Paper NS+NC-WeA3
Transition Between Particle Nature and Wave Nature of Hole in Single-Walled Carbon Nanotube Transistor by Gate Voltage

Wednesday, October 22, 2008, 2:20 pm, Room 311

We have succeeded in fabricating the convertible transistor which can operate as a resonant tunneling transistor (RTT) and also as a single hole transistor (SHT) using single-walled carbon nanotube (SWNT) by modulating the strength of the coupling between the electrode and the quantum island using the gate voltage that changes the thickness of Schottky barrier, in which RTT is the device using wave nature of hole and SHT is the device using particle nature of hole. The sample has a SWNT contacted to the source and the drain electrode by Ti metal. The distance between both electrodes is 73 nm. The gate electrode is in the back side of Si substrate. Contour plot of differential conductance characteristic as a function of gate voltage and drain voltage at 7.3 K is measured. When the gate voltage VG is relative low at around VG =-10 V to -15, the plot clearly shows the Coulomb diamond characteristic. This means the device shows the particle nature of hole. Additionally, line shape quantum levels are appeared at both sides of Coulomb diamonds. The Coulomb diamonds are getting blurred with negatively increasing gate voltage around VG=-15 V to -20 V. The quantum levels are, however, still remaining. Finally, at relative high gate voltage at VG=-20 V to -25 V, Coulomb blockade is lifted and Coulomb diamonds are disappeared. However, quantum levels are still remaining, and current oscillate owing to the resonant tunneling through quantum levels. Thus, only by modulating the gate bias, the device shows the Coulomb blockade phenomena, that means the particle nature of hoe at low gate bias, and also shows the coherent oscillation of hole that means the wave nature of hoe at negatively high gate bias.