Stability diagram of unilateral buckling patterns of strip-delaminated films

Abstract

Thin films deposited on substrates are usually submitted to large residual compression stresses, causing delamination and buckling of the film into various patterns. The present study is focused on the different equilibria arising on strip-shaped delaminated areas. The three most common types of buckling patterns observed on such strips are known as the straight-sided wrinkles, bubble pattern, and telephone cord blisters. The stability of those equilibria as a function of the two stress components of the loading is investigated. The Föppl-Von Karman model for elastic plates is used for theoretical aspects. The post-critical equilibrium paths of the buckling patterns are investigated numerically by means of the finite-element method. The substrate is assumed to be rigid and the contact to be frictionless. The equilibrium solutions can be classified into families of homologous equilibria allowing the identification of dimensionless parameters for the study of stability. A mapping of the different stable post-critical equilibria is given. It is shown that the straight-sided wrinkles and the bubbles are associated with anisotropy of stresses and/or of elastic properties, whereas the telephone cords are stable at high isotropic stresses. The morphological transitions are experimentally evidenced by in situ atomic force microscopy observations of a nickel 50-nm-thick film under stress.

Competing failure mechanisms in thin films: Application to layer transfer

“…17 Also, these cracks follow a wavy trajectory, also referred to as "telephone-cord-like" patterns, characteristic of thin film buckling. 18,19 This is strong evidence in support of the predictions of Sec. IV: at first, the thin film buckles from a highly compressive stress, resulting in a network of buckling zones with a characteristic wavy geometry.…”

A review of theoretical analysis techniques for cracking and corrosive degradation of film-substrate systems

“… Cohesive zone modelling limitations: When the cohesive zone law is used to model the growth of a long pre-existing crack in the solid (e.g. [24,36,42,45,95]), the simulation generally proceeds without difficulty. However, for the case which uses cohesive zones to model crack nucleation, convergence difficulties arise at the point where the crack first nucleates.…”

The effect of interface adhesion on buckling and cracking of hard thin films

“…12,13 A large body of work exists, including finite-element method (FEM) simulations, in which the formation of different buckling patterns in hard films deposited on rigid substrates is studied, by utilizing a delaminated strip with constant width. 10,[12][13][14][15] This approach is valid when the interface strength is infinite at the delamination front. 14,16 It has been shown that by taking into account interface adhesion using a cohesive zone model, the kinematics of a propagating telephone cord buckle can be simulated.…”

“…4 In these types of films, a maximal hardness (30-50 GPa) can be achieved at Si contents of 6-12%. 5 It is well-known that compressive residual stresses generated during the growth of sputter-deposited thin films [6][7][8][9][10][11] may lead to film decohesion by buckling and delamination, which is detrimental to the integrity and performance of the films. 11 Depending on several factors such as residual stress, film thickness and interface toughness, delamination can localize and propagate across the film as a buckle of various shapes such as straight-sided wrinkles, telephone cords buckles or circular blisters.…”