448 Optical Phonon Modes of InP/II-VI Core-Shell Nanostructures - a Raman and Infrared Study

Friday, November 6, 2009: 5:00 PM
Pancho Villa (Camino Real Hotel)
Felicia S. Manciu , Department of Physics, The University of Texas at El Paso, El Paso, TX
The main focus of this presentation is to demonstrate the usefulness of Raman scattering spectroscopy and infrared absorption spectroscopy for several purposes related to nanotechnology.  More specifically, we use these tools to probe the quality of InP/ZnSe core-shell nanostructures, determine their shell thicknesses, and reveal some interesting new physics.  We consider optical phonon modes, such as surface/interface modes, which are dependent on the nanoparticle dimensions. They can also provide an estimate of the ratio of the shell material thickness to the core radius for core-shell nanostructures.  This estimate is based on a comparison with a dielectric continuum model. For InP/ZnSe core-shell nanostructures, reasonable agreement is obtained between the Raman and infrared absorption results, and the calculations as well. In addition, temperature dependent measurements reveal an interesting resonant Raman effect, in which different (InP, ZnSe, and ZnSe surface) modes are selected at different temperatures by the laser photon energy. Besides the above spectroscopic characterizations, the experimental samples, which were synthesized by colloidal chemistry, were also subjected to X-ray diffraction and TEM analysis. The results obtained with the latter techniques corroborate well with those of the spectroscopy.