Growth orientation of silicon (Si) nanowires is the key in tailoring the optical and electrical characteristics of semiconductor devices. To date, however, the distribution and dictator are still unclear. In this work, Si nanowires are grown via thermal annealing of nickel (Ni) coated Si wafers. The morphology, growth orientation and the relation to the seeding Ni catalyst particles are examined via high resolution transmission electron microscopy and selected area electron diffraction pattern. Statistical results show that Si nanowires prefer to be along the < 112 > orientation, followed by the ones in the < 110 >, < 111 >, < 001 >, < 113 > and < 133 > orientations. Besides surface energy that is commonly believed to control the nanowire's growth, this work found that the nanowire's growth Follows certain structure-sensitive principle at the wire/catalyst interface to minimize the mismatch in lattice spacing and dihedral angle. (C) 2014 Elsevier B.V. All rights reserved.