Solubility of Co clusters in Co-implanted ZnO thin films by 200 MeV Ag15+ ions irradiation

Abstract

We have investigated the structural, electrical resistivity, pink noise (1/f noise) and magnetic properties of 200 MeV Ag15+ ions (fluence similar to 1 x 10(12) ions cm(-2)) irradiated Co-implanted ZnO thin films. The ZnO films were grown on Al2O3 substrate by the PA-MBE technique and 80 keV Co ion implantation with 1 x 1016 ions cm(-2) dose value. The structural studies of an unirradiated film show the presence of Co clusters, which dissolve in the ZnO matrix on swift heavy ion (SHI) irradiation. The temperature-dependent electrical resistivity plots of pristine (unirradiated) and irradiated films demonstrated semiconducting nature. The resistivity data were fitted in the Mott's variable range hopping (VRH) model and the activation energies were estimated. The magnitude of normalized noise S-V/V-2 increases with decrease in temperature and estimated Hooge's parameters have higher values as compared to other semiconductors. We observe a clear magnetic hysteresis loop with coercivity similar to 65 Oe for both the films at room temperature, establishing the ferromagnetic nature. The correlation between the electrical transport and magnetic properties in the present system formulates it to be a potential aspirant for the spintronics-oriented devices.