Electrostatic force microscopy characterization of trioctylphosphine oxideself-assembled monolayers on graphite

We have studied the self-assembling behavior of trioctylphosphine oxide (TO PO) on a highly oriented pyrolytic graphite surface. TOPO forms stripe-like structures in registry with the underlying graphite lattice. Using electro static force microscopy, we have also measured the charge, dipole, and diel ectric constant of these monolayer films. The crystalline stripe phase has a net positive charge of about 2 x 10(-5) electron charge per TOPO molecule . The surface dipole due to adsorption is extremely small; this result impl ies that the dipole moment of TOPO is oriented parallel to the surface. Per fect image charges are not formed inside the graphite.