1. Center for Semiconductor Components and Nanotechnologies (CCSNano), University of Campinas, CEP 13083-870 Campinas, São Paulo, Brazil and School of Electrical and Computer Engineering, University of Campinas, P. Box 6101, 13083-970 Campinas, São Paulo, Brazil
2. Center for Semiconductor Components and Nanotechnologies (CCSNano), University of Campinas, CEP 13083-870 Campinas, São Paulo, Brazil