High-quality CdSxSe1-x nanobelts of variable composition (0

Ternary alloy CdSSe nanowires and nanoribbons were successfully grown through a one-step thermal evaporation route using Au as a catalyst. The nanostructures obtained are uniform in diameter, and have smooth surfaces. High-resolution transmission electron microscopy, energy dispersive x-ray spectra and x-ray diffraction showed that both the nanowires and the nanoribbons have high-quality single-crystalline nature, and their compositions can be determined as CdS(0.6)Se(0.4) and CdS(0.3)Se(0.7), respectively. The mechanisms of formation of these two different nanostructures were discussed. The photoluminescence measurements showed very strong band-edge emission for both samples, which further demonstrates the single-crystal nature of the as-obtained CdSSe alloys. This finding may be extended for fabricating other composition-tunable 1D ternary alloy nanostructures.

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We address the question of whether the superconducting transition temperature (T c ) of high-Tc cuprates is enhanced when randomly distributed dopant atoms form an ordered array in the charge reservoir layers. This study is possible for the Sr 2 CuO 3+δ superconductor with K 2 NiF 4 -type structure in which oxygen atoms only partially occupy the apical sites next to the CuO 2 planes and act as hole-dopants. We show that remarkable T c enhancement up to 95K in this mono CuO2 layered HTS is associated with the apical oxygen ordering, not to the hole concentration change. The result points a route toward further enhancement of T c in cuprate superconductors.

We investigate by angle-resolved photoemission the electronic structure of in situ grown tetragonal CuO, a synthetic quasi-two-dimensional edge-sharing cuprate. We show that, in spite of the very different nature of the copper oxide layers, with twice as many Cu in the CuO layers of tetragonal CuO as compared to the CuO 2 layers of the high-T c cuprates, the low-energy electronic excitations are surprisingly similar, with a Zhang-Rice singlet dispersing on weakly coupled cupratelike sublattices. This system should thus be considered as a member of the high-T c cuprate family, with, however, interesting differences due to the intralayer coupling between the cupratelike sublattices.