In this report period, ZnO nanoarrays were grown via a low temperature hydrothermal method. The effects of the additives involved in the growth procedure i.e. ammonium hydroxide and sodium citrate were studied in terms of the morphological, optical and the scintillation properties of the ZnO nanostructures. ZnO NRs grown on a silica substrate showed high quality structural and optical properties. The addition of sodium citrate was found to reduce defects significantly and correspondingly increased the intrinsic near-band edge (NBE) UV emission intensity at ~380 nm. Annealing in a 10% H2 + 90% N2 atmosphere was performed to obtain high quality nanostructures. Highly tapered NRs were obtained towards the end of the structure. Time growth studies were conducted to monitor the tapering process and the tapering effect on photoluminescence (PL) as well as reflectance spectra were presented. Tapered ZnO NRs showed excellent anti-reflection properties. As grown ZnO NRs were found to have high alpha particle responses. ZnO NRs were then doped with Al, Ga and In and the structural, optical and scintillation properties were monitored. It was seen that optical and scintillation properties were improved by doping ZnO NRs. For the final report period, ZnO NR scintillators were first doped with enriched 6Li isotope, which acted as a radiator layer for alpha particles. Initial measurements on thermal neutron detection showed a thermal neutron response, which is a milestone in the project. Studies were then directed to advanced simulation using SRIM software to optimize the scintillator thickness and high doping of 6Li in ZnO NR structures to improve the thermal neutron response. The optimized scintillator design resulted in improved thermal neutron response of the ZnO:Li NR arrays, which is a breakthrough in the literature as the thermal neutron detection properties have not been reported for hydrothermally grown ZnO:Li NR arrays yet.
Vertically well-aligned tapered ZnO NR arrays with enhanced light absorption and optical coupling were grown in this project. The novel design of this ZnO NR arrays led to improved structural, optical, and scintillation properties.The alpha particle response obtained in thermal neutron measurements is a milestone in the project and constitutes first time measurements in the literature to the best of our knowledge. The optimized scintillator design resulted in improved thermal neutron response of the ZnO:Li NR arrays, which is a breakthrough in the literature as the thermal neutron detection properties have not been reported for hydrothermally grown ZnO:Li NR arrays yet. Results of the project were presented in an international conference and in a seminar at the host institution, and also were published in a SCI indexed journal. The researcher was involved in external collaborations and this collaboration resulted in publication of an article in a SCI indexed journal as well. The latest results of the project were submitted in a journal, which is in process.
