Effects of material mismatch on interfacial cracking of ferroelectric film/substrate structures

This study investigates the effect of material mismatch on interfacial cracking in ferroelectric film/substrate structures, models the interfacial misfit strain using a Somigliana screw dislocation dipole, and solves the generalized stress functions, the stress intensity factor (SIF) and the electric displacement intensity factor (EDIF) in piezoelectric coupled field based on an equivalent model and the complex potential method. The results show that: (1) The lattice mismatch degree is the major factor influencing EDIF and SIF; (2) The effects of the elastic and dielectric constant ratios of substrate to film on EDIF depend on the mismatch effects resulting from the other two constant ratios of generalized stiffness, respectively, however the piezoelectric constant ratio can affect EDIF independently; (3) The increasing elastic constant ratio can lead to a monotonic and significant increase of SIF; and when the piezoelectric constant ratio is greater than 1, it can cause an obviously change in SIF; however dielectric constant ratio has little effect on SIF; and (4) The modest adjustment of the piezoelectric constant ratio within a specific range could be a potential route to decrease the failure risk of the ferroelectric film deposited on a piezoelectric substrate.