Video-rate atomic force microscope for functional gas and liquid environments

Scanning Probe Microscopy (SPM) has contributed greatly to the advancement of science since the first atom-resolved image of silicon surface by scanning tunneling microscope in 1983. The high expectation since then has been that video-rate imaging by atomic force microscope (AFM) would usher in the next level of understanding in bio-molecular dynamics in cell membranes and molecular dynamics in heterogeneous catalysis along with applications in nanoscale metrology in nanotechnology industries. However, the current status of high speed AFM, and in particular liquid imaging, has lagged behind the forecasted time table. Molecular Vista, Inc. (MVI) in collaboration with the University of Utah (UU) will develop a high speed (~ 10 frames/second) atomic force microscope (HS AFM) for real-time in-situ characterization of electrochemical, photoelectrochemical, and fuel cell reactions. The goal is to develop a user-friendly, high resolution and ultrafast AFM for functional gas and liquid environment to support basic science. The proposed instrument is expected to have roughly a thousand-fold increase in throughput compared to typical commercially available systems with comparable scan range and resolution. In Phase I, MVI will develop an encapsulation for a unique force sensor called length extension resonantor (LER) for passivation against corrosive liquid while maintaining high quality factor (Q) in liquid a prerequisite for high sensitivity measurements in liquid. We will also prototype a high-bandwidth demodulation circuitry for high speed frequency modulation AFM (FM AFM), which will allow precise control of LER at high speeds. Our research institution partner, UU, will also prototype a high-speed sample scanner. Finally, we plan to demonstrate the feasibility of high speed imaging in air using the above prototypes. Phase II proposal will focus on (1) incorporation of HS scanner into an AFM head (as opposed to the sample scanner), (2) design of user-friendly LER housing, (3) integration of high-bandwidth electronics into SPM controller, (4) environmental chamber for gas/liquid imaging, (5) sample scanner with slow-z piezo for large samples such as silicon wafer, and (6) sample stage. The anticipated public benefit is estimated to be truly significant. As many manufacturing industries now fabricate products that are either nanoscale in size, utilize nanoscale ingredients, or nanoscale features are critical in its proper operation, the need for nanoscale metrology is greater than ever. A high speed AFM with self-sensing force sensor would enable affordable, automated, and easy-to-service tool for metrology applications ranging from examining surface finish of fabricated parts, reviewing defects on patterned, un-patterned silicon wafers, and photo masks, and measuring critical dimensions of nanoscale devices, which would significantly grow the SPM market size. Additionally, the ability to operate such an AFM in true noncontact FM-AFM mode in liquid should enable studies of biomolecule dynamics on cell membrane surfaces and provide invaluable insight to the discovery and evaluation of new and more effective drugs. Key Words: high speed atomic force microscopy, self-sensing force detector, environmental AFM Summary for Members of Congress: A video-rate imaging tool with molecular spatial resolution is needed for advancement of fundamental understanding in diverse scientific fields with great implications for high-tech industries. Molecular Vista, Inc. plans to develop a new sensor and the required platform to support such a sensor to produce such an imaging tool.