Influence of Er concentration on the emission properties of Er-doped Si-rich silica films obtained by reactive magnetron co-sputtering

Abstract

Er-doped silicon-rich silicon oxide (SRSO) thin films have been fabricated by reactive magnetron sputtering of a pure silica target topped by chips of Er2O3. The incorporation of silicon excess in the films is due to the introduction of hydrogen in the plasma which reduces accordingly the oxygen released by the silica target. The incorporated Er content [Er] in the films was controlled by the sputtered surface ratio of Er2O3 chips with respect to that of silica target. The photoluminescence (PL) intensity at 1.54 μm from samples obtained with different [Er] values and annealing temperature were compared for the same amount of Si excess and interpreted in terms of sensitizing action of Si nanoclusters (Si–NCs) towards the neighboring Er ions. Some onset of concentration-related effects (up conversion, quenching) was suspected for [Er] ∼3 × 1020 cm−3 through the decrease of the lifetime emission from ∼6 ms for [Er] = 5 × 1019 cm−3 to about 3.5 ms. These effects were compensated by a better coupling rate between the Si–NCs and the neighbouring Er ions. This was achieved through some adjustments of the processing parameters: the decrease of the plasma pressure that led to the improvement of the PL by a factor of 3, and the decrease of the annealing temperature from 1100 °C to 900 °C that induced a 2.5 times increase of the 1.54 μm emission.