Study on the electronic and optical properties of La-, Ce- and Nd-doped SnO₂

To study the influence of rare earth element doping on the electronics structure and properties of SnO₂, the lattice parameters, band structures, density of states, electron density differences and optical properties are investigated by density functional theory based on the plane wave pseudopotential method. The calculated results show that the bond lengths change the most due to La doping and the least for Nd, which indicates that the lattice distortion caused by rare-earth-doped SnO₂ is related to the covalent radius of the doping atom. The band gap of SnO₂ reduces the most due to La doping, but it is found that spin-up levels are in the forbidden band for Nd doping. The results show that Nd-doped SnO₂ is half-metal material due to the existence of spin-up f electrons, and significant hybrid effects are induced by Nd 4f and O 2p states. The charge density difference shows that rare earth doping causes redistribution of the electrons of SnO₂, and the metal property enhances. La atoms lose the most electrons and Nd atoms lose the least, which is consistent with the calculated results of band gaps. The calculated results of optical properties show that the imaginary part of the dielectric function has a red shift and the optical anisotropy of SnO₂ is not strong, which indicates that the SnO₂ crystal may have a preferred orientation along [0 0 1].