AVS 49th International Symposium
    Organic Films and Devices Wednesday Sessions
       Session OF+EL+SC-WeA

Paper OF+EL+SC-WeA8
Zero-bias Anomaly in Molecular Monolayer Tunneling

Wednesday, November 6, 2002, 4:20 pm, Room C-102

Session: Molecular and Organic Films and Devices
Presenter: D.R. Stewart, Hewlett-Packard Laboratories
Authors: D.R. Stewart, Hewlett-Packard Laboratories
D.A.A. Ohlberg, Hewlett-Packard Laboratories
P.A. Beck, Hewlett-Packard Laboratories
R.S. Williams, Hewlett-Packard Laboratories
Correspondent: Click to Email
Electron tunneling is the dominant transport mechanism in nearly all proposed molecular electronic devices. Standard tunneling theory is normally used to predict device behavior, yet few experimental investigations of molecular tunneling exist due to the difficulty in constructing high quality molecular monolayer films. We describe detailed electronic transport characterization of several planar electrode / Langmuir-Blodgett (LB) molecular monolayer / electrode systems that show a large zero-bias anomaly and an anomalous exponential temperature dependence. Single-species LB monolayers of C@sub 22@, C@sub 20@, C@sub 18@, C@sub 16@ and C@sub 14@ carboxylic acid alkanes were sandwiched between upper and lower platinum electrodes, with active device areas of 7-200µm@super 2@. Current and differential conductance were measured as a function of voltage ±1V and temperature 2-300K. Below 40K, device characteristics were constant. Surprisingly, from 40-300K device currents were exponential in temperature. A very wide ±150mV dip in conductance was also present and temperature activated. Both results contradict standard tunnel theory, indicating that the electronic transport is not yet understood even in this simplest symmetric alkane monolayer system.