1. Department
of Electronics and Telecommunications, Norwegian University of Science and Technology (NTNU), Trondheim, 7491, Norway
2. Department
of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, 7491, Norway
3. SINTEF Materials and Chemistry, 7456 Trondheim, Norway
4. Gatan Inc., 5794 W Las
Positas Boulevard, Pleasanton, California 94588, United States
5. Institute
for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan