1. Division of Microstructure Physics, Department of Physics, Chalmers University of Technology, 41296 Göteborg, Sweden
2. Division of Solar Cell Technology, Department of Materials Science and Engineering, Uppsala University, 75121 Uppsala, Sweden
3. Center of Materials Science and Nanotechnology, Department of Physics, University of Oslo, 0316 Oslo, Norway
4. Division of Applied Materials Physics, Department of Materials Science and Engineering, KTH Royal Institute of Technology, 10044 Stockholm, Sweden