[1] Natl Acad Sci Ukraine, Lashkarev Inst Semicond Phys, Nauki Av 45, UA-03028 Kiev, Ukraine
[2] Natl Acad Sci Belarus, Sci & Pract Ctr Mat Sci, P Brovki Str 19, Minsk 220072, BELARUS
[3] PAS, Inst Low Temp & Struct Res, 2 Okolna St,POB 1410, PL-50950 Wroclaw 2, Poland
[4] Natl Acad Sci Ukraine, Bakul Inst Superhard Mat, Avtozavodska Str 2, UA-04074 Kiev, Ukraine