Probing the emission properties of color centers in MgAl2O4 wafers using hard X-ray nanoprobes.

In this study, we used hard X-ray-excited optical luminescence (XEOL) to investigate the emission properties of MgAl 2 O 4 wafers with a crystal orientation of (100), (110), or (111). MgAl 2 O 4 (110) exhibited the lowest XEOL emission intensity because the (110) orientation is thermochemical unstable and therefore unfavorable for generating oxygen vacancies. By fitting XEOL spectra, we identified 13 and 6 clear emission peaks corresponding to the color centers in MgAl 2 O 4 wafers and the 2E g →4A 2g radiative transition of Cr ion impurities, respectively. Using an X-ray nanoprobe, we obtained an X-ray fluorescence spectroscopy (XRF) map of the elemental distribution of Cr with 100 nm spatial resolution. X-ray absorption spectroscopy (XAS) revealed that the valence state of the Cr ion impurities was Cr3+. We thus also clearly demonstrate the advantages of combining XEOL, XRF, and XAS in the X-ray nanoprobe beamline by obtaining emission spectra using XEOL and using XRF and XAS to analyze elemental distributions and valence states to further elucidate the emissions of samples. • The emission properties of the color centers in MgAl 2 O 4 wafers has been investigated by XEOL. • We identified 13 clear emission peaks corresponding to the color centers in MgAl 2 O 4 wafers. • X-ray absorption spectroscopy (XAS) revealed that the valence state of the Cr ion impurities was Cr3+. [ABSTRACT FROM AUTHOR]