Alkanethiol self-assembled monolayers as the dielectric of capacitors with nanoscale thickness

Alkanethiol self-assembled monolayers (SAMs) on a mercury surface are used to build a junction consisting of two opposing mercury surfaces with interposed SAMs: Hg-SAM/SAM-Hg. The liquid mercury surface provides a support for the SAM that is smooth, compliant, foe of defects, and without the incommensurate lattice properties that characterize solid metal surfaces. The thickness of the dielectric (similar to 30-90 Angstrom) in this junction can be easily changed by using alkanethiols with different lengths. From capacitance measurements, a dielectric constant of 2.7+/-0.3 is calculated for the SAMs. The conductivity of SAMs on the Hg surface is sigma=6+/-2 X 10(-15) Omega(-1) cm(-1), a value close to that of bulk polyethylene. The junction sustains an electric field of 6 MV/cm. (C) 1998 American Institute of Physics. [S0003-6951(98)03114-3].