Solid State Phenomena Vols. 121-123

Abstract: A novel and thermally stable hierarchically porous yttrium doped zirconia material with crystallized framework has been synthesized in a facile process. XRD, nitrogen adsorption analysis, FESEM, FETEM, were used for the structural characterizations. This novel hierarchically porous zirconia shows a well-defined ordered macroporous structure, a broad distributed mesoviods, and a very uniform mesoporous pore-distribution. Small amount of yttrium can be helpful to increase the thermal stability of the prepared hierarchically porous zirconium oxide.

Abstract: Large-scaled ZnO nanowires have been successfully synthesized by heating and evaporating zinc powders directly without the assistance of any catalysts or additives. We acquired disarrayed and arrayed ZnO nanowires respectively on Si(100) substrates and c-oriented ZnO thin film. The disarrayed ZnO nanowires are about 40nm in diameter and 10μm in length, evenly and randomly distributed on the substrate; while the arrayed nanowires are about 60nm in diameter and 3-4μm in length, well aligned along the normal direction of the substrate. XRD and TEM results reveal that in both kinds of the products, most of the synthesized ZnO nanowires are single crystalline in a hexagonal structure and grow along the [001] direction. During the growth process of arrayed ZnO nanowires, the c-oriented ZnO thin film control the growth direction. Photoluminescence spectrums were measured showing that both of the disarrayed and arrayed ZnO nanowires have a strong ultraviolet emission around 380nm. Such results suggest the synthesized ZnO nanowires, especially arrayed nanowires can be applied to excellent optoelectronic devices.

Abstract: We report that entirely end-bonded multi-walled carbon nanotubes (MWNTs) within Tomonaga-Luttinger liquid (TLL) states at high temperatures can show superconductivity with the transition temperature Tc as high as 12K that is approximately 40-times larger than those in ropes of single-walled nanotubes. We find that emergence of this superconductivity is very sensitive to junction structures of Au electrode/MWNTs. This indicates that MWNTs with optimal numbers of electrically activated shells can allow the superconductivity that overcomes the TLL sates, due to intershell effects.

Abstract: Highly ordered single-crystal iron nanowire arrays with different diameters have been fabricated in anodic aluminum oxide (AAO) templates by DC electrodeposition method. The Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) show that the iron nanowires are highly uniform and exhibit a single crystal structure. The X-ray diffraction (XRD) patterns of iron nanowire arrays indicate that most of the iron nanowire arrays have the obvious preferred orientation along the [200] direction. From the hysteresis loops of the iron nanowires, it reveals that the easy magnetization axes of nanowire arrays are along the long axis. The sample with smaller diameter (d=35nm) has a high square ratio (up to 98%) and a high coercive filed (1265Oe) when the external magnetic field is applied along axis of the nanowires. When the diameter decreases, the square ratio and the coercive field increase due to the single-domain structure and the strong shape anisotropy in the smaller diameter nanowire arrays.

Abstract: The traditional precipitation method and a novel inorganic-organic hybrid method were used to control the morphology of nanocrystalline CeO2. By adjusting the methods and the preparation conditions, spherical and rode-shaped cerium dioxides with the nanoparticle sizes were prepared. Their structures and properties were characterized by XRD, BET and TEM.

Abstract: Direct Wafer Bonding has been widely developed and is very attractive for a lot of applications. Using original techniques based on direct bonding enable to carry out specific engineered substrates. Various illustrations are given among which twisted Si-Si bonded substrates, where buried dislocation networks play a key role in the subsequent elaboration of nanostructures.