Low temperature electron transport spectroscopy of mechanically templated carbon nanotube single electron transistors

We report electronic transport investigations of mechanically templated carbon nanotube single electron transistors (SETs). The devices were fabricated on a Si/SiO₂ substrate by controllably placing individual single walled carbon nanotubes (SWNTs) between the source and drain electrodes via dielectrophoresis with a 100 nm wide local Al/Al₂O₃ bottom gate in the middle. From the low temperature electronic transport measurements, we show that a quantum dot is formed whose charging energy can be tuned from 10 to 90 meV by varying both the local gate and Si backgate. The temperature dependent measurements show that the Coulomb oscillations persist up to 250 K. The transport properties can be explained by a simple potential configuration, which suggests that two tunnel barriers are formed due to the bending of the SWNT at the local gate edges and that the size of the dot and tunnel barrier transparency can be tuned by the gates allowing the operation of SET in a wide temperature range and thereby realizing a controllable and tunable SET. Our simple fabrication technique and its tunability over a large temperature range could facilitate large scale fabrication of SET for practical applications.