Probe into the reflection from GaP nanoparticles via different solutions of radiative transfer equation

The reflection and absorption spectra of gallium phosphide (GaP) nanoparticles were measured. The radiative transfer equation (RTE) for the medium with scattering and absorption is solved by three different solutions. The ratio of the absorption and scattering coefficients (E _a/E _s) of the GaP nanoparticles layer is calculated from the reflection spectrum via the three solutions, respectively, and the result derived with the three-flux model is closest to the exact solution given by Giovanelli. The E _a/E _s curves all exhibit the energy band gaps of GaP nanoparticles, which are consistent with the absorption spectrum measurement. The shape of the reflection spectrum is mainly determined by the absorption, and the scattering only influences its intensity. The energy band structure of the powder sample plays an important role in the reflection phenomenon, and the reflectance data can be used for quantitative analyses.