Study of electronic structure and conductivity of Nb-doped SrTiO3 by density function theory

The electronic structure and conductivity of Nb doped SrTiO₃ are investigated by the first-principles calculation of plane wave ultra-soft pseudo-potential based on the density function theory (DFT). The calculated results reveal that due to the electron doping, the Fermi level ships into conduction bands(CBs) for SrTi_1-xNb_xO₃ with x=0.125 and the system shows n type degenerate semiconductor feature. The density of states (DOS) moves towards low energies and the interaction between Nb atom and its nearest neighbor O atom enhances with increased doping concentration. The overlapped area of orbitals between those of Nb and oxygen atoms enlarges, thus the electron communization movement of the SrTi_1-xNb_xO₃ system intensifies, resulting in that the conductivity of Nb-doped SrTO₃ is well improved. Furthermore, the partial density of states (PDOS) of O2p state at the bottom of the CBs changes significantly after Nb doping, implying that the Nb doping effects on the electronic structure near the band gap of SrTiO₃ cannot be described by the rigid band model. Nb-doped SrTiO₃ with variable electronic conductivity provides the possibility of fabricating devices with multi-layer structures and the calculated results enables more precise monitoring and controlling during the fabrication as possible.