Scaling during shadowing growth of isolated nanocolumns

We observed a scaling behavior during the shadowing growth of isolated Si, Co, Cu, and W nanocolumnar structures on Si substrates using the oblique angle deposition with substrate rotation (also known as glancing angle deposition or simply GLAD). The width of the isolated columns, W, grew as a function of column length, d, in a power law form, Wsimilar tod(p), where p is the growth exponent and was measured to be similar to0.28-0.34. It is argued that shadowing without diffusion should lead to p=0.50 and would cross over to 0.31 if one considers surface diffusion. It is of great interest to determine the mechanisms that would affect the value of p since it is an important factor that would control the shape, final size, and spacing of the isolated nanocolumns eventually produced.