K W Hipps - Controlled Manipulation of Self-Organized Ni(II)−Octaethylporphyrin Molecules Deposited from Solution on HOPG with a Scanning Tunneling Microscope

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  Publication Details (including relevant citation   information):

  Scudiero, L., Hipps, K. W. The Journal of Physical Chemistry   C 2007 111 (47) 17516-17520

  Abstract: The controlled manipulation of a   physisorbed self-assembled monolayer is demonstrated at room   temperature for the first time. Patterns are drawn in a NiOEP   monolayer supported on freshly cleaved highly ordered pyrolytic   graphite (HOPG) surface using a scanning tunneling microscope   (STM) under ambient conditions. STM images acquired before and   after pattern formation at low gap resistance reveal the creation   of molecule-free regions. In these cleared regions, STM images   display the two-dimensional HOPG lattice with atomic spacing of   2.5 Å and pattern depth of about 1.2 Å, typical of the STM   apparent height for a monolayer NiOEP film on graphite. These   molecule-free regions are created by removal of NiOEP molecules   from the surface when the STM is operated at a very high current   set point (tunneling resistance of about 120 MΩ or less) as   confirmed by the absence of molecular buildup around the   patterned areas in the STM images. We show that the removed   molecules are not collecting at the boundaries of the scanned   regions and discuss their fate. Once the molecular film is   damaged, the size of the uncovered area keeps on growing with   subsequent scans. We also observe that two different monolayer   structures (triclinic and tetragonal) form under the same   experimental conditions.

  Address (URL): http://dx.doi.org/10.1021/jp075175a