Characterization and optimization of scan speed for tapping-mode atomic force microscopy

Sulchek, Todd; Yaralioglu, G.G.; Quate, C. F.; Minne, S. C.

doi:10.1063/1.1488679

Cited by 135 publications

(111 citation statements)

References 15 publications

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“…Methods to actively control Q have previously been proposed 10,17 , although generally to increase, rather than decrease Q. These methods could be used to decrease the Q by a small amount 17,18 , which could provide a modest additional increase in the detection bandwidth in parallel with our approach.…”

mentioning

confidence: 88%

Harnessing the damping properties of materials for high-speed atomic force microscopy

et al. 2015

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The success of high-speed atomic force microscopy in imaging molecular motors 1 , enzymes 2 and microbes 3 in liquid environments suggests that the technique could be of significant value in a variety of areas of nanotechnology. However, the majority of atomic force microscopy experiments are performed in air, and the tapping-mode detection speed of current highspeed cantilevers is an order of magnitude lower in air than in liquids. Traditional approaches to increasing the imaging rate of atomic force microscopy have involved reducing the size of the cantilever 4,5 , but further reductions in size will require a fundamental change in the detection method of the microscope [6][7][8] . Here, we show that high-speed imaging in air can instead be achieved by changing the cantilever material. We use cantilevers fabricated from polymers, which can mimic the high damping environment of liquids. With this approach, SU-8 polymer cantilevers are developed that have an imaging-in-air detection bandwidth that is 19 times faster than those of conventional cantilevers of similar size, resonance frequency and spring constant.A primary research goal in atomic force microscopy (AFM) is to increase the imaging speed, improve its ease of use and expand its potential range of applications 9 . In the most widely used AFM mode (a.c. mode or tapping mode) the detection speed (mechanical bandwidth, BW) of the AFM cantilever fundamentally limits the imaging speed. The bandwidth is a measure of the maximum rate of topography change the cantilever can accurately detect. It is related to the cantilever resonance as BW ∝ f 0 /Q, where the cantilever resonance frequency f 0 is primarily determined by the cantilever mass and elastic modulus, and the quality factor Q is determined by the cantilever damping 10 . When the oscillating cantilever experiences a change in boundary condition (that is, topography), it requires several cycles to reach a new steady-state amplitude (Fig. 1a). A cantilever with higher resonance frequency runs through the required number of cycles more quickly, thereby enabling faster imaging (Fig. 1b). The number of required oscillatory cycles is determined by the damping of the cantilever, characterized by Q. A cantilever with low resonance frequency and low Q can therefore be equally as fast as a cantilever with high resonance frequency and high Q (compare Fig. 1b and c). From a detection bandwidth perspective, the ideal combination is a high resonance frequency and low quality factor (Fig. 1d).The development of current high-speed AFM (HS-AFM) technology was enabled by the miniaturization of silicon and silicon nitride (SiN) cantilevers to x-y dimensions below 10 µm (the approach taken in Fig. 1b), resulting in cantilevers with megahertz resonance frequencies 4,5 . Modelling and an improved understanding of cantilever behaviour in fluids has greatly benefited this geometric optimization. For nearly all cantilevers, viscous damping in the surrounding medium determines Q (ref. 11). In liquid, viscous damping yields Q ≈ 2...

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confidence: 88%

Harnessing the damping properties of materials for high-speed atomic force microscopy

et al. 2015

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“…Due to nonlinear interactions with the surface, the tip oscillation amplitude responds almost instantaneously to a step up in the surface (see the left side of Figure 23). However, when there is a step down in the surface height, the response time of the cantilever oscillation will be proportional to Q/ω o , where ω o is its resonant frequency (see the right side of Figure 23) [98]. The flywheel action (the Wile E. Coyote effect), also introduces a limitation on the imaging speed without imaging artifacts.…”

Section: Tip/ Cantilevermentioning

confidence: 99%

A Tutorial on the Mechanisms, Dynamics, and Control of Atomic Force Microscopes

Abramovitch

Andersson

Pao

et al. 2007

2007 American Control Conference

184

128

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Abstract-The Atomic Force Microscope (AFM) is one of the most versatile tools in nanotechnology. For control engineers this instrument is particularly interesting, since its ability to image the surface of a sample is entirely dependent upon the use of a feedback loop. This paper will present a tutorial on the control of AFMs. We take the reader on a walk around the control loop and discuss each of the individual technology components. The major imaging modes are described from a controls perspective and recent advances geared at increasing the performance of these microscopes are highlighted.

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“…In this report we show that excellent damping can be accomplished by a novel method of active vibration control of the z-actuators. Because the quality factor (Q) of the z-actuators' resonance is markedly reduced by this method, the response speed is greatly 5 enhanced. Although the phase delay is pronounced with this active damping, it can be compensated by means of an inverse transform function method.…”

Section: Introductionmentioning

confidence: 99%

“…To overcome the low 3 resonant frequency of conventional sample-stage scanners, Sulcheck et al used a cantilever with an integrated zinc oxide piezo actuator capable of deflecting itself to keep the tip-sample interaction force constant. [3][4][5] They achieved a feedback bandwidth (i.e., imaging bandwidth) of 38 kHz and a frame rate of ~4/sec. 3 However, the self-actuating cantilever inevitably becomes very stiff, and hence is inappropriate for the imaging of soft samples.…”

Section: Introductionmentioning

confidence: 99%

Active damping of the scanner for high-speed atomic force microscopy

Kodera¹,

Yamashita²,

Ando³

2005

Review of Scientific Instruments

173

119

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The scanner that moves the sample stage in three dimensions is a crucial device that limits the imaging rate of atomic force microscopy. This limitation derives mainly from the resonant vibrations of the scanner in the z-direction (the most frequent scanning direction). Resonance originates in the scanner's mechanical structure as well as in the z-piezo actuator itself. We previously demonstrated that the resonance originating in the structure can be minimized by a counter-balancing method. Here we report that the latter resonance from the actuator can be eliminated by a novel, active damping method, with the result the bandwidth of the z-scanner nearly reaches the first resonant frequency (150 kHz) of the z-piezo actuator.2

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Characterization and optimization of scan speed for tapping-mode atomic force microscopy

Cited by 135 publications

References 15 publications

Harnessing the damping properties of materials for high-speed atomic force microscopy

Harnessing the damping properties of materials for high-speed atomic force microscopy

A Tutorial on the Mechanisms, Dynamics, and Control of Atomic Force Microscopes

Active damping of the scanner for high-speed atomic force microscopy

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