The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Alexis Baratoff - One of the best experts on this subject based on the ideXlab platform.
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Theory of single atom manipulation with a scanning probe tip: Force signatures, Constant-Height, and Constant-force scans
Physical Review B, 2003Co-Authors: Laurent Pizzagalli, Alexis BaratoffAbstract:International audienceWe report theoretical results predicting the atomic manipulation of a silver atom on a Si(001) surface by a scanning probe tip, and providing insight into the manipulation phenomena. A molecular mechanics technique has been used, the system being described by a quantum chemistry method for the short-range interactions and an analytical model for the long-range ones. Taking into account several shapes, orientations, and chemical natures of the scanning tip, we observed four different ways to manipulate the deposited atom in a Constant-Height mode. In particular, the manipulation is predicted to be possible with a Si(111) tip for different tip shapes and adatom locations on the silicon surface. The calculation of the forces during the manipulation revealed that specific variations can be associated with each kind of process. These force signatures, such as the tip Height signatures observed in scanning tunneling microscope experiments, could be used to deduce the process involved in an experiment. Finally, we present preliminary results about the manipulation in Constant-force mode
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Theory of single atom manipulation with a scanning probe tip: Force signatures, Constant-Height, and Constant-force scans
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2003Co-Authors: Laurent Pizzagalli, Alexis BaratoffAbstract:We report theoretical results predicting the atomic manipulation of a silver atom on a Si(001) surface by a scanning probe tip, and providing insight into the manipulation phenomena. A molecular mechanics technique has been used, the system being described by a quantum chemistry method for the short-range interactions and an analytical model for the long-range ones. Taking into account several shapes, orientations, and chemical natures of the scanning tip, we observed four different ways to manipulate the deposited atom in a Constant-Height mode. In particular, the manipulation is predicted to be possible with a Si(111) tip for different tip shapes and adatom locations on the silicon surface. The calculation of the forces during the manipulation revealed that specific variations can be associated with each kind of process. These force signatures, such as the tip Height signatures observed in scanning tunneling microscope experiments, could be used to deduce the process involved in an experiment. Finally, we present preliminary results about the manipulation in Constant-force mode.
Laurent Pizzagalli - One of the best experts on this subject based on the ideXlab platform.
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Theory of single atom manipulation with a scanning probe tip: Force signatures, Constant-Height, and Constant-force scans
Physical Review B, 2003Co-Authors: Laurent Pizzagalli, Alexis BaratoffAbstract:International audienceWe report theoretical results predicting the atomic manipulation of a silver atom on a Si(001) surface by a scanning probe tip, and providing insight into the manipulation phenomena. A molecular mechanics technique has been used, the system being described by a quantum chemistry method for the short-range interactions and an analytical model for the long-range ones. Taking into account several shapes, orientations, and chemical natures of the scanning tip, we observed four different ways to manipulate the deposited atom in a Constant-Height mode. In particular, the manipulation is predicted to be possible with a Si(111) tip for different tip shapes and adatom locations on the silicon surface. The calculation of the forces during the manipulation revealed that specific variations can be associated with each kind of process. These force signatures, such as the tip Height signatures observed in scanning tunneling microscope experiments, could be used to deduce the process involved in an experiment. Finally, we present preliminary results about the manipulation in Constant-force mode
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Theory of single atom manipulation with a scanning probe tip: Force signatures, Constant-Height, and Constant-force scans
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2003Co-Authors: Laurent Pizzagalli, Alexis BaratoffAbstract:We report theoretical results predicting the atomic manipulation of a silver atom on a Si(001) surface by a scanning probe tip, and providing insight into the manipulation phenomena. A molecular mechanics technique has been used, the system being described by a quantum chemistry method for the short-range interactions and an analytical model for the long-range ones. Taking into account several shapes, orientations, and chemical natures of the scanning tip, we observed four different ways to manipulate the deposited atom in a Constant-Height mode. In particular, the manipulation is predicted to be possible with a Si(111) tip for different tip shapes and adatom locations on the silicon surface. The calculation of the forces during the manipulation revealed that specific variations can be associated with each kind of process. These force signatures, such as the tip Height signatures observed in scanning tunneling microscope experiments, could be used to deduce the process involved in an experiment. Finally, we present preliminary results about the manipulation in Constant-force mode.
