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MRSEC Seed Project: Optical Properties of Dilute Magnetic Wide-Band-Gap Semiconductor Multilayers and Nanostructures

The Materials Research Science and Engineering Center at the University of Nebraska was established in fall of 2002 by the National Science Foundation to carry out research on new magnetic structures and materials at the nanometer scale, or a width of about four atoms.

Our Seed Project "Optical Properties of Dilute Magnetic Wide-Band-Gap Semiconductor Multilayers and Nanostructures" (PI Mathias Schubert, Co-PIs Roger Kirby, David Sellmyer) investigates optical properties related to magnetic moments embedded in semiconductor multilayers, clusters, and nanostructures. Special focus is directed to novel piezo-electric wide band gap semiconductor materials with magnetic ion incorporation and high free-charge-carrier densities. In this second phase of our Seed project the influence of lateral patterning with nanostructure dimensions on the magnetism-induced optical properties, as well as the influence of free charge carrier densities is subject to research based on our results obtained from the studies of single layers and heterostructures within the first phase.

In this procet we investigate magnetic moments in embedded clusters and nanostructures, which have recently become available to us, or which are in preparation. In particular, we intend determination of spin polarization, hys- teresis behavior, and optical transport parameters (longitudinal and transverse mobility, effective mass, and density) of free charge carriers in wide band gap magnetic ion alloyed semiconductors as a function of geometry, dimension, electron density, and composition.

We will investigate existing and available ZnO nanostructures alloyed with Mn, Co, Cd, and co-doped with Al and Ge for variable free electron density, prepared previously by Pulsed Laser Deposition at the Semiconductor Physics Group at University of Leipzig (coorperation with Professor Dr. Marius Grundmann, Dr. Heidemarie Schmidt and Michael Lorenz).

We prepare nanostructures by sputtering and ion-beam deposition techniques at the University of Nebraska-Lincoln. We will complete the setup of a new spectroscopic magnetooptic Kerr microscope for high-resolution, high-sensitivity, high-accuracy studies of very small magnetooptic complex-valued birefringence from near infrared to ultra violet wavelengths. This instrument will help us to identify magnetic moment related coupling mechanisms of electron wave functions and band structure parameters with external and internal magnetic induction fields. Magnetooptic generalized ellipsometry in the Terahertz-Farinfrared domain for optical transport measurements, and Raman scattering for defect identification will provide important information for understanding of the incorporation of magnetic moments. We will continue our international collaboration through exchange visits and joint research efforts of graduate and post graduate researchers.

For further information please contact M. Schubert.

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