Materials World Network, SusChEM: Collaborative: Electron-Lattice Dynamics at an Atomically Controlled Buried Interface

技术摘要一项国际合作研究计划汇集了来自德国（马尔堡大学）、日本（国家材料科学研究所）和美国（匹兹堡大学和佛罗里达大学）的科学家，将研究GaP/Si埋层界面的结构和动力学性质之间的相关性，以便对这种材料进行基本的理解和实际应用。差距/Si界面是一种具有潜在应用的材料，对高效太阳能电池和硅光电子器件具有高度的可持续性影响。掩埋界面，激发态，光与非平衡电荷分布的相互作用代表了凝聚态物理实验和理论前沿的挑战。通过结合材料生长，结构表征，超快电子和声子光谱以及理论方面的专业知识，该团队将研究GaP/Si界面的结构和超快光电特性之间的关系。在两种电子材料之间的界面处的光学和电荷输运性质取决于它们之间的能带对准，以及界面的原子尺度结构，这些结构以微妙的方式难以通过实验和理论表征。该团队将采用相干声子光谱来研究界面电子和晶格子系统对带隙激发的超快响应。预计界面载流子分布和内建电场将对耦合载流子-晶格动力学产生重大影响。通过与组成材料（单晶Si和GaP）的动力学进行比较，该团队将确定可归因于界面存在的超快响应的组成部分。将研究在不同条件下生长的材料的界面响应，这些条件影响原子到纳米尺度上的材料组成和晶体结构。 通过光谱测量和理论模拟，研究小组将确定材料结构如何影响GaP/Si界面的光学和电子特性。材料生长和分析与超快光谱测量的紧密集成将使GaP/Si材料优化用于实际应用。实验方法将适用于广泛的技术上重要的电子材料的界面现象的研究。 学生将在与技术劳动力高度相关的领域接受培训，并将通过合作实验室之间的交流获得全球经验。非技术性摘要优化的电子材料能够有效地产生和利用能源，促进经济的持续发展。差距/Si界面具有在用于太阳能到电能转换的高效太阳能电池中应用的潜力，以及用于实现基于Si的电子器件内的光信号处理的潜力。然而，这种复合材料的功能取决于它们之间的界面。尽管GaP和Si的晶格的尺寸几乎相同，使得能够在Si上生长几乎无缺陷的GaP覆盖层，但是它们不同的离子和共价特征导致界面处的电子性质突然改变。因此，复合材料的光学和电学性质强烈地依赖于界面的原子尺度结构和组成。研究界面的结构和电子性质之间的关系是非常困难的，因为它需要能够生长具有特定特性的材料，将原子结构与生长参数相关联，表征结构和电子性质之间的关系，以及开发一个理论模型，可以关闭结构和功能研究之间的反馈。这是一个由来自德国（马尔堡大学）、日本（国家材料科学研究所）和美国（匹兹堡大学和佛罗里达大学）的科学家组成的合作团队，将研究基于特定材料生长差距/Si界面的结构-功能关系，通过电子显微镜进行结构表征，调查界面特定的电子结构和光学响应，以及理论。通过研究获得的方法和理解将适用于电子材料之间广泛界面的类似研究。 学生将在与技术劳动力高度相关的领域接受培训，并将通过合作实验室之间的交流获得全球经验。

Technical AbstractAn international collaborative research program bringing together scientists from Germany (Marburg University), Japan (National Institute for Materials Science) and the USA (Universities of Pittsburgh and Florida) will investigate the correlation between the structural and dynamical properties of GaP/Si buried interfaces in order to enable the fundamental understanding and practical applications of such materials. The GaP/Si interface is a material with potential applications having a high sustainability impact for high efficiency solar cells and silicon optoelectronics. Buried interfaces, excited states, and interaction of light with nonequilibrium charge distributions represent challenges at the forefront of condensed matter physics experiment and theory. By combining expertise in materials growth, structure characterization, ultrafast electronic and phonon spectroscopy, and theory, the team will investigate the relationship between the structural and ultrafast optoelectronic properties of GaP/Si interfaces. The optical and charge transport properties at an interface between two electronic materials depend on the band alignment between them, and the atomic scale structure of the interface in subtle ways that are difficult to characterize by experiment and theory. The team will employ coherent phonon spectroscopy to investigate the ultrafast response of the interfacial electronic and lattice subsystems to band gap excitation. It is expected that the interfacial carrier distributions and the built-in electric fields will substantially influence the coupled carrier-lattice dynamics. By comparison with the dynamics of the component materials (single crystal Si and GaP), the team will identify the components of the ultrafast response that can be attributed to the existence of the interface. The interface response will be investigated for materials grown under different conditions that influence the material composition and crystalline structure on the atomic to the nanometer scales. From the spectroscopic measurements and theoretical simulations the team will identify how the material structure affects the optical and electronic properties of GaP/Si interface. The tight integration of material growth and analysis, with ultrafast spectroscopic measurements will enable GaP/Si material optimization for practical applications. The experimental methodology will be applicable to studies of a broad range of interfacial phenomena of technologically important electronic materials. Students will be trained in an area highly relevant to the technical workforce and will gain global experience through the exchange among the partner laboratories. Non-technical Abstract Optimized electronic materials enable efficient generation and utilization of energy for continued economic development. The GaP/Si interface has the potential for applications in high efficiency solar cells for solar-to-electrical energy conversion, as well as for enabling optical signal processing within Si based electronic devices. The function of such composite materials, however, depends on the interface between them. Even though the dimensions of the crystalline lattices of GaP and Si are nearly identical, enabling growth of nearly defect free GaP overlayers on Si, their disparate ionic and covalent characters cause the electronic properties at the interface to change abruptly. Therefore, the optical and electronic properties of the composite materials strongly depend on the atomic scale structure and composition of the interface. Studying the relationship between the structure and electronic properties of interfaces is extremely difficult because it requires the ability to grow materials with particular characteristics, to correlate the atomic structure with the growth parameters, to characterize the relationship between the structure and electronic properties, as well as to develop a theoretical model for the interface that can close the feedback between the structural and functional investigations. This is a collaborative team involving scientists from Germany (Marburg University), Japan (National Institute for Materials Science) and the USA (Universities of Pittsburgh and Florida) that will study the structure-function relationship of the GaP/Si interface based on specific materials growth, structure characterization by electron microscopy, investigation of the interface-specific electronic structure and optical response, as well as theory. The methodology and understanding obtained through the study will be applicable to similar studies of a broad range of interfaces between electronic materials. Students will be trained in an area highly relevant to the technical workforce and will gain global experience through the exchange among the partner laboratories.