Surface potential analyses of single-walled carbon nanotube/metal interfaces.

The band structure of a single-walled carbon nanotube (SWNT)/metal system, including a shift in the vacuum level which appears at the SWNT/metal interface, was characterized by using a Kelvin-probe force microscopy method. In the SWNT/gold system, the shift (Δ) of the vacuum level was observed to be +5.2 meV, which is one order of magnitude smaller than previously observed. When we carried out carrier doping of the SWNTs, the observed Δ was downshifted from +5.2 to -52 meV, which introduced some upshift in the band structure of the doped SWNTs. This change induced easier hole injection, which coincides with the field effect transistor characteristics of undoped and doped SWNT transistors. A similar analysis was also carried out for a SWNT/ferromagnet system. [ABSTRACT FROM AUTHOR]