Effect of Mn doping on structural, optical and magnetic properties of ZnO films fabricated by sol–gel spin coating method

We have fabricated undoped ZnO and Mn-doped ZnO thin films on glass substrates using sol–gel spin coating method and investigated their structural, optical, magnetic and magnetoresistance properties depending on the Mn doping ratio. X-ray diffraction (XRD) patterns showed that all the films under study are predominantly crystalized in a single-phase wurtzite structure. Scanning electron microscope (SEM) images revealed that the films become more homogeneous, continuous and pinhole-free coatings as the Mn content of the films increases. Optical characterizations by UV–visible spectrometer indicated that transmittance spectra of all films have a high transmittance above 85% in visible region, while they show the absorbance spectra in 300–400 nm range. In addition, it was observed that the optical energy band edges shift to red with increasing Mn content, due to probably increasing the carrier concentration. The refractive index and the dielectric constant are also affect by the Mn content. Magnetic measurements by vibrating sample magnetometer showed that the film magnetic properties change from diamagnetic to ferromagnetic as the Mn content increases. Furthermore, it was found that the magnetoresistance measurements support their magnetic behavior of the films.