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Multilayer Adhesion

by Jean-Yvon Faou - published on

The chemical and mechanical stability of films and interfaces in a multilayer defines the reliability of the full stack. Optimization of the interface properties involves control of both chemistry and structure. For example, changing the order in which films in a ZnO/Ag stack are deposited affects the interfacial toughness, due to a different interface structure [1].

In the Superlayer adhesion test, an interface is loaded by means of an overlayer under high compression. If the elastic energy stored in the superlayer is large enough, fracture of a weak interface and buckling of the coating may occur. The threshold thickness of the superlayer above which delamination occurs is determined by adhesion. In the common case of biaxial compression, the so-called telephone-cord buckles are formed which allow for relaxation of stress in both in-plane directions.

In figure one, a Mo superlayer under compressive stress of 1.5 GPa is applied to a stack ZnO(30nm)/Ag(10nm)/ZnO(30nm) on glass. The critical thickness is 550 nm in this case.

Superlayer test on ZnO/Ag/ZnO stack.

Publications

Asymmetric Silver to Oxide Adhesion in Multilayers Deposited on Glass by Sputtering pdf HAL
E. Barthel, O Kerjan, P. Nael and N. Nadaud Thin Solid Films, 473(2) (2005) 272-7.