Formation of a quantum dot in a single-walled carbon nanotube using the Al top-gates

We have fabricated gate-controlled carbon-nanotube single-electron devices by utilizing the line-shaped Al top-gates. A quantum dot is formed in the single-walled carbon nanotube between two Al top-gates fabricated using the electron-beam lithography technique. The deposited top-gates flatten the single-walled carbon nanotube locally and the deformed regions play the role of tunneling barrier, whose potential is controlled by the top-gates. We have also investigated the temperature dependence of the conductance G for the devices with the Al top-gates. The power-law dependence, G∝T^α, is observed at high temperatures. However, the exponent α increases as the barrier potential is enhanced.