Ideal Scan Path for High-Speed Atomic Force Microscopy

2010

Abstract A spiral scanning method for high-speed Atomic Force Microscopy (AFM) is described in this paper. In this method, the sample is scanned in a spiral pattern instead of the conventional raster pattern. A spiral scan can be produced by applying single frequency cosine and sine signals with slowly varying amplitudes to the x axis and y axis of an AFM scanner respectively.

Measurement Science and Technology, 2020

In recent years, there has been growth in the development of high-speed AFMs, which offer the possibility of video rate scanning and long-range scanning over several hundred micrometres. However, until recently these instruments have been lacking full traceable metrology. In this paper traceable metrology, using optical interferometry, has been added to an open-loop contact-mode high-speed AFM to provide traceability both for short-range video rate images and large-area scans made using a combination of a high-speed dual-axis scanner and long-range positioning system. Using optical interferometry to determine stages’ positions and cantilever displacement enables the direct formation of images, obviating the need for complex post-processing corrections to compensate for lateral stage error. The application of metrology increases the spatial accuracy and linearisation of the high-speed AFM measurements, enabling the generation of very large traceable composite images.

Proceedings, 2005 IEEE/ASME International Conference on Advanced Intelligent Mechatronics., 2005

The atomic force microscope (AFM) is limited in imaging speed by the bandwidth and dynamic behavior of the actuators and mechanical parts. For high-speed imaging all AFM components have to be optimized in performance. Here, we present improvements of the force sensor, the scanner, the controller, and the data acquisition system. By combining all these improvements, the next generation AFMs will enable imaging speeds more than two orders of magnitude faster than current commercial AFM systems.

2006 American Control Conference, 2006

A new scanner design for a high-speed atomic force microscope (AFM) is presented and discussed in terms of modeling and control. The lowest resonance frequency of this scanner is above 22 kHz. The X and Y scan ranges are 13 micrometers and the Z range is 4.3 micrometers. The focus of this contribution is on the vertical positioning direction of the scanner, being the crucial axis of motion with the highest bandwidth and precision requirements for gentle imaging with the atomic force microscope. A mathematical model of the scanner dynamics is presented that will enable more accurate topography measurements with the high-speed AFM system.

2012

Tracking of triangular or sawtooth waveforms is a major difficulty for achieving high-speed operation in many scanning applications such as scanning probe microscopy. Such non-smooth waveforms contain high order harmonics of the scan frequency that can excite mechanical resonant modes of the positioning system, limiting the scan range and bandwidth. Hence, fast raster scanning often leads to image distortion. This paper proposes analysis and design methodologies for a nonlinear and smooth closed curve, known as Lissajous pattern, which allows much faster operations compared to the ordinary scan patterns. A simple closed-form measure is formulated for the image resolution of the Lissajous pattern. This enables us to systematically determine the scan parameters. Using internal model controllers (IMC), this non-raster scan method is implemented on a commercial atomic force microscope driven by a low resonance frequency positioning stage. To reduce the tracking errors due to actuator nonlinearities, higher order harmonic oscillators are included in the IMC controllers. This results in significant improvement compared to the traditional IMC method. It is shown that the proposed IMC controller achieves much better tracking performances compared to integral controllers when the noise rejection performances is a concern.

When compared to other common microscopy techniques (optical, SEM, TEM), the atomic force microscope's (AFM's) broad potential for nanoscale imaging and characterization of numerous physical surface properties has been somewhat offset by its slow imaging speed. 1 Thus, the AFM has sometimes been seen as a powerful " specialty tool " to use when other suitable techniques are not available. The AFM community has spent considerable effort over the last decade looking for ways to address the speed limitation of AFMs, and through this research many of the fundamental technological challenges have been addressed on an academic scale. 2-4 Driven by the researcher's quest for discovery, many of these efforts were aimed at improving the time-resolution of the AFM in order to view dynamic processes on the nanoscale; 2,5 while some also anticipated the need for the versatility and productivity of a fast general-purpose AFM. 3 Bruker's Dimension FastScan™ development t...

Review of Scientific Instruments, 2014

This paper demonstrates a high-speed spiral imaging technique for an atomic force microscope (AFM). As an alternative to traditional raster scanning, an approach of gradient pulsing using a spiral line is implemented and spirals are generated by applying single-frequency cosine and sine waves of slowly varying amplitudes to the X and Y-axes of the AFM's piezoelectric tube scanner (PTS). Due to these single-frequency sinusoidal input signals, the scanning process can be faster than that of conventional raster scanning. A linear quadratic Gaussian controller is designed to track the reference sinusoid and a vibration compensator is combined to damp the resonant mode of the PTS. An internal model of the reference sinusoidal signal is included in the plant model and an integrator for the system error is introduced in the proposed control scheme. As a result, the phase error between the input and output sinusoids from the X and Y-PTSs is reduced. The spirals produced have particularly narrowband frequency measures which change slowly over time, thereby making it possible for the scanner to achieve improved tracking and continuous high-speed scanning rather than being restricted to the back and forth motion of raster scanning. As part of the post-processing of the experimental data, a fifth-order Butterworth filter is used to filter noises in the signals emanating from the position sensors and a Gaussian image filter is used to filter the images. A comparison of images scanned using the proposed controller (spiral) and the AFM PI controller (raster) shows improvement in the scanning rate using the proposed method.

