Influences of growth temperature on the crystalline characteristics and optical properties for ZnO films deposited by reactive magnetron sputtering

Using reactive radio-frequency magnetron sputtering, ZnO films with strong c-axis orientation have been deposited on Si (100) substrates at temperatures ranging from room temperature (RT) to 750 degrees C. We have studied the influence of growth temperature on the structural characteristics of the as-deposited films in morphology, grain size, microstructure, and residual stress by using atomic force microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. With the measurement of the tran!;mission spectra and photoluminescence (PL) properties, the relationship between the crystallinity and optical properties of ZnO films have been discussed. it is found that the grain size increases with temperature up to 500 degrees C, and then decreases at 750 degrees C. ZnO grains have an epitaxial relationship with Si (100) substrate for the films deposited at the temperatures ranging from RT to 750 degrees C. The films deposited below 500 degrees C are in the states of compressive strain while the film deposited at 750 degrees C is in tensile. The difference in growth temperature results in the variation of refractive index, extinction coefficient, optical energy gap, and PL properties of the films. It is concluded that growth temperature dominates the PL behavior of ZnO films. We also discuss the physical mechanism affecting the PL behavior.