Paper NS-ThM1
Single Charge Sensing by Carbon Nanotube Single-Hole Transistor

Thursday, October 18, 2007, 8:00 am, Room 616

We have succeeded in detecting the single charge transition near the channel of single walled carbon nanotube (SWNT) single-hole transistor (SHT). Abrupt discrete switching of the source-drain current is observed in the electrical measurements of SWNT SHT. These random telegraph signals (RTS) are attributed to charge fluctuating near the SWNT SHT conduction channels. The sample has a back gate FET structure with the source-drain spacing of 73 nm. The channel is formed by thermal CVD grown single walled carbon nanotube on the SiO2 substrate. The silicon dioxide layer was deposited on the SWNT SHT to prevent the adsorption & desorption of the molecules to the carbon nanotube channel. In the drain current-gate voltage characteristics of SWNT SHT under the drain voltage of 11 mV at 7.3 K, drain current showed periodic peaks and valleys structure, with two. The large period of 3 V was attributed to Coulomb oscillation characteristic,d the small period of 0.5 V to the quantum interference property of hole. The drain current was observed only in negative gate voltage region, which indicates that the measured SWNT SHT has the p type semiconductor property. The SWNT SHT shows random telegraph signals (RTS), which were attributed to fluctuating charge traps near the SWNT SHT conduction channels. The RTS appeared two levels, upper level and lower level in drain current, the occupation probabilities of which was depended on the applied gate voltage. Using the simple model we assumed, we could estimate the distance between the trap and the channel of SWNT SHT to be L=1.03 nm. The potential energy barrier between the trap state and the Fermi level of carbon nanotube channel was also founded to be 3.2 meV. Thus, using the carbon nanotube single hole transistor, we have succeeded in detecting and analyzing the single charge transition.