Anomalous low-temperature field evaporation and atomic relaxation of the tungsten surface

The anomalous low-temperature field evaporation of atomic complexes on the (211) face of single-crystal tungsten is investigated by the methods of fie ld ion microscopy. It is shown that as the size of the close-packed atomic islands decreases, the tangential rate of evaporation at 21 K increases by 2-3 orders of magnitude. The experimental results can be used to reveal and investigate atomic relaxation effects at steps on faces with low Miller in dices. A method is proposed for determining the subatomic displacements of atoms on the steps as the size of the islands decreases. The observed relax ation effects can be described in a consistent manner in a model of linearl y distributed surface forces. The observed size relaxation effect is treate d as a response to an increase in the energy of the elastic stresses as the diameter of the atomic islands decreases. (C) 2000 American Institute of P hysics. [S1063-777X(00)00912-9].