1. City, University of London, Northampton Square, Clerkenwell, London EC1V 0HB, United Kingdom
2. Electrical Engineering Program, COPPE, Universidade Federal do Rio de Janeiro, 21941-972 Rio de Janeiro, RJ, Brazil
3. Brazilian Center for Physics Research, Xavier Sigaud 150, 22290-180 Rio de Janeiro, RJ, Brazil
4. Nanotechnology Engineering Program, COPPE, Universidade Federal do Rio de Janeiro, 21941-972 Rio de Janeiro, RJ, Brazil