The effect of thickness on the properties of heavily Al-doped ZnO films by simultaneous rf and dc magnetron sputtering

For heavily Al-doped ZnO (ZnO:Al) films, there was a tendency for the c-axis to be perpendicular to the substrate, and further increasing in crystallinity or degree of orientation by increasing the film thickness. The surface of ZnO:Al films exhibited the hillocks growth obviously with the decrease of film thickness. There was the close relation among the film thickness, surface roughness, and carrier mobility. Generally, the resistivity and visible transmission of film decreased with the increase of film thickness. However, in this work the proper film thickness could result in lower resistivity and visible transmission, respectively. With the increase of film thickness, the transmission in UV region decreased obviously. As the results, film thickness affected the properties of ZnO:Al films significantly.