Evaluation of crack-healing behavior in SiNx/SiC nanolaminated thin film by microbending test

The purpose of this study is to evaluate the crack-healing behavior of SiNx/SiC nanolaminated films quantitatively. SiNx/SiC nanolaminated films were fabricated by alternating ion-beam assisted deposition of SiN, and SiC. The fabricated nanolaminated films consisted of four layers with the top layer being Si Nx. Smooth and notched microbeam specimens were fabricated using a focused ion beam (FIB) system. The nanosized notch was introduced in form of an imitational crack on the film surface by FIB. Some notched samples were heated at 1000 degrees C for 24 to 96 h in air. The fracture strength was evaluated by bending tests using a nanoindentation system. After heating, the notch was filled with reaction products. Energy dispersive X-ray (EDX) analysis revealed that the reaction products contained oxide compounds, most likely SiO2. The fracture load of the notched specimens recovered with increasing heating time. The filling of the notch with oxidation products caused the recovery of the fracture load. However, the recovery was not complete compared with the strength of a smooth sample. It is concluded that the filling of a notch with oxidation products recovers the mechanical strength of SiNx/SiC nanolaminated films only to a certain extent.