Spectra, energy levels and crystal field calculation of Er3+ doped in AlN nanoparticles

Optical properties of Er-doped AlN nanoparticles (NPs) synthesized by Inert Gas Condensation (IGC) on silicon (111) substrates were investigated. Transmission electron microscopy (TEM) and high resolution TEM (HR-TEM) were used to study the shapes, morphologies and size of the synthesized AlN:Er3+ NPs which have a spherical shape with a mean diameter between 12 nm and 15 nm. The optical properties of AlN:Er3+ NPs were assessed from low temperature cathodoluminescence spectra (CL). The CL spectra show visible and near infrared sharp and broad emission lines associated with Er3+ ions. The observed Er3+ ion transition lines broadening is due to the surface defect in studied NPs. Comparative investigations of the luminescent properties of AlN:Er3+NPs with those of AlN:Er3+ thin films show the presence of some similarities between the lattice sites occupied by Er3+ ions in these hosts. It was found that in AlN NPs the Er3+ ion occupy a second optical center which is the VN-Er complex beside the ordinary substitutional ErAl center observed in the case of AlN:Er3+ epilayers. Assuming the presence of these two sites occupied by Er3+ ions, the majority of CL emission lines were attributed. The experimental Stark energy levels of Er3+ ion manifolds are established for the Er-doped AlN NPs and the correspondent crystal field parameters are calculated.