| AVS 54th International Symposium | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuM |
| Session: | Molecular Electronics |
| Presenter: | N. Gergel-Hackett, National Institute of Standards and Technology |
| Authors: | N. Gergel-Hackett, National Institute of Standards and Technology L.J. Richter, National Institute of Standards and Technology C.D. Zangmeister, National Institute of Standards and Technology C.A. Hacker, National Institute of Standards and Technology C.A. Richter, National Institute of Standards and Technology |
| Correspondent: | Click to Email |
It is important for the advancement of the field of molecular electronics to develop an improved understanding the electron transport through molecular junctions, specifically silicon-based junctions that may enable the integration of molecular devices with traditional semiconducting technologies. In this work we examine the effects of molecular length and dipole on the electrical behavior of a metal-molecule-silicon, planar, enclosed devices. Devices with alkanethiol molecules of different lengths, with semi-fluorinated and non-fluorinated molecules, and with differently doped silicon were characterized to systematically understand the energetics of the metal-molecule-silicon junction and how the electron transport through the device is affected. We characterized devices with monolayers of various chainlengths of alkanethiols and observed the device current to decrease with increased molecular length. This inverse dependence on chainlength has been widely observed from metal-molecule-metal devices, but is an important characterization metric for silicon-based devices. However, we observed a different dependence of the current density on the chainlength than has been observed for metal-molecule-metal junctions. We attribute this difference in dependence to the Schottky barrier between top metal and bottom silicon contact in the metal-molecule-silicon devices that is not present in metal-molecule-metal devices. This will be explained in greater detail. We also compare the electrical characteristics of alkanethiol molecules with those of semi-fluorinated alkanethiols. The molecular dipole is dramatically different for semi-fluorinated alkanethiols than for non-fluorinated alkanethiols, and we observed current-voltage characteristics that depend on the fluorination. In order to confirm that the differences in current observed were due to the molecular dipoles shifting the Schottky contact barrier, we characterized devices with differently doped substrates. The relative effects of the molecular dipoles on the different starting Schottky contact barriers are used to develop an energetic model of the junction and the effects of surface dipoles. The observed changes in electrical behaviors as a result of changes in the chainlength and dipole of the molecular monolayer help us to understand the electrical transport through these devices and to verify that the energetic behavior of the devices has a molecular dependence.