Growth of vertical epitaxial Si(100) nanowires on Si(100) substrates is demonstrated (see figure) using a combination of an anodic aluminum oxide template, catalytic An particles embedded in nanopores directly on the Si substrate by using electroless deposition, and vapor-liquid-solid growth using SiH4. HF acid treatment of the porous alumina template is important to realize a direct contact between deposited An in the AAO nanopores and the Si substrate.