Surface diffusion limitation in laser focused atomic deposition

We have previously demonstrated that an optical standing wave can be used to focus a neutral atomic beam into a structure which is deposited on a substrate, under conditions that are compatible with molecular beam epitaxy. We have made structures in sodium with linewidths of δ ≈ 45 nm and contrast better than 10:1. Here, we observe that the condition of the surface prior to deposition is critical in producing these features. With certain surface conditions, apparently the mobility of the atoms on the surface reduces the contrast of the grating to approximately 1:1. We discuss the condition necessary during deposition to insure that the resolution of the deposited features is retained.