[1] Russian Acad Sci, Inst Microelect Technol & High Pur Mat, Chernogolovka 142432, Moscow Oblast, Russia
[2] Russian Acad Sci, Inst Solid State Phys, Chernogolovka 142432, Moscow Oblast, Russia
[3] Natl Acad Sci Ukraine, Inst Single Crystals, State Sci Inst, UA-61178 Kharkov, Ukraine
[4] Univ Paris 06, CNRS, UMR 7588, Inst NanoSci Paris, F-75015 Paris, France