A Displacement-energy Model Approach for Evaluating the Interfacial Stress in Multilayer Film Structures Based on the Interactions of Grains at the Interface

Abstract

For multilayer film structures, mechanical failure is usually taken place at the interface. To deeply understand the typical issue, it is first essential to know the stress status at the interlayer surface. For this aim, in this work, the author presented displacement-energy models (DEM) for accurately calculating the interfacial stress in multilayer film structures and the impact of the morphology and size of the interacting grains at the interface. The stress-inducing mechanisms are related to the displacement-energy phenomenon of the interacting grains in the structure caused by the deposition technique. In contrast, the interfacial residual stress-evolution in the deposited films is determined from the change in the lattice constant between interacting grains as a function of temperature and time during the deposition and cool-down process. The interacting grains understudied have different morphology with flat and curved surfaces and sizes. Concerning the yttrium barium copper oxide (YBCO) films deposited on the lanthanum aluminum oxide (LaAlO 3 ) substrate, the computed results showed that the morphology and size of the interacting grains affect the net interfacial residual stresses in the YBCO films significantly. Also, the results of the DEM models agree well with the measured value by the X-ray diffraction method (XRD). Specifically, the computed stress in the YBCO films for the interacting grains with spherical surfaces is 0.18 GPa. Similarly, that measured by the XRD method is 0.178± 0.053 GPa. In the future, the findings of this study could be essential in the defect inspection of several Multilayer Engineering Materials, including composites for various applications, which often consist of grains with different morphology and size.