| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 100 === Anatase titanium dioxide (A-TiO2) were grown on top of carbon nanotube (CNT) bundle arrays by metal organic chemical vapor deposition (MOCVD) using titanium-tetraisopropoxide (TTIP, Ti[OCH(CH3)2]4) as the source reagents. The N-doped A-TiO2/CNTs nanocomposite was then fabricated with nitrogen plasma treatment.
The surface morphology, structural and spectroscopic properties of the A-TiO2/CNTs and N-doped A-TiO2/CNTs nanocomposites were characterized using Field-emission scanning electron microscopy (FESEM), Raman spectroscopy, Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The FESEM image showed a dense coalescence of A-TiO2 with uniform size distribution on the nanotube walls. Raman spectra revealed that nanostructural A-TiO2 had been deposited on the CNT nanocrystals and a new vibration mode of D^'-band at higher wavenumber side was also found. The XPS spectra in the region of N 1s, Ti 2p and O 1s provided a conclusive evidence of the formation of O-Ti-N bond during nitrogen treatment process. The TEM image of A-TiO2 deposited CNT showed uniform distribution, and random directions of A-TiO2 had been grown on the surface of the CNT.
The current density versus electric field measurements yielded turn-on field of 1.8 V/?慆 and 1.0 V/?慆 at a current density of 10 ?嫀/cm2, threshold field of 3.6 V/?慆 and 1.9 V/?慆 at a current density of 1 mA/cm2, and field enhancement factor of 2700 and 3000 for the A-TiO2/CNTs and N-doped A-TiO2/CNTs nanocomposites, respectively. Long term stability studies were also carried out. The results indicated that nitrogen doping decreased the turn-on field and threshold field of A-TiO2/CNTs, providing stable field emission applications. The probable mechanisms of field emission enhancement for N-doped A-TiO2/CNTs composite were proposed and discussed.
|
|---|
