Characteristics and Functionality of Cantilevers and Scanners in Atomic Force Microscopy (original) (raw)
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Design and control of atomic force microscopes
Proceedings of the 2003 American Control Conference, 2003., 2003
Models for two atomic force microscope (AFM) designs were presented, namely, cantilever-on-scanner and sample-an-scanner design. It was found that coupling between scanner's bending and extension motion is present in both designs, making the scanner bending mode observable from the output. As a result, the ultimate feedback bandwidth is limited by the lowerfrequency bending mode in contrast to being ideally limited by the extension mode. Simulation and experimentaldata provided insight into pole-zero flipping and changes in the system dynamics as a function of force set-paint and input amplitude. Closed loop performance under integral and PID control were compared. It was found that PID control offers lower bandwidth over integral control if high-frequency rollloff and step response overshoot constraints were to be met. In addition, integral controller has a single gain compared 3 for PID; which makes it easier for parameter tuning by AFM users.
MODEL OF THE CANTILEVER USED AS A WEAK FORCE SENSOR IN ATOMIC FORCE MICROSCOPY
2005
New types of weak forces measurements with Atomic Force Microscope (AFM) are very challenging for experimental physics and call for new studies on control strategies operating the AFM. It is thus necessary to first develop a precise model of the cantilever with its sharp tip, in interaction with the scanned sample. This paper presents a model of the cantilever, that is based on beam theory and taking into account the influence of the long distance interaction forces.
A Compact Vertical Scanner for Atomic Force Microscopes
A compact vertical scanner for an atomic force microscope (AFM) is developed. The vertical scanner is designed to have no interference with the optical microscope for viewing the cantilever. The theoretical stiffness and resonance of the scanner are derived and verified via finite element analysis. An optimal design process that maximizes the resonance frequency is performed. To evaluate the scanner's performance, experiments are performed to evaluate the travel range, resonance frequency, and feedback noise level. In addition, an AFM image using the proposed vertical scanner is generated.
Imaging using lateral bending modes of atomic force microscope cantilevers
Applied Physics Letters, 2004
Interpreting atomic force microscopy measurements of hydrodynamic and surface forces with nonlinear parametric estimation Rev. Sci. Instrum. 83, 103702 Nonlinear multimode dynamics and internal resonances of the scan process in noncontacting atomic force microscopy J. Appl. Phys. 112, 074314 The importance of cantilever dynamics in the interpretation of Kelvin probe force microscopy J. Appl. Phys. 112, 064510 (2012) Analysis of the lateral resolution of electrostatic force gradient microscopy
Monitoring of an atomic force microscope cantilever with a compact disk pickup
Review of Scientific Instruments, 1999
In the present study we test a compact disk pickup as the cantilever position sensor in an atomic force microscope ͑AFM͒. The pickup is placed on top of the optical microscope used for the visual inspection and alignment of the specimen. The AFM is also equipped with its own cantilever movement sensor system. Both the built-in and the new detection devices are simultaneously active for comparison purposes. Two different measurements are performed in sequence on the same sample each using one sensor at a time as the error signal source for the AFM feedback loop. The pickup has demonstrated good sensitivity as well as excellent performance in terms of compactness, reliability, and cost.
Control and Systems Approaches to Atomic Force Microscopy
IFAC Proceedings Volumes, 2008
The atomic force microscope (AFM) and its derivative technologies have heralded a new era in science and technology. AFM and related instruments were primarily designed by physicists. In recent years there is a substantial presence of engineers with controls and systems background who are contributing to AFM related technologies. This article provides a tutorial on the control and systems approaches to AFM. This paper also delineates the impact controls and systems perspectives have on AFM related research and indicates future directions.
Design of an atomic force microscope and first results
Surface Science, 1987
We present a design of an atomic force microscope (AFM) which allows easy accessibility to the sample, the force sensing tip and lever, and the tunneling tip in order to study these components in detail. Force sensing tip and lever are made from one piece of a metallic glass with an integrated electrochemically etched tip. Measurements in air show a good reproducibility. Monatomic steps were resolved on highly oriented pyrolytic graphite (HOPG).
Atomic force microscopy is a convenient and exceptionally rich source of information about materials on the nano-scale. The instrument can be configured to operate in a large number of modes. The main task of AFM is to produce reliable and repeatable measurement of surface and intermolecular forces, which are needed for surface analysis and provide plentiful of information regarding other features of specimen. These diverse modes measure different atomic forces that are acting between apex and specimen surface and are used for producing topographical image of the sample with high molecular resolution. The force measurement is by way of cantilever deflection measures. The cantilever can be made by piezoelectric material, whereas it is a piezoelectric stage that moves the specimen with respect to the tip. The cantilever is affected by position, tip-sample separation, it’s material, and different forces. A beam of laser focused on the force sensing/imposing lever and reflected onto a sensitive detector which is position sensing photo diode PSPD. Due to high resolution and small contact areas there is no need of vacuum and problems due to contamination and roughness are minimized.