[1] Oak Ridge Natl Lab, Ctr Nanophase Mat Sci, Oak Ridge, TN 37831 USA
[2] Univ Arizona, Dept Mat Sci & Engn, Tucson, AZ 85721 USA
[3] Univ Arizona, James C Wyant Coll Opt Sci, Tucson, AZ 85721 USA
[4] Univ Arizona, Dept Elect & Comp Engn, Tucson, AZ 85721 USA
[5] Univ Maryland, Dept Elect & Comp Engn, College Pk, MD 20742 USA
[6] Oak Ridge Natl Lab, Mat Sci & Technol Div, Oak Ridge, TN 37831 USA