Bingjian Qian

Band gap tunable Sn-doped PbSe nanocrystals: solvothermal synthesis and first-principles calculations

We have reported that the Sn-doped PbSe nanocrystals could be synthesized via a facile solution-based method. Structural and optical characterizations were employed to investigate the properties of the nanocrystals. The x value could be altered across the entire range from 0.58 to 1 by modulating the ratio of cation precursor contents. The band gap energy of the Sn-doped PbSe nanocrystals could be tuned and changed in a nearly linearly way with respect to the x value. Furthermore, using oleylamine as the solvent promoted the nanocrystals to self-assemble as nano-flowers. The theoretical analysis based on first-principles calculations and density of states (DOS) in the VASP code demonstrates the validity of the experimentally obtained band gap variation and values. The band gap energy values at the edge of the solar spectrum render them as competitive candidates for solar applications.

Group III dopant segregation and semiconductor-to-metal transition in ZnO nanowires: a first principles study

The doping modulation in semiconductor nanomaterials is key to achieving high-efficiency nanodevices. Group III dopants in ZnO nanowires are predicted to tend to segregate to the surface and induce a metallic transition at high doping concentrations due to the delocalization of donor electron wave functions.

Spontaneous formation of graphene-like stripes on high-index diamond C(331) surface

We employ first-principles density functional theory calculations to study the surface reconstruction, energetic stability, and electronic structure of diamond C(331) surface. Spontaneous formation of graphene-like stripes on the reconstructed surface is found to occur as the surface terrace C atoms transform from sp3 to sp2 hybridization upon structural relaxation. The comparison of the calculated absolute surface energies of C(331), C(111), and C(110) surfaces demonstrates the energetic stability of the graphitic-like C(331) surface. Local density of electronic states analysis reveals the occurrence of localized electronic states near the Fermi level, which may have a significant impact on the surface conductivity.