Optical and electronic properties of lead sulfide spherical nano particle

Abstract

In this paper optical and electronic properties of lead sulfide spherical nano particle are studied using the density functional theory. To this end, a lead sulfide unit cell with Fm-3 m(225) symmetry is converted to a 1 nm spherical nanocluster, and then is placed into a 2 nm supercell structure. Total density of state (DOS) and partial density of states (PDOS) are considered to study electronic properties. The highest energy level of the valence band and its lowest energy level originate from 3p of sulfur atom and 5d of Lead atom respectively. The absorption coefficient, conductivity, dielectric function, loss function, reflective index, and reflectivity spectrum are studied to investigate optical properties for radiation power up to 35 eV. The analyses identify that the imaginary part of dielectric function has two main regions representing the ohmic resistance of PbS at the regions. The real part of the dielectric function has a static dielectric constant of 6.5 (ε(0) = 6.4) representing the plasma frequency of lead sulfide spherical nano particle. Moreover, the material has maximum light absorption for photons with 10 eV energy which relates to the ultraviolet spectrum. However, it shows considerable absorption for photons with 5 eV and 30 eV energy. The static refractive index is found to be 2.5 (n(0) = 2.5) and maximum refractivity occurs in the visible region for photons with energy less than 3 eV. Analysis of the conductivity of lead sulfide spherical nano particle shows that it is a semiconductor material with a significant loss for photons with 2−6 eV energy at the visible range.