Unraveling the effect of 600 keV carbon ion irradiation on the structural and magnetic properties of ZnO thin film

600 keV 12C+ carbon ions have been irradiated upon 800 nm thin ZnO film. The thin ZnO films have been grown by pulsed laser deposition technique upon SiO2/Si substrate. The glancing incidence X-ray diffraction study exhibits the hexagonal wurtzite crystal structure of ZnO, having space group P63mc. Systematic X-ray diffraction analysis of both unirradiated and irradiated samples, reveals that the strain decreases in the sample post irradiation. Room temperature magnetization studies have been performed using SQUID-VSM. As the 600 keV carbon ion fluence is varied, an onset of ferromagnetic ordering in the ZnO thin film is observed. The maximum average magnetic moment induced by each carbon ion is found to be about 6.71 mu B. X-ray photoelectron spectroscopy has been utilized to analyze the oxidation state of the C/O/Zn, which also rules out the presence of any transition metal elements in carbon ions irradiated ZnO thin film samples. The chemical and structural analysis of the samples have been examined by Raman spectroscopy. It reveals a red shift in A1 (LO) mode, which confirms the presence of tensile strain in the sample post irradiation. These experimental results, clearly indicate that oxygen vacancies and strain in the film trigger the onset of ferromagnetism in the ZnO thin film system.