Atomic contact potential variations of Si(111)-7 × 7 analyzed by Kelvin probe force microscopy

Kawai, Shigeki; Glatzel, Thilo; Hug, H. J.; Meyer, Ernst

doi:10.1088/0957-4484/21/24/245704

Cited by 47 publications

(34 citation statements)

References 57 publications

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“…We evaluated the SNR for each scheme using practi- Figure 2 shows plots of the SNR for each method as a function of oscillation amplitude of the flexural mode used for tip-sample distance regulation. SNRs for the conventional schemes were consistent to a similar analysis recently published by Kawai et al [8]. Assuming that a typical oscillation amplitude in FM-AFM using the first flexural mode is 10 nm, and that 1 nm is typical of 2nd-FM-AFM, we can compare SNRs of the conventional schemes at an oscillation amplitude of 10 nm and SA-KFM schemes at 1 nm, as indicated by the arrows in Fig.…”

Section: Kfm Using Small Oscillation Amplitude Fm-afm In the Secosupporting

confidence: 88%

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Highly Sensitive Electrostatic Force Detection Using Small Amplitude Frequency-Modulation Atomic Force Microscopy in the Second Flexural Mode

Nishi

Hosokawa

Kobayashi

et al. 2011

e-J. Surf. Sci. Nanotechnol.

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We propose a novel scheme of highly sensitive electrostatic force detection using a small oscillation amplitude of a cantilever in the second flexural mode of frequency-modulation atomic force microscopy, which is useful for Kelvinprobe force microscopy (KFM) and electrostatic force microscopy (EFM). In this novel scheme, the cantilever is mechanically oscillated at the second flexural resonance frequency with a small oscillation amplitude, while the electrostatic force detection is carried out at the first flexural resonance frequency. Because of the reduced average tip-sample distance and the low spring constant and high quality factor of the first flexural mode, the sensitivity for electrostatic force detection becomes very high. We calculated signal-to-noise ratios (SNRs) for the proposed scheme and conventional schemes, and found that the SNR of the proposed scheme is higher than that of conventional schemes. We also performed KFM/EFM measurements using the proposed and conventional schemes on metal phthalocyanine thin films.

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Section: Kfm Using Small Oscillation Amplitude Fm-afm In the Secosupporting

confidence: 88%

“…In this scheme, both electrostatic force detection and tip-sample distance regulation are carried out in the first flexural mode (1st-FM-KFM). Both schemes are sensitive enough to achieve atomic resolution in surface potential images [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Highly Sensitive Electrostatic Force Detection Using Small Amplitude Frequency-Modulation Atomic Force Microscopy in the Second Flexural Mode

Nishi

Hosokawa

Kobayashi

et al. 2011

e-J. Surf. Sci. Nanotechnol.

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“…5 and 11, C ′ would be larger if the cantilever area is larger whereas C ′′ would be unaffected, whereas both quantities would be larger if the cone angle is broader or if the sample is a metal rather than an insulator, but C ′′ would be more strongly affected. On the other hand a and a ′ would be larger if the tip apex is charged 43 rather than neutral, or if the sample is a semiconductor with a reconstructed surface which exposes partially charged species like Si(111) 7×7 16,30 . From this point of view the system studied here is especially challenging.…”

Section: Discussion and Experimental Limitationsmentioning

confidence: 99%

“…An analogous procedure could be applied to determine a and C ′ from the AM-KPFM signal F ω , then a itself by inversion, using suitably modified algorithms 77,78 . Because the AM-KPFM signal/ratio is much superior if the modulation frequency f is at the second cantilever resonance 30 , ∆V AM LCP D could be determined more accurately even if it is smaller than in FM-KPFM. In any case, note that the slope a reflects variations of the electrostatic potential outside the sample surface which are, however, locally enhanced by the proximity of the tip apex.…”

