COMPARATIVE CATHODOLUMINESCENCE OF NANOSTRUCTURED AlN AND AlN NANOTUBE/CsI SCINTILLATOR COMPOSITES

Abstract

The cathodoluminescence (CL) response of commercially available aluminium nitride powder, plasma-synthesized AlN nanoparticles, AlN nanotubes, and AlN nanotube/CsI composites was comparatively analysed in the 80–300 K temperature range. The nanostructured material was produced by a highly nonequilibrium direct-current arc-plasma route and contained two characteristic nanotube populations: hollow tubes with diameters of approximately 25–30 nm and thinner, frequently helical tubes with diameters of 2–3 nm; both populations had lengths on the order of 700 nm. At 80 K the commercial AlN powder exhibited a dominant band at 3.47 eV, whereas nanoparticles emitted predominantly near 3.66 eV. The nanotube spectrum was substantially more complex and included components near 2.2, 3.0, and 3.5 eV, indicating a broader distribution of defect and surface-related radiative channels. A single-channel Mott–Seitz treatment of the temperature-dependent 3.47 eV emission yielded an apparent activation energy of about 24 meV. The absence of a measurable peak shift or linewidth broadening, together with the small fitted energy, indicates that the intensity loss cannot be described as conventional thermal quenching alone and is more consistently explained by carrier migration to non-radiative surface states. Addition of 0.25–0.50 wt.% AlN nanotubes to CsI modified the host emission profile, particularly at 80 K, providing spectral evidence consistent with radiative reabsorption and/or interfacial energy redistribution. The results demonstrate that AlN morphology strongly controls the balance between intrinsic, impurity-related, and surface-mediated recombination and underline the potential of AlN/CsI composites for tunable ultraviolet–visible scintillation materials.