Growth of lanthanide-doped YF3 thin films by pulsed liquid injection MOCVD: Influence of deposition parameters on film microstructure

Yttrium fluoride (YF3) is a potential candidate as an ideal host material for rare-earth (RE) ions that allow the up- and down-conversion of light. We describe the deposition of Er/Yb co-doped YF3 thin films on Si(111) wafers using low pressure pulsed liquid injection MOCVD. Films were grown through the thermal decomposition of Y/RE(hfac)3 precursors dissolved in dimethoxyethane (0.05 M) under 5 torr of an O2/Ar atmosphere at different substrate temperatures between 450 °C and 650 °C. The film microstructure strongly depends on the operational conditions of the deposition and an optimization of the gas flow, oxygen content, pulse duration and deposition temperature was achieved. Under optimized conditions, films deposited at 590 °C showed the best quality and no crack formation was observed on Si(111) for a film thickness < 100 nm. These films have been characterized by SEM, AFM, XRD and Raman techniques. Optical measurements, including the dispersion of the refractive index and light transmission, were performed on the Er/Yb:YF3 films grown under optimized conditions.