Ultra-short suspended single-wall carbon nanotube transistors

We describe a method to fabricate clean suspended single-wall carbon nanotube (SWCNT) transistors hosting a single quantum dot ranging in length from a few 10 s of nm down to ≈3 nm. We first align narrow gold bow-tie junctions on top of individual SWCNTs and suspend the devices. We then use a feedback-controlled electromigration to break the gold junctions and expose nm-sized sections of SWCNTs. We measure electron transport in these devices at low temperature and show that they form clean and tunable single-electron transistors. These ultra-short suspended transistors offer the prospect of studying THz oscillators with strong electron-vibron coupling

Wiedemann–Franz Relation and Thermal-Transistor Effect in Suspended Graphene

We extract experimentally the electronic thermal conductivity, <i>K</i>_e, in suspended graphene that we dope using a back-gate electrode. We make use of two-point dc electron transport at low bias voltages and intermediate temperatures (50–160 K), where the electron and lattice temperatures are decoupled. The thermal conductivity is proportional to the charge conductivity times the temperature, confirming that the Wiedemann–Franz relation is obeyed in suspended graphene. We extract an estimate of the Lorenz coefficient as 1.1–1.7 × 10^–8 W ΩK^–2. <i>K</i>_e shows a transistor effect and can be tuned with the back-gate by more than a factor of 2 as the charge carrier density ranges from ∼0.5 to 1.8 × 10¹¹ cm^–2