Affiliation: | a Nanomaterials Laboratory, High Resolution Beam Station, National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki 305-0003, Japan b Moscow State Engineering Physics Institute, Kashirskoe sh. 31, Moscow 115409, Russia c University of Tsukuba, 1-1 Ten-nodai, Tsukuba, Ibaraki 305-0006, Japan |