Effect of thermal annealing treatments on the optical properties of rare-earth-doped AlN films

Abstract

Aluminium–nitrogen (AlN) films doped with samarium, europium or ytterbium have been prepared by conventional radio frequency sputtering. Because of the deposition method and conditions the as-deposited films are amorphous with Sm, Eu or Yb concentrations at low 0.5 at%. After deposition the films were submitted to cumulative isochronal thermal annealing (TA) treatments and investigated by optical transmission spectroscopy, photo- (PL) and cathodoluminescence (CL) measurements. For comparison purposes one undoped AlN film was also prepared and investigated in detail. The experimental results indicate that (a) all samples exhibit PL and CL at room temperature, (b) the main spectral features present in the AlN samples are due to defect-related transitions (undoped film) or the rare-earth (RE) ions, (c) in both cases (undoped and Sm-, Eu- or Yb-doped films) the luminescence intensity scales with the temperature of TA and (d) for the present AlN samples, there is a clear relationship between their luminescence intensity and respective energy of optical bandgaps. Finally, the effect of TA on the excitation–recombination mechanisms involving the RE ions is presented and discussed.

Thermal activation and temperature dependent PL and CL of Tb doped amorphous AlN and SiN thin films

“…Therefore, the light efficiency concerning solely this mechanism should be very low. Nonetheless, as reported previously, the light emission intensity upon this excitation source is rather high [5,9,12,17]. In this sense, other exci- tation paths beside the direct resonant excitation of the RE must play an essential role in the sub-bandgap photon excitation.…”

“…First the light emission intensity obeys the increase of luminescent centres by activating more REs in the matrix. This activation mechanism is still under discussion [5,[14][15][16][17]. Nonetheless the coordination of the RE with oxygen and other impurities seems to play a key role [18].…”

Reduction of Photoluminescence Quenching by Deuteration of Ytterbium-Doped Amorphous Carbon-Based Photonic Materials

“…A shift in the electronic structure would be supported by the larger width of the observed PL signal as compared to the reported widths from Yb doped ceramic [11,14,18,30], oxide [21,22,24,25] based host films, and Yb 2 O 3 crystalline films [33]. This wider luminescence spectra were also observed in Yb doped AlN films, where the host AlN films are essentially amorphous in form with AlN nanocrystals embedded in the matrix [54]. Nevertheless, the Yb4d XPS spectra suggest the Yb 3+ state is mostly preserved in the a-C:D:F(Yb) films, leading to the observed PL.…”

Concentration quenching and thermal activation of the luminescence from terbium‐doped a ‐SiC:H and c ‐AlN thin films

“…Recently, crystalline and amorphous AlN and SiC hosts have been investigated for some REs [8][9][10][11]. However there is still lack in the study on the behavior of the concentration quenching in these matrices.…”