OSTJThe effect of uniaxial applied stress on dislocation networks present in the atomic surface layer ofAu(111 ) was studied. The measurements were made using a novel instrument combining ultrahigh vacuum scanned-probe microscopy with an in-situ stress-strain testing machine. The technique provides microscopic information, up to atomic resolution, about the large scale plasticity of surface layers under applied loads. The herringbone reconstruction of the Au{111) surface is a classic example of a strain stabilized dislocation network. We find that under 0.5°/0 uniaxially applied compressive strain a dramatic restructuring of the network takes place. The three-fold orientational degeneracy of the system is removed and threading edge dislocations are annihilated.

Using scanning tunneling microscopy on Cu/Ru͑0001͒ thin films we have located the depth at which the cores of misfit dislocations lie below the film surface. The procedure is based on matching areas with unknown structure to areas with a known stacking sequence in the same film. Our results show that dislocations occur not only at the Cu/Ru interface, but also at various levels within the Cu films. Our analysis method should be applicable to the characterization of dislocation structures in other ultrathin film systems.

Using scanning tunneling microscopy we have observed thermally induced dislocation glide in monolayer Cu films on Ru(0001) at room temperature. The motion is governed by a Peierls barrier that depends on the detailed structure of the dislocations, in particular upon whether the threading dislocations that terminate them are dissociated or not. Calculations based on the Frenkel-Kontorova model reproduce the threading dislocation structure and provide estimates of the Peierls barrier and dislocation stiffness which are consistent with experiment.

We have coupled electron microscopy and energy dispersive spectroscopy experiments with ab-initio modeling to study the solubility and diffusion of Au in Bi 2 Te 3 . We found that thermal annealing of Au films results in Au concentrations in Bi 2 Te 3 above the previously reported solubility limit. The time scale of Au diffusion into Bi 2 Te 3 is also much greater than expected. To explain our observations, we calculate defect formation energies and diffusion barriers within DFT. We identify an interstitial mechanism consistent with the previously observed low solubility and (rapid) anisotropic diffusion. However, the lower formation energies of substitutional defects suggest that they may be active in our experiments and explain the high observed concentrations.1 arXiv:1305.0528v2 [cond-mat.mtrl-sci] 21 Jul 2013 with the Keys and Dutton report of low Au solubility. To explain the result we use density functional theory (DFT) to compute the formation energies of isolated Au defects and their diffusivities. We find interstitial site formation energies and diffusivities are consistent with Keys and Dutton measurements. However, our calculations also suggest a second slower stage of diffusion, associated with lower energy Au substitution in the Bi 2 Te 3 lattice, that occurs after the initial rapid diffusion, accounting for our experimental results. This result suggests the solubilities of metals in highly doped, polycrystalline, or vacancyrich Bi 2 Te 3 may be significantly higher than measured in pristine single-crystal specimens

No abstract