Mn-Doped XAlO₃ (X = Y, Tb) Single-Crystalline Films Grown onto YAlO₃ Substrates: Raman Spectroscopy Study toward Visualization of Mechanical Stress

Abstract

Single-crystalline films (SCFs) of perovskites TbAlO3 (TbAP) and YAlO3 (YAP) doped with Mn ions were grown using the liquid-phase epitaxy (LPE) method on YAlO3 single-crystal (SC) substrates and investigated using Raman spectroscopy. The cross-section of the above-mentioned epitaxial structures was probed to obtain Raman signals of TbAP:Mn, YAP:Mn SCFs, and the YAP SC substrate. The undisturbed Raman signals of TbAP:Mn and YAP:Mn were recorded. For the TbAP:Mn sample, due to the difference in lattice constants between the SCF and the substrate, significant changes in the Raman spectra were observed. Over the interface between the SCF and the substrate, called the transition layer, gradual changes in the Raman spectra were observed. The changes are connected with the replacement of Tb3+ ions with Y3+ cations and are manifested as shifts of the modes assigned to translational, librational, and internal vibrations. Angular-dependent measurements of polarized spectra allowed determination of the TbAP:Mn SCF orientation in the ac plane (010). High-resolution luminescence spectra confirmed electronic transition attributed to Tb3+ cations and Nd3+ trace impurities in the YAP substrate. The Raman map recorded for the region close to the transition layer showed a shift of the Raman band at 552 cm–1 (YAP) related to the changes in the lattice constants and mechanical stress.

Micro-Inclusion Engineering via Sc Incompatibility for Luminescence and Photoconversion Control in Ce3+-Doped Tb3Al5−xScxO12 Garnet

“…This phenomenon explains the observed deviation from Vegard’s law in the experimental data. Discrepancies from Vegard’s law have been well-documented, where deviations are often attributable to factors such as differences in individual component sizes and structural compatibility [ 45 ]. This preference provides strong evidence of the inherent limitations in incorporating solutes into a solid matrix when the solute atoms are significantly different in size compared to the solvent atoms [ 12 , 34 ].…”

“…Corroborated by PXRD and EDS analyses, the presence of TbAlO 3 perovskite as a predominant secondary phase inclusion is also evident from the Raman inspection (see Figure 5 a, lower panel). Notably, the Raman spectrum collected on the main central inclusion of the Tb 2.85 Ce 0.15 Al 4.5 Sc 0.5 O 12 crystal (x = 0.5) exhibits intense modes at 100, 113, 146, 247, 325, 381, 397, 414, 473, 525, and 538 cm −1 , which are characteristic fingerprints of the orthorhombic perovskite structure ( Pnma space group) of TbAlO 3 [ 45 ]. In contrast, the Raman spectrum of the Ce 3+ -doped Tb 3 Al 5−x Sc x O 12 crystal, where x = 3.0 ( Figure 5 a, upper panel), exhibits a distinctly different spectral profile, with well-defined modes observed at approximately 113, 156, 310, 326, 360, and 380 cm −1 , accompanied by the most intense Raman activity occurring between 400 and 600 cm −1 .…”