STM and TEM studies of a model catalyst: Pd/MoS2(0001)

Combined in situ scanning tunnelling microscopy (STM) and ex situ transmiss ion electron microscopy (TEM) experiments performed on the same samples hav e been used to characterize in detail a model catalyst: Pd/MoS2(0001). The Pd clusters were epitaxially grown under ultrahigh vacuum conditions by con densing a calibrated beam of atoms on a natural single crystal of MoS2 kept at high temperature (T = 220 degrees C). Atomic-resolution STM images of t he clean MoS2(0001) surface were found to vary with the tip to sample dista nce, in good agreement with the theoretical predictions of Altibelli et al. [Surf. Sci. 367 (1996) 209] for the origin of contrast in such images. TEM and STM investigations of the statistical properties of the Pd clusters (s patial and size distributions, epitaxial orientation) are shown to be coher ent and complementary. (C) 2000 Elsevier Science B.V. All rights reserved.