Aligned defects behaviour of β-FeSi2 thin film on Si(100) substrate prepared by ion beam sputter deposition

β-FeSi2 is one of the possible candidates for a compound semiconductor. Epitaxial β-FeSi2 films grown on a Si substrate are technologically important for microelectronic and silicon-based optoelectronic applications. In earlier studies, we clarified that the treatment of the Si substrate surface greatly influences the crystal structure of the film. Among several surface treatment procedures, it has been reported that the sputter etching (SE) of the substrate with subsequent thermal annealing is fairly effective in obtaining a film that has a favorable epitaxial orientation relationship of β-FeSi2(100)//Si(100) with atomically smooth interface by choosing better conditions. Even though the obtained films have good quality, anomalous patterns were sometime observed in the dark field image of the obtained film by cross-sectional TEM observation. They formed a horizontal line along the β-FeSi2/Si interface. Higher magnification image shows that these spots are aggregated defects. The 'lines' tend to appear in the samples, which are irradiated in higher energy. However, they are also occasionally observed in 1 keV Ne+ irradiated sample. It can be related to the diffusion process of the silicon atoms and the defects formed in the silicon through Ne+ irradiation. Formation behavior of these 'aligned' defects will be discussed in the present study.