1. Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08540, United States
2. IBM Research−Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
3. Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
4. Corporate Strategic Research, ExxonMobil Research and Engineering Company, 1545 Route 22 E., Annandale, New Jersey 08801, United States