[1] Univ Texas Austin, Elect & Comp Engn, Microelect Res Ctr, Austin, TX 78758 USA
[2] Univ Wisconsin, Mat Sci & Engn, Madison, WI 53706 USA
[3] Sandia Natl Labs, POB 5800, Albuquerque, NM 87185 USA
[4] Air Force Res Lab, Munit Directorate, Eglin, FL 32542 USA
[5] Ohio State Univ, Elect & Comp Engn, Columbus, OH 43210 USA