Optical and structural properties of $Er2O3$ films grown by magnetron sputtering

The structural properties and the room temperature luminescence of $Er2O3$ thin films deposited by magnetron sputtering have been studied. In spite of the well-known high reactivity of rare earth oxides towards silicon, films characterized by good morphological properties have been obtained by using a $SiO2$ interlayer between the film and the silicon substrate. The evolution of the properties of the $Er2O3$ films due to thermal annealing processes in oxygen ambient performed at temperatures in the range of $800–1200°C$ has been investigated in detail. The existence of well defined annealing conditions (rapid treatments at a temperature of $1100°C$ or higher) allowing to avoid the occurrence of extensive chemical reactions with the oxidized substrate has been demonstrated; under these conditions, the thermal process has a beneficial effect on both structural and optical properties of the film, and an increase of the photoluminescence (PL) intensity by about a factor of 40 with respect to the as-deposited material has been observed. The enhanced efficiency of the photon emission process has been correlated with the longer lifetime of the PL signal. Finally, the conditions leading to a reaction of $Er2O3$ with the substrate have been also identified, and evidences about the formation of silicate-like phases have been collected.