Thermally stimulated electron delocalization and luminescence quenching of Ce impurities in GdAlO 3
2005; American Physical Society; Volume: 71; Issue: 4 Linguagem: Inglês
10.1103/physrevb.71.045121
ISSN1550-235X
AutoresErik van der Kolk, P. Dorenbos, J.T.M. de Haas, C.W.E. van Eijk,
Tópico(s)Solid-state spectroscopy and crystallography
ResumoA combined photoconductivity and luminescence quenching study, both temperature and spectrally resolved, has revealed the role played by electron delocalization in luminescence quenching of ${\mathrm{Ce}}^{3+}$ impurities in the wide band-gap inorganic insulator ${\mathrm{GdAlO}}_{3}$. The anticorrelation found between the temperature behavior of photocurrent and luminescence intensity strongly suggests that luminescence quenching and photoconduction are intimately related by the same process, i.e., thermal stimulated ionization of optically excited ${\mathrm{Ce}}^{3+}$ centers: ${\mathrm{Ce}}^{3+}\ensuremath{\rightarrow}{\mathrm{Ce}}^{4+}+\text{electron}$. Quantitative modeling of experimental data using rate equations, however, reveals a 0.05-eV smaller activation energy for luminescence quenching than for photocurrent generation which indicates that quenching predominantly proceeds via the formation of a Ce bound exciton at the originally excited Ce ion. A second quenching process, dominant below 230 K, seems mediated by energy transfer from ${\mathrm{Ce}}^{3+}$ via the ${\mathrm{Gd}}^{3+}$ sublattice to ${\mathrm{Ce}}^{4+}$ centers resulting in hole conductivity via a charge transfer excitation: ${\mathrm{Ce}}^{4+}\ensuremath{\rightarrow}{\mathrm{Ce}}^{3+}+\text{hole}$.
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