3 research outputs found
Carbon nanotube junctions and devices
No full textIn this thesis Postma presents transport experiments performed on individual single-wall carbon nanotubes. Carbon nanotubes are molecules entirely made of carbon atoms. The electronic properties are determined by the exact symmetry of the nanotube lattice, resulting in either metallic or semiconducting behaviour. Due to their small diameter, electronic motion is directed in the length direction of the nanotube, making them ideal systems to study e.g. one-dimensional transport phenomena. First, we present mK-temperature current-voltage characteristics of an individual single-wall carbon nanotube showing Coulomb blockade and resonant tunnelling through individual molecular levels. We then report electrical transport measurements on carbon nanotubes with naturally occurring intramolecular junctions. We find that a metal-semiconductor junction behaves like a rectifying diode, whereas the conductance of a metal-metal junction behaves like a tunnel junction with associated power-law dependencies described by a Luttinger liquid model for tunnelling between the two nanotube segments. In order to further study carbon nanotube intramolecular junctions, we developed an atomic force microscope (AFM) manipulation technique, by means of which carbon nanotube junctions such as buckles and crossings are created. The electronic transport properties of these manipulated structures show that they form electronic nanometer-size tunnel junctions. Thereafter, room-temperature single-electron transistors are realized within metallic carbon nanotubes. The devices feature a short (down to 20 nm) nanotube section that is created by AFM manipulation. Coulomb charging is observed at room temperature. We observe unconventional power-law dependencies in the transport properties for which we develop a resonant-tunnelling Luttinger-liquid model. Finally, the low-frequency electronic noise properties of metallic carbon nanotubes are investigated. The noise power exhibits a 1/f frequency dependence that is three orders of magnitude smaller at 8 K than at 300 K. As a demonstration of how these noise properties affect nanotube devices, we present a preliminary investigation of the noise characteristics of an intramolecular carbon nanotube single-electron transistor.Applied Science
Electrical transport through carbon nanotube junctions created by mechanical manipulation
No full textCorrelated tunneling in intramolecular carbon nanotube quantum dots
No full textWe investigate correlated electronic transport in single-walled carbon nanotubes with two intramolecular tunneling barriers. We suggest that below a characteristic temperature the long-range nature of the Coulomb interaction becomes crucial to determine the temperature dependence of the maximum {\it G} of the conductance peak. Correlated sequential tunneling dominates transport yielding the power law {\it G}–1}$, typical for tunneling between the ends of two Luttinger liquids. Our predictions are in agreement with recent measurements
