Study On The Radiation Damage In(Co,Cu)-doped ZnO And As-grown ZnO Single Crystals Irradiated By Fast Neutrons

Recently, as-grown ZnO and (Co, Cu)-doped ZnO semiconductor materials have gained considerable interest for their excellent physical properties. There have great potential space applications for these semiconductor materials, so their property of radiation hardness should be very greatly investigated.Co-doped and Cu-doped ZnO and as-grown ZnO single crystals were irradiated by fast neutrons (En=2.5MeV, fluence 2.9×1010cm-2) from D-D reaction of ZF-300-ⅡIntense Neutron Generator of LanZhou University at room temperature. The (Co,Cu)-doped samples were prepared by ion implantation, and the implantation doses of Co ions are 1×1014,5×1016and 1 X 1017cm-2 respectively, the dose of Cu ions is 5×1016 cm-2. The structural and optical properties of all irradiated samples were investigated by X-ray diffraction (XRD), photoluminescence (PL) and optical transmittance measured at room temperature. Some preliminary experimental results as follows:(1) The results from XRD spectra indicate that all the fast-neutron-irradiated samples are still of wurtzite structure and in highly c-axis orientation, and the nanoparticles of metallic cobalt and cobalt oxides in Co-doped ZnO are disappeared after irradiation, and the Cu nanoparticles in Cu-doped ZnO are also disappeared.(2) The analysis of PL spectra of all samples irradiated shows some information to us. A great number oxygen vacancies (Vo) and antisite oxygen (OZn) are possibly introduced in the as-grown ZnO, and a few defects of interstitial zinc (Znj) and interstitial oxygen (Oi) are also introduced after irradiation. The defects of interstitial cobalt impurities and zinc vacancies (VZn) are produced in the Co-doped ZnO. VZn and the defects of lattice distortion are introduced in Cu-doped ZnO after neutron-irradiation.(3) Compared with unirradiated samples, the transmittance of all neutron-irradiated samples decreases by a little. At the same time, the change of Cu-doped ZnO is the largest in all samples, and the change of pure ZnO is the least. The measurement results also show that a great many Co2+ions substituted for Zn2+ions move away from the lattice site due to the fast-neutron collision, and the Cu nanoparticles in Cu-doped ZnO are disappeared after irradiation. (4) The changes of band gap suggest further that the nanoparticles of metallic cobalt and cobalt oxides in Co-doped ZnO are disappeared after irradiation. The appearance of blueshift in the peak position of the UV emission in Co-doped ZnO with the lowest Co concentration coincides with the change of band gap, and the redshift of UV emission peak of Cu-doped ZnO is also corresponding with the result of band gap.This work is helpful for the study of point defects of ZnO, and shows that pure ZnO and Co-doped and Cu-doped ZnO semiconductors still have perfect wurtzite structure. These semiconductors have the great radiation hardness and have potential space and other radiation environment applications.