Thermal Annealing of Gold Thin Films on the Structure and Surface Morphology Using RF Magnetron Sputtering

Gold (Au) thin films were deposited on SiO2 substrate under argon (Ar) gas environment using RF (radio frequency) magnetron sputtering at room temperature for various deposition times. These samples have been annealed at the temperature range of 250-450 °C. The change of the structural and surface morphological properties of both as-deposited and annealed films has been studied using an AFM (atomic force microscope), XRD (X-ray diffraction) and Raman scattering. The improvement of crystallinity was observed at the annealing temperature of 350 °C and degradation was found thereafter. In agreement with XRD and Raman measurements, both crystallite size and crystalline volume fraction were found to be increased having maximum at 350 °C and decreased afterward. This result can be explained by simple kinetic theory where sticking probabilities, Au structures agglomerated on SiO2 surfaces and surface coverage of Au atoms must be considered. Moreover, it can also be explained by the occurrence of two competing phenomena like roughening induced grain growth and smoothing induced inhibition of grain growth with increasing annealing time. Growth mechanisms are also discussed.