Collaborative Research: Programmable Metal-Assisted Chemical Etching for Three-Dimensional Functional Metamaterials

超材料是一种人工构造的材料，它表现出不寻常的、但有利的、在自然界中不易发现的电磁特性。特殊的性质产生于以周期性排列的复杂结构特征的区域。目前，光学超材料的制造主要是基于固有的二维图像化过程，而基于聚合物结构的三维光学超材料的展示有限。目前还没有直接制造三维晶体半导体基超材料的制造技术。该奖项探索了一种独特的可编程金属辅助化学蚀刻工艺，用于三维功能超材料的可扩展纳米制造。这种方法将克服目前基于功能超材料的集成光子学的障碍，从而实现对光的完全控制。多用途的制造方法和材料功能将不可避免地影响三维电子和光子学，组织工程和能量转换/存储的生产。通过吸引包括妇女和少数民族在内的学生参与这一新兴研究领域，颁奖活动将有助于确保他们在当今全球环境中的能力和领导力。针对高中教师、学生和公众的外展活动将提高认识，并为我们未来的劳动力做好准备，以拥抱新兴的美国纳米制造业。金属辅助化学蚀刻是一种基于各向异性溶液的蚀刻方法，它违背了湿法蚀刻的教科书定义。利用该技术，通过在半导体本体中雕刻图案金属模板来形成三维高纵横比半导体纳米结构。在受控条件下，蚀刻只发生在金属和半导体之间的界面上。结果，当底层半导体被侵蚀时，金属层下降或深入到半导体中。在这项研究中，随着蚀刻的进行，通过编程磁场来引导铁磁性金属催化剂的运动，并通过编程金属催化剂在Si或更高指数III-V半导体中刻蚀时的轨迹来形成任意三维曲线纳米结构。由于其与集成电路制造的兼容性，该方法可扩展到高需求功能光学超材料的大批量制造。在纳米制造和光子学方面的互补专业知识的合作努力，将为制造三维微纳米级半导体和金属介电结构的能力提供一个跨越式的进步，具有前所未有的形状和尺寸控制，以及新型功能光学和其他材料和设备的开发。

Metamaterials are artificially structured materials that exhibit unusual, but advantageous, electromagnetic properties not readily found in nature. The special properties arise from regions of complex structural features organized in a periodic arrangement. Currently, the fabrication of the optical metamaterials is largely based on intrinsic two-dimensional patterning processes, with limited demonstrations of three-dimensional optical metamaterials mostly based on polymer structures. There are no manufacturing techniques for direct fabrication of three-dimensional crystalline semiconductor-based metamaterials. This award explores a unique programmable metal-assisted chemical etching process for the scalable nano-manufacturing of three-dimensional functional metamaterials. Such an approach will overcome the current roadblocks towards integrated photonics based on functional metamaterials to enable complete control of light. The versatile fabrication methodology and materials functionalities will inevitably impact the production of three-dimensional electronics and photonics, tissue engineering, and energy conversion/storage. By engaging students including women and minorities in this emerging field of research, the award activities will help ensure their competence and leadership in today's global environment. Outreach activities targeting high school teachers, students, and the general public will raise awareness and prepare our future workforce to embrace the emerging US nano-manufacturing industry.Metal-assisted chemical etching is an anisotropic solution-based etching method that defies the textbook definition of wet etching. By this technique, three-dimensional high aspect-ratio semiconductor nanostructures are formed by engraving patterned metal template into the body of the semiconductor. Under controlled conditions, etching occurs only at the interface between the metal and the semiconductor. As a result, the metal layer descends or digs into the semiconductor as the underlying semiconductor is eroded. In this study, as etching proceeds, a magnetic field is programmed to guide the movement of ferromagnetic-metal catalyst and arbitrary three-dimensional curvilinear nanostructures are formed by programming the trajectory of the metal catalyst as it engraves into the body of Si or higher index III-V semiconductors. Because of its compatibility with integrated circuit manufacturing, this method is scalable for high-volume manufacturing of highly desired functional optical metamaterials. The collaborative effort with complementary expertise in nanofabrication and photonics, respectively, is positioned to provide a leap-ahead advance in capabilities for manufacturing three-dimensional micro- and nano-scale semiconductor and metallo-dielectric structures with unprecedented control of shape and dimensions, and for development of novel functional optical and other materials and devices.