Molecular dynamics simulation and experimental study on formation mechanism of micro-hole and cracks in nano-imprinting diamond

Diamond nano-imprint microhole forming technology is a new type of microhole forming method. However, there will always be some unqualified microholes and cracks in the manufacture of microholes. In order to obtain better microhole quality, it is crucial to study the mechanism of microhole formation. In this paper, the indentation process of single crystal copper by a conical indenter is simulated by molecular dynamics. After the indentation is completed, microholes and cracks will form on the surface of the copper sheet. Dislocation analysis will be conducted on the microholes and surrounding cracks, and then the microstructure and morphology will be demonstrated to explain the formation mechanism of microholes and cracks. The influence of different indentation speeds and temperatures on the energy change of the system is discussed. In addition, this article established an experimental device for diamond indentation of copper sheets, and conducted indentation microholes experiments to observe microholes and cracks through scanning electron microscopy. The results show that when the diamond indenter is pressed down, the number of atoms in contact between the diamond indenter particles and the copper surface gradually increases, causing local stress concentration and the formation of new dislocations. Among them, 1/6<112> shockley dislocation is the main dislocation type. When the strain energy stored in the lattice increases beyond a certain value, the lattice structure of the copper atoms in the contact area is broken, resulting in internal defects, gradually forming microholes and surrounding cracks. The increase in the imprinting speed will accelerate the plastic deformation of the copper sheet. This paper reveals the mechanism of the formation of microholes and cracks, laying the foundation for high-quality micropore manufacturing.