Understanding the role of Niobium, Molybdenum and Tungsten in realizing of the transparentn-type SnO2.

ABSTRACT

Based on the density functional theory, the defective band structures (DBSs), ionization energy and formation energy for Niobium (Nb), Molybdenum (Mo) and Tungsten (W)-doped SnO2are calculated. The DBSs show Nb, Mo and W substituting Sn (labeled as NbSn, MoSnand WSn) could form the localized impurity states which are above the conduction band minimum (CBM). These characteristics can be attributed to the energy of dopants' d-orbitals are much higher than that of Sn-s and -d orbital as well as O-2p orbitals, and the dopants with their neighboring atoms would form the non-bonding impurity states. The DBSs confirm NbSn, MoSnand WSnare typicaln-type defects in SnO2. The ionization energiesϵ(0/+) for NbSn, MoSnand WSnare higher than 0.22 eV above CBM, indicating these defects could be fully ionized. We find the NbO and MoO3are promising dopant sources, as the thermodynamic equilibrium fabrication scheme is considered. Taking Nb-doped SnO2as an example, we find a few NbSncould induce high conductivity (541 S cm-1). These results suggest that SnO2containing NbSn, MoSnand WSnare promisingn-type semiconductors. Our findings would provide a better understanding of then-type properties in Nb, Mo and W-doped SnO2.