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Fabrication of semiconducting nanowires (NWs) using vapor-liquid-solid (VLS) growth is a promising alternative to the classical top down approach using micro- / nano-fabrication techniques. The growth of NWs in predefined locations and with predictable orientations is an important requirement for future integration. We have carried out an extensive study on the VLS growth of SiNWs on Si (111) oriented substrates. Arrays of individual seeds were patterned by electron beam lithography followed by Au evaporation and lift-off. SiNWs were grown using diluted silane as precursor gas at 4 Torr in a CVD reactor. The silane partial pressure, substrate temperature and seed diameter were systematically varied to obtain the growth rate of the SiNWs and the rate of sidewall deposition. Activation energies of 0.8 eV for the NW growth and 1.3 eV for the deposition on Si surface were extracted. In addition, experiments were conducted to investigate the influence of gas phase doping on the epitaxial growth of SiNW. Compared to NWs that are grown from a thin film nucleated substrate, the deterministic patterning of uniform diameter seeds allowed direct extraction of the nucleation yield of the SiNW which was close to 100%. The yield of vertically grown <111> NWs depends sensitively on partial pressure of the silane and less on the growth temperature. At 80mTorr partial pressure, up to 60 % of the NWs grow in the vertical <111> direction showing that the four possible <111> growth directions are not equivalent in the VLS nucleation process. This suggests that even higher vertical growth yields might be possible, for example by modifying the nucleation conditions. |