1. Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Via Romea 4, 35020 Legnaro, Padova, Italy, Department of Physics, University of Trento, Via Sommarive 14, 38050 Povo, Trento, Italy, Department of Materials Engineering, University of Trento, Via Mesiano 77, 38050 Povo (TN), Italy, and Department of Electronics and Informatics, University of Padua, Via Gradenigo 6A, 35131 Padua, Italy