We investigated the formation mechanism of peculiar structures on vicinal Si(110) surfaces caused by annealing. The shapes of the peculiar structures strongly depended on the tilt angle of the vicinal surface from the exact Si(110) surface. The size of these structures varied with temperature and pressure during annealing. The dependence of the peculiar structure size on the annealing conditions can be explained by considering nucleation of the peculiar structures that is strongly related to Si surface diffusion during the annealing. (C) 2012 Elsevier B. V. All rights reserved.