PhD Impurity Luminescence and Selective Vacuum-Ultraviolet Excitation in a Nominally Undoped YAlO₃ Crystal

Номиналды қоспаланбаған YAlO₃ кристалының қоспалық люминесценциясы және селективті вакуумдық-ультракүлгін қозуы

Abstract

The emission spectrum of a nominally undoped yttrium aluminate (YAlO₃) single crystal under excitation at 7.75 eV and the excitation spectra of nine emission channels were investigated at 300 K. The measurements were performed at beamline P66 of the PETRA III synchrotron radiation facility at DESY. A combined analysis of the original spectra, normalized dependences, and inter-channel intensity ratios revealed two distinct groups of excitation behavior. The emission channels at 352.6, 465, 523.6, and 794.6 nm exhibit an excitation maximum near 7.85 eV, whereas the 724.4 and 749.4 nm channels are predominantly excited in the 6.8–6.9 eV range and show a correlation coefficient of 0.982.

The 722.7/725.0 nm doublet is assigned to Cr³⁺ ions, while the sequence of lines at 875.5, 884.4, and 891.9 nm, together with a weak group at 915–916 nm, is consistent with the Stark structure of Nd³⁺. For the remaining spectral regions, testable assignments to Tm³⁺, Er³⁺, and other rare-earth centers are proposed without claiming their unambiguous identification. The common excitation behavior of the red emission channels and an energy separation of approximately 462 cm⁻¹ support a possible vibronic origin of the band near 750 nm.

It is shown that the excitation maximum near 7.85 eV alone does not provide sufficient evidence for an excitonic mechanism in the absence of a validated correction for the incident photon flux. The limitations of lamp-based spectroscopy and the conditions required for reliable identification of trace impurities are discussed.