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，利用尖端尖端的软悬臂梁提供了优异的横向和垂直表面形貌分辨率。然而，为了探测固体表面的机械性能并获得关于亚表面界面和缺陷的信息，AFM悬臂需要更坚硬。人们可以通过在超声频率表面振动AFM悬臂来增加AFM的有效刚度，同时保持出色的横向分辨率和低直流或攻丝接触力。这项研究计划旨在研究超声原子力显微镜技术在薄膜材料性能和界面的无损、定量测量方面的潜力，更具体地说，用于电子互连结构和其他纳米级器件中亚表面缺陷的原位成像。拟议的创新研究计划有以下具体目标：(A)开发超声频率下AFM悬臂梁尖端与图案化表面和亚表面缺陷相互作用的理论模型；(B)开发将敲击模式成像与超声波AFM相结合的测量方法，以与样品具有可重复的、间歇的接触力，用于定量、现场测量；以及超声波AFM，以在纳米尺度向样品表面施加剪应力，以增强对界面缺陷的敏感性。此外，这些技术将应用于利用AFM悬臂梁的声辐射压力驱动的生物和化学应用的流体环境中。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计划做出长期贡献。从少数群体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。除了对纳米技术领域的学生进行动手培训外，还将与佐治亚理工学院的其他教职员工合作开发一门研究生级别的扫描探针显微镜课程。

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.