Measurement of thermopower and current-voltage characteristics of molecular junctions to identify orbital alignment

作者：Tan Aaron; Sadat Seid; Reddy Pramod^*

来源：Applied Physics Letters, 2010, 96(1): 013110.

DOI：10.1063/1.3291521

• atomic force microscopy
• Fermi level
• gold
• MIM structures
• molecular electronics
• monolayers
• organic compounds
• Seebeck effect

We report an experimental technique that concurrently measures the Seebeck coefficient and the current-voltage (I-V) characteristics of a molecular junction to determine the identity and the effective energetic separation of the molecular orbital closest to the electrodes' Fermi level. Junctions created by contacting a gold-coated atomic force microscope tip with a monolayer of molecules assembled on a gold substrate were found to have a Seebeck coefficient of (+16.9 +/- 1.4) mu V/K. This positive value unambiguously shows that the highest occupied molecular orbital (HOMO) dominates charge transport. Further, by analyzing the (I-V) characteristics, the HOMO level is estimated to be similar to 0.69 eV with respect to the Fermi level.

• 出版日期2010-1-4