Effect of Temperature on the Nanoindentation Behavior of Monocrystalline Silicon by Molecular Dynamics Simulations

Under external loads, monocrystalline silicon experiences intricate phase transformations that can profoundly impact its performance and processing behavior. A comprehensive analysis of deformation behavior and principles of silicon (Si) is crucial for its processing and applications. In this study, molecular dynamics (MD) simulations are performed within the range of 1 to 900 K, to investigate the influence of temperature on the mechanical properties and deformation behavior of monocrystalline silicon during nanoindentation. The findings reveal a decline in the hardness and elastic modulus of monocrystalline silicon with increasing temperature. At lower temperature, the activation of plastic deformation within the sample is delayed. The subsequent sudden release of stored elastic energy manifests as a pop-in event on the P-h curve. This forms a quadruple symmetric phase transformation region mainly consisting of Si-II, bct-5, and Si-XIII, where Si-XIII and bct-5 phases are interspersed around the Si-II phase. As the temperature increases, plastic deformation in the sample activates earlier. In the subsequent loading process, higher temperature expedites the formation and transformation of Si-XIII. During the unloading process, higher temperature diminishes the stability of the bct-5. At high temperature, dislocation-induced deformation occurs in the sample, and a new phase caused by dislocation is extracted. Furthermore, the structural deformation of monocrystalline silicon shows anisotropy, and the phase transformation process exhibits dependence on crystal orientation. This research offers a novel understanding of the deformation behavior and phase transformation mechanisms of monocrystalline silicon, providing valuable theoretical support for both the manufacturing and application of monocrystalline silicon products.