Simultaneous current-, force-, and work-function measurement with atomic resolution

Herz, Markus; Schiller, C. H.; Giessibl, Franz J.; Mannhart, J.

doi:10.1063/1.1900316

Cited by 25 publications

(12 citation statements)

References 13 publications

(34 reference statements)

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“…Simultaneous measurements as close as possible to true STM mode are best accomplished using sub-angstrom oscillation amplitudes. 2, 3 The Si͑111͒ 7 ϫ 7 surface has been studied by many groups using standard nc-AFM methods ever since the first true atomic resolution images reported by Giessibl. 4 We have previously presented some limited AFM/STM results using sub-angstrom oscillation amplitudes.…”

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confidence: 99%

Local force gradients on Si(111) during simultaneous scanning tunneling/atomic force microscopy

Özer

O’Brien

Pethica

2007

Applied Physics Letters

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The authors report simultaneous scanning tunneling and force imaging of Si(111) 7×7 with sub-angstrom oscillation amplitudes. Both constant height and constant current scans with tungsten tips/levers always showed larger attractive stiffness over corner holes than over adatoms, the opposite of theoretical expectations. Constant height scans show that this cannot be explained by interaction of tip motion with long range forces. Silicon levers, however, sometimes exhibited inversions of force contrast following local tip changes. The authors suggest that there may be charge variations between atomic sites on the surface, which produce electrostatic tip forces additional to the covalent forces usually regarded as dominant.

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confidence: 99%

Local force gradients on Si(111) during simultaneous scanning tunneling/atomic force microscopy

Özer

O’Brien

Pethica

2007

Applied Physics Letters

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“…This method has been successfully used to study atomic [31,32] and molecular adsorbates [33,34]. As has been previously suggested by Herz et al, we combine this method with the oscillating tip of an AFM to measure κ [35]. Figure 2(a) is a STM image of PTCDA in the herringbone phase.…”

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confidence: 98%

Intramolecular Force Contrast and Dynamic Current-Distance Measurements at Room Temperature

et al. 2015

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Scanning probe microscopy can be used to probe the internal atomic structure of flat organic molecules. This technique requires an unreactive tip and has, until now, been demonstrated only at liquid helium and liquid nitrogen temperatures. We demonstrate intramolecular and intermolecular force contrast at room temperature on PTCDA molecules adsorbed on a Ag=Sið111Þ-ð ffiffi ffi 3 p × ffiffi ffi 3 p Þ surface. The oscillating force sensor allows us to dynamically measure the vertical decay constant of the tunneling current. The precision of this method is increased by quantifying the transimpedance of the current to voltage converter and accounting for the tip oscillation. This measurement yields a clear contrast between neighboring molecules, which we attribute to the different charge states.

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“…Hence, with decreasing current set point, the radius of the respective sphere increases and thus also the lateral extent of the protrusion in the image. From this simple geometric effect described above, it follows that the line contours will become more sparse just next to a local corrugation of the sample, resulting in an apparent increase of the current decay length [5,13,14], even though in this thought experiment the contact potential was homogeneous. Analogous arguments apply for sharp step edges.…”

Section: Preliminary Considerationsmentioning

confidence: 99%

“…However, for strongly corrugated samples, from very basic arguments, one can show that the geometry will affect I (z) spectra [5,13,14] even if the work function is assumed to be constant over the sample, as will be discussed further below. In the past, maps of the current-distance decay constant on molecular and submolecular length scales have been extracted and interpreted in various aspects [15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Local tunneling decay length and Kelvin probe force spectroscopy

et al. 2015

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In the past, current-distance spectroscopy has been widely applied to determine variations of the work function at surfaces. While for homogeneous sample areas this technique is commonly accepted to yield at least qualitative results, its applicability to atomic-scale variations has not been proven neither right nor wrong. Here we benchmark measurements of the current-distance decay constant against the well established Kelvin probe force spectroscopy for four distinctly different cases with atomic-scale variations of the local contact potential. The two techniques yield quite different results. Whereas the maps of the current-distance decay constant are consistent with being topographical artifacts, the Kelvin probe force spectroscopy maps show variations of the local contact potential difference in agreement with expected surface dipoles. This comparison clarifies that maps of the current-distance decay constant are not suited to directly characterize contact potential variations at surfaces on atomic length scales.

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Simultaneous current-, force-, and work-function measurement with atomic resolution

Cited by 25 publications

References 13 publications

Local force gradients on Si(111) during simultaneous scanning tunneling/atomic force microscopy

Local force gradients on Si(111) during simultaneous scanning tunneling/atomic force microscopy

Intramolecular Force Contrast and Dynamic Current-Distance Measurements at Room Temperature

Local tunneling decay length and Kelvin probe force spectroscopy

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