CAREER: Quantitative Ultrasonic Atomic Force Microscopy of Thin Films and Subsurface Interfaces

原子力显微镜（AFM）已经成为纳米科学和纳米技术不可缺少的工具，它使用带有尖锐尖端的软悬臂梁提供了出色的横向和垂直表面形貌分辨率。然而，为了探测固体表面的力学性能并获得有关亚表面界面和缺陷的信息，AFM悬臂梁需要更硬。人们可以通过在超声频率表面振动AFM悬臂梁来增加AFM的有效刚度，同时在低直流电或轻叩接触力下保持出色的横向分辨率。本研究计划旨在研究超声AFM技术在薄膜材料特性和界面的非破坏性定量测量方面的潜力，更具体地说，是在电子互连结构和其他纳米级器件的亚表面缺陷的原位成像方面的潜力。提出的创新研究计划有以下具体目标：(a)发展超声频率下原子力显微镜悬臂尖端与图案表面和亚表面缺陷相互作用的理论模型；(b)发展将攻丝模式成像与超声原子力显微镜相结合的测量方法，从而与样品产生可重复的、间歇性的接触力，用于定量的原位测量；以及在纳米尺度上对样品表面施加剪切应力的超声原子力显微镜，以增强对界面缺陷的灵敏度。此外，这些技术将应用于流体环境，用于生物和化学应用，使用声辐射压力驱动AFM悬臂梁。教育发展计划的重点是通过指导参与的研究生和本科生、支持高中生科学项目和K-12教育工作者，为当地K-12教育机构和佐治亚理工学院之间的伙伴关系项目做出长期贡献。从少数民族和代表性不足的群体中挑选的本科生研究助理将参与研究项目，以及来自不同学科的研究生。除了在纳米技术领域对学生进行实际培训外，还将与佐治亚理工学院的其他教员合作开发一门关于扫描探针显微镜的研究生课程。

The atomic force microscope (AFM) has become an indispensable tool for nanoscience and nanotechnology providing excellent lateral and vertical surface topography resolution non-destructively using soft cantilevers with sharp tips. To probe the mechanical properties of solid surfaces and obtain information about subsurface interfaces and defects, however, the AFM cantilever needs to be stiffer. One can increase the effective stiffness of the AFM by vibrating the AFM cantilever at ultrasonic frequencies surfaces while maintaining the outstanding lateral resolution with low DC or tapping contact force. This research proposal aims to investigate the potential of ultrasonic AFM techniques for non-destructive, quantitative measurements of thin film material properties and interfaces, and more specifically, for in-situ imaging of subsurface defects in electronic interconnect structures and other nanoscale devices. The proposed innovative research plan has the following specific aims: (a) Development of theoretical models of the interactions of the AFM cantilever tip and patterned surfaces and subsurface defects at ultrasonic frequencies, (b) Development of measurement methods combining tapping mode imaging with ultrasonic AFM to have repeatable, intermittent contact force with the samples for quantitative, in-situ measurements, and an ultrasonic AFM to apply shear stresses to the sample surface at the nanoscale for enhanced sensitivity to interface defects. Furthermore, these techniques will be applied in fluidic environments for biological and chemical applications using acoustic radiation pressure actuation of AFM cantilevers. The educational development plan is focused on long-term contributions to the partnership programs between the local K-12 education institutions and Georgia Tech through mentoring of participating graduate and undergraduate students, supporting high school student science projects, and K-12 educators. Undergraduate research assistants selected from minorities and underrepresented groups will be involved in the research project as well as graduate students from different disciplines. In addition to hands on training of students in the nanotechnology area, a graduate level course on Scanning Probe Microscopy will be developed in collaboration with other faculty members at Georgia Tech.