This Small Business Innovation Research Phase I project will demonstrate the feasibility of using MOSFET-embedded cantilevers for integrated electronic detection of cantilever deflection for scanning near-field ultrasound holography (SNFUH). This synergistic combination of the scanning probe microscopy (SPM) platform and scanning near-field ultrasound holography will provide nanoscale lateral spatial resolution, and has the potential for comparable depth resolution. The performance of SNFUH has been constrained by its implementation as part of a conventional single-cantilever SPM platform, where the low frequency response (~600 kHz) optical detector limited achievable depth resolution and throughput. We propose to overcome this major limitation to the conventional SPM platform by developing an all-electronic feedback approach to enable parallel scanning and high resolution SNFUH imaging. The core of the proposed work lies in the "out-of-the-box" innovation of an all-electronic MOSFET-embedded microcantilever that can be fabricated by standard semiconductor techniques. Our preliminary design has shown excellent sensitivity and a usable bandwidth of ~100MHz. This Phase I work will demonstrate the feasibility of high throughput sub-surface scanning. Phase II research will focus on developing a parallel array of MOSFET-embedded microcantilevers.
The broader impact/commercial potential of this project will be the development of a nanoscale imaging tool which will be immediately applicable in the semiconductor industry for failure analysis and process development, and which will find utility in probing the interactions of engineered nanomaterials in biological systems. The tool will combine the ultrahigh spatial resolution of a near field technique (atomic force microscopy or AFM) with the ability to image defects inside optically dense materials (both soft and hard) using ultrasound, non-destructively and in a conceptually simple fashion. The project efforts will lead directly to the development of a highly parallel array of MOSFET-embedded cantilever probes coupled with all-electronic feedback control for high-resolution and high-throughput SNFUH sub-surface imaging. Furthermore, the method of integrated electronic detection which we will develop will also find application in existing AFM platforms, lowering their cost and simplifying their use.
