Scattering States of Ionized Dopants Probed by Low Temperature Scanning Tunneling Spectroscopy

Wittneven, Chr.; Dombrowski, R.; Morgenstern, Markus; Wiesendanger, R.

doi:10.1103/physrevlett.81.5616

Cited by 87 publications

(36 citation statements)

References 24 publications

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“…Since we are interested in the LDOS probed at a spatially constant tip-sample distance z, we compensate the varying z by independently recording I (z) curves and the local z(x,y), i.e., a constant-current image. Dividing dI/dV (V ,x,y) by I (z(x,y)) rescales different dI/dV curves, as if they have been measured at a constant z(x,y) [20]. For the sake of simplicity, we call the doubly renormalized curves dI/dV scaled (V ).…”

Section: Sample Preparation and Stm/sts Experimentsmentioning

confidence: 99%

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Exploring the subsurface atomic structure of the epitaxially grown phase-change material Ge2Sb2Te5

et al. 2017

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Scanning tunneling microscopy (STM) and spectroscopy (STS) in combination with density functional theory (DFT) calculations are employed to study the surface and subsurface properties of the metastable phase of the phase-change material Ge 2 Sb 2 Te 5 as grown by molecular beam epitaxy. The (111) surface is covered by an intact Te layer, which nevertheless permits the detection of the more disordered subsurface layer made of Ge and Sb atoms. Centrally, we find that the subsurface layer is significantly more ordered than expected for metastable Ge 2 Sb 2 Te 5 . First, we show that vacancies are nearly absent within the subsurface layer. Secondly, the potential fluctuation, tracked by the spatial variation of the valence band onset, is significantly less than expected for a random distribution of atoms and vacancies in the subsurface layer. The strength of the fluctuation is compatible with the potential distribution of charged acceptors without being influenced by other types of defects. Thirdly, DFT calculations predict a partially tetrahedral Ge bonding within a disordered subsurface layer, exhibiting a clear fingerprint in the local density of states as a peak close to the conduction band onset. This peak is absent in the STS data implying the absence of tetrahedral Ge, which is likely due to the missing vacancies required for structural relaxation around the shorter tetrahedral Ge bonds. Finally, isolated defect configurations with a low density of 10 −4 nm −2 are identified by comparison of STM and DFT data, which corroborates the significantly improved order in the epitaxial films driven by the buildup of vacancy layers.

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Section: Sample Preparation and Stm/sts Experimentsmentioning

confidence: 99%

“…This allows the direct determination of the corresponding structure-property relationship between atomic arrangement and electronic structure in real space. The probed local DOS, portraying the electronic structure, is dominated by the surface layer, but is also influenced by deeper layers [20].…”

Section: Introductionmentioning

confidence: 99%

Exploring the subsurface atomic structure of the epitaxially grown phase-change material Ge2Sb2Te5

et al. 2017

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“…[23][24][25] Under constant current feedback, the STM tip traces approximately the constant integrated LDOS surface, since the total tunnelling current at a tip position (x,y) is given by (in the tunnelling regime, with tip-sample distance z 4 4 Å ) 23,26,27 IðV b ; x; yÞ / where V b is the bias voltage (defined as the sample bias with respect to the tip), r t and r s are the tip and sample DOS, respectively, E is the energy, and T is the transmission coefficient. By differentiating the tunnelling current, one obtains …”

Section: Scanning Tunnelling Microscopymentioning

confidence: 99%

Single-molecule chemistry and physics explored by low-temperature scanning probe microscopy

2011

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It is well known that scanning probe techniques such as scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) routinely offer atomic scale information on the geometric and the electronic structure of solids. Recent developments in STM and especially in non-contact AFM have allowed imaging and spectroscopy of individual molecules on surfaces with unprecedented spatial resolution, which makes it possible to study chemistry and physics at the single molecule level. In this feature article, we first review the physical concepts underlying image contrast in STM and AFM. We then focus on the key experimental considerations and use selected examples to demonstrate the capabilities of modern day low-temperature scanning probe microscopy in providing chemical insight at the single molecule level.

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“…Of particular interest is its ability to observe the standing electron wave patterns (Friedel oscillations) generated by scattering from defects and steps on certain surfaces (5-7). The observation of these scattered electron states has proved beneficial in exploring adsorption on surfaces (8), the depth of impurities in solids (9)(10)(11), and the mixing of surface and bulk electron states (12). Previously, it has been shown that it is necessary to narrow the STM tip local density of states to image electron standing waves on graphite (13).…”

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Nanoscale imaging of chemical interactions: Fluorine on graphite

Kelly

Mickelson²,

Hauge³

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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Using C60-functionalized scanning tunneling microscope tips, we have investigated the adsorption of fluorine on graphite. Based on characteristics of the accompanying electron standing waves, we are able to distinguish the fluorine adatoms that have bonded ionically to the graphite surface from those that have formed covalent bonds with the surface. This result permits determination of the ratio of ionic to covalent C-F bonds on graphite obtained by gas phase fluorination, which seems to be temperatureindependent between 200 and 300°C under the reaction conditions used.

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Scattering States of Ionized Dopants Probed by Low Temperature Scanning Tunneling Spectroscopy

Cited by 87 publications

References 24 publications

Exploring the subsurface atomic structure of the epitaxially grown phase-change material Ge2Sb2Te5

Exploring the subsurface atomic structure of the epitaxially grown phase-change material Ge2Sb2Te5

Single-molecule chemistry and physics explored by low-temperature scanning probe microscopy

Nanoscale imaging of chemical interactions: Fluorine on graphite

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