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The dual role of Cr3+ in trapping holes and electrons in lanthanide co-doped GdAlO3 and LaAlO3

Abstract

Trivalent Nd, Dy, Ho, Er, Tm, Sm, Eu usually act as electron trapping centers in wide band gap compounds, whereas trivalent Ce, Tb, and Pr act as hole trapping centers. When a deep electron trap is combined with a shallow hole trap, then during the thermoluminescence glow the hole is released generating recombination luminescence at the electron trap. However in case of a shallow electron trap, the electron will be released to recombine at the hole trapping center. With the knowledge on location of the lanthanide levels within the band gap one may engineer the depth of the electron trap, the depth of the hole trap, and where the recombination will take place. This all has been tested and verified for the lanthanides in GdAlO3 in [Luo et. al J. Phys. Chem. C 120 (2016) 5916.]. In this work Cr3+ is combined with various trivalent lanthanides in GdAlO3. By combining thermoluminescence with optical spectroscopy data, a consistent interpretation of all data is obtained. Cr3+} can, other than all lanthanides, act both as a deep electron trap and as deep hole trap. From the results we will deduce the location of the Cr2+ and Cr3+ levels within the band gap and with respect to the vacuum level. Besides thermoluminescence recombination via the conduction band, evidence is found for athermal (tunneling) recombination. Results on GdAO3 are compared with results on LaAlO3. A related system but with lower lying conduction band and higher lying valence band that reduces the trap depths of the lanthanides and Cr in a predictive fashion.

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Publication details

The article was received on 06 Mar 2018, accepted on 17 Apr 2018 and first published on 17 Apr 2018


Article type: Paper
DOI: 10.1039/C8TC01100A
Citation: J. Mater. Chem. C, 2018, Accepted Manuscript
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    The dual role of Cr3+ in trapping holes and electrons in lanthanide co-doped GdAlO3 and LaAlO3

    P. Dorenbos and H. Luo, J. Mater. Chem. C, 2018, Accepted Manuscript , DOI: 10.1039/C8TC01100A

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