Digitally tunable, wide-band amplitude, phase, and frequency detection for atomic-resolution scanning force microscopy

Khan, Zahid; Leung, Carl; Tahir, Bilal; Hoogenboom, Bart W.

doi:10.1063/1.3458009

Cited by 14 publications

(5 citation statements)

References 27 publications

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“…Further details of the setup can be found elsewhere. 23,[26][27][28] Commercially available AFM cantilevers were used (Nanosensors PPP-NCH) for imaging in tapping mode in air as well as in FM mode in water, and triangular silicon nitride cantilevers (Bruker AFM Probes-MLCT) were used for imaging in contact mode and for force spectroscopy under water. Contact-mode force spectroscopy data were analyzed and averaged in Matlab.…”

Section: Experimental Methodsmentioning

confidence: 99%

Resolving the structure of a model hydrophobic surface: DODAB monolayers on mica

et al. 2012

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The properties and interactions of hydrophobic surfaces in water are determining factors in a wide range of industrial applications, and represent a fundamental scientific problem that is far from solved. Langmuir-Blodgett (LB) lipid monolayers have often been used as model hydrophobic surfaces, but are only metastable, which compromises the interpretation of experiments. Using frequency-modulation atomic force microscopy (FM-AFM), we find that LB-deposited monolayers of dioctadecyldimethylammonium bromide (DODAB) on mica undergo two transitions upon immersion in water: (i) a rapid molecular rearrangement from a complete monolayer coverage to a more densely packed monolayer with holes exposing the mica substrate, followed by; (ii) a gradual flipping of lipids in the monolayer to form bilayers, at a timescale of many days, orders of magnitudes slower than previously reported. The (meta)stability of the monolayer shows little dependence on the deposition pressure (5-25 mN m 21 ), but strongly depends on the cleanliness of the preparation and, in AFM experiments, is reduced from days to minutes when the force applied by the AFM tip is not kept to well below 1 nN. When properly prepared and analysed, the DODAB/mica surface thus yields a well-defined structure of sufficient stability to study intersurface forces, albeit with a heterogeneity that gives rise to very distinct forces above the bare mica on one hand, and on the monolayer and bilayer areas on the other.

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Section: Experimental Methodsmentioning

confidence: 99%

Resolving the structure of a model hydrophobic surface: DODAB monolayers on mica

et al. 2012

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“…Therefore, it is an ongoing interest in AFM to improve the bandwidth of beam deflection sensors. 9,10 In this article, we report on a new, low noise, high bandwidth quadrant photodiode deflection sensor based on translinear bipolar junction transistors (BJT) capable of detecting signals in excess of 20 MHz.…”

Section: Introductionmentioning

confidence: 99%

A high frequency sensor for optical beam deflection atomic force microscopy

Enning

Ziegler

Nievergelt

et al. 2011

Review of Scientific Instruments

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We demonstrate a novel electronic readout for quadrant photodiode based optical beam deflection setups. In our readout, the signals used to calculate the deflections remain as currents, instead of undergoing an immediate conversion to voltages. Bipolar current mirrors are used to perform all mathematical operations at the transistor level, including the signal normalizing division. This method has numerous advantages, leading to significantly simpler designs that avoid large voltage swings and parasitic capacitances. The bandwidth of our readout is solely limited by the capacitance of the quadrant photodiode junctions, making the effective bandwidth a function of the intensity of photocurrents and thus the applied power of the beam deflection laser. Using commercially available components and laser intensities of 1-4 mW we achieved a 3 dB bandwidth of 20 MHz with deflection sensitivities of up to 0.5-1 V/nm and deflection noise levels below 4.5 fm/Hz. Atomic resolution imaging of muscovite mica using FM-AFM in water demonstrates the sensitivity of this novel readout.

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“…PLL is the most common method to detect the resonance frequency of TF. Various home-build and commercial versions are available [18][19][20]. The circuit presented in figure 1 is a modified version of the hybrid analogy digital PLL reported earlier [17], which consists of two parts: the basic circuit to provide normal PLL functions and the extra one to generate the phase shifted output.…”

Section: Methodsmentioning

confidence: 99%

Calibrating conservative and dissipative response of electrically-driven quartz tuning forks

Hao

Wang

Peng

et al. 2016

Preprint

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Determining sensor parameters is a prerequisite for quantitative force measurement. Here we report a direct, high-precision calibration method for quartz tuning fork(TF) sensors that are popular in the field of nanomechanical measurement. In the method, conservative and dissipative forces with controlled amplitudes are applied to one prong of TF directly to mimic the tip-sample interaction, and the responses of the sensor are measured at the same time to extract sensor parameters. The method, for the first time, allows force gradient and damping coefficient which correspond to the conservative and dissipative interactions to be measured simultaneously. The calibration result shows surprisingly that, unlike cantilevers, the frequency shift for TFs depends on both the conservative and dissipative forces, which may be ascribed to the complex dynamics. The effectiveness of the method is testified by force spectrum measurement with a calibrated TF. The method is generic for all kinds of sensors used for non-contact atomic force microscopy(NC-AFM) and is an important improvement for quantitative nanomechanical measurement.

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Digitally tunable, wide-band amplitude, phase, and frequency detection for atomic-resolution scanning force microscopy

Cited by 14 publications

References 27 publications

Resolving the structure of a model hydrophobic surface: DODAB monolayers on mica

Resolving the structure of a model hydrophobic surface: DODAB monolayers on mica

A high frequency sensor for optical beam deflection atomic force microscopy

Calibrating conservative and dissipative response of electrically-driven quartz tuning forks

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