EFFECTS OF AN ELECTRIC-FIELD IN ATOMIC MANIPULATIONS

Some recent scanning-tunneling-microscopy (STM) experiments on atomic-scale manipulation of material surfaces are explained in terms of high-temperature field evaporation, directional walks in an applied field gradient, and the formation of liquid-metal cone, etc. The evaporation fields for metals and the charge states of ions formed by an electric field in the STM configuration are shown to depend on the tip-to-sample distance. The possibility of field evaporating as negative ions is also considered. We find this possibility exists especially for alkali metals and adsorbed atoms of large electron affinity and noble gases. Favorable physical conditions for atomic manipulations are also discussed. In addition, a method for creating a thermally stable top surface layer with an atomic pattern of embedded foreign atoms of one's design, using electric-field manipulations and atomic replacement, is described.