Luminescence of rare earth-doped Si-ZrO2 co-sputtered films

Er-doped Si-yttria-stabilized zirconia (YSZ) thin film samples were prepared by rf co-sputtering. Chemical composition of the samples was determined using energy-dispersive spectroscopy (EDS) and the structure of the films by X-ray diffraction (XRD). The samples were annealed to 700 °C. Photoluminescence (PL) measurements were performed for the visible and infrared. By exciting with the 488-nm-laser line the Er3+ emissions 2H11/2→4I15/2, 4S3/2→4I15/2, 4F9/2→4I15/2 and a narrow 4I13/2→4I15/2 emission were observed. The 4I11/2→4I15/2 emissions for the same excitation wavelength were weak. Excitation wavelength dependence of the 4I13/2→4I15/2 emissions indicated that the emissions were due to a combination of energy transfer from Si nanoparticles (np) to Er ions and energy transfer from defects in the matrix to the Er ions for excitations resonant with the energy levels of such defects. 4I13/2→4I15/2 emission decay measurements show two decaying populations of Er ions according to their locations with respect to other ions or any non-radiative defects. 4I11/2→4I15/2 emission dependence on 4I13/2→4I15/2 emission showed that the former was possibly due to a combination of downconversion from higher levels of the Er ions, energy transfer from Si nanoparticles and upconversion transfer processes. We concluded that Er-doped Si-YSZ is a promising material for photonic applications being easily broadband excited using low-pumping powers.