| Summary: | 碩士 === 國立中興大學 === 材料科學與工程學系所 === 99 === We have synthesized tellurium nanotubes by a vapor transport process and carefully investigated the growth mechanism of tellurium nanotubes by examining their structural evolution during the synthesis process. The CO and NO2 gas sensing properties of the tellurium nanotubes-based gas sensor devices were also measured. The tellurium nanotubes can be synthesized on Si substrates without using metal catalysts in a horizontal furnace. The optimum source and substrate temperatures were 560℃ and 110℃, respectively. The typical diameters of tellurium nanotubes were ~600 nm, the thickness of the tube walls were about 80~100 nm and the lengths were up to 10 um. The as-deposited products were confirmed to be single-crystalline trigonal Te with hexagonal cross-section grown along the [0001] direction. The growth mechanism of tellurium nanotubes can be divided into several steps. First, Te nanoparticles are nucleated on the Si substrate in the initial stage. Then these nanoparticles will gradually develop into the sheet-like structure (nanosheets) lying horizontally on the substrate. After these nanosheets cover the entire surface and they will stack with each other. Some of the nanosheets which have certain horizontal angles with respect to the substrate surface will begin to grow out of the substrate, and gradually develop into three-face screen-like nanostructures. As the Te source atoms are kept supplying, these three-face screen-like nanostructures will subsequently evolve to four-face and six-face groove-like nanostructures. Eventually, the six-face groove-like nanostructures will close the small gaps to grow into nanotubes. The gas sensor device fabricated by tellurium nanotubes exhibited the capabilities of detecting low-concentration CO and NO2 gases at room temperature. In addition, the CO and NO2 gases can be simultaneously detected by tellurium nanotubes based gas sensors. Therefore, tellurium nanotubes have a great potential for applications for CO and NO2 gas sensors.
|
|---|
