Raman spectroscopy of Ce3+ doped Lu3Al5O12 single crystalline films grown onto Y3Al5O12 substrate

Single crystalline film (SCF) of Lu3Al5O12 (LuAG) garnet doped with Ce3+ ions grown onto Y3Al5O12 (YAG) substrate has been studied for the first time by Raman spectroscopy. In order to record undisturbed spectra (separated signals) of LuAG:Ce SCF and YAG substrate, the sample was broken and the spectra were measured of particular parts of the cross-section. Due to Ce3+ doping and intense Ce3+ luminescence the Raman spectra had to be measured using the excitation wavelength of 785 nm. The Raman modes recorded for LuAG:Ce SCF and YAG substrate are overlapped with electronic transitions attributed to rare earth (RE) trace impurities of the sample. Moreover, many intense lines were recorded in the spectral range above 900 cm−1 in which the first- and higher-order Raman modes do not occur. The lines above 900 cm−1 were assigned to 4f-4f electronic transitions of RE3+ trace impurities present both in SCF and the substrate. The main identified RE impurity ions were Nd3+, Yb3+, Er3+, and Eu3+. Both the Raman map and the map obtained on the basis of electronic transitions allow distinction between the SCF, substrate, and transition layer of the sample investigated. In the temperature range 80–318 K, a strong increase in the intensities of a few lines assigned to electronic transitions was observed with decreasing temperature. Some anomaly in the temperature dependence of intensity at about 180 K for some lines recorded for SCF and YAG substrate was observed. © 2019