We have measured the potential profiles of the contact potential difference
(CPD) between Al-evaporated substrates and dispersed carbon nanotubes (CNT
s) by Kelvin probe force microscopy (KFM) using both a conventional Au-coat
ed Si (Au-Si) probe and a CNT probe. The lateral resolutions of both topogr
aphy and the potential distribution image were improved by using the CNT pr
obe. The CPD has been measured for CNTs with various diameters. We observed
that the CPD increases with an increase in the diameter. This indicates th
at the work function of CNTs increases with an increase in the diameter.