Structure and Reactivity of Epitaxial Metal Films

该项目属于分析化学和表面化学的一般领域，以及薄膜结构和生长以及多相催化的子领域。研究了金属薄膜和金属合金薄膜的电子性能和结构的变化及其催化活性。薄膜将在金属和云母衬底上外延生长。利用低能电子衍射、俄歇电子能谱和氦散射对其生长方式和结构进行表征。要研究的化学反应包括一氧化碳的解离反应、氢分子与氘的原子交换反应以及碳氢化合物与氢原子的反应。分子束将被用来避免壁效应。利用金-钯合金薄膜研究系综效应，采用离子表面散射光谱法测定合金表层成分。这些薄膜催化研究的结果将提供在极低压力条件下大型金属单晶表面上的化学反应性与支撑金属晶体（特征直径为20- 100埃，通常用作商业催化剂）在高压条件下的反应性之间的相关性。维度对电子特性的影响将被评估。

This project is in the general area of analytical and surface chemistry and in the subfields of structure and growth of thin films and heterogeneous catalysis. Variation of the electronic properties and structure of thin metal and metal alloy films will be investigated and correlated with their catalytic activity. The films will be grown epitaxially on metal and mica substrates. Their growth mode and structure will be characterized by low energy electron diffraction, Auger electron spectroscopy and helium scattering. Chemical rections to be studied include the dissociation of carbon monoxide, atomic exchange reactions of molecular hydrogen and deuterium, and the reactions of hydrocarbons with atomic hydrogen. Molecular beams will be employed to avoid wall effects. Ensemble effects will be investigated using gold-palladium alloy films, employing ion surface scattering spectrometry to determine the alloy surface layer composition. The results of these catalytic studies with thin films will provide a correlation between chemical reactivity on large metal single-crystal surfaces under very low pressure conditions and reactivity on supported metal crystallites, with characteristic diameters 20- 100 Angstroms, of the type commonly employed as comercial catalysts under high pressure conditions. Effects of dimensionality on electronic properties will be assessed.