Structural, magnetic, electrical and optical studies of Cr doped nanostructured ZnO thin films for spintronics application

Abstract

A series of Cr-doped ZnO thin film has been prepared by E-Beam evaporation technique. These thin films were characterized for finding change or variation in the structural, morphological, optical properties due to varying doping concentration of Cr using x-ray diffraction(XRD), Scanning electron microscopy(SEM), UV–vis spectroscopy and Photoluminescence (PL) spectrometry. The crystallite size and root mean square roughness (rms) were found to be in the range of 14 to 22 nm and 7 to 28 nm respectively for various thin films. The optical absorption was measured by UV–visible in the wavelength range of 280 to 700 nm and on increasing the doping concentration blue shift was observed. Optical band gap were found to be increased with increasing doping concentration. The electrical transport property such that resistivity, sheet resistance, and conductivity were analyzed by the Hall measurement setup and resistivity were found to be 1.39 × 10−2, 8.16 × 10−3 , 1.43 × 10−2, 9.53 × 10−2Ω-cm for pure ZnO 5% ,10% and 15% Cr doped thin film respectively. Two probe I-V characterization was also done to find out the effect of doping on current conduction. The resistance values was found to be maximum for 5% Cr whereas a increment in resistance has been observed on further increasing in the doping concentration. The samples were also investigated in the superconducting quantum interference detector (SQUID) at 300 K as well as at 5 K for magnetic characterization. It has been observed that the thin film with 5% Cr doping exhibited ferromagnetic behavior whereas paramagnetic behavior was observed on further increase in Cr concentration.