Strain in b-FeSi2 modulated by Ge segregation in solid-phase growth of [a-Si/a-FeSiGe]n stacked structure

Solid-phase growth of the [a-Si/a-FeSiGe]n (n: 1, 2, 4; total thickness: 500 nm) stacked structure has been investigated. After annealing at 700 8C, the [a-SiGe/b-FeSi2(Ge)]n stacked structures were formed. From the analysis of the X-ray diffraction spectra, it was found that b-FeSi2(Ge) was strained by 0.4–0.5% for n ¼ 1. With increasing n, the strains decreased, which was due to segregation of Ge atoms from the a-FeSiGe layers to the a-Si layers. After annealing at 800 8C, agglomeration of b-FeSi2 occurred and Ge atoms vanished completely from the b-FeSi2 lattice. Thus, nanocrystals of relaxed b-FeSi2 and c-Si0.7Ge0.3 were formed. These new structures can be useful for formation of opto-electrical devices.