Effects of nano-grain structures and surface defects on fracture of micro-scaled polysilicon components

This study examines a simple fracture model for microscopically heterogeneous polysilicon components when Griffith theory applicable only to homogeneous materials fails. The strength-limiting micro/nano- surface defect a₀ is linked to the nano-scaled grain size G of polysilicon and bulk fracture properties. Here the a₀/G ratio is not large enough for polysilicon to be considered as homogeneous. Two polysilicon materials, with laminated grain structures (G = 125 nm) and columnar grain structures (G = 285 nm), have been analyzed. The simple fracture model together with a normal distribution methodology can be used to predict both the mean and 96% reliability fracture curves for the micro/nano-crack range bridging the classic Griffith theory and the non-linear fracture model.