Applied Surface Science, Vol.434, 211-214, 2018
Atomic structure and potential energy of beta-Si3N4/diamond interface in the process of detachment: A first-principles study
Peeling is regarded as a main technique barrier for the application of coating. Many factors affects the peeling of coating. Among them, the interfacial properties between coating and substrate plays a vital role. In this work, the beta-Si3N4/diamond interface is conducted as the sample to study the changes in atomic structure and potential energy in the process of detachment by the first-principles calculations. The beta-Si3N4/diamond (2 x 2) crystal unit is used as the calculated model. The detachment is simulated by moving up beta-Si3N4 far from diamond by the 0.1 angstrom of each step. The results show that in the beginning of detachment, the bonds in the interface keep a constant length, rather than extension like spring. When the distance between beta-Si3N4 and diamond reaches a certain distance, the interfacial bonds would suddenly break, and the elongated beta-Si3N4 resumes its original statues indicating that the interface between two surfaces may exist a threshold value to control the peeling. When the external force is less than this threshold value, the peeling of coating would not occur. However, once the external force is greater than this one, the peeling would immediately present. The interface presents the brittle failure in the process of detachment, which is in good agreement with the experimental observation. Meanwhile, the different physical properties between van der Waals and quantum effects lead to the transient status in the process of detachment, where although the interfacial bonds are broken, the adhesive strength is still strong due to its low negative adsorption energy. (C) 2017 Elsevier B.V. All rights reserved.