1. Centre Énergie, Matériaux, Télécommunications, Institut National de la Recherche Scientifique, 1650 Lionel Boulet boulevard, Varennes, Quebec J3X 1S2, Canada
2. Center for the Physics of Materials, Departments of Physics and Chemistry, McGill University, 801 Sherbrooke St. W., Montreal, Quebec H3A 2K6, Canada
3. Condensed Matter and Materials Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551-0808, USA
4. Centre for Self-Assembled Chemical Structures, McGill University, 801 Sherbrooke St. W., Montreal, Quebec H3A 2K6, Canada