We manipulate and measure the properties of single, isolated molecules and of bundles of molecules, selectively placed into monolayer films. The structure of these films is determined by controlling the defect type and density in the films in order to tune their properties. We then process the films to insert single molecules, to insert bundles of molecules, or to graft new molecular terraces onto existing domains by using these defects to advantage. The inserted molecules can function as molecular switches or serve as the anchor points for polymerization. We also prepare films with well defined interfaces between separated components so that insertion, deposition, or reaction can be directed to these molecularly sharp boundaries.
We connect our scanning tunneling microscopy measurements to electron transfer phenomena that are ubiquitous in such areas as biochemistry and electrochemistry by separating the transconductance into components arising from transport through the molecule vs. the tunneling gap outside the film. We show how these components can be measured independently. We switch the conductance states of measured numbers of molecular switches using the electric field applied by the scanning tunneling microscope. We demonstrate how proximity can affect electronic structure, potentially limiting ultimate device densities or providing new opportunities for coupling and tuning devices or components.
Paul S. Weiss
Department of Chemistry, The Pennsylvania State University
152 Davey Laboratory
University Park, PA 16802-6300 USA