Ion beam sputter deposition of Ag films: Influence of process parameters on electrical and optical properties, and average grain sizes

• Ion beam sputter deposition under systematic variation of process parameters.
• Film characterization: thickness, electrical, optical and structural properties.
• Electrical resistivity changes considerably with ion species and polar emission angle.
• Electrical and optical data reveal a strong correlation with grain sizes.
• Change of film properties related to changing properties of film-forming particles.

Ion beam sputter deposition is used to grow several sets of Ag films under systematic variation of ion beam parameters, such as ion species and ion energy, and geometrical parameters, such as ion incidence angle and polar emission angle. The films are characterized concerning their thickness by profilometry, their electrical properties by 4-point-probe-measurements, their optical properties by spectroscopic ellipsometry, and their average grain sizes by X-ray diffraction. Systematic influences of the growth parameters on film properties are revealed. The film thicknesses show a cosine-like angular distribution. The electrical resistivity increases for all sets with increasing emission angle and is found to be considerably smaller for Ag films grown by sputtering with Xe ions than for the Ag films grown by sputtering with Ar ions. Increasing the ion energy or the ion incidence angle also increases the electrical resistivity. The optical properties, which are the result of free charge carrier absorption, follow the same trends. The observed trends can be partly assigned to changes in the average grain size, which are tentatively attributed to different energetic and angular distributions of the sputtered and back-scattered particles.