Internal stress and surface morphology of zinc oxide thin films deposited by filtered cathodic vacuum arc technique

A radius of curvature technique was used to study stresses in zinc oxide (ZnO) films prepared by filtered cathodic vacuum arc. To deposit the films, a pure zinc target was used and O₂ was fed into the chamber. It was found that stresses in ZnO films are strongly correlated to the growth parameters of substrate temperature, substrate bias and oxygen pressure. The films prepared for studying the effect of substrate bias and oxygen pressure exhibited only compressive stress. For the films prepared to investigate the effect of substrate temperature, a transition from compressive to tensile stress was observed when the temperature was varied from 100 to 420 °C. The tensile stress is attributed to thermal stress caused by the difference in thermal expansion coefficients of the film and the substrate. Atomic force microscope images of the films were obtained to study their surface morphology. It is found that the surface morphology is significantly influenced by the growth parameters.