[1] Fraunhofer Inst Elect Microsyst & Solid State Tech, D-80686 Munich, Germany
[2] Tech Univ Munich, Chair Micro & Nanosyst Technol, D-85748 Garching, Germany
[3] Indian Inst Technol Kanpur, Kanpur 208016, Uttar Pradesh, India
[4] Univ Ulm, D-89069 Ulm, Germany