Imaging the Surface of a Polycrystalline Electrodeposited Cu Film in Real Time Using In Situ High-Speed AFM

Abstract

We studied the surface evolution of polycrystalline Cu films electrodeposited from an organic additive-free acid sulphate electrolyte on to a gold microelectrode using a high-speed Atomic Force Microscope (HS-AFM) which images an area of 2 × 2 μm at 2 frames per second and a resolution of 1000 × 1000 pixels. The ability to acquire data at this rate opens even fast growth processes to in situ investigation. Real-time images from a film deposited at ∼0.5 nm s−1 revealed many interesting phenomena, most significantly highly non-uniform grain growth rates with several examples of grains showing accelerated growth compared to their neighbours. Grain overgrowth was also observed in different regions of the sample. Surface roughness scaling and slope analysis provided evidence for structural coarsening of the film and an increase in the mean slope θ with increasing film thickness t. We show how both grain overgrowth and an increase in θ can contribute to the coarsening of the surface structure as deposition proceeds.