Cluster shapes in STM images of isolate clusters and cluster materials

The formation of cluster images in a scanning tunneling microscope (STM) has been modeled using isolate C-60 molecules deposited on top of crystalline monolayers of C-60 on Ge(100) and Si(100) containing vacancies. C-60 molecules occupy positions above vacancies and depending on the dimensions of the latter protrude to a different height above the surface. A simple model of the image formation is suggested and the variation of the shape of C60 molecules in STM images as a function of their apparent height is explained by the convolution of their images with that of the tip and by scattering of tunneling electrons on vacancies below C-60 molecules. (C) 2000 Elsevier Science B.V. All rights reserved.