Atomic structure and potential energy of β-Si_3N_4/diamond interface in the process of detachment: A first-principles study

摘要

Highlights•Rapid changes in distance and energy occur in the processing of detachment.•Interfacial bonds are broken, but interface still has a large adhesive strength.•Alternation between vdW and quantum effects leads to the discontinued force fields.•A transient and unstable stage maybe exist during the detachment of the interface.AbstractPeeling 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, theβ-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. Theβ-Si3N4/diamond (2×2) crystal unit is used as the calculated model. The detachment is simulated by moving upβ-Si3N4far from diamond by the 0.1Å 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 betweenβ-Si3N4and diamond reaches a certain distance, the interfacial bonds would suddenly break, and the elongatedβ-Si3N4resumes 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.