MRI: Development of an in-situ controlled Atomic Layer Deposition Tool (iCALD) for the Preparation of 3D Photonic Materials with Ultrahigh Aspect Ratios

光学材料由具有超高宽高比的三维结构和涂有超薄保形层的光学材料组成，使大量的有源和无源器件和组件能够在红外和太赫兹光谱范围内工作。这些材料的应用包括具有前所未有灵敏度的环境传感器和增强三维微光学结构的多功能涂层。提议的原位控制原子层沉积（iCALD）仪器将在北卡罗来纳大学夏洛特分校（UNC）开发，并集成在光电子和光通信中心的洁净室设施中，将使这些光学材料的制造成为可能。iCALD仪器能够实现几乎任意几何形状的保形涂层结构，这将改变现有洁净室设施合成和制造的材料、结构和光学器件的使用和范围。iCALD仪器将使来自北卡罗来纳大学夏洛特校区五个部门的40多名教职员工、他们的学生以及国内和国际合作者能够进行研究。此外，这一独特的仪器将供两个nsf资助的工业/大学合作研究中心（I/ ucrc），超材料中心和自由光学中心的研究使用。通过这些中心，iCALD的发展将为工业资助的研究项目带来新的机会，并直接使全国30多个工业合作伙伴受益。光学中心与两个I/ ucrc一起创造了一个环境，由于其研究成果商业化的潜力，以及对硕士和博士生的高级培训，开发的iCALD仪器将产生非常重大的影响。该项目旨在开发这种独特的iCALD仪器，用于合成三维光子材料。这种新型材料由超高宽高比的三维结构组成，涂有超薄的保形层。使用原子层沉积（ALD）技术为这种结构和表面制备保形涂层需要精确控制许多关键的ALD工艺参数，以确保超薄薄膜的质量、厚度和一致性。因此，必须使用非接触式原位测量技术获得的层厚度和合格信息来控制ALD工艺参数。iCALD仪器将允许现场监测和控制逐层沉积过程，通过使用创新的原位米勒矩阵椭偏仪在红外波长下工作。iCALD仪器将能够精确控制超薄涂层，具有亚纳米精度，沉积在特征尺寸为几百纳米的结构上。因此，iCALD仪器将允许以前所未有的精度制造新型红外和太赫兹光子材料。基于这些新颖的三维光子材料，可以制造出大量在红外和太赫兹光谱范围内工作的有源和无源器件和组件。此外，iCALD仪器将提供关于任意几何结构的逐层沉积的有价值的见解，这尚未得到实验证明。该项目开发的受控沉积和原位监测能力将进一步扩展对制造超高纵横比结构所需的原子层沉积过程的关键理解。该仪器有望显著改善三维光子材料的光学材料性能。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。

Optical materials composed of three-dimensional structures with ultra-high aspect ratios and coated with ultra-thin conformal layers enable a vast array of active and passive devices and components operating in the infrared and terahertz spectral range. Applications for these materials include environmental sensors with unprecedented sensitivity and multifunctional coatings to enhance three-dimensional micro-optical structures. The proposed in-situ controlled, atomic layer deposition (iCALD) instrument which will be developed at the University of North Carolina (UNC) at Charlotte and integrated in the cleanroom facility of the Center for Optoelectronics and Optical Communications will enable the fabrication of these optical materials. The ability to conformally coat structures with virtually arbitrary geometries enabled by the iCALD instrument will transform the use and scope of materials, structures, and optical devices, synthesized and fabricated using the existing cleanroom facilities. The iCALD instrument will enable research by over 40 faculty members from five departments across the UNC Charlotte campus, their students, and national and international collaborators. In addition, this unique instrument will be accessible for research organized in two NSF-funded Industry/University Cooperative Research Centers (I/UCRCs), the Center for Metamaterials and the Center for Freeform Optics. Through these Centers the iCALD development will lead to new opportunities for industry funded research projects and directly benefit more than 30 industry partners nationwide. The Optics Center together with the two I/UCRCs create an environment where the developed iCALD instrument will have a very significant impact due to its potential for commercialization of research results, along with enabling advanced training of MS and PhD students.The project aims to develop this unique iCALD instrument for the synthesis of three-dimensional photonic materials. This new class of materials is composed of three-dimensional structures with ultra-high aspect ratios, coated with ultra-thin conformal layers. The preparation of conformal coatings for such structures and surfaces using atomic layer deposition (ALD) techniques requires the precise control of numerous crucial ALD process parameters to ensure quality, thickness, and conformity of the ultra-thin films. It is therefore imperative to control the ALD process parameters using layer thickness and conformity information obtained from non-contact, in-situ, measurement techniques. The iCALD instrument will allow in-situ monitoring and control of the layer-by-layer deposition process by using an innovative in-situ Mueller matrix ellipsometer operating at infrared wavelengths. The iCALD instrument will enable the accurate control of ultra-thin coatings, with sub-nanometer accuracy, deposited onto structures with feature sizes on the order of several hundred nanometers. The iCALD instrument thereby will allow the fabrication of novel infrared and terahertz photonic materials with unprecedented accuracy. Based on these novel three-dimensional photonic materials, a vast array of active and passive devices and components operating in the infrared and terahertz spectral range can be made. In addition, the iCALD instrument will provide valuable insights about layer-by-layer deposition onto structures with arbitrary geometries, which have not been demonstrated experimentally yet. The controlled deposition and in-situ monitoring capabilities developed by this project will further expand crucial understanding of the atomic layer deposition process required for the fabrication of structures with ultra-high aspect ratios. Significant improvement of the optical material properties of three-dimensional photonic materials enabled by this instrument is anticipated.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.