کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5367431 | 1388365 | 2011 | 5 صفحه PDF | دانلود رایگان |

Thermionic emission from vertically grown carbon nanotubes (CNTs) by water-assisted chemical vapor deposition (WA-CVD) is investigated. I-V characteristics of WA-CNT samples exhibit strong Schottky effect leading to field proportionality factor β â¼Â 104 cmâ1in contrast to β â¼Â 200 cmâ1 for the bare tungsten substrate. Non-contact atomic force microscopy imaging of CNT samples show propensity of nanoasperities over a scale of micron size over which the tungsten surface is seen to be atomically smooth. The values of root mean-square roughness for CNTs and W were found to be 24.2 nm and 0.44 nm respectively. The Richardson-Dushman plots yield work function values of ΦCNT â 4.5 and ΦW â 4.3 eV. Current versus time data shows that CNT cathodes are fifteen times noisier than tungsten cathode presumably due to increased importance of individual atomic events on the sharp CNT tips of bristle like structures. Power spectral density of current exhibited 1/fξ behavior with ξ â 1.5, and 2 for W and CNTs. The former suggests surface diffusion whereas the latter indicates adsorption/desorption of atomic/molecular species as a dominant mechanism of noise generation.
Journal: Applied Surface Science - Volume 257, Issue 23, 15 September 2011, Pages 10306-10310