1. Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, and Department of Microelectronics and Information Technology, Royal Institute of Technology, Kista, SE-164 40, Sweden
2. Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045
3. Department of Structural Chemistry, Stockholm University, Stockholm, SE-106 91, Sweden
4. Department of Microelectronics and Information Technology, Royal Institute of Technology, Kista, SE-164 40, Sweden