Enhanced Ultraviolet Emission from Mg Doped SnO2 Nanocrystals at Room Temperature and Its Modulation upon H2 Annealing

Photoluminescence (PL) and absorption features of high-quality nanocrystalline Sn1-xMgxO2 series (0 ≤ x ≤ 0.03) were investigated at room temperature. Although particle sizes of as-synthesized samples are larger than Bohr radius (aB), Fermi edge absorption is observed both in undoped and doped samples. Incorporation of Mg 2p states near valence band maxima (VBM) widens the band gap (Eg) consistently and stable, high-yield room temperature free exciton (RTFE) emission (3.81 eV) results. Deconvolution of each UV emission reveals band tail emission (3.54 eV) along with excitonic recombination. A feeble green emission (2.34 eV) is also observed and its intensity strongly depends on tensile strain (η) and formation energy (Ef) of oxygen vacancy (VO) and hydrogen at VO (HO). H2 annealing at 300 °C introduces interesting doping dependent modulation in UV emission intensity. Elemental projective density of states (DOS) exhibit Sn 5s–H 1s hybridization in undoped passivated supercell and Mg 2p–H 1s hybridization i...