AVS 53rd International Symposium
    Electronic Materials and Processing Friday Sessions
       Session EM-FrM

Paper EM-FrM3
Temperature Dependent Conduction and Charge Tunneling in Nanoparticle-Molecule-Nanoparticle Bridging Structures

Friday, November 17, 2006, 8:40 am, Room 2001

Session: Molecular Electronics
Presenter: J.-S. Na, North Carolina State University
Authors: J.-S. Na, North Carolina State University
J. Ayres, North Carolina State University
K. Chandra, North Carolina State University
C.B. Gorman, North Carolina State University
G.N. Parsons, North Carolina State University
Correspondent: Click to Email
Although electronic transport across organic molecules has been widely investigated, the conduction mechanisms across a single molecule is still not well defined because of instability of metal-molecule contacts, uncertainty of number of molecules in the junction, and unavailability of temperature variable current-voltage measurements. Here we report the dielectrophoretic trapping, contact stability, and conduction characteristics of a nanoparticle/molecule/nanoparticle bridge assembly, where two ~40nm nanoparticles are linked by a phenylacetylene oligomer. The molecule/nanoparticle structures are assembled across a nanoscale (~70nm) electrode gap fabricated by angled e-beam evaporation. The nanoparticle/molecule structures are trapped by applying a dielectrophoretic force across the nanoscale electrode gap. At the optimum trapping conditions (2VAC, 1MHz, and 60s), a success rate of ~78% is achieved. Current versus voltage through the nanoparticle/molecule structure is consistent with a single molecule present between the nanoparticles, and IV results are obtained as a function of temperature (80K to 293K) and time in ambient. Analyses of ln(I/V@super 2@) versus 1/V indicates a transition from direct tunneling to Fowler-Nordheim tunneling, independent of temperature. A nonlinear fit of the IV data to the Simmons tunneling model results in barrier height of about 0.12eV, suggesting charge transport proceeds through hole tunneling. The stability of the nanoparticle electrode structure and molecular conduction over several weeks will also be presented and discussed.