1. Transport Results S51 3nm Ti / 60nm Au / C10-dithiol / 20nm Au Nanotransfer printed (50 micron pads) 10-07-09

2. Device S51-F02

3. data taken: 9-29-09

5. Differential Conductance data taken: 9-29-09

6. Zoom -Differential Conductance data taken: 9-29-09

7. Device S51-F07

8. data taken: 9-29-09

10. Differential Conductance

11. Analysis

12. Au SiOx / Si Substrate SAM Au (nTP) - + I e-e- e-e- Conduction is not good this way (positive Vbias): Au SiOx / Si Substrate SAM Au (nTP) - + I e-e- e-e- Conduction shows tunneling this way (negative Vbias): Problem is getting electrons from SAM to the nTP gold at this interface One-way Conduction

13. Conclusions Possible reasons for poor conductance at positive Vbias and temperature dependence (procedure steps differing from sample prep. for cAFM measurements): Oxidation of thiol end group on exposure to air during nanotransfer printing (Surf. Sci. 576 (2005) 188-196) R-SH  R-SOH  RSO 2 H  RSO 3 H (Patai, Chemistry of the Thiol Group II, 1974) UV-light exposure during lithography - is also known to promote oxidation with co- adsorbed O 2 (JACS 115 (1993) 3342) Samples degrade over time. Oxygen likely the culprit here (adsorbed, then reacted). Solution (next batch): Prepare samples in glovebox. Thus, no exposure to oxygen before covering with photoresist. Glovebox is also being renewed and new filters installed. Measure samples immediately after preparation.