Abstract
We fabricate and characterize carbon-fiber tips for their use in combined scanning tunneling and force microscopy based on piezoelectric quartz tuning fork force sensors. An electrochemical fabrication procedure to etch the tips is used to yield reproducible sub-100-nm apex. We also study electron transport through single-molecule junctions formed by a single octanethiol molecule bonded by the thiol anchoring group to a gold electrode and linked to a carbon tip by the methyl group. We observe the presence of conductance plateaus during the stretching of the molecular bridge, which is the signature of the formation of a molecular junction.
Highlights
Understanding electron transport through a single molecule is a basic goal in molecular electronics [1]
Using the scanning tunneling microscope (STM) break-junction technique, we have measured the electrical conductance of several hundreds of octanethiol-based single-molecule bridges (CH3-C7H14-SH) in which the thiol anchoring group is bound to a gold electrode, and the methyl group is linked to a carbon electrode
We have fabricated and characterized carbon-fiber tips for their use in combined STM/atomic force microscope (AFM) based on quartz tuning fork force sensors
Summary
Understanding electron transport through a single molecule is a basic goal in molecular electronics [1]. A primary goal is to find reliable ways to form a stable mechanical and electrical connection between the molecule and macroscopic electrodes. The mechanical and electrical properties of a molecular junction are determined by the molecular structure and by the chemical nature of the electrodes [2]. We have explored the use of carbon-based tips as contact electrodes to form molecular junctions [3]. Using the scanning tunneling microscope (STM) break-junction technique, we have measured the electrical conductance of several hundreds of octanethiol-based single-molecule bridges (CH3-C7H14-SH) in which the thiol anchoring group is bound to a gold electrode, and the methyl group is linked to a carbon electrode. In order to form single-molecule junctions with a carbon electrode, we provide an STM with a carbon-fiber tip [4,5]. The microscopic structure of the tip is composed by graphitic planes aligned parallel to the fiber longitudinal axis,
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