1. Materials Processing and Evaluation Department, Space Materials Laboratory, The Aerospace Corporation, P.O. Box 92957/M2-248, Los Angeles, California 90009
2. Department of Chemistry & Biochemistry and California NanoSystems Institute, University of California, Los Angeles, California 90095-1569
3. Department of Materials Science and Engineering and California NanoSystems Institute, University of California, Los Angeles, California, 90095