Characterization of Probe Dynamic Behaviors in Critical Dimension Atomic Force Microscopy (original) (raw)
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Journal of Applied Physics, 2009
The mechanism of dynamic force modes has been successfully applied to many atomic force microscopy ͑AFM͒ applications, such as tapping mode and phase imaging. The high-order flexural vibration modes are recent advancement of AFM dynamic force modes. AFM optical lever detection sensitivity plays a major role in dynamic force modes because it determines the accuracy in mapping surface morphology, distinguishing various tip-surface interactions, and measuring the strength of the tip-surface interactions. In this work, we have analyzed optimization and calibration of the optical lever detection sensitivity for an AFM cantilever-tip ensemble vibrating in high-order flexural modes and simultaneously experiencing a wide range and variety of tip-sample interactions. It is found that the optimal detection sensitivity depends on the vibration mode, the ratio of the force constant of tip-sample interactions to the cantilever stiffness, as well as the incident laser spot size and its location on the cantilever. It is also found that the optimal detection sensitivity is less dependent on the strength of tip-sample interactions for high-order flexural modes relative to the fundamental mode, i.e., tapping mode. When the force constant of tip-sample interactions significantly exceeds the cantilever stiffness, the optimal detection sensitivity occurs only when the laser spot locates at a certain distance from the cantilever-tip end. Thus, in addition to the "globally optimized detection sensitivity," the "tip optimized detection sensitivity" is also determined. Finally, we have proposed a calibration method to determine the actual AFM detection sensitivity in high-order flexural vibration modes against the static end-load sensitivity that is obtained traditionally by measuring a force-distance curve on a hard substrate in the contact mode.
Dynamic Nanoimpedance Characterization of the Atomic Force Microscope Tip-Surface Contact
Microscopy and Microanalysis, 2014
Nanoimpedance measurements, using the dynamic impedance spectroscopy technique, were carried out during loading and unloading force of a probe on three kinds of materials of different resistivity. These materials were: gold, boron-doped diamond, and AISI 304 stainless steel. Changes of impedance spectra versus applied force were registered and differences in the tip-to-sample contact character on each material were revealed. To enable comparison between materials and phases, a new standardization method is proposed, which simulates conditions of initial contact.
Simulation of atomic force microscopy operation via three-dimensional finite element modelling
Nanotechnology, 2009
Numerical modelling of atomic force microscopy cantilever designs and experiments is presented with the aim of exploring friction mechanisms at the microscale. As a starting point for this work, comparisons between finite element (FE) models and previously reported mathematical models for stiffness calibration of cantilevers (beam and V-shaped) are presented and discrepancies highlighted. A colloid probe (comprising a plain cantilever on which a particle is adhered) model was developed, and its normal and shear interaction were investigated, exploring the response of the probe accounting for inevitable imperfections in its manufacture. The material properties of the cantilever had significant impact on both the normal response and the lateral response. The sensitivity of the mechanical response in both directions was explored and it was found to be higher in terms of normal rather than lateral sensitivity. In lateral measurements, generic response stages were identified, comprising a first stage of twisting, followed by lateral bending, and then slipping. This was present in the two cantilever types explored (beam and V-shaped). Additionally, a model was designed to explore the dynamic sensitivity by comparing the simulation of a hysteresis loop with a previously reported experiment, and the results show good agreement in the response pattern. The ability to simulate the scan over an inclined surface representing the flank of an asperity was also demonstrated.
Beilstein Journal of Nanotechnology, 2014
We present a theoretical framework for the dynamic calibration of the higher eigenmode parameters (stiffness and optical lever inverse responsivity) of a cantilever. The method is based on the tip–surface force reconstruction technique and does not require any prior knowledge of the eigenmode shape or the particular form of the tip–surface interaction. The calibration method proposed requires a single-point force measurement by using a multimodal drive and its accuracy is independent of the unknown physical amplitude of a higher eigenmode.
