The characteristic length study of Si spirals during growth

The growing transition of Si spirals by glancing angle deposition on the nanosphere-array substrate is investigated via the three-dimensional Kinetic Monte Carlo technique, based on the fine diamond lattice structure. We employed the pitch as the characteristic length to indicate the spiral growth during substrate rotation, and analyzed its dependencies on rotational speed and deposition rate. We found that the spiral arms broaden with increasing height during film growth, and the diameter of intrinsic structure can be obtained by fitting the growth exponent. Spirals or screw-like geometries will be formed under a slow substrate rotation, with a larger-than-diameter pitch. Once the pitch is comparable to the diameter at a very rotational speed, the spiral structure will degenerate into pillars. The critical rotational speed is predicted according to this numerical relation, and the competition mechanism between the lateral growth and the vertical growth is also proposed.