The effect of using EBL with devices incorporating CNT has also been investigated. The effect on metallic and
semiconducting CNT exposure in the channel of the transistor devices was examined and a physical mechanism for the
variations discussed. We show that the subsequent generation of trap states along the CNT channel varies the conduction
mechanism of the nanotube and has a significant effect on device performance. Metallic and semiconducting CNT react
very differently, with an apparent increased localization effect in the metallic tubes responsible for dramatic decreases in
conductance.
Seung Jin Chae, Fethullah Günes, Ki Kang Kim, Eun Sung Kim, Gang Hee Han, Soo Min Kim, Hyeon-Jin Shin, Seon-Mi Yoon, Jae-Young Choi, Min Ho Park, Cheol Woong Yang, Didier Pribat, Young Hee Lee
Highly crystalline few-graphene layers were synthesized on poly-nickel, Ni(111) and Ni-deposited substrates by
optimizing the mixing ratio of C2H2/H2 and C2H4/H2 and growth time. The hydrogen effect was investigated to minimize
defects and maintain uniformity of the synthesized few-layer graphenes. Using the optimized ratio of hydrogen and
acetylene mixture, few graphene layers with large sizes of up to 4 inches in diameter were also synthesized on Ni
evaporated Si substrate with different thicknesses and were transferred successfully onto PET film. We also found that
the wrinkles, different from inherent ripples, were formed in the graphene layer independent of the location of the grain
boundary of poly-Ni substrate and growth conditions. This was attributed to the formation of a step terrace followed by
the terrace bunching to result in higher wrinkles due to the thermal mismatch existing between Ni substrate and graphene
layers during thermal quenching. A sheet resistance of 233 Ω/sq was obtained at a transmittance of 65%.
Nanodispersion of single-walled carbon nanotubes (SWCNTs) has been systematically investigated with the use of
sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP) surfactant in de-ionized water. A high concentration of
nanodispersed SWCNTs up to 0.08 mg/mL was achieved with introduction of an additional dispersant of PVP by
optimizing surfactant concentration, sonication time, and centrifugation speed, which was crucial to obtaining a high
concentration of SWCNTs in the supernatant solution. We also demonstrate that diameters of the nanodispersed
nanotubes can be sorted out by controlling the centrifugation speed and furthermore the saturated SWCNT concentration
was nearly constant, independent of the initial concentration at high centrifugation speed. Two dispersion states were
identified depending on the centrifugation speed: an intermediate dispersion of nanodispersion mixed with
macrodispersion (I) and nanodispersion (II). This was verified by Raman spectroscopy, scanning probe microscopy,
optical absorption spectroscopy, and photoluminescence measurements. The obtained SWCNT solution was stable up to
about ten days. Some aggregated SWCNT solution after a long period of time was fully recovered to initial state of
dispersion after re-sonication for a few minutes. Our systematic study on high concentration nanodispersion of SWCNTs
with selective diameters provides an opportunity to extend the application areas of high quality SWCNTs in large
quantity.
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