Zhang Qi-Feng

Low-Field Emission from Iron Oxide-Filled Carbon Nanotube Arrays

Arrays of multi-walled carbon nanotubes (MWCNTs) filled with iron oxide have been fabricated by a one-step route based on the pyrolysis of ferrocene under a well-chosen synthesis condition. The MWCNT arrays were observed with a scanning electron microscope, with which an energy dispersive x-ray spectrum (EDXS) was also acquired, and they are analysed by x-ray diffraction. Furthermore, individual MWCNTs were studied by using selected area electron diffraction (SAED) and the EDXS in a transmission electron microscopy observation. All the observation and analysis confirmed that the MWCNTs were filled with iron oxide. Field emission from these arrays of iron oxide-filled MWCNTs was measured and the turn-on field was determined to range from 0.83–1.01 V/μm, appearing to be much lower than those of arrays of pure MWCNTs and arrays of nitrogen-doped MWCNTs fabricated in similar ways. The possible reasons of the observed low-field emission are discussed.

Field emission from zinc oxide nanowires

An array of random-oriented zinc oxide nanowires (ZnO NWs) was fabricated on silicon substrate by thermal evaporation. After a thermal evaporation process, the silicon substrate was covered with a large number of uniformly distributed ZnO islands, from which non-aligned NWs with a diameter of several ten nanometres were grown. During this process, the temperature around the substrate was intentionally kept below 500 degrees C for practical consideration. From these ZnO NWs field emission was achieved. The turn-on field, under which a 10μA/cm2 current density was extracted, was measured to be 3.0V/μm. Also, the emission site distribution was investigated using the transparent anode technique. The field emission was observed to have occurred from the whole sample surface. These results suggest that ZnO NWs have great potential application in flat panel displays.

Fluorescence Microscopy of Nanoscale Silver Oxide Thin Films

The experimental conditions for photoactivated intermittent fluorescence from nanoscale silver oxide were studied with fluorescence microscopy. Strong fluorescence was observed from the Ag2O particles with size of 10-20 nm excited with both blue and green light. We observed the saturation of photoexcitation with blue light and explained the experimental results using the model of agglomeration of silver atoms to form small clusters and the fluorescence of Ag2 and Ag3 clusters.

Microstructral evolution of well-aligned ZnO nanorods array films in aqueous solution

By means of scanning electron microscopope and X-ray diffraction, microstructural evolution of well-aligned ZnO nanorod array films was studied. The films were prepared on a glass using direct deposition method in an aqueous solution. The experimental results show that the highly oriented rods grew from the randomly oriented crystals. Those rod-like randomly oriented crystals began to impinge on other neighboring crystals and their growth became physically limited; only the rods perpendicular to the substrate were allowed to grow freely. This kinetically controlled nucleation and growth would be responsible for producing the uniformly oriented nanorods. During the ZnO rods’ growth, the topology of their top faces changed from flat, prismatic to finally flat.