High-spin configuration of Mn in Bi2Se3 three-dimensional topological insulator

Abstract Electron paramagnetic resonance was used to investigate Mn impurity in Bi 2 Se 3 topological insulator grown by the vertical Bridgman method. Mn in high-spin S =5/2, Mn 2+ , configuration was detected regardless of the conductivity type of the host material. This means that Mn 2+ (d 5 ) energy level is located within the valence band, and Mn 1+ (d 6 ) energy level is outside the energy gap of Bi 2 Se 3 . The electron paramagnetic resonance spectrum of Mn 2+ in Bi 2 Se 3 is characterized by the isotropic g-factor | g |=1.91 and large axial parameter D =−4.20 GHz h. This corresponds to the zero-field splitting of the Kramers doublets equal to 8.4 GHz h and 16.8 GHz h, respectively, which is comparable to the Zeeman splitting for the X-band. Mn in Bi 2 Se 3 acts as an acceptor, effectively reducing native-high electron concentration, compensating selenium vacancies, and resulting in p-type conductivity. However, Mn-doping simultaneously favors formation of native donor defects, most probably selenium vacancies. For high Mn-doping it may lead to the resultant n-type conductivity related with strong non-stoichiometry and degradation of the crystal structure - switching from Bi 2 Se 3 to BiSe phase.