The strength of submicron-sized materials

Recent rapid advancements in nano- and micro-machinery technologies call for an urgent need to understand the mechanical behaviour of materials of dimensions in the sub-micron regime. The initial yield strength of submicron crystals exhibits remarkable statistical scatter as well as dependence upon size and time under load. Submicron-sized materials are also found to creep many orders of magnitude faster than bulk counterparts. In this paper, the recent experimental evidence for these phenomena is reviewed. Theoretical explanation of these phenomena is also discussed. The statistical scatter and time dependence of the yield strength are interpreted by a scaling model derived from atomistic simulations. The results indicate that, within a certain load range, the strength of a sub-micron sized material is not deterministic and can only be described by a survival probability. The much faster creep in the submicron regime is interpreted in terms of the much shorter diffusion length compared to bulk creep.