Effects of High-Power Impulse Magnetron Sputtering on the Early Growth of Noble Metals on Weakly-Interacting Surfaces

This thesis investigates how high-power impulse magnetron sputtering (HiPIMS) influences the early growth of noble-metal thin films on weakly interacting silicon dioxide and polymer substrates. Compared with direct-current magnetron sputtering (DCMS), HiPIMS provides a higher ionized flux fraction and increased ion energy, offering additional control over film-growth dynamics. The early stages are particularly important because the morphology formed within the first few nanometers determines interface properties, film continuity, electrical performance, and subsequent film evolution.

Silver, gold, and copper films are deposited using DCMS, HiPIMS, and bipolar HiPIMS under systematically varied ion-energy and substrate conditions. In situ grazing-incidence small-angle X-ray scattering (GISAXS), complemented by scanning electron microscopy (SEM) and electrical measurements, were used to monitor nucleation, island growth, coalescence, and percolation. The results show that nucleation below approximately 4 nm is relatively insensitive to the deposition method. HiPIMS primarily affects subsequent island growth and coalescence stages, increasing surface coverage and shifting the electrical percolation threshold to lower thicknesses. These effects are particularly pronounced on polymer substrates. Gold and silver exhibit similar island-growth behavior, whereas copper forms continuous films at substantially lower thicknesses. The studies further demonstrate that ultrathin silver films continue to restructure after deposition is stopped through diffusion-driven coalescence, with HiPIMS films maintaining higher surface coverage than DCMS films.

The results provide both fundamental insight into early thin-film growth and as well as practical guidance for developing thin metallic coatings for transparent and flexible electrodes, optical applications, and plasmonic structures.