Effect of energetic particle bombardment on microstructure of zinc oxide films deposited by RF magnetron sputtering

Zinc oxide (ZnO) films have been deposited on glass substrates by rf magnetron sputtering with Ar/O-2 working gases. The crystallite size of the films was characterized by X-ray diffraction (XRD) analysis. At a deposition pressure of 1.0 Pa, the average crystallite size decreased with increasing O-2 flow rate. Optical emission spectroscopy (OES) results showed that the average crystallite size can be controlled by the emission intensity ratio of O*/Ar. The XRD results of the ZnO deposited in both Ar/O-2 and O-2 working gases revealed that the bombardment of the energetic oxygen particles to the growing surface suppresses the surface migration of the sputtered adatoms and that of energetic argon particles enhances the surface migration of the adatoms. The crystallite size and total volume of the crystallite fraction in the film are affected by the flux of both energetic oxygen and argon particles present in the plasma, and are determined by the competition processes of the bombardment of energetic oxygen and argon under a constant deposition pressure.