Molecular electronics provides a potential new avenue for the development of electronic devices at the nanometer scale. Here, we use a modified scanning tunneling microscope (STM) in a break-junction setup to study systems of light activated single-molecule switches. The molecular systems we study include a stilbene backbone with methylsulfide linker groups that can bind to gold. These molecules bridge the gap between the gold electrodes of the STM, forming a single molecule circuit, allowing us to measure the current passing across the molecule. We measure the electrical conductance of thousands of junctions to determine a characteristic conductance for each molecule. Next, we shine ultraviolet (UV) light on these junctions and observe the effects on single-molecule junction conductance under illumination over time. In particular, we find that under UV light these systems can undergo a photoisomerization reaction between trans and cis forms and can furthermore cyclize into a phenanthrene derivative in the presence of oxygen. We show that these system can act as switches that display conductance changes upon exposure to UV light.

Light activated switching in single molecule circuits

247th National Meeting (2014)

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