Identification of internal residual stress parameters in silicon/silicon nitride bilayers for implementation of a crystalline micro-undulator

Recent experiments on bent Si monocrystals performed at Semiconductors and Sensors Laboratory of the University of Ferrara open up the possibility for development of highly efficient crystalline micro- undulators. In this contribution, we report on a promising line of research which considers the curvature induced by deposition of Si3N4 on a Si monocrystal circular plate. Our goal is to identify the residual stress induced by Si3N4 deposition. Firstly, we study the equilibrium problem of a composite thin plate made by two different incrementally linear elastic materials with stressed reference configura- tions. Then, we establish a relationship between the residual stress and the plate deformation on the basis of an analytical solution obtained in the framework of finite elasticity. This is used to obtain a first identification of residual stress from displacement measurements.