Dominique Barchiesi - One of the best experts on this subject based on the ideXlab platform.
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characterization of reflection scanning near field optical microscopy and scanning tunnelling optical microscopy photon scanning tunnelling microscopy working in preliminary approach Constant Height scanning mode
Journal of Microscopy, 1999Co-Authors: Dominique BarchiesiAbstract:The resolution in near-field images is currently determined by the visual inspection of recorded images. One of the major questions in near-field optical microscopy is ‘what resolution can be reached, the tip-to-sample distance being known?’ This knowledge is critical when choosing the scanning step and the distance between the tip and the sample, in a preliminary scan. This preliminary scan is often the only way to detect the interesting parts of the sample, with limited risk of tip crash and topographical artefacts. The method proposed here needs two scans of the same area, of the same sample, in Constant Height mode, recorded at two tip-to-sample distances. The pseudo-transfer function is the ratio of the Fourier transform of these two data maps. This function enables the evaluation of the limit of resolution. Theoretical considerations are introduced to assess the method.
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Characterization of reflection scanning near-field optical microscopy and scanning tunnelling optical microscopy/photon scanning tunnelling microscopy working in preliminary approach Constant Height scanning mode.
Journal of microscopy, 1999Co-Authors: Dominique BarchiesiAbstract:The resolution in near-field images is currently determined by the visual inspection of recorded images. One of the major questions in near-field optical microscopy is ‘what resolution can be reached, the tip-to-sample distance being known?’ This knowledge is critical when choosing the scanning step and the distance between the tip and the sample, in a preliminary scan. This preliminary scan is often the only way to detect the interesting parts of the sample, with limited risk of tip crash and topographical artefacts. The method proposed here needs two scans of the same area, of the same sample, in Constant Height mode, recorded at two tip-to-sample distances. The pseudo-transfer function is the ratio of the Fourier transform of these two data maps. This function enables the evaluation of the limit of resolution. Theoretical considerations are introduced to assess the method.
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reflection scanning near field optical microscopy r snom in Constant Height mode with a dielectric probe image interpretation and resolution for high topographic variations
Ultramicroscopy, 1998Co-Authors: Dominique Barchiesi, O Bergossi, Christian Pieralli, Michel SpajerAbstract:Abstract The understanding of the correlation between the near-field images that are recorded by scanning near-field optical microscopy (SNOM) and the local optical properties of the sample surface (topography, index, etc.) is a condition for the development of such microscopes. The aim of this paper is to show that the “Constant Height imaging” (CHI) mode provides useful near-field characterizations, even in case of high-relief samples. Actually, the CHI near-field signal is free from perturbations brought by usual feedback regulation systems. Furthermore, we show a comparison between experimental and theoretical data to explain near-field image formation. Finally, we develop a specific method based on the Fourier spectral analysis to characterize the experimental SNOM setup working in CHI mode.
Beatrice Palano - One of the best experts on this subject based on the ideXlab platform.
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Boolean language operations on nondeterministic automata with a pushdown of Constant Height
Journal of Computer and System Sciences, 2017Co-Authors: Zuzana Bednarova, Viliam Geffert, Carlo Mereghetti, Beatrice PalanoAbstract:We study the size-cost of Boolean operations on Constant Height nondeterministic pushdown automata, i.e. on pushdown automata with a Constant limit on the size of the pushdown. For intersection, we show an exponential simulation and prove that the exponential blow-up is necessary. For union, instead, we provide a linear trade-off while, for complement, we show a double-exponential simulation and prove a single-exponential lower bound.
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removing nondeterminism in Constant Height pushdown automata
Information & Computation, 2014Co-Authors: Zuzana Bednarova, Viliam Geffert, Carlo Mereghetti, Beatrice PalanoAbstract:We study the descriptional cost of removing nondeterminism in Constant Height pushdown automata-i.e., pushdown automata with a built-in Constant limit on the Height of the pushdown. We show a double-exponential size increase when converting a Constant Height nondeterministic pushdown automaton into an equivalent deterministic device. Moreover, we prove that such a double-exponential blow-up cannot be avoided by certifying its optimality. As a direct consequence, we get that eliminating nondeterminism in classical finite state automata is single-exponential even with the help of a Constant Height pushdown store.
