Impact of rapid thermal annealing on structural, optical and electrical properties of DC sputtered doped and co-doped ZnO thin film

We report a crucial change in structural properties which dramatically modified optical and electrical properties in annealed aluminium-boron and gallium-aluminum co-doped ZnO thin films grown using DC magnetron sputtering. Under vacuum, ambient films were annealed at 600 °C for 2 min and it was found that the transmission of annealed samples improved compared to pristine, doped, and co-doped ZnO thin films. The X-ray diffraction (XRD) patterns of pristine films exhibits a preferable growth orientation in 〈002〉 phases, however, after annealing signature of other peaks became prominent. Moreover, slender increase in crystallite size was also observed from XRD analysis. The surface morphology was studied using scanning electron microscopy (SEM). The surface morphology exhibits different structure which depending on the growth temperature was discussed in detail. The electrical properties viz. resistivity, mobility, and carrier concentration of both pristine and annealed ZnO thin films were measured at room temperature. An enhancement in the electrical properties of doped and co-doped ZnO thin films was noted after annealing. More significantly, it was found that annealed thin films showed the resistivity of the order ∼10−4 ohm cm with the enhanced optical transmittance. Such a transparent and conducting zinc-oxide thin film can be used as a window layer in solar cell.