K W Hipps - A Scanning Tunneling Microscopy and Spectroscopy Study of Vanadyl Phthalocyanine on Au(111):  the Effect of Oxygen Binding and Orbital Mediated Tunneling on the Apparent Corrugation

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      Publication Details (including relevant citation   information):

      Barlow, Dan E., Hipps, K. W. The Journal of Physical   Chemistry B 2000 104 (25)   5993-6000

      Abstract: Submolecular resolution STM images of   vanadyl phthalocyanine (VOPc) are reported. Unlike previously   studied metal phthalocyanines, the image has neither a simple   dark or bright spot in the center. Rather, it appears to have   nodal planes running through the center of the molecule. The dark   central region is attributed to the oxygen atom reducing the   number of available states near the Fermi energy. The apparent   height of the Pc ring is very bias dependent having a value of   ∼0.1 nm between −1.5 and 0.2 V (sample) bias. The apparent height   increases rapidly to a plateau of about 0.55 nm at +1.0 V sample   bias. I − V and dI/dV data taken over VOPc islands are very   different from the same measurements made on exposed Au(111)   substrate adjacent to the islands. Strong peaks in dI/dV are seen   at +1.38 and −1.8 V sample bias. The +1.38 V feature is   associated with orbital mediated tunneling via the π* LUMO of the   Pc ring. Occasionally, the tip−surface interaction generates   anomalous dark areas in the VOPc islands.

      Address (URL): http://dx.doi.org/10.1021/jp0004462