Carbon nanotube devices : quantum dots, field effect transistors and memory devices
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This thesis explores different nanoscale devices based on electron transport through carbon nanotubes. The ability of semiconducting carbon nanotubes to show field-effect-transistor (FET) behavior was explored. Local topgates on the carbon nanotube channel show excellent FET characteristics. Single-electron-transistor characteristics based on Coulomb Blockade were investigated at low temperatures. Quantum dots were created in the nanotube channel by local individual addressable topgates. Furthermore, nanoscale flash memory cells based on carbon nanotube FETs were assembled. The information was stored in redox-active molecules placed in the vicinity of the active channel. Device programming with write and erase gate pulses show on/off ratios close to 10⁴ with retention times of 20 min at room temperature. At liquid nitrogen temperatures the device stays in a stable state for up to 8 hours. At low temperatures, a strong increase in retention time was observed and single electron sensitivity was demonstrated. Endurance tests reveal very stable device characteristics upon at least 10⁵ write and erase cycles. Finally, optoelectronic memory characteristics were demonstrated on a Carbon Nanotube - molecule memory cell.