1. Department of Physics, The University of Texas at Dallas 1 , Richardson, Texas 75080, USA
2. Department of Materials Science & Engineering, The University of Texas at Dallas, Richardson 2 , Texas 75080, USA
3. Electronics Science and Technology Division, US Naval Research Laboratory 3 , Washington, DC 20375-5347, USA
4. NRC Research Associate at the Naval Research Laboratory 4 , Washington, DC 20375-5347, USA