AVS 50th International Symposium
    Nanometer Structures Thursday Sessions
       Session NS-ThM

Paper NS-ThM11
Elucidation of the Electronic Properties of Isolated Alkanethiolate-Passivated Undecagold Clusters by Low Temperature Scanning Tunneling Microscopy and Spectroscopy

Thursday, November 6, 2003, 11:40 am, Room 308

Session: Advances in Scanning Probes
Presenter: S.U. Nanayakkara, The Pennsylvania State University
Authors: S.U. Nanayakkara, The Pennsylvania State University
R.K. Smith, The Pennsylvania State University
T.P. Pearl, The Pennsylvania State University
B.A. Mantooth, The Pennsylvania State University
P.S. Weiss, The Pennsylvania State University
G. Woehrle, University of Oregon
J.E. Hutchison, University of Oregon
Correspondent: Click to Email
We have studied the electronic properties of isolated, octanethiolate-stabilized undecagold clusters [Au@sub 11@(S(CH@sub 2@)@sub 7@CH@sub 3@)@sub 10@] using low temperature scanning tunneling microscopy (STM) and spectroscopy (STS). The clusters, d@sub CORE@ = 0.8 ± 0.2 nm, were immobilized by inserted dithiol molecules in an alkanethiolate self-assembled monolayer (SAM) on Au(111). The clusters were synthesized in solution by ligand exchange of Au@sub 11@(PPh@sub 3@)@sub 8@Cl@sub 3@ with octanethiol, resulting in a complete octanethiolate ligand shell, and were subsequently deposited upon a SAM. The geometry of the STM tip-vacuum-gold cluster-SAM-Au(111) assembly can be modeled as a double barrier tunnel junction, which may give insight into controlling the movement of single or small numbers of electrons. Discrete quantum energy levels are more evident in this cluster size range where the atomic character of the metal is prominent. We have observed Coulomb blockade of these clusters at 4 K. The current-voltage characteristics show uneven spacing between adjacent current steps, showing quantized energy states. The observed, large zero-conductance gaps result from quantum size effects, where the bound octanethiolate ligand shell further reduces the free volume in which the electrons can move. This study assesses the impact of sub-nanometer sized clusters on single electron transport properties, enlightening the future of nanoscale electronics.