Gamma-ray irradiation of hydrothermal-grown bulk zinc oxide single crystals

Authors

Nobuhiko Sarukura ⋅ JP Institute of Laser Engineering, Osaka University

Abstract

Effects of different radiation environments are particularly interesting for materials used in fusion reactors. Inside these reactors, the chamber walls and diagnostic instruments are exposed to some unreacted deuterium and tritium fuels and to some reaction by-products such as neutrons, alpha-particles, x-rays, and gamma-rays. We then investigate the gamma-ray irradiation of hydrothermal-grown bulk zinc oxide (ZnO) single crystals. The bulk crystals are irradiated with gamma rays carrying 1.17 to 1.33 MeV energies from a cobalt-60 (⁶⁰Co) source. Gamma-ray radiation doses of 10 to 150 kGy are applied to the single crystals at room temperature and ambient atmosphere. The optical transmittances and photoluminescence (PL) emissions of the ZnO crystals are eventually compared before and after irradiation. The gamma-ray irradiation does not affect the optical transparency of the samples in the visible region. No radiation-induced absorption bands or color centers are observed. Gamma-ray irradiation only induces modified near-band-edge ultraviolet (UV) emissions with blue-shifted peaks and shortened lifetimes. From the values before irradiation, the peaks shift by 6 nm, and the lifetimes shorten by 0.14 to 0.53 ns. We attribute these observations to the radiation-induced defects on the bulk single crystals. Gamma rays carry substantial energy and can create defects such as vacancies or interstitials through collisions with a lattice atom. Our results nevertheless indicate that bulk ZnO single crystals have radiation resistance and improved emission lifetimes after gamma-ray irradiation. These observations give helpful insights towards the realization of short-wavelength scintillators based on ZnO that can perform well in harsh radiation environments such as inside fusion reactors.

About the Speaker

Nobuhiko Sarukura, Institute of Laser Engineering, Osaka University

Nobuhiko Sarukura, born and raised in Tokyo, obtained his undergraduate and graduate degrees from the University of Tokyo. Before landing a position as Professor at the Osaka University Institute of Laser Engineering (ILE), he worked in several institutions such as NTT, RIKEN, and the Institute of Molecular Sciences (IMS). In the research fields of optics, lasers, physics, and materials sciences, he is known for the investigation of the optical properties of different materials in the ultraviolet (UV) to terahertz (THz) region. At present, his research themes involve developing new optical materials based on oxides and fluorides useful in both science and engineering. His research undertakings implement both experimental techniques and theoretical investigations with various collaborators inside and outside Japan. These studies will hopefully lead to the development of new material applications and the advancement of next-generation industries in the near future.

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Issue

2016: Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Conference

Article ID

SPP-2016-3B-01

Section

Invited Presentations

Published

2016-08-18

How to Cite

[1]

N Sarukura, Gamma-ray irradiation of hydrothermal-grown bulk zinc oxide single crystals, Proceedings of the Samahang Pisika ng Pilipinas 34, SPP-2016-3B-01 (2016). URL: https://proceedings.spp-online.org/article/view/SPP-2016-3B-01.