Fast luminescence and low-energy photon response of long Ga-containing ZnO nanorod arrays

Long Ga-containing ZnO nanorod arrays were grown on ZnO-seeded fused-silica substrates by a hydrothermal route and investigated as thin nanostructured scintillator layers for low-energy photon response. The arrays formed a dense and continuous layer with an average thickness of 33.8 ± 1.9 μm, an apparent diameter of 0.78 ± 0.33 μm, and a density of 1.95 ± 0.08 rods μm−2. EDX analysis provided semi-quantitative evidence of weak Ga-associated signals, although Zn-L/Ga-L spectral overlap precluded determination of an exact Ga concentration or lattice location. XRD patterns of the Ga-containing and undoped arrays exhibited the characteristic (002) and (004) reflections of preferentially c-axis-oriented wurtzite ZnO but did not establish substitutional Ga incorporation. UV–vis diffuse reflectance analysis yielded a morphology-dependent apparent optical-edge energy of 3.19 ± 0.03 eV. Following forming-gas annealing at 350 °C, the Ga-containing array exhibited NBE-dominant emission at approximately 375–380 nm with a strongly suppressed relative visible contribution, whereas the similarly annealed undoped control remained visible-emission-dominant. Cathodoluminescence measurements confirmed NBE-dominant emission under electron-beam excitation and revealed spatially resolved UV emission. Time-resolved PL yielded an apparent 1.77-ns early-time component; because this value is comparable to the 1.37-ns IRF width and was obtained without reconvolution, it is interpreted as instrument-broadened rather than as a precisely resolved intrinsic lifetime. Qualitative pulse-height measurements under Am-241 irradiation showed substantially stronger detected responses from both nanorod arrays than from the ZnO-seeded control, with the Ga-containing array exhibiting a somewhat higher count response; no absolute or relative light yield was inferred. These results demonstrate NBE-dominant luminescence and a measurable qualitative low-energy photon response from a long Ga-containing ZnO nanorod architecture.