Science / Technology - Colloquium
Monday, September 25, 2006
4:00 PM-5:00 PM
Olin Hall
107
Near-field photoluminescence using a near-field scanning optical microscope (NSOM) has been a valuable tool in studying excitons in GaAs-based quantum wells. The resolution that is beyond the diffraction limit revealed striking, new results that cannot be captured by far-field photoluminescence.
We report low temperature near-field photoluminescence imaging of the electron density in a modulation doped GaAs/AlGaAs single heterojunction with a spatial resolution of 100 nm. We discovered an unusual competitiveness in the photoluminescence between the first electron subband to first heavy-hole subband transition and the second electron subband to first heavy-hole subband transition. We attribute this competitiveness to the fluctuations in the electron density which results from fluctuations in the donor (Si) density.
NSOM is itself a technique that is still under research and development. Our goal is not limited to just imaging the surface topography but extends to imaging physical properties of buried quantum structures. In the first part of the talk we will discuss the experimental setup used for near-field scanning photoluminescence experiments. In the second part we will present our results for a two-dimensional electron gas. Finally, preliminary results from near-field scanning fluorescence will be briefly discussed.
Cost: FREE
Sponsored by: WPI Physics Department, Dr. Stephen Jasperson
Suggested Audiences: College
E-mail:
snj@wpi.edu
Phone: 508-831-5392
Last Modified: September 15, 2006 at 10:39 AM
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