title: Intersublevel spectroscopy on single InAs-quantum dots by terahertz near-field microscopy.
abstract: Using scattering-type near-field infrared microscopy in combination with a free-electron laser, intersublevel transitions in buried single InAs quantum dots are investigated. The experiments are performed at room temperature on doped self-assembled quantum dots capped with a 70 nm GaAs layer. Clear near-field contrast of single dots is observed when the photon energy of the incident beam matches intersublevel transition energies, namely the p-d and s-d transition of conduction band electrons confined in the dots. The observed room-temperature line width of 5-8 meV of these resonances in the mid-infrared range is significantly below the inhomogeneously broadened spectral lines of quantum dot ensembles. The experiment highlights the strength of near-field microspectroscopy by demonstrating signals from bound-to-bound transitions of single electrons in a probe volume of the order of (100 nm)(3).
authors: Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 51 01 19, 01314 Dresden, Germany.
authors: Rainer
authors: R
authors: Jacob
authors: Stephan
authors: S
authors: Winnerl
authors: Markus
authors: M
authors: Fehrenbacher
authors: Jayeeta
authors: J
authors: Bhattacharyya
authors: Harald
authors: H
authors: Schneider
authors: Marc Tobias
authors: MT
authors: Wenzel
authors: Hans-Georg von
authors: HG
authors: Ribbeck
authors: Lukas M
authors: LM
authors: Eng
authors: Paola
authors: P
authors: Atkinson
authors: Oliver G
authors: OG
authors: Schmidt
authors: Manfred
authors: M
authors: Helm