Sensitization efficiencies in Er-doped SiOx films containing amorphous or crystalline silicon nanoclusters



A suite of SiOx films with oxygen concentrations ranging from x = 1 to 1.8 (25 at% to 3.6 at% excess silicon) were synthesized by physical vapour deposition. Erbium was incorporated by co-evaporation of erbium metal to a concentration of about 0.2 at%. A subsequent annealing step was performed at temperatures ranging from 400 °C to 1100 °C to induce phase separation and cluster growth, and to optically activate erbium ions. This range of compositions and annealing temperatures was used to generate a fluorescence map for nanocluster-sensitized Er3+. Photoluminescence (PL) spectra were measured in the visible and near-infrared wavelength regions to explore the nature of the energy transfer between Si-NCs and Er3+ ions. The highest PL intensities for undoped films occurred for samples annealed above 1000 °C, containing silicon nanocrystals. In contrast, in Er-doped films the strongest Er3+ emission at 1.54 μm was observed from films annealed at temperatures below 1000 °C, demonstrating that amorphous Si nanoclusters support effective energy transfer to the Er3+ ions. The sensitization was most efficient when the NC peak emission wavelength was near 660 nm (1.88 eV) matching the energy of the 4F9/2 band of Er3+ ions in a silica host. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)