Electronic Properties of Reduced-Dimensional, Supported Metals

*非技术摘要*纳米材料的电子性质与宏观材料的电子性质有很大的不同。电子的性质决定了几乎所有的物理、电子、磁和化学性质，随着材料尺寸的减小，电子的性质变得越来越“奇特”。这项研究将通过实验和理论来揭示金属行为背后的量子物理，因为金属的尺寸从三维宏观材料到具有纳米厚度的二维表面和薄膜，再到可以相当长但横截面只有纳米的一维纳米线。这些纳米级的金属结构将使用允许人们“转动”原子维度的方法来制造。通过逐个原子地调整“表面与体积比”，这个项目将调整潜在的电子结构和物理性质。利用最先进的实验技术，如扫描探针显微镜和基于同步加速器的光电子能谱，将对负载的纳米级金属的性质进行表征。这项研究的一个关键部分将是将实验观察到的纳米级金属的原子和电子性质与理论计算联系起来。这项研究有望增强我们对纳米尺度材料的基本理解，在纳米尺度上，“奇异”的电子相互作用使新一代新型电子、磁、光子和催化器件的发展成为可能。研究生和本科生都将参与这个项目。他们将获得知识和学习技能，使他们能够在学术和技术感兴趣的领域成为富有成效的研究人员。此外，研究人员将努力将科学的兴奋带给美国以其多样性及其重大的教育和经济挑战而闻名的美国地区的K-12儿童和普通民众。*技术摘要*该奖项支持对降维支撑金属的电子性质的实验和理论研究。基本的主题是了解空间大小、排列和尺寸在确定纳米金属材料随后的电子性质中所起的作用。这项研究将探索金属的基本物理(例如量子尺寸效应、多体效应、杂化)，因为金属的维度从块状到二维(表面/超薄膜)到一维(纳米线)到量子井/纳米阵列。该项目将调查在降维系统中有多少多体效应，回答有关费米液体理论崩溃的问题。该项目的一项关键举措将是生产与底层支持衬底(例如超薄氧化物)电子脱钩的降维金属系统，然后探索它们的性质。该项目涉及“自下而上”制造空间尺寸(尺寸和分离)到原子尺寸的金属。这些结构的生长、结构和形态将在原子尺度上进行表征。此外，还将通过高分辨率同步光电子能谱来探测金属的电子、磁性和化学性质。最后，实验结果将与全势能线性化增广平面波(FLAPW)和分子动力学(MD)理论计算相关联，以揭示受约束维度产生的新特征和不能简单地用带计算模型处理的新物理。这个项目将增加我们在纳米尺度上对金属的基本理解，在纳米尺度上，新颖的电子相互作用和动态响应可能会使新一代新型电子、磁、光子和催化器件的开发成为可能。通过参与该项目的研究活动，研究生和本科生都将接受纳米材料的生长和表征方面的培训。

**** NON-TECHNICAL ABSTRACT ****Electronic properties in nanoscale materials are quite different from those in macroscopic materials. The properties of electrons, which dictate nearly all physical, electronic, magnetic, and chemical properties, become more and more "exotic" as the size of the material decreases. This study will use both experiment and theory to reveal the quantum physics underlying the behavior of metals as their dimensions decrease from 3-D macroscopic materials to 2-D surfaces and thin-films that have nanometer thicknesses, to 1-D nanowires that can be quite long but have cross-sections of only nanometers. These nanoscale metal structures will be fabricated using approaches that allow one to "turn-the-knob" of atomic dimensionality. By adjusting the "surface-to-volume ratio" atom-by-atom this project will tune the underlying electronic structure and physical properties. Utilizing state-of-the-art experimental techniques, such as scanning probe microscopy and synchrotron-based photoelectron spectroscopy, the properties of supported nanoscale metals will be characterized. A key ingredient of this study will be to correlate experimentally observed atomic and electronic properties of supported nanoscale metals with theoretical calculations. This research is expected to enhance our basic understanding of materials with dimensions on the nanoscale, where "exotic" electron interactions allow the development of a new generation of novel electronic, magnetic, photonic, and catalytic devices. Both graduate and undergraduate students will be involved in this project. They will gain knowledge and learn skills that will enable them to become productive researchers in a field of academic and technological interest. In addition the researchers will endeavor to bring the excitement of science to both K-12 children and the general population in a region of the U.S. known for its diversity and its significant educational and economic challenges, the deep South.**** TECHNICAL ABSTRACT ****This award supports both experimental and theoretical investigations of electronic properties of reduced-dimensional, supported metals. The underlying theme is to understand the roles that spatial size, arrangement, and dimension play in establishing the ensuing electronic properties of nanophase metallic materials. This study will probe the underlying physics (e.g. quantum size effects, many body effects, hybridization) of metals as the dimensionality decreases from bulk to 2-D (surface/ultra thin-film) to 1-D (nanowire) to quantum well/nano-arrays. The project will investigate how many-body effects manifest themselves in reduced dimensional systems, answering questions concerning the breakdown of the Fermi Liquid Theory. A key initiative of this project will be to produce reduced-dimensional metal systems that are decoupled electronically from the underlying supporting substrate (e.g. ultra-thin oxides) and then probe their properties. The project involves "bottom-up" fabrication of metals with spatial dimensions (size and separation) down to the atomic size. The growth, structure, and morphology of these structures will be characterized on the atomic scale. Furthermore the electronic, magnetic, and chemical properties of the metals will be probed via high-resolution synchrotron photoelectron spectroscopy. Finally the experimental results will be correlated with Full Potential Linearized Augmented Plane Wave (FLAPW) and Molecular Dynamics (MD) theoretical calculations to reveal both the new features produced by the constrained dimensions and the new physics that cannot be simply addressed by band computational models. This project will increase our basic understanding of metals at the nanoscale, where novel electronic interactions and dynamic response may allow the development of a new generation of novel electronic, magnetic, photonic, and catalytic devices. From participation in the research activities of the project, both graduate and undergraduate students will be trained in the growth and characterization of nanoscale materials.