Influence of anisotropy on material removal and deformation mechanism based on nanoscratch tests of monocrystal silicon

With its merits of excellent electrical properties and chemical durability, monocrystal silicon has been widely used as the substrate material in photovoltaic and integrated circuit fields. However, surface and subsurface damages caused by the machining process significantly reduce the chip life and the impacts of anisotropy remain poorly understood. Herein, this study employs nanoscratch tests to explore the anisotropy dependence on material removal and deformation mechanism for monocrystal silicon. Nanoscratch tests, under varied and constant load modes, are first carried out on a silicon surface along different crystal orientations. The surface morphologies of generated groove are observed to identify the surface crack system and depict the material removal behaviors. Then, a transmission electron microscope is applied to analyze the subsurface damage characteristics of deformation regions along different scratch directions. The results present the lattice defects close to the atomic scale, such as amorphous layer, stacking faults and phase transformation, and reveal the damage evolution mechanism considering material anisotropy. In addition, a molecular dynamics simulation model of monocrystalline silicon scratch is developed to expose the diversity of dislocation and stress distribution along different crystal orientations. This work provides a theoretical basis for realizing efficient and precise machining of anisotropic hard-brittle materials.