کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5367431 1388365 2011 5 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
A comparative study of thermionic emission from vertically grown carbon nanotubes and tungsten cathodes
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
A comparative study of thermionic emission from vertically grown carbon nanotubes and tungsten cathodes
چکیده انگلیسی

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 ∼ 104 cm−1in contrast to β ∼ 200 cm−1 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 ≃ 4.5 and ΦW ≃ 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 ≃ 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.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Applied Surface Science - Volume 257, Issue 23, 15 September 2011, Pages 10306-10310
نویسندگان
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