Silicon nanowires catalyzed by Ti islands have been grown by molecular beam epitaxy using Si2H6 as the gas source and characterized by scanning electron microscopy, transmission electron microscopy, and in situ reflection high-energy electron diffraction. Two types of TiSi2 islands, one with a flat top and the other with a dome-shaped top, are formed after Ti is deposited on a Si (0 0 1) wafer and subsequently annealed. Only dome-like islands nucleate Si nanowires if the Ti deposition temperature is below 850degreesC. Some of the flat-top islands also nucleate Si nanowires if Ti is deposited at 930degreesC. The reason for the nucleation at the higher temperature is that the two types of islands have different orientation and the high deposition temperature may change the orientation of the flat-top islands. Most of the grown Si nanowires are kinked because of twinning. (C) 2002 Elsevier Science B.V. All rights reserved.