The use of field-ion microscopy (FIM) in conjunction with techniques for simulating FIM images shows promise as a method for studying the orientation, shape and structure of supported metal clusters in the nanometer-size range. Comparison of actual FIM images of MECS synthesized gold clusters with simulated images shows evidence that unannealed MECS clusters have an icosahedral structure in the 2 nm size range. This agrees with the results of a previous TEM study [22] and demonstrates the utility of the FIM method. Further studies utilizing this technique can investigate the structure, orientation and shape of a wide variety of clusters of different sizes and composition as a function of growth conditions and annealing temperature before deposition. Furthermore, the technique is one of the few that may impose an experimental constraint on the detailed predictions commonly obtained from molecular dynamic simulations of cluster structure.
ACKNOWLEDGMENTS
This work was partially funded by the National Science Foundation under contract 9522248-CTS. The authors would also like to thank Dilip Paithankar for providing the coordinates of atoms in the clusters and Thomas Castro for helpful discussions during the initial phase of this work.