Growth and characterization of pure and doped ZnO thin films.

The pure and Mg, Ga, Al, Ga-Mg and Al-Mg doped-ZnO thin films were fabricated by sol-gel spin-coating techniques and their conduction behaviour was investigated in the temperature range of 100 – 290 K and in the voltage range 0 – 30 V. The effect of dopant ion substitution on structural, optical and low temperature electrical properties of thin films were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV-Visible spectroscopy, spectro fluorophotometer and two probe resistivity measurement method, respectively. The XRD result confirmed the wurtzite structure of prepared thin films without the presence of any characteristic impurity peak of Mg, Ga and Al. The photoluminescence study had confirmed the presence of defect states in the prepared thin films. The electrical resistivity has been found to be 2.75 0¹ and 5.58 × 10² ohm - cm for Zn_0.96Ga_0.04O and Zn_0.93Mg_0.03Ga_0.04O thin film at 170 K, respectively. The decreased activation energy of Zn_0.96Ga_0.04O thin film up to 0.23 eV make it conducting at 100 K. Further, the Ga and Ga-Mg doping in ZnO thin film shifts VRH conduction mechanism up to130 K and 190 K from 230 K in case of pure ZnO thin film which makes them good conductive material at low temperature. So, the ability of Ga, Ga-Mg doped-ZnO thin films to conduct at low temperatures up to 100 K and 170 K, low activation energy and high optical transmittance makes it useful as a transparent and conductive material in optoelectronic devices.