Submicrometer optical characterization of the grain boundary of optically active Cr³⁺doped polycrystalline Al₂O₃by near-field spectroscopy

Abstract

Near-field fluorescent spectroscopy was used to characterize the grain boundary of Cr-doped polycrystalline alumina. The results show that the peak widths in near-field spectra are narrower than in spectra obtained by conventional microspectrometry, and this is attributed to the difference in spatial resolution of the two methods. The R-line peaks of Cr3+ fluorescence were observed to shift to a lower wavelength at the grain boundary compared to the bulk crystal, which is attributed to stress relief at the crystal boundary. This peak shift at the boundary decreases as a function of the time a polycrystal is annealed at 1700 °C.