1. Integrated Center for Applied Physics and Photonic Materials (IAPP) and Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, Nöthnitzer Straße 61, Dresden 01187, Germany
2. Electrical Engineering Department, Nanoelectronic Center, Technion, Haifa 32000, Israel
3. Dresden Center for Nanoanalysis (DCN) and Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, Dresden 01062, Germany