Zhu Guangping

ZnO Nanorods Produced by the Method of Arc Discharge

ZnO nanorods are fabricated by arc discharge with ZnO powder as source materials. The sample is characterized by x-ray diffraction, Raman scattering spectra, scanning electron microscopy and high-resolution transmission electron microscopy. The ZnO nanorods exhibit single crystals with the hexagonal wurtzite structure. Many of them are tetrapod-like. The diameters range from several nanometres to about 100 nm, and the main diameters of the nanorods is around 20 nm. The length-to-diameter ratio is more than 5, and the grown directions are along the [001] axis. Photoluminescence spectra show a narrow ultraviolet emission at around 389 nm and a broad green emission at around 520 nm. The growth process can be interpreted by the vapour-solid mechanism.

Disc-Capped ZnO Nanocombs

Nanocombs with a disc cap structure of ZnO have been synthesized on Si substrates by using pure Zinc powders as the source materials based on a vapour-phase transport process. The morphology and the microstructure are investigated by a scanning electron microscopy and x-ray diffraction. Based on the transmission electron microscopy and selected area electron diffraction analysis, the growth directions of three representative parts, nanoribbon stem, nanorod branch and nanodisc cap of the nanocomb are revealed. The growth mechanism of the disc-capped nanocombs is discussed based on the self-catalyzed vapour-liquid-solid process.

A Sensor-on-Chip Based on Second-Order Optical Effect of ZnO Nanowires

Strong second-order nonlinear effect of ZnO nanowires on a silicon wafer are demonstrated by using the hyper-Rayleigh scattering (HRS) measurement. The large nonlinear effect can be attributed to the following two factors: (1) the large total dipole moment caused by high surface defect density and electrostatic potential gradient, (2) coherent effect due to high crystal quality of single nanowire. Moreover, the second-order nonlinear effect is found to become weaker when the chip is put into organic solvent due to modification of surface defect caused by organic molecules. The variation of second-order signal in the solvent indicated the potential applications of ZnO nanowires as a sensor-on-chip (SoC).