(Invited) Large-Scale DFT Study of Ge/Si 3D Nanoislands and Core-Shell Nanowires

Density functional theory (DFT) calculations have been playing important roles to clarify the structures of semiconductor surfaces at atomic scale. However, DFT studies of complex nanostructures are usually impossible because conventional DFT methods cannot treat large systems containing many thousands of atoms.In this paper, we survey our large scale DFT study on (i) the growth of Ge 3D nanostructure on Si(001) substrate and (ii) the atomic and electronic structures of Si/Ge or Ge/Si core-shell nanowires, using our linear-scaling DFT code CONQUEST. The code uses large-scale DFT techniques and has high efficiency on massively parallel computers. We demonstrate that CONQUEST can calculate the atomic positions of the realistic models of nanostructures observed in experiments and can clarify the unique electronic properties of these nano-structured materials.