Search

Time resolved photoluminescence (TRPL) and transient absorption (TA) spectroscopy reveal an ultrafast charge transfer (CT) process, with an electron localization time constant 39±9 ps, between the ZnO host and the Cu dopants in Cu-doped ZnO nanowires. This CT process effectively competes with the ZnO band edge emission, resulting in the quenching of the ZnO UV emission. TRPL measurements show that the UV decay dynamics coincides with the buildup of the Cu-related green emission. TA measurements probing the state-filling of the band edge and defect states provide further support to the CT model where the bleaching dynamics concur with the TRPL lifetimes. [ABSTRACT FROM AUTHOR]

As an important class of spintronic material, ferromagneticoxidesemiconductors are characterized with both charge and spin degreesof freedom, but they often show weak magnetism and small coercivity,which limit their applications. In this work, we synthesized Nd-dopedZnO nanowire arrays which exhibit stable room temperature ferromagnetismwith a large saturation magnetic moment of 4.1 μB/Nd as well as a high coercivity of 780 Oe, indicating giant magneticanisotropy. First-principles calculations reveal that the remarkablemagnetic properties in Nd-doped ZnO nanowires can be ascribed to theintricate interplay between the spin moments and the Nd-derived orbitalmoments. Our complementary experimental and theoretical results suggestthat these magnetic oxide nanowires obtained by the bottom-up synthesisare promising as nanoscale building blocks in spintronic devices. [ABSTRACT FROM AUTHOR]

Abstract: Single-crystalline ZnO nanowires (NWs) were synthesized by a facile vapor transport method. The good orientation and high crystal quality were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) measurements. Excitation-power-dependence photoluminescence spectra of ZnO NWs show that the UV emission displayed an evident blueshift with increasing excitation power and the corresponding energy shift might be as large as 10meV. This anomalous phenomenon correlates to the band bending level caused by the surface built-in electric field due to the existence of substantial oxygen vacancies. By increasing the excitation power, the enhanced neutralization effect near the surface will reduce the built-in electric field and lead to a reduction of band bending which triggers the blueshift of the UV emission. [Copyright &y& Elsevier]

Abstract: ZnO nanowires were grown on Au-coated Si (100) substrates by the method of vapor–liquid–solid (VLS) growth processing technique. The effects of supply time of Ar gas current on morphology and microstructure of Au-catalyzed ZnO nanowires were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. The results showed that the morphologies of ZnO nanostructures strongly depended on the time of flowing Ar gas. When the time of flowing Ar gas was 90s, ZnO showed nanowires with hexagonal structure. Their diameters and lengths were 160nm and 20μm, respectively, on average, and the Raman scattering peak located at 438cm−1 reached maximum intensity. The results also showed that the ZnO growth could be patterned by controlling the initial position of Au-coated area on the Si substrates. [Copyright &y& Elsevier]