Laser Spectroscopy and
Nanoparticle Research
at The University of Texas in Austin
Nanoparticle Research
at The University of Texas in Austin
NSOM
In our NSOM project we developed a new design using an optical feedback technique. This instrument uses the intensity of the reflected light itself (as z-information) to control the distance from the optical fiber to the surface which then exerts essentially no force on the particles. To test the performance of the microscope we obtained images of calibration gratings with a resolution of 20 nm. It is important to note that measuring the diameter of an individual nanoparticle does not require a lateral spatial resolution smaller than the particle size. Since particles smaller than 50 nm are generally spherical, we need only measure the displacement dz to size the particle. The true shape of the particle can be separately confirmed with high-resolution TEM. Using the instrument we were able to measure spatially selective, photoluminescence spectra of an AlGaAs/GaAs heterostructure.
Currently we are testing a UHV version of this instrument which operates at temperatures as low as 2.5°K where phonon broadening of the photoluminescence can be essentially eliminated. Background information can be found over here:
References:
[1] G. Guttroff, J.W Keto, C.K. Shih, A. Anselm, and B.G. Streetman: A design of reflection scanning near-field optical microscope and its application to AlGaAs/GaAs heterostructures, Appl. Phys. Lett., 68(3620) (1996).
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