Stress relief patterns of Co films deposited on circular silicone oil substrates

By using the expansive and mobile properties of silicone oil, circular liquid substrates with varied thicknesses naturally form on clean glass surfaces during deposition. Continuous cobalt (Co) films have been prepared on the circular liquid substrates by a direct current magnetron sputtering method, and the stress relief patterns of the Co films are investigated. The experiment shows that the Co film is susceptible to generating cracks due to thermal expansion of the silicone oil substrate during deposition. After deposition, subsequent cooling of the system creates a high compressive stress in the film, which is relieved by formation of various wrinkling morphologies. Based on the special growth mechanism and mechanical properties of the metal film deposited on a liquid substrate, the structural characteristics of the stress relief patterns and the underlying physical mechanisms are discussed in detail.

► Silicone oil substrate can spread during deposition.
► Co film deposited on silicone oil by sputtering method.
► A modified elastic layer forms under high sputtering power.
► Cracks form during deposition while wrinkles form after deposition.
► The thickness of Co film can be measured by wrinkle wavelength.