1. Contribution from the Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, 20125 Milano, Italy, Department of Chemistry, Princeton University, Princeton, New Jersey 08540, Department of Physics, Tulane University, New Orleans, Louisiana 70118, Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, Louisiana 70806, and Department of Physics and Astronomy and the Center for Material Research and Analysis, University of Nebraska, Lincoln,...