High-quality single-crystal Si nanowires with diameters ranging from 10 to 200 nm have been successfully grown using Al catalyst via a vapor-liquid-solid mechanism. Critical issues such as the effects of surface oxidation of the Al seeding layer on the growth of Si nanowires and selective removal of metal catalyst after nanowire growth have been systematically studied. Results show that the growth of Si nanowire is strongly dependent on the surface oxidation of Al seeding layers. It is also found that metal-contamination-free Si nanowires can be achieved by selective etching of the remaining Al particles from nanowires, providing a Si nanowire as a complementary metal-oxide-semiconductor compatible building block for future nanoelectronics applications. (c) 2007 The Electrochemical Society.