Chemical Mechanisms of Inorganic Phototropic Growth

材料的受控图型对半导体集成电路制造、3-D电子学、高级功能生物材料、光学材料和催化剂支撑都很重要。在这个项目中，由材料研究部固态与材料化学和电子与光子材料项目共同支持，加州理工学院的内森·s·刘易斯教授试图开发和利用对无机光致生长的基本理解。在传统光刻中，材料生长在有光的地方，而在致光性生长中，材料生长在光源方向。通过操纵普通灯泡或led等简单光源提供的光束的波长、强度和偏振，无机光敏生长可以自发地产生复杂的、自组织的纳米级图案，这些图案可以在三维空间中实时控制。这些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等领域竞争力的基础。为了实现这个项目的目标，Lewis小组正在探索表现出无机致光性生长的材料范围，通过将致光性反应性扩展到光诱导受控蚀刻材料来研究这种现象的普遍性，并利用致光性生长来创造具有独特三维特性的材料。实验工作正在与建模和模拟相结合，以发展对无机光敏生长的机制理解。这项研究将与加州理工学院领导的太阳能和材料发现推广项目相结合，特别是在全国高中阶段使用的Juice from Juice和Project SEAL实践科学模块，特别强调由代表性不足的群体和不同学生群体组成的学区。在这个项目中，加州理工学院的Nathan S. Lewis教授正在研究无机致光性生长的机制，即在半导体电沉积过程中，自发、自组织的介孔结构沿着极化、非相干、均匀强度光束的方向排列。这些形貌是由电沉积过程中存在的光的可调谐特性（如波长、偏振和方向）所激发的半导体内电子过程的固有光学响应所决定的。这个过程是自适应的：如果光被移动或以其他方式改变，随后的生长适应变化的条件。到目前为止，这种现象只在实验中证明了非晶或多晶的硫和硫族材料。该项目将研究无机致光性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致光性生长的机制。该工作还将通过研究Se-Te合金在具有不同电子性质的衬底上的成核，来研究衬底-电解质界面如何影响有序纳米结构的早期发展。此外，光致生长将被用于设计和合成具有所需功能的复杂三维结构材料，例如具有定制光电特性的手性超材料和等离子体材料。实验观察结果将与机械模拟工具的开发相结合，该工具将全波电磁计算与蒙特卡罗质量加法相结合，以预测任意光输入下各种半导体的致光性生长所产生的结构。本项目由材料研究部固体与材料化学和电子与光子材料项目联合支持。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.