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8 Oct 2012

Volume 101, Issue 15, Articles (15xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 153501 (2012); http://dx.doi.org/10.1063/1.4756693 (3 pages)

Brandon G. Cook, William R. French, and Kálmán Varga
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Transition from planar to island growth mode in SiGe structures fabricated on SiGe/Si(001) strain-relaxed buffers

M. V. Shaleev, A. V. Novikov, D. V. Yurasov, J. M. Hartmann, O. A. Kuznetsov, D. N. Lobanov, and Z. F. Krasilnik

Appl. Phys. Lett. 101, 151601 (2012); http://dx.doi.org/10.1063/1.4758486 (4 pages)

Online Publication Date: 9 October 2012

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The specifics of the two-to-three dimensional growth mode transition of pure Ge on SiGe/Si(001) strain-relaxed buffers (SRBs) were investigated. It was shown that the critical thickness for elastic relaxation is influenced not only by the lattice mismatch between the substrate and the film but also by Ge segregation and surface roughness dependent on parameters of strained layers. Critical thickness was found to be smaller for Ge grown on SiGe strain-relaxed buffers than on pure Si(001) substrates, in spite of the lesser lattice mismatch. Insertion of thin tensile-strained Si layers between Ge and SiGe strain-relaxed buffers increased the critical thickness.
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68.55.ag Semiconductors
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
68.47.Fg Semiconductor surfaces
64.70.kg Semiconductors
81.40.Lm Deformation, plasticity, and creep

Determination of 16O and 18O sensitivity factors and charge-exchange processes in low-energy ion scattering

H. Téllez, R. J. Chater, S. Fearn, E. Symianakis, H. H. Brongersma, and J. A. Kilner

Appl. Phys. Lett. 101, 151602 (2012); http://dx.doi.org/10.1063/1.4758699 (4 pages)

Online Publication Date: 10 October 2012

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Quantitative analysis in low-energy ion scattering (LEIS) requires an understanding of the charge-exchange processes to estimate the elemental sensitivity factors. In this work, the neutralization of He+ scattered by 18O-exchanged silica at energies between 0.6 and 7 keV was studied. The process is dominated by Auger neutralization for Ei < 0.8 keV. An additional mechanism starts above the reionization threshold. This collision-induced neutralization becomes the dominant mechanism for Ei > 2 keV. The ion fractions P+ were determined for Si and O using the characteristic velocity method to quantify the surface density. The 18O/16O sensitivity ratio indicates an 18% higher sensitivity for the heavier O isotope.
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79.20.Fv Electron impact: Auger emission
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
82.20.Tr Kinetic isotope effects including muonium
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Molecular dynamics prediction of interfacial strength and validation through atomic force microscopy

Ulises Galan and Henry A. Sodano

Appl. Phys. Lett. 101, 151603 (2012); http://dx.doi.org/10.1063/1.4758988 (4 pages)

Online Publication Date: 11 October 2012

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Molecular dynamics (MD) simulations are performed to calculate the interfacial energy between zinc oxide (ZnO) and graphitic carbon. The MD model consists of a ZnO slab and a single layer of graphitic carbon. The calculation was validated experimentally by atomic force microscopy (AFM) liftoff. A polishing process was applied to create a tip with a flat surface that was subsequently coated with a ZnO film allowing force displacement measurement on highly oriented pyrolitic graphite to validate the simulations. The MD simulation and AFM lift-off show good agreement with adhesive energies of 0.303 J/m2 and 0.261 ± 0.054 J/m2, respectively.
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68.35.Np Adhesion
68.35.Gy Mechanical properties; surface strains
68.37.Ps Atomic force microscopy (AFM)
81.65.Ps Polishing, grinding, surface finishing

Quantum oscillations from a two-dimensional electron gas at a Mott/band insulator interface

Pouya Moetakef, Daniel G. Ouellette, James R. Williams, S. James Allen, Leon Balents, David Goldhaber-Gordon, and Susanne Stemmer

Appl. Phys. Lett. 101, 151604 (2012); http://dx.doi.org/10.1063/1.4758989 (4 pages) | Cited 1 time

Online Publication Date: 11 October 2012

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We report on the magnetotransport properties of a prototype Mott insulator/band insulator perovskite heterojunction in magnetic fields up to 31 T and at temperatures between 360 mK and 10 K. Shubnikov-de Haas oscillations in the magnetoresistance are observed. The oscillations are two-dimensional in nature and are interpreted as arising from either a single, spin-split subband or two subbands. In either case, the electron system that gives rise to the oscillations represents only a fraction of the electrons in the space charge layer at the interface. The temperature dependence of the oscillations is used to extract an effective mass of ∼1 me for the subband(s). The results are discussed in the context of the t2g-states that form the bottom of the conduction band of SrTiO3.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.My Galvanomagnetic and other magnetotransport effects

Absorptivity modulation on wavy molten steel surfaces: The influence of laser wavelength and angle of incidence

A. F. H. Kaplan

Appl. Phys. Lett. 101, 151605 (2012); http://dx.doi.org/10.1063/1.4759126 (4 pages)

Online Publication Date: 11 October 2012

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The modulation of the angle-dependent Fresnel absorptivity across wavy molten steel surfaces during laser materials processing, like drilling, cutting, or welding, has been calculated. The absorptivity is strongly altered by the grazing angle of incidence of the laser beam on the processing front. Owing to its specific Brewster-peak characteristics, the 10.64 μm wavelength CO2-laser shows an opposite trend with respect to roughness and angle-of-incidence compared to lasers in the wavelength range of 532-1070 nm. Plateaus or rings of Brewster-peak absorptivity can lead to hot spots on a wavy surface, often in close proximity to cold spots caused by shadow domains.
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81.05.Bx Metals, semimetals, and alloys
68.35.bd Metals and alloys
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
79.20.Ds Laser-beam impact phenomena
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