1. Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
2. MicroTribology Center μTC, Fraunhofer IWM, Wöhlerstraße 11, Freiburg 79108, Germany
3. Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Ibaraki, Japan