A comparative study of nanocrystalline silicon thin films grown on 25 nm thick catalyzing metals by dc magnetron sputtering from a highly doped Si target has been performed. In our previous study, the growth of Si was catalyzed by the silicide reactant from sputtered Si and Ni. These new experiments compared the effect of two types of catalyzing metals, Ni and Co. The structural and electrical characteristics of nano-Si were examined by scanning electron microscopy (SEM), cross-section SEM (XSEM), transmission electron microscopy (TEM), four-point-probe measurement and Schottky contact I-V measurement. The SEM and XSEM revealed that, for both catalyzing metals, the nano-Si thin films have columnar nano-grains with length of 500 nm in the vertical direction. However, the diameter of grains strongly depends on the catalyzing metals. For Co, the nano-Si grains had a typical diameter of 30 nm, while for Ni, the grains were much larger. TEM analysis showed that this difference in grain size begins at the initial growth stage. In the later-on growth, the Si grains mainly grow in a vertical direction instead of a lateral direction. This implies that the dimensions of Si nanostructures are strongly determined by the initially formed metal silicide nanoparticles. The current-voltage curve of a fabricated Al Schottky diode on P-type Co catalyzed nano-Si exhibited good rectifying characteristics. The dopant has been naturally synthesized in the Si nanocrystals during the growth of nano-Si by using a doped sputtering target. The above measured electrical properties show that metal induced grown nanocrystalline Si is applicable to various electronic and photonic devices.
