Study on Anisotropic Mechanical Properties of Single-Crystal Silicon at Different Strain Rates

To examine the impact of the strain rate on the anisotropic mechanical characteristics of single-crystal silicon, nanoindentation and micro-tensile-compression tests were performed. This study analyzed the effects of varying crystal orientations at different strain rates on load-displacement behavior, elastic modulus, hardness, fracture toughness, and true stress-strain responses. The nanoindentation results showed that at room temperature, single-crystal silicon exhibited an elastic recovery rate of approximately 42%. Notably, the elastic modulus remained unaffected by strain rate variations, whereas hardness increased with higher strain rates. Fracture toughness at room temperature displayed marked anisotropy, with the <100> orientation exhibiting the lowest value at 0.691 MPa·m^1/2 and the <110> orientation showing the highest one at 0.797 MPa·m^1/2. Additionally, tensile and compression experiments revealed that the fracture strength of <100>-oriented silicon increased from 117 MPa at a strain rate of 0.001 s^-1 to 550 MPa at a strain rate of 0.01 s^-1.