1. Electrical and Computer Engineering Program, University of California, San Diego, La Jolla, California 92093, United States
2. Materials Science and Engineering Program, University of California, San Diego, La Jolla, California 92093, United States
3. Applied Materials, Sunnyvale, California 95054, United States
4. Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, California 92093, United States