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.
