Scanning tunneling microscopy studies of metal clusters supported on TiO2 (110):: Morphology and electronic structure

被引:234
作者
Lai, X [1 ]
St Clair, TP [1 ]
Valden, M [1 ]
Goodman, DW [1 ]
机构
[1] Texas A&M Univ, Dept Chem, College Stn, TX 77842 USA
关键词
D O I
10.1016/S0079-6816(98)00034-3
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
A brief review of our laboratory's recent scanning tunneling microscopy (STM) studies on nanoclusters supported on TiO2(110) is presented. Particular emphasis is placed on the system Au/TiO2(110). The nucleation and growth of the clusters, which were vapor-deposited on TiO2(110) under ultra high vacuum (UHV) conditions, were investigated using STM. It was found that Au, Pd, and Ag clusters all grow in a three-dimensional (3D) (Volmer-Weber) fashion on TiO2(110), but that at low coverages, quasi-two dimensional (quasi-2D) Au and Pd clusters were observed. These quasi-2D clusters are characterized by heights of 1-2 atomic layers. Annealing studies show that Au and Pd clusters form large microcrystals with well-defined hexagonal shapes. Al clusters, which have a strong interaction with the substrate, are oxidized upon deposition, "wetting" the surface and forming small clusters. In addition to the topographic studies, the local electronic properties of these clusters have been studied using scanning tunneling spectroscopy (STS) to measure the cluster band gaps. The electronic structure was found to be cluster size-dependent, as seen by the appearance of a band gap as the cluster size decreased. More specifically, the onset of cluster metallic properties correlates with the transition from quasi-2D to 3D cluster growth.
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页码:25 / 52
页数:28
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