Section: Discussionmentioning

confidence: 99%

Multiscale approach for simulations of Kelvin probe force microscopy with atomic resolution

et al. 2012

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The distance dependence and atomic-scale contrast recently observed in nominal contact potential difference (CPD) signals simultaneously recorded by KPFM using non-contact atomic force microscopy (NCAFM) on defect-free surfaces of insulating, as well as semiconducting samples, have stimulated theoretical attempts to explain such effects. Especially in the case of insulators, it is not quite clear how the applied bias voltage affects electrostatic forces acting on the atomic scale. We attack this problem in two steps. First, the electrostatics of the macroscopic tip-cantilever-sample system is treated by a finite-difference method on an adjustable nonuniform mesh. Then the resulting electric field under the tip apex is inserted into a series of atomistic wavelet-based density functional theory (DFT) calculations. Results are shown for a realistic neutral but reactive silicon nano-scale tip interacting with a NaCl(001) sample. Bias-dependent forces and resulting atomic displacements are computed to within an unprecedented accuracy.Theoretical expressions for amplitude modulation (AM) and frequency modulation (FM) KPFM signals and for the corresponding local contact potential differences (LCPD) are obtained by combining the macroscopic and atomistic contributions to the electrostatic force component generated at the voltage modulation frequency, and evaluated for several tip oscillation amplitudes A up to 10 nm. For A = 0.1Å, the computed LCPD contrast is proportional to the slope of the atomistic force versus bias in the AM mode and to its derivative with respect to the tip-sample separation in the FM mode. Being essentially constant over a few Volts, this slope is the basic quantity which determines variations of the atomic-scale LCPD contrast. Already above A = 1Å, the LCPD contrasts in both modes exhibit almost the same spatial dependence as the slope. In the AM mode, this contrast is approximately proportional to A −1/2 , but remains much weaker than the contrast in the FM mode, which drops somewhat faster as A is increased. These trends are a consequence of the macroscopic contributions to the KPFM signal, which are stronger in the AM-mode and especially important if the sample is an insulator even at sub-nanometer separations where atomic-scale contrast appears.

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“…While in most cases, the probe tip is scanned in vacuum or in air, KPFM instrumentation has recently been extended for operation in media like water, 3,4 hexane, 5 and other liquids. 6,7 KPFM signal generation has been investigated for a large number of systems, 2,[7][8][9] including the contrast on different sample facets 10 and on metallic nanostructures 11,12 as well as at the atomic [13][14][15][16][17] and even submolecular 18,19 scale. Recently, a very general electrostatic model from Kantorovich et al 20 has been used in several case studies [21][22][23] to derive analytical expressions for the closed-loop amplitude modulation (AM)-KPFM and frequency modulation (FM-)KPFM signals measured for charged systems.…”

Section: Introductionmentioning

confidence: 99%

The weight function for charges—A rigorous theoretical concept for Kelvin probe force microscopy

Söngen

Rahe

Bechstein

et al. 2016

Journal of Applied Physics

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A comprehensive discussion of the physical origins of Kelvin probe force microscopy (KPFM) signals for charged systems is given. We extend the existing descriptions by including the openloop operation mode, which is relevant when performing KPFM in electrolyte solutions. We define the contribution of charges to the KPFM signal by a weight function, which depends on the electric potential and on the capacitance of the tip-sample system. We analyze the sign as well as the lateral decay of this weight function for different sample types, namely, conductive samples as well as dielectric samples with permittivities both larger and smaller than the permittivity of the surrounding medium. Depending on the surrounding medium the sign of the weight function can be positive or negative, which can lead to a contrast inversion for single charges. We furthermore demonstrate that the KPFM signal on thick dielectric samples can scale with the sample size-rendering quantitative statements regarding the charge density challenging. Thus, knowledge on the weight function for charges is crucial for qualitative as well as quantitative statements regarding charges beneath the tip. V C 2016 AIP Publishing LLC.

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Atomic contact potential variations of Si(111)-7 × 7 analyzed by Kelvin probe force microscopy

Cited by 47 publications

References 57 publications

Highly Sensitive Electrostatic Force Detection Using Small Amplitude Frequency-Modulation Atomic Force Microscopy in the Second Flexural Mode

Highly Sensitive Electrostatic Force Detection Using Small Amplitude Frequency-Modulation Atomic Force Microscopy in the Second Flexural Mode

Multiscale approach for simulations of Kelvin probe force microscopy with atomic resolution

The weight function for charges—A rigorous theoretical concept for Kelvin probe force microscopy

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