Adhesion testing of atomic layer deposited TiO₂ on glass substrate by the use of embedded SiO₂ microspheres

In this paper, the authors present a new adhesion test method, which is under development, to study the interfacial mechanical parameters of atomic layer deposited (ALD) thin films. A highly sensitive lateral force adhesion testing tool was used to measure the lateral detaching force of 8 μm diameter SiO₂ microspheres embedded in 100 nm ALD TiO₂ thin film grown in 200 °C. The resulting holes in the coating were characterized with scanning electron microscope plus energy dispersive x-ray spectroscopy and the delaminated areas were measured with image analysis software. The corresponding detaching force (F) was compared to the delaminated area (A) to calculate the critical stress value (σ), which relates to the mechanical adhesion of the coating and also includes the effect of other influencing factors such as the film cohesion. The measured critical stress (σ) of the ALD TiO₂ coating on a glass substrate was 36 ± 12 MPa based on the measurement of 43 microspheres.