The influence of II–VI lattice damage on rare earth sites as determined by site selective spectroscopy and cathodoluminescence: argon implanted ZnS:Sm 3+

Abstract

Using site selective and time resolved spectroscopy more than 10 different Sm sites have been discriminated. Beside the direct 4f-intra-shell excitation of the rare earth (RE) impurities a second indirect excitation channel via the host lattice is active with increasing laser power due to two-photon processes. The RE sites differ mainly in their ability to gain energy from this second channel. This knowledge is used to study the influence of host lattice damage — caused by Ar-implantation — on the Sm 3+ luminescence. Using cathodoluminescence (CL) and photoluminescence (PL) it is shown that the RE emission is less affected by the damage than the near-band-edge (NBE), self-activated (SA) and donor-acceptor (DA) emission. No new Sm sites have been created by the implantation and the direct 4f-4f excitation channel is still efficient, whereas the energy transfer (ET) via the ZnS lattice is disturbed leading to an intensity decrease. These results are taken as an evidence for the complex nature and the relative stability of RE centers in a II–VI lattice.