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15 Jun 1998

Volume 72, Issue 24, pp. 3097-3228

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Elastic and plastic deformation of diamondlike carbons

A. M. Stoneham, P. D. Godwin, A. P. Sutton, and S. J. Bull

Appl. Phys. Lett. 72, 3142 (1998); http://dx.doi.org/10.1063/1.121573 (3 pages) | Cited 6 times

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In exploiting tribological applications of diamondlike carbons (DLC, a-C:H), both elastic and plastic properties must be optimized. We use tight-binding molecular dynamics to generate realization of DLC, from which can be obtained properties and their dependence on the precursors used, and on the H/C ratio. Here we analyze the elastic properties and especially the rebonding events which occur under strain. Rebonding occurs only at rather large strains; in some cases, it is reversible. Hydrogen has a key role in determining the number of carbons with less than four carbon neighbors, since it is mainly these carbons which participate in the major plastic (rebonding) events. © 1998 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
62.20.D- Elasticity

Determination of the ordered structures of Pb(Mg1/3Nb2/3)O3 and Ba(Mg1/3Nb2/3)O3 by atomic-resolution Z-contrast imaging

Y. Yan, S. J. Pennycook, Z. Xu, and D. Viehland

Appl. Phys. Lett. 72, 3145 (1998); http://dx.doi.org/10.1063/1.121574 (3 pages) | Cited 62 times

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The atomic structure of ordered domains in Ba(Mg1/3Nb2/3)O3 and La-doped and undoped Pb(Mg1/3Nb2/3)O3 is studied by high-resolution Z-contrast imaging. The ordered domain structure in both doped and undoped Pb(Mg1/3Nb2/3)O3 is determined to be in agreement with the charge balanced random-layer model and inconsistent with the space-charge model. It is shown that La doping in Pb(Mg1/3Nb2/3)O3 enhances not only the domain size but also the degree of ordering. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis

Topography measurements of the critical thickness of ZnSe grown on GaAs

G. Horsburgh, K. A. Prior, W. Meredith, I. Galbraith, B. C. Cavenett, C. R. Whitehouse, G. Lacey, A. G. Cullis, P. J. Parbrook, P. Möck, and K. Mizuno

Appl. Phys. Lett. 72, 3148 (1998); http://dx.doi.org/10.1063/1.121575 (3 pages) | Cited 6 times

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Synchrotron-based x-ray topography (XRT) measurements have been used to study the initial stages of relaxation in ZnSe layers grown by molecular beam epitaxy on vertical gradient freeze Bridgman GaAs substrates. The formation of the very first strain-relieving misfit dislocations in the grown ZnSe layers has been detected in a layer of thickness 100 nm. No such dislocations have been observed in a corresponding layer of 95 nm thickness. The critical thickness for this material system is therefore estimated to be 97.5±2.5 nm, which is markedly lower than the widely accepted value of 150 nm. In contrast to the InGaAs/GaAs system, combined XRT and transmission electron microscopy studies indicate that the initial misfit dislocations observed for ZnSe/GaAs are not, in general, formed by the bending over of pre-existing threading dislocations into the interface, but by other mechanisms such as stacking fault decomposition. The critical thickness data obtained have been used to infer the maximum critical thickness of CdZnSe quantum wells possible in II–VI laser diodes. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Lk Linear defects: dislocations, disclinations
61.72.Nn Stacking faults and other planar or extended defects
68.35.Ct Interface structure and roughness
68.60.Bs Mechanical and acoustical properties

Self-regulated growth of tilted superlattices by atomic layer epitaxy

J. M. Hartmann, M. Charleux, J. Cibert, and H. Mariette

Appl. Phys. Lett. 72, 3151 (1998); http://dx.doi.org/10.1063/1.121576 (3 pages) | Cited 8 times

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We report on a self-regulated method for the growth of tilted superlattices. It relies on the reconstructed surfaces alternatively stabilized during the atomic layer epitaxy (ALE) of compound semiconductors. The c(2×2)+(2×1) Cd-stabilized and the (2×1) Te-stabilized surfaces alternatively formed during the ALE of CdTe and CdMn(Mg)Te ensure a self-regulation of the growth at 0.5 monolayer deposited per ALE cycle for both CdTe and CdMn(Mg)Te. We are thus able to overcome the problem of precise flux control inherent to tilted superlattices. © 1998 American Institute of Physics.
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81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.B- Structure of clean surfaces (and surface reconstruction)

High-resolution imaging of contact potential difference with ultrahigh vacuum noncontact atomic force microscope

Shin’ichi Kitamura and Masashi Iwatsuki

Appl. Phys. Lett. 72, 3154 (1998); http://dx.doi.org/10.1063/1.121577 (3 pages) | Cited 116 times

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An ultrahigh vacuum scanning Kelvin probe force microscope (UHV SKPM) utilizing the gradient of electrostatic force, was developed based on an ultrahigh vacuum noncontact atomic force microscope (NC-AFM) capable of atomic level imaging, and used for simultaneous observation of contact potential difference (CPD) and NC-AFM images. CPD images of a Si(111) surface with Au deposited, clearly showed the potential difference in phases between 7×7 and 5×2 structures. When Ag was deposited as a submonolayer on the Si(111) 7×7 reconstructed surface, the atomic level lateral resolution was observed in CPD images as well as in NC-AFM topographic images. © 1998 American Institute of Physics.
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73.40.Cg Contact resistance, contact potential
73.30.+y Surface double layers, Schottky barriers, and work functions
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.40.Ns Metal-nonmetal contacts
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