Effect of thickness on structural, electrical, optical and magnetic properties of Co and Al doped ZnO films deposited by sol–gel route

This paper reports deposition and characterization of Zn0.94Co0.05Al0.01O films of thickness ranging from 70 nm to 400 nm. These films were deposited on a glass (Corning, 7059) substrate using sol–gel route. The films have been characterized to study their structural, electrical, optical and magnetic properties. X-ray diffraction (XRD) and atomic force microscopy (AFM) were used to study the crystallinity and growth mode of the films. The films deposited up to a thickness of 200 nm showed improvement in crystallinity and preferential c-axis orientation. A transition in the growth mode from vertical (c-axis) to lateral (a and b-axis) was observed with further increase in the thickness of the film. The average transmittance of the films for thickness less than 200 nm was above 80% in the visible region which decreased at higher thickness of the film. The resistivity of the film was found to decrease with increase in thickness up to 200 nm. Ferromagnetism, at room temperature, was confirmed for 200 nm and 400 nm thick films.