Reproducible measurement of single-molecule conductivity.

Area of Science:

• Molecular electronics
• Nanotechnology
• Surface science

Background:

• Establishing reliable electrical contacts to individual molecules is crucial for understanding their intrinsic electronic properties.
• Previous methods often lacked reproducibility and were unable to isolate single-molecule behavior.

Purpose of the Study:

• To develop a robust method for creating through-bond electrical contacts to single molecules.
• To accurately measure the electrical resistance of single molecules.
• To differentiate intrinsic molecular properties from those of molecular assemblies.

Main Methods:

• Development of a novel technique for forming chemically bonded electrical contacts.
• Utilizing current-voltage (I-V) curve quantization to identify single-molecule junctions.
• Performing extensive measurements on over 1000 single octanedithiol molecules.

Main Results:

• Quantized current-voltage curves were observed, serving as a signature for single-molecule contacts.
• The resistance of a single octanedithiol molecule was precisely determined to be 900 ± 50 megohms.
• Nonbonded contacts exhibited significantly higher resistance (over four orders of magnitude), lower reproducibility, and different voltage dependencies.

Conclusions:

• Chemically bonded contacts are essential for accurate measurement of intrinsic molecular electronic properties.
• The developed method provides a reliable platform for single-molecule electronics research.
• This work highlights the importance of contact methodology in molecular transport studies.