A method to provide rapid in situ determination of tip radius in dynamic atomic force microscopy
The Review of scientific instruments, 2012
We provide a method to characterize the tip radius of an atomic force microscopy in situ by monitoring the dynamics of the cantilever in ambient conditions. The key concept is that the value of free amplitude for which transitions from the attractive to repulsive force regimes are observed, strongly depends on the curvature of the tip. In practice, the smaller the value of free amplitude required to observe a transition, the sharper the tip. This general behavior is remarkably independent of the properties of the sample and cantilever characteristics and shows the strong dependence of the transitions on the tip radius. The main advantage of this method is rapid in situ characterization. Rapid in situ characterization enables one to continuously monitor the tip size during experiments. Further, we show how to reproducibly shape the tip from a given initial size to any chosen larger size. This approach combined with the in situ tip size monitoring enables quantitative comparison of ma...
Near-grazing dynamics in tapping-mode atomic-force microscopy
International Journal of Non-Linear Mechanics, 2007
In tapping-mode atomic force microscopy, nonlinear e¤ects due to large variations in the force …eld on the probe tip over very small length scales and the intermittency of contact may induce strong dynamical instabilities. In this paper, a discontinuity-mapping-based analysis is employed to investigate the destabilizing e¤ects of low-velocity contact on a lumped-mass model of an oscillating atomic-forcemicroscope cantilever tip interacting with a typical sample surface. As illustrated using two tip-sample force models, the analysis qualitatively captures the potential loss of stability and disappearance of a lowcontact-velocity steady-state response. The quantitative agreement of the predictions of the discontinuitymapping-based analysis with direct numerical simulations, at least for su¢ciently low-velocity contact, supports its use in the passive redesign or active control of the tip-sample mechanism for purposes of preventing such a loss of stability.
Applied Physics Letters, 2001
We present a mechanical model for the atomic force microscope tip tapping on a sample. The model treats the tip as a forced oscillator and the sample as an elastic material with adhesive properties. It is possible to transform the model into an electrical circuit, which offers a way of simulating the problem with an electrical circuit simulator. Also, the model predicts the energy dissipation during the tip-sample interaction. We briefly discuss the model and give some simulation results to promote an understanding of energy dissipation in a tapping mode.
Characterization of Intermittent Contact in Tapping-Mode Atomic Force Microscopy
Journal of Computational and Nonlinear Dynamics, 2005
Tapping-mode atomic force microscopy has wide applications for probing the nanoscale surface and subsurface properties of a variety of materials in a variety of environments. Strongly nonlinear effects due to large variations in the force field on the probe tip over very small length scales and the intermittency of contact with the sample, however, result in strong dynamical instabilities. These can result in a sudden loss of stability of low-contact-velocity oscillations of the atomic-force-microscope tip in favor of oscillations with high contact velocity, coexistence of stable oscillatory motions, and destructive, nonrepeatable, and unreliable characterization of the nanostructure. In this paper, dynamical systems tools for piecewise-smooth systems are employed to characterize the loss of stability and associated parameter-hysteresis phenomena.
Modal interactions in contact-mode atomic force microscopes
Nonlinear Dynamics, 2008
Atomic force microscopes (AFM) are used to estimate material and surface properties. When using contact-mode AFM, the specimen or the probe is excited near resonance of a natural frequency of the system to estimate the linear coefficient of contact stiffness. Because higher modes offer lower thermal noise, higher quality factors, and higher sensitivity to stiff samples, their use in this procedure is more desirable. However, these modes are candidates for internal resonances, where the energy being fed into one mode may be channeled to another mode. If such interactions are ignored, the results obtained from the probe may be distorted. The method of multiple scales is used to derive an approximate analytical expression to the probe response in the presence of two-to-one autoparametric resonance between the second and third modes. We examine characteristics of this solution in relation to a single-mode response and consider its implications in AFM measurements.