Shuai Feng

Optical properties of CuS nanoparticles at terahertz frequencies

The low-frequency optical properties of CuS nanoparticles in the composite samples were measured by the terahertz time-domain spectroscopy. Then, the power absorption, refractive index, complex dielectric function and conductivity of pure CuS nanoparticles are extracted by applying Bruggeman effective medium theory. The measured dielectric function and conductivity are consistent with the Lorentz theory of dielectric response as well as the Drude-smith model of conductivity in the frequency range from 0.2 to 1.5 THz, respectively. In addition, the extrapolation of the measured data indicates that the absorption is dominated by the lattice vibration localized at 4.7 ± 0.2 THz and the time constant for the carrier scattering is only 64.3 fs due to increased electron interaction with interfaces and grain boundaries.

Optical property and spectroscopy studies on β-ZnS nanoparticles in the terahertz range

A simple wet-chemical route has been employed to synthesize β-ZnS nanoparticles with diameter of ca.15-20 nm. The far-infrared characteristics of β-ZnS nanoparticles are investigated by terahertz time-domain spectroscopy (THz-TDS) over the frequency range from 0.3 to 2.5 THz. The observed results show two obvious absorption features at 1.44 and 1.72 THz, which give rise to different vibration modes compared to the bulk ZnS. The theoretical calculation has been carried out for better understanding the vibration behaviors by using of density functional theory (DFT) with GAUSSIAN 03 software package. The simulated absorption spectrum was consistent with the experimental data. The results reveal that the two absorption features are mainly ascribed to different vibration modes caused by the surface atoms.