Near-Infrared Raman Spectroscopy as a Unique Tool for Characterization of Visible Luminescent ZnS Phosphor.

Abstract

Near-infrared (NIR) Raman spectroscopy has shown its unique advantages for characterization of ZnS e Cu, Al materials, emitting a strong luminescence in the visible region. We demonstrate that, because of a rapid decrease of luminescence in the NIR region, Raman spectra with 752.5-nm excitation are free from the visi ble luminescence, which usually masks Raman signals with visible excitations. By comparing the spectra of ZnS: Cu, Al samples with different luminescence efficiencies, we also find that crystal imperfections, includ ing coexistence of hexagonal domains, can lead to a reduction of luminescence properties.

Probes of Structural and Electronic Environments of Phosphor Activators: Mössbauer and Raman Spectroscopy

“…ZnS is an important host lattice for green and blue cathode ray tube (CRT) television phosphors as well as for electroluminescent and long afterglow applications. Near-infrared Raman spectroscopy has been used to characterize green-emitting ZnS:Cu,Al materials . Excitation of wavelength equal to 752.5 nm was employed so that the Raman spectra were free from the strong visible luminescence which occurs from these phosphor materials.…”

“…Near-infrared Raman spectroscopy has been used to characterize green-emitting ZnS:Cu,Al materials. 252 Excitation of wavelength equal to 752.5 nm was employed so that the Raman spectra were free from the strong visible luminescence which occurs from these phosphor materials. A strong Raman band at 350 cm -1 due to the LO mode and additional weak features around ∼220 cm -1 , probably arising from a two-phonon process, indicate that the phosphor had a cubic zinc blende lattice.…”

“…This was indicated by a Raman band at 300 cm -1 , which was attributed to the E 2 mode of ZnS in the hexagonal phase for which the cubic phase has no counterpart. It was emphasized that Raman spectroscopy is sensitive to short-range order (of the order of approximately g5 unit cells), unlike XRD, which has a coherence length of g20 unit cells, 252 allowing the detection of polymorphic modifications of the phosphor. It was pointed out that an advantage of Raman spectroscopy over XRD is that the polymorphic modifications of nanometer-sized particles can be detected by the former technique, whereas line broadening occurs when using XRD, and that hinders the ability of this latter technique to distinguish between different polymorphic modifications.…”