The Proximity effect on Semiconducting Mineral Surfaces

半导体矿物表面的邻近效应

• 批准号: 0309772
• 负责人: Udo Becker
• 金额: $ 16.7万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0309772&HistoricalAwards=false
• 关键词: Proximity; effect; Semiconducting; Mineral; Surfaces

AbstractThis project deals with a new type of reaction mechanism: the co-reaction of different species on semiconducting mineral surfaces or within a semiconducting mineral. Hereby, the reactants can be some distance apart from each other and, nonetheless, enhance or inhibit the interaction of the other reactant with the mineral. We first described this reaction mechanism, which we call the proximity effect, a year ago and have begun to evaluate the distance dependence between the reaction partners. In this project, a systematic study is proposed on such proximity effects, mainly on sulfides but also on some important reactions on oxides. The quantum mechanical evaluation of the reaction partners such as As/Au or Bi/Ag in galena and pyrite/arsenopyrite will help to understand previously described processes such as coupled substitutions and the preferred incorporation of gold into arsenopyrite and arsenian pyrite (compared with pyrite). Furthermore, the detailed description of surface diffusion processes will elucidate the mechanism of cluster or nanoparticle formation on sulfides surfaces or within the bulk. Understanding these processes is important to develop a consistent theory on the formation of gold and silver-containing ore deposits. Furthermore, the proximity effect may play an important role in the oxidation and weathering of sulfides and is, therefore, instrumental for the evaluation of environmentally important processes in acid mine drainage.In addition, environmentally and technically important reactions on oxides will be evaluated. It was previously observed that the electronic structure on hematite surface steps is significantly different from the valence band structure of flat surfaces. Therefore, the directed proximity effect will be examined along steps, which enhances electron transfer along steps on Fe2O3 surfaces and thus, the adsorption and oxidation of Mn at these steps. Furthermore, the combined attack of water and oxygen on different UO2 surfaces will be compared with the previously observed formation of oxidation patches on pyrite in light of the proximity effect. This effect helped resolve the complicated oxidation and weathering mechanism on a FeS2 (001) surface and may resolve the reaction path of uraninite corrosion, which is an unwanted effect in storing radioactive materials.Even though the proposed studies aim at a basic understanding of the proximity effect, it will have a broader impact on a wide variety of applications in environmental geochemistry, in the evaluation of ore deposits, in future options for metal extraction techniques, and for other technical applications such as the purification of drinking water using hematite as a filter material, or the evaluation of potential hazards due to the weathering of uranium oxide minerals. Due to the general character of these enhanced co-reactivity processes, the theory and findings can be applied to other fields such as physics, chemical engineering, materials science, and nuclear engineering. Early stages and planning of this project have already sparked collaborations across campus and with other universities. Finally, the new teaching program on minerals and materials surfaces at the University of Michigan can use these processes as a practical application of the interface of quantum mechanics of semiconductors and more classical approaches to mineral surface reactivity.

摘要该项目涉及一种新型的反应机制：不同物种在半导体矿物表面或半导体矿物内的共反应。 因此，反应物可以彼此相距一定距离，但是，增强或抑制了其他反应物与矿物质的相互作用。 我们首先描述了这种反应机制（我们称之为接近效应），并已开始评估反应伙伴之间的距离依赖性。 在该项目中，提出了有关此类接近效应的系统研究，主要是对硫化物的，但也针对氧化物的一些重要反应。 对galena和黄铁矿/砷氧铁矿中AS/AU或BI/AG等反应伙伴的量子机械评估将有助于理解先前描述的过程，例如耦合取代的过程，并优选将黄金掺入砷氧基和Arsenian Pyrite中（与黄铁矿相比）。 此外，表面扩散过程的详细描述将阐明硫化物表面或大块内的簇或纳米颗粒形成的机理。 了解这些过程对于发展有关含黄金和银矿床的形成的一致理论很重要。 此外，接近性效应可能在硫化物的氧化和风化中起重要作用，因此，将评估酸性矿山排水中环境重要过程的工具。此外，还将评估环境和技术上重要的对氧化物的反应。 先前观察到的是，赤铁矿表面台阶上的电子结构与平面的价带结构显着不同。 因此，将沿台阶检查定向的接近效应，从而增强电子沿Fe2O3表面的台阶的转移，从而在这些步骤上对MN的吸附和氧化。此外，根据接近效应，将水和氧对不同UO2表面的氧化斑块形成在黄铁矿上的氧化斑的形成。 这种效果有助于解决FES2（001）表面上的复杂氧化和风化机制，并可能解决铀矿腐蚀的反应路径，这在存储放射性材料方面是不必要的效果，即使该研究的旨在对邻近效应产生更广泛的影响，但在环境中的多种多样的范围内，它将在环境中的多种多样的影响，或者在环境中的范围更广泛地影响，或者在环境中的多种多样的影响，或者在环境中的各种序列，或者在环境地球上的范围内的影响，或者是在环境地球上的范围，或者是在环境中的范围。技术，以及其他技术应用，例如使用赤铁矿作为过滤器材料纯化饮用水，或者由于氧化铀矿物质的风化而对潜在危害进行评估。 由于这些增强的共反应过程的一般特征，理论和发现可以应用于其他领域，例如物理学，化学工程，材料科学和核工程。 该项目的早期阶段和计划已经引发了整个校园和其他大学的合作。 最后，密歇根大学的矿物质和材料表面的新教学计划可以使用这些过程作为半导体量子力学的界面的实际应用，以及对矿物表面反应性的更多经典方法。