71 research outputs found
Mechanically-Induced Transport Switching Effect in Graphene-based Nanojunctions
We report a theoretical study suggesting a novel type of electronic switching
effect, driven by the geometrical reconstruction of nanoscale graphene-based
junctions. We considered junction struc- tures which have alternative
metastable configurations transformed by rotations of local carbon dimers. The
use of external mechanical strain allows a control of the energy barrier
heights of the potential profiles and also changes the reaction character from
endothermic to exothermic or vice-versa. The reshaping of the atomic details of
the junction encode binary electronic ON or OFF states, with ON/OFF
transmission ratio that can reach up to 10^4-10^5. Our results suggest the
possibility to design modern logical switching devices or mechanophore sensors,
monitored by mechanical strain and structural rearrangements.Comment: 10 pages, 4 figure
Modeling graphene-based nanoelectromechanical devices
We report on a theoretical study of charge transport properties of graphene nanoribbons under external mechanical stress. The influence of mechanical forces on the ribbon conductance is shown to be strongly dependent on the ribbon edge symmetry, i.e., zigzag versus armchair. In contrast to zigzag-edge nanoribbons which remain robust against high strain deformations, a stretching-induced metal-semiconductor transition is obtained for armchair-edge configurations. Our results point out that armchair edge ribbons are consequently much better suited for electromechanical applications.Fil: Poetschke, M.. Technische Universität Dresden; AlemaniaFil: Rocha, C. G.. Technische Universität Dresden; AlemaniaFil: Foa Torres, Luis Eduardo Francisco. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Roche, Serge. Technische Universität Dresden; Alemania. Universite Grenoble Alpes. Institut Nanosciences et Cryogenie - Commissariat a L´Energie Atomique et Aux Energies Alternatives. Institut Nanosciences et Cryogenie; Francia. Centro de Investigación en Nanociencia y Nanotecnología (CIN2); EspañaFil: Cuniberti, G.. Technische Universität Dresden; Alemani
Nanoscale ear drum: Graphene based nanoscale sensors
The difficulty in determining the mass of a sample increases as its size
diminishes. At the nanoscale, there are no direct methods for resolving the
mass of single molecules or nanoparticles and so more sophisticated approaches
based on electromechanical phenomena are required. More importantly, one
demands that such nanoelectromechanical techniques could provide not only
information about the mass of the target molecules but also about their
geometrical properties. In this sense, we report a theoretical study that
illustrates in detail how graphene membranes can operate as
nanoelectromechanical mass-sensor devices. Wide graphene sheets were exposed to
different types and amounts of molecules and molecular dynamic simulations were
employed to treat these doping processes statistically. We demonstrate that the
mass variation effect and information about the graphene-molecule interactions
can be inferred through dynamical response functions. Our results confirm the
potential use of graphene as mass detector devices with remarkable precision in
estimating variations in mass at molecular scale and other physical properties
of the dopants
Socio-economic status is inversely related to bed net use in Gabon
This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
Towards an universal memory based on self-organized quantum dots
A concept of a memory device based on self-organized quantum dots (QDs) is presented, which has the potential to fulfill the requirements of an universal memory. We demonstrate here a hole storage time of 1.6 s at room temperature in InAs/GaAs QDs with an additional Al0.9Ga0.1As barrier. This value is already three orders of magnitude longer than the typical DRAM refresh time. The connection between localization energy and storage time for different QD/matrix material combinations enables us to predict a retention time of more than 10 years in In(Ga)Sb/AlAs QDs, like in a Flash memory. Furthermore, we demonstrate a very fast write time below 20 ns for our memory concept in GaSb/GaAs QDs around 100 K. The write time is at the moment only limited by the parasitic cut off frequency of the RC low pass. Hence, an universal QD-based Flash memory-having a storage time in the order of years in combination with a fast write access time below 20 ns-seems feasible. (c) 2007 Elsevier B.V. All rights reserved
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