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DCFS - Queue Automata of Constant Length
Descriptional Complexity of Formal Systems, 2013Co-Authors: Sebastian Jakobi, Carlo Mereghetti, Katja Meckel, Beatrice PalanoAbstract:We introduce and study the notion of Constant length queue automata, as a formalism for representing regular languages. We show that their descriptional power outperforms that of traditional finite state automata, of Constant Height pushdown automata, and of straight line programs for regular expressions, by providing optimal exponential and double-exponential size gaps. Moreover, we prove that Constant Height pushdown automata can be simulated by Constant length queue automata paying only by a linear size increase, and that removing nondeterminism in Constant length queue automata requires an optimal exponential size blow-up, against the optimal double-exponential cost for determinizing Constant Height pushdown automata.
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removing nondeterminism in Constant Height pushdown automata
Descriptional Complexity of Formal Systems, 2012Co-Authors: Zuzana Bednarova, Viliam Geffert, Carlo Mereghetti, Beatrice PalanoAbstract:We study the descriptional cost of converting Constant Height nondeterministic pushdown automata into equivalent deterministic devices. We show a double-exponential upper bound for this conversion, together with a super-exponential lower bound.
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The size-cost of Boolean operations on Constant Height deterministic pushdown automata
Theoretical Computer Science, 2012Co-Authors: Zuzana Bednarova, Viliam Geffert, Carlo Mereghetti, Beatrice PalanoAbstract:We study the size-cost of Boolean operations on Constant Height deterministic pushdown automata, i.e., on the traditional pushdown automata with a built-in Constant limit on the Height of the pushdown. We design a simulation showing that a complement can be obtained with a polynomial tradeoff. For intersection and union, we show an exponential simulation, and prove that the exponential blow-up cannot be avoided.
Andrew Winslow - One of the best experts on this subject based on the ideXlab platform.
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size dependent tile self assembly Constant Height rectangles and stability
International Symposium on Algorithms and Computation, 2015Co-Authors: Sándor P. Fekete, Robert T. Schweller, Andrew WinslowAbstract:We introduce a new model of algorithmic tile self-assembly called size-dependent assembly. In previous models, supertiles are stable when the total strength of the bonds between any two halves exceeds some Constant temperature. In this model, this Constant temperature requirement is replaced by an nondecreasing temperature function\(\tau : \mathbb {N} \rightarrow \mathbb {N}\) that depends on the size of the smaller of the two halves. This generalization allows supertiles to become unstable and break apart, and captures the increased forces that large structures may place on the bonds holding them together.
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ISAAC - Size-Dependent Tile Self-Assembly: Constant-Height Rectangles and Stability
Algorithms and Computation, 2015Co-Authors: Sándor P. Fekete, Robert T. Schweller, Andrew WinslowAbstract:We introduce a new model of algorithmic tile self-assembly called size-dependent assembly. In previous models, supertiles are stable when the total strength of the bonds between any two halves exceeds some Constant temperature. In this model, this Constant temperature requirement is replaced by an nondecreasing temperature function\(\tau : \mathbb {N} \rightarrow \mathbb {N}\) that depends on the size of the smaller of the two halves. This generalization allows supertiles to become unstable and break apart, and captures the increased forces that large structures may place on the bonds holding them together.
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Size-Dependent Tile Self-Assembly: Constant-Height Rectangles and Stability
arXiv: Computational Geometry, 2015Co-Authors: Sándor P. Fekete, Robert T. Schweller, Andrew WinslowAbstract:We introduce a new model of algorithmic tile self-assembly called size-dependent assembly. In previous models, supertiles are stable when the total strength of the bonds between any two halves exceeds some Constant temperature. In this model, this Constant temperature requirement is replaced by an nondecreasing temperature function $\tau : \mathbb{N} \rightarrow \mathbb{N}$ that depends on the size of the smaller of the two halves. This generalization allows supertiles to become unstable and break apart, and captures the increased forces that large structures may place on the bonds holding them together. We demonstrate the power of this model in two ways. First, we give fixed tile sets that assemble Constant-Height rectangles and squares of arbitrary input size given an appropriate temperature function. Second, we prove that deciding whether a supertile is stable is coNP-complete. Both results contrast with known results for fixed temperature.