Magnetoresistance as a function of manganese doping in Mn-zinc nitride thin films

We present the thin films growth and study of manganese doped zinc nitride by RF/DC magnetron sputtering to investigate the optimum doping concentration that can result in the material to be dilute magnetic semiconductor. We studied the grown films using spectrophotometry, X-ray diffraction, Hall effect measurement, atomic force microscopy and X-ray photoelectron spectroscopy. We observed the effect of manganese doping concentration on the surface morphology, optical, electronic, and magnetic properties of the films. The grown films were found to be polycrystalline in nature. However, a prominent Zn₃N₂ (411) peak was present in all the films. Bandgap of the grown films was dependent on the manganese concentration in the films, a red-shift in the bandgap was observed for Mn doped samples. Hall effect measurement revealed that all the grown films were n-type semiconductors and carrier density of the films was lower for manganese doped films whereas Hall mobility was higher for Mn doped samples. Manganese was found to be in the second (Mn⁺²) and third (Mn⁺³) oxidation states for low doped samples. But as the concentration of manganese in the films was increased the samples were found to be in 3rd and 4th oxidation states. Manganese oxidation state was directly related to the magnetism of the samples. A negative magnetoresistance was found for samples with lower manganese concentration but higher doped samples exhibited zero or positive magnetoresistance.