Shudong Luo

Growth of ZnO hexagonal nanoprisms

We show the success of large-scale growth of ZnO hexagonal nanoprisms on silicon substrates by a two-staged mechanism. In the first stage, the catalyst nanoparticles assisted the nucleation via the vapour–liquid–solid (VLS) mechanism to form polyhedral nanoparticles. In the second stage, the nanoprism was grown up by anisotropic homoepitaxy, layer by layer, on the c-face of the polyhedral nanoparticle. The surface of the nanoprism consists of the ultraflat {0001} and planes. The nanoprism is 200–500 nm in width and controllably sized in length, of high crystalline quality and excellent optical quality. This nanoprism would be an interesting building block for highly efficient nanolasers.

Template-free synthesis of helical hexagonal microtubes of indium nitride

Single crystalline indium nitride (InN) helical microtubes with a hexagonal hollow cross section have been synthesized in bulk quantities by nitriding indium oxide powder in ammonia flux. As-prepared InN microtubes grow along the [0001] direction with typical outer diameters of 1–3μm, wall thickness of 50–80nm and lengths up to hundreds of microns. The InN microtubes exhibit both right-handed and left-handed helicities with helical angles ranging from zero to about 30°. Variation of helicity can be observed in a single tube. A number of observations demonstrate that the growth of the tubular structure occurs by the spiraling of the warped InN nanobelts. Photoluminescence spectrum of the microtubes presents a strong emission peak centered at 700nm at room temperature.

Electrochemical fabrication and structure of NixZn1−x alloy nanowires

NixZn1?x alloy nanowires were successfully prepared by the templated electrodeposition technique. The morphology and the microstructures of as-deposited nanowires were examined by scanning electron microscope, x-ray diffraction, transmission electron microscope and electron diffraction. It is demonstrated that the content of magnetic element Ni in the nanowires can be easily adjusted by changing the ingredients of the electrolyte, the deposited current density and the deposited voltage, which is critical to tune the magnetic property of the nanowires. X-ray diffraction and electron diffraction analysis indicate that the NixZn1?x nanowires exhibit different structures with the variation in the quantity of nickel in the nanowires. It is expected that these heterogeneous alloy nanowires will have a potential application in nanoscale giant-magnetoresistance devices.

Efficiently producing single-walled carbon nanotube rings and investigation of their field emission properties

Single-walled carbon nanotube (SWNT) rings with a diameter of about 100 nm have been prepared by thermally decomposing hydrocarbon in a floating catalyst system. These rings appeared to consist mostly of SWNT toroids. High resolution transmission electron microscopy showed that these rings were composed of tens of SWNTs with a tightly packed arrangement. The production of SWNT rings was improved through optimizing various growth parameters, such as growth temperature, sublimation temperature of the catalyst, different gas flows and different catalyst components. The growth mechanism of the SWNT rings is discussed. In the field emission measurements we found that field emission from a halved ring is better than that from a whole SWNT ring, which contributed to the better emission from two opened ends of the nanotubes of the halved SWNT ring.

Anodizing behavior of aluminum foil patterned with SiO2 mask

SiO 2 -Patterned anodic aluminum oxide (AAO) is fabricated on the surface of aluminum (Al) foil by combining both photolithography and anodizing technique. Tilted pores and ridge-like features on the Al surface are observed under the SiO 2 mask by scanning electron microscopy characterization. A mechanism based on the deflection of electric field due to the existence of SiO 2 barrier on Al surface has been proposed to explain the observed anodizing behavior. Moreover, large-scale ordered metallic Al patterns are also revealed by removing the AAO film and SiO 2 mask.

Template synthesis, characterization and magnetic property of Fe nanowires-filled amorphous carbon nanotubes array

A Fe nanowires-filled amorphous carbon nanotubes (FeNW-filled a-CNTs) array was synthesized by sequential growth of electrodeposited Fe nanowires and subsequent chemical vapour deposition of amorphous CNTs in the nanochannels of alumina template. Structural characterizations of as-prepared FeNW-filled a-CNTs were carried out via field emission scanning electron microscope (FE-SEM), x-ray diffraction (XRD), elemental mapping, high-resolution transmission electron microscope (HRTEM) and Raman scattering. The formation mechanism of such Fe/C nanoheterostructure was proposed according to the detailed HRTEM analyses. Furthermore, the room temperature magnetic property of the as-prepared FeNW-filled a-CNTs array was also investigated, and obvious anisotropic behaviour in magnetization was observed.

Patterned anodic aluminium oxide fabricated with a Ta mask

Electrochemical anodization was applied to an aluminium (Al) sheet patterned with a metallic tantalum (Ta) mask, which gave rise to the formation of patterned anodic aluminium oxide (AAO). The morphological evolution of the AAO porous structure with anodizing time was characterized by scanning electron microscopy. Lateral anodizing of the Al sheet gradually developed underneath the metallic Ta mask with the increase of anodizing time. This has given us further understanding of the Al anodizing behaviour compared with our previous work with a SiO2 masked Al sheet. By controlling the anodizing time and the size of the metal mask, deep lithography of the Al substrate can be realized, and a mushroom-like Ta–Al microstructure with a high aspect ratio was created on the Al surface after removal of the AAO film. This Ta–Al microstructure has been studied in detail, and it was found to exhibit pronounced hydrophobic properties.

Conformal conversion from helical hexagonal InN microtubes to In2O3 counterparts

Cubic In2O3 microtubes were prepared by thermally oxidizing InN counterparts under controlled conditions. Similar to the starting InN sample, the converted In2O3 microtubes are hexagonal in cross section and exhibit helical motifs of both right-handed and left-handed architectures with helical angles of 0°–30°. InN microtubes can be retrieved by renitridation of the oxide microtubes. This work demonstrates that it is feasible to fabricate specific oxide nano-/microstructures from its corresponding nitride counterparts via controlled oxidation manner and vice versa. Temperature-dependent Raman scattering in both InN and In2O3 microtubes was measured and obvious downshifts of Raman modes were observed with increasing temperature.

Secondary growth of small ZnO tripodlike arms on the end of nanowires

Small zinc oxide tripodlike arms were assembled at the end of nanowires through thermal evaporation of zinc powder in a horizontal tube furnace. These arms are hundreds of nanometers in length, and they are tens of nanometers in diameter, similar to that of the based nanowires. High-resolution transmission electron microscopy investigation exhibits that they are wurtzite structure and have clear twin planes at the junction of the arms and the based nanowires. The growth mechanism, Raman, and photoluminescence properties were discussed.