Seeding of silicon wire growth by out-diffused metal precipitates.

We propose the out-diffused metal precipitates (OMP) method to seed metal catalysts for bottom-up silicon wire growth. We fi rst in-diffuse the silicon substrate with a fastdiffusing metal (e.g., copper), and then anneal with a temperature profi le tuned to out-diffuse the metal to favorable nucleation sites on the surface. Vapor–liquid–solid (VLS) silicon wire growth on seeds from the OMP method is demonstrated. The OMP method has the potential to seed wires of any size at any position on a three-dimensional surface, in a high-throughput manner. Silicon nanowires and microwires have potential for applications in integrated circuits, [ 1 ] solar cells, [ 2–5 ] lithium batteries, [ 6 ] and biological sensors. [ 7 ] For example, Kelzenberg et al. [ 4 ] have demonstrated enhanced light absorption and decreased materials usage in solar cells fabricated from silicon microwire arrays, with distinct performance advantages over nanowire-based solar cells. A common bottom-up approach to synthesizing silicon wires is the VLS method, in which liquid metal droplets are used to catalyze crystalline wire growth. In the VLS method, fi rst proposed by Wagner, [ 8 ]