FRACTURE OF SILICON AT LOW LENGTH SCALES

摘要

At small length scales, perhaps no material is more industrially important than silicon. It enabled the information age, and micro-electro-mechanical systems (MEMS) made of silicon are increasingly integrated into our daily lives via smartphones. Classically, silicon is known as a brittle material, whose sharp brittle-ductile transition (BDT) occurs within a matter of one or two degrees Celsius at a temperature between 500 and 800 °C depending on the microstructure, strain rate, and crystal orientation [1]. However, recent advances in sample miniturization has revealed that plastic compressive deformation can occur in silicon at room temperature if the sample size is reduced below 400 nm [2]. This raised the question of whether silicon's intrinsic fracture toughness also changed at reduced length scales. The development of many new micro-geometries for measurement of fracture toughness allowed this question to be comprehensively answered for the micron length scale - with the answer being no [3]. However, this didn't necessitate that the BDT was unaffected.