We use optically assisted scanning tunneling microscopy (STM) to study laser absorption and intermolecular energy transfer between single quantum dots (QDs) and carbon nanotubes (CNTs). Single PbS QDs and CNTs are deposited onto gold, crystalline silicon carbide (c-SiC) and amorphous silicon carbide (a-SiC) surfaces by matrix-assisted dry contact transfer. Adsorbed molecules are excited with modulated 532 nm light and the modulated tunneling current proportional to the optical absorption signal is detected by STM with a lock-in amplifier. Absorption of individual QDs varies significantly on all surfaces.  Single QD absorption is strongly dependent on the sample bias voltage on the gold surface, reflecting different excited states. The dependence is weaker on the c-SiC surface and on the a-SiC surface, where the absorption signal is either dominated by tip heating or substrate absorption. In arrays of QDs, absorbed energy is funneled to one or a few QDs. Evidence of energy transfer between single QDs and single CNTs will also be discussed.

Imaging intermolecular energy transfer between single quantum dots and carbon nanotubes

251st National Meeting (2016)

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