[1] Vilnius Univ, Fac Chem & Geosci, Dept Phys Chem, Naugarduko 24, LT-03225 Vilnius, Lithuania
[2] Tomsk Polytech Univ, Laser & Light Technol, 30 Lenin Ave, Tomsk 634050, Russia
[3] Tech Univ Chemnitz, Semicond Phys, Reichenhainer Str 70, D-09126 Chemnitz, Germany
[4] Cluster Excellence Ctr Adv Elect Dresden Carbon P, Cfaed, Wurzburger Str 46, D-01187 Dresden, Germany
[5] Ctr Phys Sci & Technol, State Res Inst, Lab Nanotechnol, Savanoriu Ave 231, LT-02300 Vilnius, Lithuania
[6] Tech Univ Chemnitz, Inst Phys, Solid Surface Anal, Reichenhainer Str 70, D-09107 Chemnitz, Germany