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][3][4][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 ] a metal catalyst is seeded onto the surface of a silicon substrate, and nanowires are grown by chemical vapor deposition (CVD) with a gas such as silane or silicon tetrachloride. The metal catalyst generally used is gold; [ 9 ] however other metals such as copper [10][11][12][13][14][15] have been utilized successfully.Many techniques have been demonstrated for seeding metal catalysts on silicon substrates. A standard method is to deposit a thin metal layer, typically nanometers thick, and heat the substrate until the fi lm dewets into droplets. However, on a smooth surface the positions of these droplets are random, and fi lm thickness gives only limited control over wire diameters. [ 16 ] To gain control over position of the droplets, an ordered array of pits on the substrate can be created with a combination of photolithography and potassium hydroxide etching (e.g., on a < 100 > silicon substrate). The periodic curvature of the metal fi lm guides the dewetting of the layer. [ 16 ] Photolithography can also be used with a lift-off procedure to pattern the metal catalyst. This has been demonstrated by Choi et al. [ 17 ] with gold droplets patterned into potassium hydroxide etched pits, and by Kayes et al. [ 18 ] with gold and copper islands separated by an oxide. For smaller feature sizes, nanoimprint or nanosphere lithography techniques are used. In nanoimprint lithography, e-beam lithography is used to create a stamp to pattern resist, and is followed by a lift-off procedure. [ 19 ] Nanosphere lithography, in which a metal (e.g., gold) is patterned by a layer of polystyrene nanospheres, has been shown to successfully create ordered arrays of nanowires in a hexagonal pattern with a gold catalyst. [ 20,21 ] Other techniques for metal catalyst seeding include electrodeposition of gold into an anodized alumina [ 9 , 22 ] or other oxide template, [ 23 ] using block...