Rare earth element doping effect on the bonding and the transport property of δ-MoN

Combining non-equilibrium Green's function technique with density functional theory, the rare earth element doping effect on the bonding and the transport property of δ-MoN were theoretically investigated. The Mo-N bond lengths become more uneven after dopings. Some Mo-N bonds were heavily lengthened by the La- and Gd-dopings, resulting in obvious damages of their bonding. Evident covalent-like La-N and Gd-N bonds were formed in La-MoN and Gd-MoN, respectively, while the Yb atom underwent an ionic-like interaction with its neighboring N atoms in Yb-MoN. A clear drop of the conductivity was found after La- and Gd-dopings. On the contrary, the conductivity was improved upon the Yb-doping. This case was rationalized from the carrier density and the scattering of the carriers. The backscattering effect was evident at the impurities. The La- and Gd-dopings could not effectively increase the carrier density near the Fermi level, while the Yb atom could offer f-carriers to transfer from the valence band to the conduction band.