Paper NS-MoA3
Controlled Manipulation of Self-Organized Ni (II)-Octaethylporphyrin Molecules Deposited from Solution on HOPG with a Scanning Tunneling Microscope

Monday, October 15, 2007, 2:40 pm, Room 616

We have investigated the controlled manipulation of self-assembled NiOEP molecules adsorbed from a benzene solution onto a freshly cleaved high ordered pyrolytic graphite surface using the scanning tunneling microscope (STM) under ambient conditions. STM images acquired before and after scans of different patterns at a high current setpoint value reveal the creation of molecule free regions. In these cleared regions STM images reveal a 2D HOPG lattice with atomic spacing of 2.5 Å and a pattern depth of about 1.2 Å which is a typical STM height value for a monolayer NiOEP film on graphite. These molecule free regions are created by the transfer of NiOEP molecules from the surface to the tip when the STM is operated at very high current setpoint (tunneling resistance of about 120 MΩ or less). Once the molecules are picked up by the tip they then diffuse along the wire as confirmed by the absence of molecular build-ups around the patterned areas of the STM images. Furthermore, once the molecular film is damaged the size of the uncovered area keeps on growing larger with subsequent scans. In the case of square scans performed at high current setpoint values the freshly created regions exhibit straight edges with directions that are dictated by the lattice vectors of the underlying graphite substrate.