1. Interdisciplinary Center of Nanoscience and Micro‐NanoTechnology School of Technology Pontifical Catholic University of Rio Grande do Sul Porto Alegre RS 90619‐900 Brazil
2. Ion Implantation Laboratory Federal University of Rio Grande do Sul Porto Alegre RS 90040‐060 Brazil
3. Centre de Recherche sur les Ions, les Matériaux et la Photonique CEA‐CNRS‐ENSICAEN‐Université de Caen CIMAP‐GANIL Bd. H. Becquerel CS 65133 Caen cedex 5 14076 France