AVS 49th International Symposium
    Surface Science Friday Sessions
       Session SS-FrM

Paper SS-FrM9
Conductance Switching in Single Molecules

Friday, November 8, 2002, 11:00 am, Room C-110

Session: Self-Assembly at Surfaces
Presenter: Z.J. Donhauser, The Pennsylvania State University
Authors: Z.J. Donhauser, The Pennsylvania State University
T.P. Pearl, The Pennsylvania State University
P.S. Weiss, The Pennsylvania State University
Correspondent: Click to Email
We have studied functionalized phenylene ethynylene oligomers as candidate molecular electronic devices using scanning tunneling microscopy (STM). A simple self-assembly strategy has been demonstrated that allows us to control monolayer structure, placement of individual molecules, and switching activity of individual molecules. Alkanethiolate self-assembled monolayers (SAMs) were used as host matrices to isolate and to insulate individual candidate molecular electronic devices. The isolated molecules were individually addressed and electrically probed using STM imaging and spectroscopy. The guest molecules exhibit reversible conductance switching, manifested as a change in the topographic height in STM images. High and low conductance states are visible when the molecules are inserted in dodecanethiolate SAMs, but the low conductance states are of the same height or lower than the host matrix. Using thin alkanethiolate matrices (as low as octanethiolate) reveals that the molecules can occupy at least three discrete conductance states. The amount and rate of active switching can be mediated by the structure of the host matrix. Poorly ordered SAMs were produced using a short deposition time; molecules inserted in these monolayers have a high switching activity. Well-ordered SAMs were produced using a vapor annealing procedure, which has been demonstrated with mixed alkanethiolate monolayers. Guest molecules inserted in vapor annealed SAMs have a low switching activity.