The surface morphology of thin Au films deposited on Si(001) substrates by sputter deposition

Abstract

Thin (100nm) gold films were deposited on the native oxide of Si(001) substrates by direct current magnetron sputtering. The effects of the deposition rate, the target/substrate distance, the substrate orientation, substrate bias, and substrate temperature on the surface morphology of the gold film have been studied using atomic force microscopy. It was observed that the deposition of Au on Si(001) is characterized, in most cases, by hemi-spherical particles distributed uniformly on the surface. Decreasing the target/substrate distance caused both the average particle diameter and the height to increase. However, at a target/substrate distance of 5cm using a deposition rate of 0.1Å/s, samples with different morphologies were produced characterized by the coalescence of the surface Au particles. Increasing the relative angle from 0° to 90° between the substrate and the sputtering target caused the average particle diameter to decrease by approximately 8.7% and the average particle height to increase by approximately 52.3%. Applying a high negative voltage to the substrate during the deposition caused a small decrease of approximately 10.2% in the average particle size and a change of 26.2% to the average particle height. Lowering the substrate temperature from 12 to −11°C during the deposition process caused a decrease of 21.6% in the average grain size and an increase of 44.7% in the average grain height. By adjusting the above parameters it was possible to obtain samples with an average particle size ranging from 25.8 to 180nm with root-mean-square roughness values ranging from 0.8 to 21nm. The results of this work provide an understanding on how to produce a wide range of surface morphologies of thin Au films on Si(001+native oxide) for applications such as cantilever sensing and for producing bio-functionalized tips for atomic-force microscopy.