NEW PHENOMENA IN HOMOEPITAXIAL GROWTH OF METALS

The growth of Pt(111) by Pt vapour deposition is studied by He diffraction as a function of substrate temperature and deposition rate. At a deposition rate of about 2.5 x 10(-2) monolayers/second several growth modes are observed: layer-by-layer (2D-) growth at 450 K less-than-or-similar-to T(s) less-than-or-similar-to 800 K, multilayer (3D-) growth at 340 K less-than-or-similar-to T(s) less-than-or-similar-to 450 K and reentrant layer-by-layer (2D-) growth at T(s) less-than-or-similar-to 340 K. The observed growth modes and in particular the reentrant 2D-growth are shown to be characteristic of growing Pt(111) under clean conditions, i.e. not influenced by contaminants. The influence of the intra- and interlayer mass transport on the growth mode is discussed in the light of experimental and simulation results. The 3D-growth mode is attributed to the existence of an activation barrier which suppresses the descent of adatoms from the top of the growing adatom islands onto the lower terraces. The barrier can be overcome by thermal adatoms at T(s) greater-than-or-similar-to 450 K enabling interlayer mass transport which leads to 2D-growth. The reentrant 2D-growth occurs due to a break down of this barrier for small, irregularly shaped islands.