1. Department of Materials Science and Nanoengineering, Rice University, 6100 Main Street, Houston 77005, Texas, United States
2. Applied Physics Department, State University of Campinas − UNICAMP Campinas, Campinas, São Paulo 13083−859, Brazil
3. Department of Physics and Meteorology, São Paulo State University (Unesp), School of Sciences, Bauru, SP 17033-360, Brazil