We describe an approach for controlling electrostatic barriers in molecular
electronics devices which uses anisotropic dielectric material to modify t
he analytic form of the effective electrostatic interactions within the dev
ice. We study the one-dimensional geometry relevant to interfaces between c
arbon nanotubes and find that the bound charge induced in a uniaxial dielec
tric can replace the bare electrostatic interaction between charges with se
paration z by an effective -log(z) interaction or a confining \z\ interacti
on. We use these models to study the depletion region formed at heterojunct
ions between segments of doped carbon nanotubes. (C) 2001 American Institut
e of Physics.