Understanding deformation mechanisms in silicon is critical for reliable design of miniaturized devices operating at high temperatures. Bulk silicon is brittle, but it becomes ductile at about 540 °C. It creeps (deforms plastically with time) at high temperatures (∼800 °C). However, the effect of small size on ductility and creep of silicon remains elusive. Here, we report that silicon at small scales may deform plastically with time at lower temperatures (400 °C) above a threshold stress. We achieve this stress by bending single-crystal silicon microbeams using an in situ thermomechanical testing stage. Small size, together with bending, localize high stress near the surface of the beam close to the anchor. This localization offers flaw tolerance, allowing ductility to win over fracture. Our combined scanning, transmission electron microscopy, and atomic force microscopy analysis reveals that as the threshold stress is approached, multiple dislocation nucleation sites appear simultaneously from the high-stressed surface of the beam with a uniform spacing of about 200 nm between them. Dislocations then emanate from these sites with time, lowering the stress while bending the beam plastically. This process continues until the effective shear stress drops and dislocation activities stop. A simple mechanistic model is presented to relate dislocation nucleation with plasticity in silicon.

了解硅的变形机理对于在高温下运行的小型器件的可靠设计至关重要。块状硅很脆，但在约540°C时会变得易延展。它会在高温（约800°C）下蠕变（随时间而塑性变形）。但是，小尺寸对硅的延展性和蠕变的影响仍然难以捉摸。在这里，我们报告说，在高于阈值应力的较低温度（400°C）下，小规模的硅可能会随时间塑性变形。我们通过使用原位热机械测试台弯曲单晶硅微束来实现这一应力。小尺寸加上弯曲，使高应力集中在靠近锚杆的梁表面附近。这种局部化提供了缺陷容限，允许延展性克服断裂。我们的组合扫描，透射电子显微镜，原子力显微镜分析表明，随着接近阈值应力，光束的高应力表面同时出现多个位错成核位点，它们之间的均匀间距约为200 nm。然后，随着时间的流逝，这些位置会产生位错，从而降低应力，同时使光束塑性弯曲。这个过程一直持续到有效剪切应力下降和位错活动停止为止。提出了一种简单的机理模型，将位错形核与硅的可塑性联系起来。在塑性弯曲梁的同时降低应力。这个过程一直持续到有效剪切应力下降和位错活动停止为止。提出了一种简单的机理模型，将位错形核与硅的可塑性联系起来。在塑性弯曲梁的同时降低应力。这个过程一直持续到有效剪切应力下降和位错活动停止为止。提出了一种简单的机理模型，将位错形核与硅的可塑性联系起来。