We employ an ab initio calculation based on density functional theory to investigate the ideal strength of face-centered cubic crystal Au under uniaxial stress along the [100] direction. We show that the stability of the perfect Au crystal under tensile stress is determined by the tetragonal shear stiffness modulus, with an ideal tensile strength of 4.2 GPa and the corresponding Lagrangian tensile strain of ∼ 0.07. The potential bifurcation from the primary uniaxial loading path is along the tetragonal shear. Under compressive stress, there is a stress-free body-centered cubic phase, which is unstable and ready to transform to a stress-free body-centered tetragonal phase with lower internal energy. The stable region is from - 1.6 to 4.2 GPa in the ideal strength, or from - 0.07 to 0.07 in the Lagrangian strain.

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A series of nanostructured GaN Films have been prepared on Si substrates. Field emission measurements show that the oriented nanostructured GaN film with a thickness of 40 nm has an ultralow threshold field of 1.2 V / m at 1 mA/ cm 2 and yields a stable emission current of 40 mA/ cm 2 at 2.8 V / m, which is comparable to those of carbon nanotubes. A polarization field emission enhancement mechanism with ballistic electron transport is proposed to explain the origin of this ultralow-threshold field emission phenomenon.

We report on the shape and polarization control of site-controlled multiple and single InAs quantum dots (QDs) on InP pyramids grown by selective-area metal-organic vapor phase epitaxy. With increasing growth temperature the QDs elongate causing strong linear polarization of the photoluminescence. With reduced pyramid base/pyramid top area/QD number, the degree of polarization decreases, attributed to the symmetric pyramid top, reaching zero for single QDs grown at lower temperature. This control of linear polarization is important for entangled photon sources operating in the 1.55 μm wavelength region.

Articles you may be interested inHeteroepitaxy of InP on Si(001) by selective-area metal organic vapor-phase epitaxy in sub-50nm width trenches: The role of the nucleation layer and the recess engineering InGaAs heterostructure formation in catalyst-free GaAs nanopillars by selective-area metal-organic vapor phase epitaxy Appl. Phys. Lett. 97, 243102 (2010); 10.1063/1.3526734 Mid-infrared emission from InAs quantum dots, wells, and dots on well nanostructures grown on InP (100) by metal organic vapor phase epitaxy Erratum: "Size-dependent photoluminescence of hexagonal nanopillars with single InGaAs/GaAs quantum wells fabricated by selective-area metal organic vapor phase epitaxy" [Appl. Phys. Lett. 89, 203110 (2006)] Appl. Phys. Lett. 92, 059901 (2008); 10.1063/1.2841828 Formation of single and double self-organized InAs quantum dot by selective area metal-organic vapor phase epitaxy Appl.

While it has been well demonstrated that quantum dots (QDs) play an important role in biological labeling both in vitro and in vivo, there is no report describing the cellular nanostructure basis of receptor-mediated endocytosis. Here, nanostructure evolution responses to the endocytosis of transferrin (Tf)-conjugated QDs were characterized by atomic force microscopy (AFM). AFM-based nanostructure analysis demonstrated that the Tf-conjugated QDs were specifically and tightly bound to the cell receptors and the nanostructure evolution is highly correlated with the cell membrane receptor-mediated transduction. Consistently, confocal microscopic and flow cytometry results have demonstrated the specificity and dynamic property of Tf-QD binding and internalization. We found that the internalization of Tf-QD is linearly related to time. Moreover, while the nanoparticles on the cell membrane increased, the endocytosis was still very active, suggesting that QD nanoparticles did not interfere sterically with the binding and function of receptors. Therefore, ligand-conjugated QDs are potentially useful in biological labeling of cells at a nanometer scale.

A low temperature alternating supply epitaxy grown p-type 3C–SiC thin film is further etched to enhance the photoelectrocatalytic performance.