak intensity, resolution and the interval of the peak position between the film and Si substrate. By using this method, 200-nm-thick (101)/(110)-oriented β-FeSi₂ film grown on (111)Si substrate by metalorganic chemical vapor deposition (MOCVD) was analyzed. The interaxial angles of each (101)- and (110)-oriented variant were found to be almost 90° by using the inclination angle, psi, scan and the reciprocal space mapping measurement, a-, b- and c-axes lattice parameter combinations of (101)- and (110)oriented variants were (0.9893 nm, 0.7800 nm and 0.7821 nm), and (0.9893 nm, 0.7798 nm and 0.7824 nm), respectively, obtained from the selected diffraction peaks measurement, i.e., (406)/(460), (533) and (800) diffraction peaks. These results show that large strain did not remain in this film. Moreover, the volume fraction ratio of (101)- and (110)-oriented variants was estimated for the first time to be 45/55 from the peak fitting of (406) and (460) diffraction peaks.