Adsorption of cobalt phthalocyanine on Ag terminated Si(111)

We have investigated the adsorption of cobalt phthalocyanine on the Ag/Si(1 11)-(root 3 x root 3)R30 degrees surface using scanning tunnelling microsco py. The molecules are found to diffuse freely on the surface and form a hig hly ordered close-packed array as the coverage approaches a monolayer. A mo del for the ordering of the molecules on this surface is proposed based on images acquired for sample biases in the range - 1.5 V --> -1.6 V for which it is possible to image the surface through the molecular layer. (C) 1999 Elsevier Science B.V. All rights reserved.