Mechatronics, 2008

A novel design of a scanning unit for atomic force microscopy (AFM) is presented that enables scanning speeds three orders of magnitude faster than compared to conventional AFMs. The new scanner is designed for high mechanical resonance frequencies, based on a new scanner design, which is optimized using finite element analysis. For high-speed scanning a new controller, based on input-shaping techniques, has been developed that reduces imaging artifacts due to the scanner's dynamics. The implementation of the new AFM system offers imaging capabilities of several thousand lines per second with a scanning range of 13 lm in both scanning directions, and the freedom to choose the fast scan-axis in any arbitrary direction in the X-Y-plane.

1998

An expandable system has been developed to operate multiple probes for the atomic force microscope in parallel at high speeds. The combined improvements from parallelism and enhanced tip speed in this system represent an increase in throughput by over two orders of magnitude. A modular cantilever design has been replicated to produce an array of 50 cantilevers with a 200 m pitch. This design contains a dedicated integrated sensor and integrated actuator where the cells can be repeated indefinitely. Electrical shielding within the array virtually eliminates coupling between the actuators and sensors. The reduced coupling simplifies the control electronics, facilitating the design of a computer system to automate the parallel high-speed arrays. This automated system has been applied to four cantilevers within the array of 50 cantilevers, with a 20 kHz bandwidth and a noise level of less than 50 Å. For typical samples, this bandwidth allows us to scan the probes at 4 mm/s.

Micro & Nano Letters, 2012

A systematic procedure for designing a high-speed, compact serial-kinematic X YZ scanner for atomic force microscopy is presented in this Letter. Analytical stiffness calculations are used to estimate the first natural frequency and travel range of the scanner. Design and characterisation of the scanner are presented. Results of finite-element analysis and experimentation on the scanner revealed natural frequencies of 10, 7.5 and 64 kHz for X, Y and Z stages, respectively. Maximum travel range of 8, 6 and 2 mm were measured along x, y and z directions. Performance evaluations were conducted by implementing the scanner in a commercial atomic force microscope. Images of a 6 × 4.5 mm area of a calibration grating were captured at line rates of 10, 50, 78, 100, 120 and 150 Hz with 256 × 256 pixel resolution. Limitations in design and suggestions for improvement of the scanner performance are discussed.

IEEE Access, 2019

The invention of the nanotechnology adds a new branch to investigate and control the physical properties of matters at atomic level. The aim of this technology is to image the characteristics of metals, biological organs, and polymers. Scanning probe microscopy (SPM) opens a new branch to analysis the atomic properties of the matters. Atomic force microscopy (AFM), a branch of SPM, is a versatile tool of nanotechnology to image both conductive and non-conductive matters with high resolution. Commercial AFM uses raster scanning technique to produce image of the matters that is responsible for low scanning speed and image quality. The performances of AFM are hampered due to low bandwidth of the scanning unit and vertical Proportional-Integral (PI) controller and may damage the surface of the samples. Different nonraster scanning techniques such as sinusoidal, rotational, spiral, cycloid, and lissajous scanning have been proposed to overcome the limitations of raster scanning method by providing high scanning speed, image quality, and resolution. This paper presents a survey of raster and non-raster scanning methods for high speed AFM and provides a compression between them in term of scanning speed, bandwidth and highest achievable scanning frequency. The control techniques applied to the AFM for improving raster, sinusoidal, spiral, cycloid, and lissajous scanning methods are studied in this paper to find most optimum scanning technique for AFM. INDEX TERMS Atomic force microscopy, raster scanning method, sinusoidal scanning method, rotational scanning method, spiral scanning method, cycloid scanning method, Lissajous scanning method, scanning speed, resolution.

2011

Abstract In recent years, the atomic force microscope (AFM) has become an important tool in nanotechnology research. It was first conceived to generate 3-D images of conducting as well as nonconducting surfaces with a high degree of accuracy. Presently, it is also being used in applications that involve manipulation of material surfaces at a nanoscale. In this paper, we describe a new scanning method for fast atomic force microscopy.

Small, 2013

The atomic force microscope (AFM) has become integrated into standard characterisation procedures in many different areas of research. Nonetheless, typical imaging rates of commercial microscopes are still very slow, much to the frustration of the user. Developments in instrumentation for "high-speed AFM" (HSAFM) have been ongoing since the 1990s, and now nanometer resolution imaging at video rate is readily achievable. Despite thorough investigation of samples of a biological nature, use of HSAFM instruments to image samples of interest to materials scientists, or to carry out AFM lithography, has been minimal. This review gives a summary of different approaches to and advances in the development of high-speed AFMs, highlights important discoveries made with new instruments, and briefl y discusses new possibilities for HSAFM in materials science.

Methods in Molecular Biology, 2018

The advent of high-speed atomic force microscopy (HS-AFM) in recent years has opened up new horizons for the study of structure, function and dynamics of biological molecules. HS-AFM is capable of 1000 times faster imaging than conventional AFM. This circumstance uniquely enables the observation of the dynamics of all the molecules present in the imaging area. In the last ten years, the HS-AFM has gone from a prototype-state technology that only a few labs in the world had access to (including ours) to an established commercialized technology that is present in tens of labs around the world. In this protocol chapter we share with the readers our practical know-how on high resolution HS-AFM imaging.

Review of Scientific Instruments, 2009

A large scan area high-speed scan stage for atomic force microscopy using the resonant oscillation of a quartz bar has been constructed. The sample scanner can be used for high-speed imaging in both air and liquid environments. The well-defined time-position response of the scan stage due to the use of resonance allows highly linearized images to be obtained with a scan size up to 37.5 m in 0.7 s. The scanner is demonstrated for imaging highly topographic silicon test samples and a semicrystalline polymer undergoing crystallization in air, while images of a polymer and a living bacteria, S. aureus, are obtained in liquid.