1. Post-Graduate Program in Physics, Federal University of Pelotas, 96160-000, Capão do Leão, RS, Brazil
2. Kavli Institute of Nanoscience, Delft University of Tecnology, 2628CJ Delft, The Netherlands
3. Post-Graduate Program in Materials Science and Engineering, Federal University of Pelotas, 96010-610, Pelotas, RS, Brazil