STRUCTURE DETERMINATION OF DISORDERED METALLIC SUB-MONOLAYERS BY HELIUM SCATTERING - A THEORETICAL AND EXPERIMENTAL-STUDY

An approach based on He scattering is used to develop an atomic-level structural model for an epitaxially grown disordered submonolayer of A g on Pt(111) at 38 K. Quantum scattering calculations are used to fit structural models to the measured angular intensity distribution of He atoms scattered from this system. The structure obtained corresponds to narrowly size-dispersed compact clusters with a modest translationa l disorder, and not to fractals, which might be expected due to the lo w surface temperature. The clusters are up to two layers in height, th e lower one having only a few defects. The relations between specific features of the angular scattering distribution, and properties such a s the cluster sizes and shapes, the inter-cluster distance distributio n, etc, are discussed. The results demonstrate the usefulness of He sc attering as a tool for unraveling new complex surface phases. (C) 1998 Elsevier Science B.V. All rights reserved.