Professor Robert Taylor

Abstract:

Modification of the band structure of single-walled carbon nanotubes (SWNTs) through encapsulation of the inorganic material manganese ditelluride (MnTe2) is reported. We show that this leads to a global reduction of their 1st (E11^S) and 2nd (E22^S) band gap energies by a similar percentage (up to 3.8%) and interpret this as due to a lowering of the carbon-carbon transfer integrals. © 2007 American Institute of Physics.

Abstract:

We present a systematic investigation of free-carrier screening in coupled asymmetric GaN quantum discs with embedded AlGaN barriers using time-integrated and time-resolved micro-photoluminescence measurements, supported by three-dimensional multi-band k.p computational modeling. Free-carrier screening effects decreased with the barrier thickness, which indicates that the source of the free-carriers were carriers tunneling through the barrier. © 2007 American Institute of Physics.

Abstract:

Micro-photoluminescence properties of single InGaN/GaN quantum dots (QDs) are investigated using sub-bandgap excitation by 1 ps pulses from a Ti:sapphire laser. This results in almost complete suppression of background emission arising from the underlying quantum well to which the QDs are coupled. Photoluminescence excitation spectra undertaken using this technique show evidence of p-states. The non-linear intensity dependence of the emission is also discussed. © 2007 American Institute of Physics.

Abstract:

By using two-photon absorption spectroscopy we have performed time-integrated and time-resolved photoluminescence measurements on several coupled asymmetric GaN quantum discs, with embedded AlGaN barriers. We observe free-carrier screening, with an enhancement due to tunneling between the coupled quantum discs. © 2007 American Institute of Physics.