Texture evolution in adsorbed monoatomic layers

The evolution of a monoatomic layer, deposited on a substrate, is described by a dynamical model of the reaction-diffusion type. This model takes into account the possible coexistence of two types of gains with different orientations with respect to the substrate. It combines reaction (adsorption and desorption) and nonlinear diffusion terms, which, close to the critical point of the order-disorder transition of the adsorbed layer, are of the Cahn–Hilliard type. At high temperatures, uniform grain distributions are expected to develop. At low temperatures, uniform grain distributions may become spatially unstable for sufficiently high adatom mobility. Nanoscale spatial patterns may then develop, which correspond to grain distributions, where grains with different orientations coexist. Links with atomistic simulations and experiments are discussed. It is argued that, for Al or Cu layers, deposited on substrates like TiN, Si2, Ta, etc., instability temperatures and critical wavelengths are well in the experimentally accessible range.