Based on scanning tunneling microscopy observations, we have investigated the formation and self-stabilization of Ge nanowires on Si(1 1 3) during Ge deposition. Under zero Ge flux, we observed a shape transition from nanowires to dot-like islands by annealing at 430degreesC, which is a favorable temperature for nanowire formation during deposition. The nanowires are, therefore, metastable and are formed Under a kinetically limited growth condition. We find that the strain of the nanowire is relaxed anisotropically. During growth the nanowire shape is effectively self-stabilizing. which leads to elongated growth of the islands. (C) 2002 Elsevier Science B.V. All rights reserved.