Photoluminescence of Er-doped ZnO nanoparticle films via direct and indirect excitation

Abstract

Photoluminescence (PL) of Er-doped ZnO nanoparticle films was studied. The films were grown on silicon (100) or fused silica substrates using e -beam evaporation and subsequently annealed at 700 °C in air for an hour. PL was measured at two excitation wavelengths, 325 and 514.5 nm. The 325 nm was used for exciting the host semiconductor ZnO while 514.5 nm was used for directly exciting Er 3+ ions in the ZnO host. Er 3+ luminescence was observed from annealed films using either indirect (325 nm) or direct (514.5 nm) excitations. It has been found that the indirect excitation is significantly more efficient than the direct excitation in producing 1.54 μm photoluminescence. With indirect excitation, the Er 3+ luminescence observed is attributed to energy transfer from ZnO host to the Er 3+ ions doped. Energy transfer from e-h pairs resulting from ZnO host excitation may provide efficient routes for exciting Er 3+ ions inside nano-crystalline particles of the films.