Mechanical Properties of Directionally Solidified Polycrystalline Silicon at the Micro-/Nano-scale
HUANG Zheyuan1,2,3, WANG Wenxian1,2,3, YAN Zhifeng1,2,3, ZHANG Tingting1,2,3
1 School of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024; 2 The New Material Key Laboratory of Interface Science and Engineering at the Ministry of Education, Taiyuan 030024; 3 Shanxi Key Laboratory of Advanced Magnesium-based Materials, Taiyuan 030024;
Abstract: Nano-indentation was used to test the hardnesses and moduli of directionally solidified polycrystalline silicon parallel to (vertical) and perpendicular to (cross-sectional) the crystal growth direction, in order to analyze the variational principle of hardness and modulus with the change of microstructure anisotropy. The hardness and modulus before indentation cracking were mea-sured via Berkovich indenter by continuous stiffness method and the distances from indentation center to crack tip were measured via SEM. Then the samples′ fracture toughnesses were calculated all at once which can avoid cracking influence on hardness and modulus. The results show that cross-sectional (110) surface′s hardness and modulus are lower than those of vertical section (111) surface, but the fracture toughness has a contrary trend. The analysis of 3D survey scanning function in indentation cracks suggested that shear sliding steps are the main causes of crack initiation. We obtained the critical indentation size by fitting the crack length and indentation size under different loadings, and it coincided well with the theoretical value.
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2017, Vol. 31 
