An Integrated Magnetic Actuation System for High-Speed Atomic Force Microscopy

High-speed atomic force microscopy enables in situ studies of dynamic phenomena at the nanometer-scale. This paper presents the design, fabrication, and evaluation of an integrated magnetic actuation system for high-speed atomic force microscopy. The proposed system consists of a microcantilever probe with an attached permanent magnet particle and a microactuator for generation of magnetic field. Novel geometries are proposed for the probe, the magnetic particle, and the actuator that together result in a high bandwidth and adequate actuation gain. A lumped parameter model is developed for the probe's dynamics and employed to optimize its design. Subsequently the integrated actuation system has been fabricated and evaluated. The actuator has been shown to generate actuation fields as high as 216 G with associated temperature rise of less than 8 degrees C. The probe has been evaluated to have an Eigen-frequency of 104 kHz with an actuation gain of 1 nm/G in air. Characterization of the probe in water reveals the reduction in Eigen-frequency to be merely 23%, which is nearly 3-fold less than that of a conventional probe. Finally, the developed actuation system has been employed to perform high-speed dynamic mode imaging of a grating inside aqueous medium at various imaging rates up to 1.25 frames/s

Design and Evaluation of Torsional Probes for Multifrequency Atomic Force Microscopy

Multifrequency atomic force microscopy is a powerful nanoscale imaging and characterization technique that involves excitation of the atomic force microscope (AFM) probe and measurement of its response at multiple frequencies. This paper reports the design, fabrication, and evaluation of AFM probes with a specified set of torsional eigen-frequencies that facilitate enhancement of sensitivity in multifrequency AFM. A general approach is proposed to design the probes, which includes the design of their generic geometry, adoption of a simple lumped-parameter model, guidelines for determination of the initial dimensions, and an iterative scheme to obtain a probe with the specified eigen-frequencies. The proposed approach is employed to design a harmonic probe wherein the second and the third eigen-frequencies are the corresponding harmonics of the first eigen-frequency. The probe is subsequently fabricated and evaluated. The experimentally evaluated eigen-frequencies and associated mode shapes are shown to closely match the theoretical results. Finally, a simulation study is performed to demonstrate significant improvements in sensitivity to the second-and the third-harmonic spectral components of the tip-sample interaction force with the harmonic probe compared to that of a conventional probe

Design and Evaluation of Flexural Harmonic Probes for Multifrequency Atomic Force Microscopy

Multifrequency atomic force microscopy involves excitation of the cantilever probe and measurement of its response at multiple frequencies. This enables performing simultaneous material characterization and topography estimation. This paper reports the design, fabrication and evaluation of micro-cantilever probes with specified flexural eigen-frequencies. These frequencies are chosen to enhance the sensitivity to tip-sample forces in multifrequency atomic force microscopy. The probe's design involves choosing a suitable nominal geometry, development of a lumped parameter model for its flexural dynamics and iteratively tuning the dimensions so that the targeted eigen-frequencies are obtained. Using this approach, a cantilever probe having flexural eigen-frequencies in the ratio 1:2 is designed. A prototype of the designed probe has been fabricated and evaluated. The experimentally evaluated eigen-frequencies match the target frequencies by 99.7%

A high speed X-Y nanopositioner with integrated optical motion sensing

High speed in-plane (X-Y) nanopositioners are of central importance in scanning probe microscopy for performing fast imaging and manipulation. Reducing the size of the nanopositioning stage improves the response speed of the positioner but also introduces challenges in integration of conventional motion sensors. This paper presents the design and development of a novel high speed flexure-guided, piezo-electrically actuated nanopositioner with integrated optical beam deflection-based motion sensing. The sensing strategy eliminates spatial constraints even for small stages. A simple lumped-parameter model is proposed for the nanopositioner. Subsequently, the model is used to design and fabricate the nanopositioner. The measurement system is integrated with the nanopositioning stage and is employed to characterize the quasi-static and dynamic response of the stage. Finally, the in-plane motion measurements are employed to control the stage when it is commanded to track both slow- and fast-varying position signals. In both cases, the use of control is shown to significantly improve the tracking accuracy. © 2019 Author(s)

Direct Measurement of Three-Dimensional Forces in Atomic Force Microscopy

Direct measurement of three-dimensional (3-D) forces between an atomic force microscope (AFM) probe and the sample benefits diverse applications of AFM, including force spectroscopy, nanometrology, and manipulation. This paper presents the design and evaluation of a measurement system, wherein the deflection of the AFM probe is obtained at two points to enable direct measurement of all the three components of 3-D tip-sample forces in real time. The optimal locations for measurement of deflection on the probe are derived for a conventional AFM probe. Further, a new optimal geometry is proposed for the probe that enables measurement of 3-D forces with identical sensitivity and nearly identical resolution along all three axes. Subsequently, the designed measurement system and the optimized AFM probe are both fabricated and evaluated. The evaluation demonstrates accurate measurement of tip-sample forces with minimal cross-sensitivities. Finally, the real-time measurement system is employed as part of a feedback control system to regulate the normal component of the interaction force, and to perform force-controlled scribing of a groove on the surface of polymethyl methacrylate

A two-axis in-plane motion measurement system based on optical beam deflection

Measurement of in-plane motion with high resolution and large bandwidth enables model-identification and real-time control of motion-stages. This paper presents an optical beam deflection based system for measurement of in-plane motion of both macro- and micro-scale motion stages. A curved reflector is integrated with the motion stage to achieve sensitivity to in-plane translational motion along two axes. Under optimal settings, the measurement system is shown to theoretically achieve sub-angstrom measurement resolution over a bandwidth in excess of 1 kHz and negligible cross-sensitivity to linear motion. Subsequently, the proposed technique is experimentally demonstrated by measuring the in-plane motion of a piezo flexure stage and a scanning probe microcantilever. For the former case, reflective spherical balls of different radii are employed to measure the in-plane motion and the measured sensitivities are shown to agree with theoretical values, on average, to within 8.3%. For the latter case, a prototype polydimethylsiloxane micro-reflector is integrated with the microcantilever. The measured in-plane motion of the microcantilever probe is used to identify nonlinearities and the transient dynamics of the piezo-stage upon which the probe is mounted. These are subsequently compensated by means of feedback control. (C) 2013 AIP Publishing LLC

Note: Design and development of an integrated three-dimensional scanner for atomic force microscopy

A compact scanning head for the Atomic Force Microscope (AFM) greatly enhances the portability of AFM and facilitates easy integration with other tools. This paper reports the design and development of a three-dimensional (3D) scanner integrated into an AFM micro-probe. The scanner is realized by means of a novel design for the AFM probe along with a magnetic actuation system. The integrated scanner, the actuation system, and their associated mechanical mounts are fabricated and evaluated. The experimentally calibrated actuation ranges are shown to be over 1 mu m along all the three axes. (c) 2013 AIP Publishing LLC