Tunable up-conversion and down-conversion photoluminescence of HfO2:Er3+ and HfO2:Er3+/Yb3+ coatings formed by plasma electrolytic oxidation of hafnium
Source abstract
Abstract
This study examines the structural and photoluminescent properties of HfO2 coatings doped with Er3+ and co-doped with Yb3+, prepared on hafnium substrates using the plasma electrolytic oxidation (PEO) technique with electrolytes containing Er2O3 and Yb2O3 particles. The coatings are crystalline and consist of monoclinic and tetragonal phases of HfO2 Incorporation of Er and Yb into the HfO2 lattice induces a phase transformation, stabilizing the tetragonal phase. Up-conversion (UC) photoluminescence (PL) of HfO2:Er3+ and HfO2:Er3+/Yb3+ under 980 nm excitation shows characteristic green (2H11/2 4S3/2 → 4I15/2) and red (4F9/2 → 4I15/2) emissions from Er3+. Increasing the Er3+ concentration enhances the total UC PL intensity, with a disproportionate increase in red emission, attributed to concentration-dependent cross-relaxation processes that populate the 4I13/2 level, followed by excited state absorption. Co-doping HfO2:Er3+ with Yb3+ results in a significant enhancement of UC PL intensity, up to 30 times at the optimal Yb2O3 concentration of 1 g/L in the electrolyte. This enhancement is due to efficient energy transfer from the Yb3+ sensitizer to the Er3+ activator. Furthermore, the Er3+ red emission is preferentially enhanced due to a phonon-assisted Er3+ to Yb3+ energy back-transfer process, which efficiently depopulates the green-emitting 4S3/2 level and increases the population of the red-emitting 4F9/2 level. Down-conversion (DC) PL excitation and emission spectra of HfO2:Er3+ and HfO2:Er3+/Yb3+ display sharp peaks corresponding to f–f transitions of Er3+, with intensities directly proportional to the Er3+ concentration. In HfO2:Er3+/Yb3+, the DC PL intensity decreases as the Yb3+ concentration increases, particularly for the green emission. This reduction is attributed to energy transfer via cross-relaxation from excited Er3+ to Yb3+, which quenches the visible emission from Er3+,.
Source: openaire · Quality: candidate unverified · Source record ↗
Research context
OpenAlex topics: Luminescence Properties of Advanced Materials · Silicon Nanostructures and Photoluminescence · Semiconductor materials and devices
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
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