Strength of silicon containing nanoscale flaws

Silicon is a principal material in submicrometer-scale devices. Components in such devices are subject to intense local stress concentrations from nanoscale contacts during function. Questions arise as to the fundamental nature and extent of any strength-degrading damage incurred at such contacts on otherwise pristine surfaces. Here, a simple bilayer test procedure is adapted to probe the strengths of selected areas of silicon surfaces after nanoindentation with a Berkovich diamond. Analogous tests on silicate glass surfaces are used as a control. The strengths increase with diminishing contact penetration in both materials, even below thresholds for visible cracking at the impression corners. However, the strength levels in the subthreshold region are much lower in the silicon, indicating exceptionally high brittleness and vulnerability to small-scale damage in this material. The results have important implications in the design of devices with silicon components.