|
Research on carbon nanotubes has been going on intensively because of their wide potential applications in several areas. In special, future nanoelectronics and field-emission displays may be improved and size-reduced with the use of carbon nanotubes as conducting devices. It is therefore of interest to develop new techniques to produce doped carbon nanotubes. Arch-discharge methods are not well adequate for doping due to the large amounts of by-products. Chemical vapor deposition methods are promising but there is contamination due to the metal catalysts used. In this work, we investigate a method of growth boron doped carbon nanotubes with a polymer catalyst (polyethylene glycol) by hot filament chemical vapor deposition. Copper substrates have been used. After cleaning, the substrates have been coated with polyethyleneglicol previously diluted in ethanol and then dried in a hot-plate in air at 373 K for 10 min. In the sequence, the samples were immersed in the reaction chamber of a hot-filament CVD system fed with ethanol and B2O3 highly diluted in argon (65 % vol.) and hydrogen (34.5 % vol.). A total flow rate of about 100 sccm, regulated by precision mass flow, and a total pressure of about 20 Torr were maintained throughout. The deposition temperature was 793 K and the deposition time was 20 min. There was no need of chemical treatment for purification of the as-deposited carbon films. These effects are discussed in relation to the morphological data obtained by scanning electron microscopy (SEM), Field emission scanning electron microscopy (FESEM) and results from Raman spectroscopic analyses of samples. Threshold field achieved for electron emission was 2.5 Volts/micron. |