A Multispectral Detector Based on Arrays of Carbon Nanotubes
Abstract
This project focused on studying carbon nanotube quantum dots under terahertz irradiation for potential applications as detectors in the frequency range 0.3-10 THz. The basic physical principle is photon assisted tunneling. A carbon nanotube of finite length has a discrete energy spectrum and can be described as a one-dimensional quantum well. The length of the well is typically the distance between the source and drain electrodes attached to the nanotube. A voltage applied to a nearby gate electrode shifts the Fermi energy in the nanotube by capacitively inducing charges and populating or depleting the energy levels in the nanotube quantum dot. Here we consider the case in which the source and drain electrodes are weakly coupled to the nanotube and a substantial charging energy is necessary to add an electron to the dot. In this case, the current as a function of gate voltage will show sharp peaks corresponding to resonant elastic tunneling of electrons, one at a time, occurring when the Fermi energies of the leads are aligned with an energy level in the dot. Coulomb blockade occurs between the peaks and the voltage interval between adjacent peaks is characterized by the energy level spacing and the charging energy of the dot. When an electromagnetic field is present, transport can also occur via photon assisted tunneling, that is inelastic tunneling with absorption or emission of photons. Photon assisted tunneling generates side peaks in the Coulomb blockade regions: the voltage interval between the side peak and the main peak is determined by the photon energy (hn @ 4 meV at 1 THz) and the height of the side peaks is related to the intensity of the electromagnetic field.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 15, 2009
- Accession Number
- ADA513020
Entities
People
- Paola Barbara
Organizations
- Georgetown University