1. Ira A. Fulton Schools of Engineering, Arizona State University, 551 E. Tyler Mall, Tempe, Arizona 85287, USA
2. Centre Suisse d'Electronique et de Microtechnique (CSEM), Rue Jaquet-Droz 1, 2002 Neuchâtel, Switzerland
3. Photovoltaics and Thin Film Electronics Laboratory, Institute of Microengineering, École Polytechnique Fédérale de Lausanne, Rue de la Maladière 71b, 2002 Neuchâtel 2, Switzerland
4. Peter Grunberg Institut, Forschungzentrum Jülich PGI 5, Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons, 52425 Jülich, Germany