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[en] The following outlines the optimized pulsed laser deposition (PLD) procedure used to prepare Nd0.67Sr0.33MnO3 (NSMO) temperature sensors at Towson University (Prof. Rajeswari Kolagani) for the LCLS XTOD Total Energy Monitor. The samples have a sharp metal/insulator transition at T ∼ 200 K and are optimized for operation at T ∼ 180 K, where their sensitivity is the highest. These samples are epitaxial multilayer structures of Si/YSZ/CeO/NSMO, where these abbreviations are defined in table 1. In this heterostructure, YSZ serves as a buffer layer to prevent deleterious chemical reactions, and also serves to de-oxygenate the amorphous SiO2 surface layer to generate a crystalline template for epitaxy. CeO and BTO serve as template layers to minimize the effects of thermal and lattice mismatch strains, respectively. More details on the buffer and template layer scheme are included in the attached manuscript accepted for publication in Sensor Letters (G. Yong et al., 2008)
[en] The symmetry of the similarity of the surface step structure in zinc blende (sphalerite) type structures is investigated by studying the crystal planes that are parallel to the [01 anti 1] axis. The symmetry transformations of the similar plane pairs are derived. Plane sets (111) and (311) are the planes of symmetry. The similarity of the surface step structure exists among three sets of planes. The surface geometric characteristics of similar planes are discussed. The result can be applied to explain dual epitaxy and optimize the interface quality by designing dual epitaxy in the heteroepitaxy. (orig.)
[en] In this Letter, we re-examen a one-dimensional model of epitaxial growth that describes pyramidal structures characterized by the absence of a preferred slope [L. Golubovic, Phys. Rev. Lett. 78 (1997) 90]. A similarity approach shows that the typical mound lateral size and the interfacial width growth with time like t1/2 and t1/4, respectively. This result was previously presented by Golubovic. Our contribution provides a mathematical justification for the existence of similarity solutions which correspond to, or predict, the typical coarsening process.
[en] A dual-timescale model of stressed solid-phase epitaxial growth is developed to provide a basis for the atomistic interpretation of experiments where the macroscopic growth velocity of (0 0 1) Si was studied as a function of uniaxial stress applied in the plane of the growth interface. The model builds upon prior empirical modeling, but is a significant improvement as it provides solid physical bases as to the origin of growth being dual-timescale and more accurately models growth kinetics.
[en] Metal organic vapour phase epitaxy (GaAs)1-x(Ge2)x alloy layers, 0 and lt;x and lt;0.22, were grown at temperatures between 640 and 690 C, on vicinal (001) GaAs substrates. Phase separation occurred in all the layers. The phase-separated microstructure changed with alloy composition, growth temperature, and substrate orientation. In x(approx) 0.1 layers grown at 640 C, Ge segregation occurred on(lbrace)115(rbrace)B planes associated with a(lbrace)115(rbrace)B surface faceting. Increase in growth temperature led to the formation of large, (001)-oriented, irregular-shaped platelets of Ge-rich material. Growth on(lbrace)115(rbrace)B substrates resulted in a ''natural superlattice'' of GaAs/Ge along the growth direction
[en] Two main reconstructions have been reported for the α-Sn(111) surfaces (epitaxially grown on InSb(111), namely 2 x 2 and a metastable 3 x 3. The paper discusses the possible nature of these reconstructions, based on first-principles electronic structure calculations carried out in our group. The lowest surface energy is attained by an 'adatom-restatom' (AR) reconstruction, whose basic building block can be either c(4 x 2) or 2 x 2, analogous to those of Si(111)7 x 7, and of Ge(111)c(2 x 8). The paper proposes that Sn(111)2 x 2 could be explained by the AR model, and computes surface core level shifts, as a prediction for future experiments. For the 3 x 3, the scenario appears less obvious, and are considered two different models: a dimer-adatom-stacking fault (DAS) model and a distorted √3 x √3, inspired by existing Charge-Density-Wave (CDW) distorted surfaces. Both models yield a higher surface energy when compared to the 2 x 2 AR, the DAS only slightly worse than the other. Thus the nature of the metastable 3 x 3, possibly a result of growth kinetics, remains an open issue
[en] A pinch-off phenomenon is discovered in the evolution of 2D wormlike nanoclusters formed in homoepitaxial adlayers. This feature is shown to distinguish mass transport via periphery diffusion from other mechanisms. Continuum modeling of such evolution accurately describes experimental observations, particularly if one incorporates the anisotropy in step-edge line tension
[en] A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon. 11 figs
[en] The impact of hydrostatic pressure on magnetic anisotropy energies in (Ga, Mn)As thin films with in-plane and out-of-plane magnetic easy axes predefined by epitaxial strain was investigated. In both types of sample we observed a clear increase in both in-plane and out-of-plane anisotropy parameters with pressure. The out-of-plane anisotropy constant is well reproduced by the mean-field p–d Zener model; however, the changes in uniaxial anisotropy are much larger than expected in the Mn–Mn dimer scenario. (paper)