Surface Morphology of Gold thin films using RF Magnetron Sputtering

Gold (Au) thin films are offering various applications such as nanosensors and biosensing devices. It is crucial to understand the growth mechanism of films at initial phase of deposition. Thin Au layers were sputter deposited on both glass and silicon substrates with Ar gas at various sputtering times [tS], and their thickness and surface morphology were studied by atomic force microscopy (AFM). The deposited layers on glass substrate were transformed from continuous to discontinuous for longer [tS] except for the film prepared at 35 min. However Au-layers on silicon substrates were found to be almost continuous with increasing [tS]. The growth rate on the silicon substrate is constant and on the glass substrate increases with increasing layer thickness. Different sticking probabilities of Au atoms and regions with gold coverage on bare glass substrate might be considered to explain it. AFM analysis shows that the gold layers on the glass substrate consist of gold islands with significantly different thicknesses and relatively larger grains at the initial stages of the deposition. On the other hand, gold coverage of the silicon substrate is moderately homogeneous, containing of tiny gold grains. On the glass substrate, the gold clusters of different sizes are clearly observed.