Role of applied bias and tip electronic structure in the scanning tunneling microscopy imaging of highly oriented pyrolytic graphite

Teobaldi, Gilberto; Inami, Eiichi; Kanasaki, J.; Tanimura, Katsumi; Shluger, AL

doi:10.1103/physrevb.85.085433

Cited by 19 publications

(79 citation statements)

References 69 publications

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“…We considered blunt and sharp tungsten tip models following Refs. [48,49] to investigate the effect of tip sharpness on the apparent step height. The blunt tip is represented by an adatom adsorbed on the hollow site of the W(110) surface, and the sharp tip is modeled as a pyramid of three-atoms height on the W(110) surface.…”

Section: Experimental and Computational Detailsmentioning

confidence: 99%

Spilling of electronic states in Pb quantum wells

2016

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Energy-dependent apparent step heights of two-dimensional ultra-thin Pb islands grown on the Si(111)6×6Au surface have been investigated by a combination of scanning tunneling microscopy, first-principles density functional theory and the particle in a box model calculations. The apparent step height shows the thickness and energy dependent oscillatory behavior, which is directly related to the spilling of electron states into the vacuum exhibiting a quantum size effect. This has been unambiguously proven by extensive first-principles scanning tunneling microscopy and spectroscopy simulations. An electronic contribution to the apparent step height is directly determined. At certain energies it reaches values as high as a half of the atomic contribution. The applicability of the particle in a box model to the spilling of electron states is also discussed.

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Section: Experimental and Computational Detailsmentioning

confidence: 99%

Spilling of electronic states in Pb quantum wells

2016

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“…Recent studies 27,[44][45][46][47] explored the role of the higher orbitals in tip state based on Chen's proposal. We have also coupled the same derivative rule with our TB wave function.…”

Section: S3 Calculation Of Spatially-resolved Stm Imagesmentioning

confidence: 99%

Spatial metrology of dopants in silicon with exact lattice site precision

Usman¹,

Bocquel²,

Salfi³

et al. 2016

Nature Nanotech

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The aggressive scaling of silicon-based nanoelectronics has reached the regime where device function is affected not only by the presence of individual dopants, but more critically their position in the structure. The quantitative determination of the positions of subsurface dopant atoms is an important issue in a range of applications from channel doping in ultra-scaled transistors to quantum information processing, and hence poses a significant challenge. Here, we establish a metrology combining low-temperature scanning tunnelling microscopy (STM) imaging and a comprehensive quantum treatment of the dopant-STM system to pin-point the exact lattice-site location of sub-surface dopants in silicon. The technique is underpinned by the observation that STM images of sub-surface dopants typically contain many atomic-sized features in ordered patterns, which are highly sensitive to the details of the STM tip orbital and the absolute lattice-site position of the dopant atom itself. We demonstrate the technique on two types of dopant samples in silicon -the first where phosphorus dopants are placed with high precision, and a second containing randomly placed arsenic dopants. Based on the quantitative agreement between STM measurements and multi-million-atom calculations, the precise lattice site of these dopants is determined, demonstrating that the metrology works to depths of about 36 lattice planes. The ability to uniquely determine the exact positions of subsurface dopants down to depths of 5 nm will provide critical knowledge in the design and optimisation of nanoscale devices for both classical and quantum computing applications.As we approach the ultimate regime of Feynman's vision 1 of nanotechnology based on atom-by-atom fabrication 2-5 , there is a critical need to match advances in miniaturisation with atomically precise metrology. In conventional CMOS 6 and tunnelling field effect 7,8 transistors the key relationship between doping profile and performance is now dominated by the positions of just a few dopant atoms, and currently cannot be quantitatively determined. Beyond conventional nanoelectronic devices, in quantum processors based on phosphorus dopants in silicon 9 the precise locations of the individual dopants is critical to the design and operation of spin-based quantum logic gates. Previous studies on locating subsurface dopant positions in semiconductors either provide donor depths based on statistical evidence 10 , or only qualitatively locate dopants within a few nanometers region (of the order of 2.5 nm or more)11 . The key metrological challenge in all of the ultra-scaled applications is the ability to determine the position of dopant atoms in the silicon crystal substrate with lattice-site precision, which will drastically transform our understanding at the most fundamental scale leading to devices with optimised functionalities.In this work, we present an atomically precise metrology and demonstrate the pinpointing of the position of subsurface phosphorous (P) and arsenic (As) dopants in si...

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“…We used a blunt W(110) tip. Motivated by a previous simulation [45], it has been modeled by a slab consisting of three atomic layers having one W apex atom on both surfaces, i.e., with a double vacuum boundary. In this system the apex atoms have been relaxed on both sides.…”

Section: A Computational Detailsmentioning

confidence: 99%

Orbital-dependent electron tunneling within the atom superposition approach: Theory and application to W(110)

2012

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We introduce an orbital dependent electron tunneling model and implement it within the atom superposition approach for simulating scanning tunneling microscopy (STM) and spectroscopy (STS). Applying our method, we analyze the convergence and the orbital contributions to the tunneling current and the corrugation of constant current STM images above the W(110) surface.In accordance with a previous study [Heinze et al., Phys. Rev. B 58, 16432 (1998)], we find atomic contrast reversal depending on the bias voltage. Additionally, we analyze this effect depending on the tip-sample distance using different tip models, and find two qualitatively different behaviors based on the tip orbital composition. As an explanation, we highlight the role of the real space shape of the orbitals involved in the tunneling. STM images calculated by our model agree well with Tersoff-Hamann and Bardeen results. The computational efficiency of our model is remarkable as the k-point samplings of the surface and tip Brillouin zones do not affect the computation time, in contrast to the Bardeen method.

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Role of applied bias and tip electronic structure in the scanning tunneling microscopy imaging of highly oriented pyrolytic graphite

Cited by 19 publications

References 69 publications

Spilling of electronic states in Pb quantum wells

Spilling of electronic states in Pb quantum wells

Spatial metrology of dopants in silicon with exact lattice site precision

Orbital-dependent electron tunneling within the atom superposition approach: Theory and application to W(110)

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