Reassignment of electronic transitions in the laser-activated spectrum of nanocrystalline Y2O3:Er3

• Published in: Journal of luminescence 2018-04, Vol.196, p.337-346
• Main Authors: den Engelsen, D., Fern, G.R., Ireland, T.G., Silver, J.
• Format: Article
• Language: English
• Subjects: Assignment; Cross-relaxation; Hot band; Laser energy; Line width; Temperature behaviour
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2017.12.053

The laser-activated spectra of nanocrystalline Y2O3:Er3+ recorded at various temperatures and two excitation energies are described and analysed herein. Based on recently published modified values of the C2-type Stark splitting of Er3+ in the cubic Y2O3 lattice, the Er3+ multiplets in the observed spectra have been re-assigned. The upconversion routes of three 2H11/2 → 4I15/2 hot bands from 4S3/2 Kramers doublets have been traced, based on an Arrhenius-type analysis of these hot bands. We observed 5 peaks in the 2H11/2 → 4I15/2 hot band region with a different temperature behaviour. These bands belong to the 2P3/2 → 4I9/2 multiplet and their deviating temperature behaviour has been explained in terms of a cross relaxation mechanism. From the ratio between the laser-activated spectra that were recorded at different excitation energies we concluded that the two-photon absorption process becomes more efficient upon increasing the excitation energy. We have also put forward an explanation for the gradual broadening of the fluorescence bands of the 2H11/2 → 4I15/2 multiplet in going from 518nm to 542nm. The higher Stark splitting levels are due to a stronger electrostatic field of the host lattice and experience therefore a higher electron-phonon interaction, which explains the observed increase of FWHM at larger wavelengths.