Study of ‘Germanium and Nanoparticles' Optical Absorption Properties

The optical absorption characteristics of noncrystalline and crystalline Ge nanoparticles with diametersranging from ∼ 2.5 to 15 Å have been investigated using timedependent density functional theory at the B3LYP/6-31Glevel. On certain chosen Ge nanoparticles, hydrogen passivation and phosphorus doping were also computed. Theoptical absorption spectra of non-crystalline Ge nanoparticles evolve from numerous peaks to a continuous wide band ascluster size increases, while also exhibiting a consistent redshift. For both non-crystalline and crystalline Genanoparticles, doping phosphorus causes the absorption spectra to move toward the lower energy region. In contrastto crystalline Ge nanoparticles, non-crystalline Ge nanoparticles exhibit higher absorption in the visible range,independent of phosphorus doping