· e-mail: pkolb@physics.umd.edu
· Office: (301) 935-6460
· Lab: (301) 935-6419
· FAX: (301) 935-6723
· Address: Laboratory for Physical Sciences and Department of Physics, University of Maryland, 8050 Greenmead Dr., College Park, MD 20740
Ph.D. in Physics,
B.S. in Physics,
Research Project: Studies of Low Dimensional Systems with Near-Field Scanning Optical Microscopy (NSOM) at Cryogenic Temperatures (4K) and High Magnetic Field (17 T).
Near-Field Photoluminesence of GaAsQuantum Dots. P. W. KOLB, H. D. DREW, D. B. ROMERO Laboratory for Physical Sciences, University of Maryland, College Park, MD 20740, R. S. DECCA, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202 We have performed Near-Field Photoluminescence (PL) studies of naturally occurring Quantum Dots (QDs) in GaAs/AlGaAs Quantum Wells (QWs) of 2 nm thickness. QDs can arise in QWs from monolayer fluctuations, confining excitons in the plane of the QWs. The size of this confinement helps determine the ground state energy of the exciton in each QD. Conventional far-field PL spectra of narrow QWs typically show peaks that are inhomogeneously broadened. Spectroscopy on individual QDs was accomplished by means of Near-field Scanning Optical Microscopy (NSOM) at 4 K with a resolution of 150 nm. The PL spectra show the presence of excitonic lines with instrumentation-limited linewidth. Surprisingly, we find the tendency of excitons with the same energy to clump together spatially. As a preliminary explanation, we propose that some monolayer islands could be dumbbell-shaped. In this picture, a single excitonic wavefunction vanishes in the constricture. In future work, we plan to do PL with magnetic fields up to 17 Tesla and perform Photoluminescence Excitation (PLE) on these unusual dots. We also plan to optically intestigate QDs formed by a gated heterojunction.
Most recent data:
Focusing on a couple of peaks while scanning:
Click on the links to learn a little more:
experimental set
up
other peaks
a striking "coincidence"
Reference: Q. Wu, R. Grober, D. Gammon, and D. S. Katzer, Phys. Rev. Lett. 83, 2652 (1999)
how NSOM works an exotic dot for... ...future experiments
Reprint: Capacitive Sensor for micropositioning in two dimensions, P.. W. Kolb, R. S. Decca, and H. D. Drew, Rev. Sci. Instrum. 69, 310 (1998) pdf
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Last Modified: May 10, 2004