Investigation of fracture toughness and microstructure of micro-scaled multilayer-DLC/silicon system via pillar splitting method

Abstract

The fracture toughness of multilayer diamond like carbon (DLC) coated silicon microstructures was characterized using the pillar splitting method in this study. Two types of coating layers with different properties were alternately deposited by plasma-enhanced chemical vapor deposition at −200 V and −600 V, respectively, with the same total coating thickness (0.3 μm). The effects of different numbers of layers (2, 4, 8, and 12) of DLC coatings on the fracture behavior and fracture toughness enhancement of the coating/silicon system were investigated. Pillar splitting experiments showed that the fracture toughness of the coated samples was significantly increased by 24.6%–63.6% compared to bare silicon ones. With an increasing number of layers of DLC coatings, the protective effect of the coatings on the silicon substrate was continuously enhanced. The trends of finite element cohesive zone modeling simulations were highly consistent with experimental results. During the splitting process, a nonlinear deformation stage was observed for the first time in the load-displacement curve, which was attributed to stress discontinuity, increased interfacial dislocations, and energy absorption at the layer interfaces. The multilayer coating technology has broad prospects for improving the fracture toughness of materials and enhancing the stability and reliability of micro/nano devices.