Investigation of optical properties of zinc oxide nanocrystalline materials

The optical properties of Zinc Oxide (ZnO) nanowires are studied using two parallel channels of photon conduction. First is the coherent motion of electrons within the ZnO nanowire termed as Drude carriers and second is the incoherent hopping of electrons from one ZnO nanowire to another nanowire. The model has the relaxation rate as one of the material dependent free physical parameters. The frequency-dependent relaxation rates are presented in terms of memory functions. A peak in optical conductivity obtained near zero-frequency, which occurs due to Drude carriers, i.e., the incoherent motion of electrons whereas, frequency becomes saturated at very-low values at higher frequencies near the far-infrared region. A peak in optical conductivity is observed around mid-infrared frequencies due to the hopping of carriers from one ZnO nanoparticle to another. This is evidenced that both the Drude and hopping carriers contribute to optical conductivity in ZnO nanowire. The modal based on these two contribution schemes successfully explains the optical conductivity phenomena in ZnO nanowires.