Chemical Mechanisms of Inorganic Phototropic Growth

第1部分：非技术概述材料的受控图案化对于半导体集成电路制造、3D电子学、先进功能生物材料、光学材料和催化剂载体非常重要。在这个项目中，由材料研究部的固态和材料化学以及电子和光子材料计划共同支持，加州理工学院的内森·S·刘易斯教授试图发展和利用对无机光致生长的基本理解。在传统的光刻中，材料在有光的地方生长，而在光致生长中，材料朝着光源生长。通过操纵由普通灯泡或LED等简单光源提供的光束的波长、强度和偏振，无机光致生长可以自发产生复杂的、自组织的纳米级图案，可以实时地在三维方向上进行控制。这种科学研究是国家在材料研究、信息、光通信、纳米技术和化学传感方面的竞争力的基础。为了实现该项目的目标，Lewis Group正在探索表现出无机光致生长的材料范围，通过将光致反应扩展到材料的光致可控刻蚀来研究这种现象的普遍性，并利用光致生长来创造具有独特三维性能的材料。实验工作正在与建模和模拟相结合，以发展对无机光致生长的机理理解。这项研究将与加州理工大学领导的太阳能和材料发现推广计划相结合，特别是在全国高中层面使用的果汁和海豹计划动手科学模块，特别强调由代表性不足的群体和不同的学生群体组成的学区。第二部分：技术概述在这个项目中，加州理工大学的内森·S·刘易斯教授正在研究无机光致生长的机制，即在半导体的电沉积过程中，产生自发的、自组织的、沿偏振、非相干、均匀强度光束方向排列的介观结构。形貌是由半导体中电子过程的固有光学响应决定的，该响应由电沉积期间存在的光的可调特性(例如，波长、偏振和方向)所刺激。这个过程是自适应的：如果灯光被移动或以其他方式改变，随后的生长将适应改变的条件。到目前为止，这种现象只在非晶态或多晶硫化物和硫化物材料中得到了实验证明。这个项目将研究无机光致生长是否可以扩展到其他材料，以及晶格结构和光电性质如何影响无机光致生长的机制。这项工作还将通过研究不同电子性质的衬底上Se-Te合金的形核来研究衬底-电解液界面如何影响有序纳米结构的早期发展。此外，还将利用光致生长来设计和合成具有所需功能的复杂的三维结构材料，如具有定制光电性能的手性超材料和等离子体材料。实验观测将与开发一种机械模拟工具相结合，该工具将全波电磁计算与基于蒙特卡洛的质量增加相结合，以预测在任意光学输入下各种半导体的光致生长所产生的结构。该项目由材料研究部的固态和材料化学以及电子和光子材料计划共同支持。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Part 1: Non-Technical Summary Controlled patterning of materials is important for semiconductor integrated circuit fabrication, 3-D electronics, advanced functional biomaterials, optical materials, and catalyst supports. In this project, jointly supported by the Solid State and Materials Chemistry and Electronic and Photonic Materials Programs in the Division of Materials Research, Professor Nathan S. Lewis of the California Institute of Technology seeks to develop and exploit a fundamental understanding of inorganic phototropic growth. In conventional lithography, materials grow where light is present, whereas in phototropic growth, the materials grow toward the light source. By manipulating the wavelength, intensity, and polarization of the light beams provided by sources as simple as ordinary light bulbs or LEDs, inorganic phototropic growth can spontaneously produce complex, self-organized nanoscale patterns that can be controlled in three dimensions in real time. Such scientific research is foundational to national competitiveness in materials research, information, optical-communications, nanotechnology, and chemical-sensing. To meet the objective of this project, the Lewis Group is exploring the range of materials that exhibit inorganic phototropic growth, examining the generality of the phenomenon by expanding phototropic reactivity to light-induced controlled etching of materials, and using phototropic growth to create materials with unique three-dimensional properties. The experimental work is being integrated with modeling and simulation to develop a mechanistic understanding of inorganic phototropic growth. The research will be integrated with solar energy and materials-discovery outreach programs led by Caltech, specifically the Juice from Juice and Project SEAL hands-on science modules for use at the high-school level throughout the country, with special emphasis on school districts comprising underrepresented groups and diverse student populations. Part 2: Technical SummaryIn this project, Professor Nathan S. Lewis of the California Institute of Technology is examining the mechanisms underlying inorganic phototropic growth, i.e., the production of spontaneous, self-organized mesostructures aligned along the direction of a polarized, incoherent, uniform intensity light beam during electrodeposition of semiconductors. The morphologies are determined by the inherent optical response of the electronic processes within semiconductors stimulated by the tunable properties (e.g. wavelength, polarization, and direction) of the light present during the electrodeposition. The process is adaptive: if the light is moved or otherwise changed, subsequent growth adapts to the changed conditions. To date, this phenomenon has been demonstrated experimentally only for amorphous or polycrystalline chalcogen and chalcogenide materials. This project will investigate whether inorganic phototropic growth can be extended to other materials and how lattice structures and optoelectronic properties influence the mechanisms of inorganic phototropic growth. The work will also investigate how substrate-electrolyte interfaces affect the early-stage development of the ordered nanostructures by studying nucleation of Se-Te alloys on substrates with varied electronic properties. In addition, phototropic growth will be exploited to design and synthesize complex three-dimensionally structured materials with desired functionality, such as chiral metamaterials and plasmonic materials with tailored optoelectronic properties. The experimental observations will be used in conjunction with development of a mechanistic simulation tool that combines full-wave electromagnetic calculations with Monte-Carlo-based mass addition to predict the structures produced by phototropic growth of a variety of semiconductors under arbitrary optical inputs. This project is jointly supported by the Solid State and Materials Chemistry and Electronic and Photonic Materials Programs in the Division of Materials Research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.