103 research outputs found
Diffusional Kinetics of SiGe Dimers on Si(100) Using Atom-Tracking Scanning Tunneling Microscopy
Quantitative measurements of the diffusion of adsorbed mixed Ge-Si dimers on the Si(100) surface have been made as a function of temperature using atom-tracking scanning tunneling microscopy. These mixed dimers are distinguishable from pure Si-Si dimers by their characteristic kinetics--a 180-degree rotation between two highly buckled configurations. At temperatures at which the mixed dimers diffuse, atomic-exchange events occur, in which the Ge atom in the adsorbed dimer exchanges with a substrate Si atom. Re-exchange can also occur when the diffusing Si-Si dimer revisits the original site of exchange
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Diffusion Kinetics in the Pd/Cu(001) Surface Alloy
We use atom-tracking scanning tunneling microscopy to study the diffusion of Pd in the Pd/Cu(001) surface alloy. By following the motion of individual Pd atoms incorporated in the surface, we show that Pd diffuses by a vacancy-exchange, mechanism. We measure an effective activation energy for the diffusion of incorporated Pd atoms of 0.88 eV, which is consistent with an ab initio calculated barrier of 0.94 eV
Unusually strong space-charge-limited current in thin wires
The current-voltage characteristics of thin wires are often observed to be
nonlinear, and this behavior has been ascribed to Schottky barriers at the
contacts. We present electronic transport measurements on GaN nanorods and
demonstrate that the nonlinear behavior originates instead from
space-charge-limited current. A theory of space-charge-limited current in thin
wires corroborates the experiments, and shows that poor screening in high
aspect ratio materials leads to a dramatic enhancement of space-charge limited
current, resulting in new scaling in terms of the aspect ratio.Comment: 4 pages, 3 figures, to appear in Physical Review Letter
Structure and Stability of Si(114)-(2x1)
We describe a recently discovered stable planar surface of silicon, Si(114).
This high-index surface, oriented 19.5 degrees away from (001) toward (111),
undergoes a 2x1 reconstruction. We propose a complete model for the
reconstructed surface based on scanning tunneling microscopy images and
first-principles total-energy calculations. The structure and stability of
Si(114)-(2x1) arises from a balance between surface dangling bond reduction and
surface stress relief, and provides a key to understanding the morphology of a
family of surfaces oriented between (001) and (114).Comment: REVTeX, 4 pages + 3 figures. A preprint with high-resolution figures
is available at http://cst-www.nrl.navy.mil/papers/si114.ps . To be published
in Phys. Rev. Let
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