1. Materials Department, University of California Santa Barbara, Santa Barbara, California 93106, USA
2. Quintessent Inc., Santa Barbara, California 93102, USA
3. Department of Electronic and Computer Engineering, University of California Santa Barbara, Santa Barbara, California 93106, USA
4. Intel Corp., Santa Clara, California 95054, USA
5. Department of Material Science and Engineering, Stanford University, Stanford, California 94305, USA