Significant negative differential resistance predicted in scanning tunneling spectroscopy for a C60 monolayer on a metal surface
Journal
Physical Review B - Condensed Matter and Materials Physics
Journal Volume
80
Journal Issue
7
Pages
075403-1 - 075403-6
Date Issued
2009
Author(s)
Abstract
We theoretically predict the occurrence of negative differential resistance (NDR) in scanning tunneling spectroscopy for a pure C60 monolayer deposited on a metal surface using metal tips, namely, on a Cu(111) surface and using various W tips. It is proposed that the likely reason why NDR has not been observed under such conditions is that NDR can be reduced if an oxidized or Cu-terminated tip is used. A detailed decomposition of the total tunneling current into its contributions from individual molecular orbitals reveals that only some of the orbitals on the tip and on the C60 can be "matched up" to give a contribution to the current and that the NDR is a consequence of the mismatch between these specific orbitals within particular ranges of bias voltage. Moreover, the NDR characteristics, including the peak positions and the peak-to-valley ratios, are found to depend on the tip material, tip geometry, and tip-to-molecule position. © 2009 The American Physical Society.
Type
journal article