Surface diffusion of water on clean and Au-covered tungsten field emitter tips

Field emission microscopy measurements of the diffusion of Theta greater th an or equal to 1 water doses, deposited on a thermally clean and gold preco vered (Theta(Au) = 2.5 and 4) tungsten emitter, are presented. In the tempe rature range 118-127 K, the diffusion proceeded with a sharp boundary and t he activation energy ranging from 28 to 38 kJ/mol, depending on the Au cove rage and the crystallographic direction. The average value of 30 kJ/mol was determined for diffusion on the Au (Theta(Au) = 2.5) precovered emitter. T he computer processing of the field emission patterns was applied to elabor ate the observations of the diffusion with a sharp boundary. (C) 1999 Elsev ier Science Ltd. All rights reserved.