dc and ac transport properties of Mn-doped ZnO thin films grown by pulsed laser ablation

MnxZn1-xO (x=0.20) thin films were deposited on Pt coated Si substrates using pulsed laser ablation technique. The structural characteristics of the films were investigated by X-ray diffraction (XRD), while the dielectric response of the films was studied as a function of frequency and ambient temperature by employing impedance spectroscopy. It was found that all the films deposited on Pt coated Si substrates had c-axis preferred orientation perpendicular to the substrate, with full width at half maximum (FWHM) of the (002) X-ray reflection line being less than 0.5 degrees. The dc and ac electrical conductivity of Mn-doped ZnO films were investigated as a function of temperature. The ac conductivity, sigma(ac)(omega), varies as sigma(ac)(omega)=A omega(s) with s in the range 0.4-0.9. The complex impedance plot showed data points lying on a single semicircle, implying the response originated from a single capacitive element corresponding to the bulk grains. The value of the activation energy computed from the Arrhenius plot of both dc and ac conductivities with 1000/T were 0.2 eV suggesting hopping conduction mechanism. The optical properties of Zn0.8Mn0.2O thin films were studied in the wavelength range 300-900 nm. The data were analyzed in the light of the existing theories and reflected a Burstein-Moss shift in these films. The films show magnetic properties, which are best described by a Curie-Weiss type behavior. (c) 2006 Elsevier B.V. All rights reserved.