Effect Of Small Size, Stress Localization And Stress Gradient On The Strength Of Silicon

小尺寸、应力局部化和应力梯度对硅强度的影响

• 批准号: 1562694
• 负责人: Taher Saif
• 金额: $ 35.57万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-05-01 至 2020-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1562694&HistoricalAwards=false
• 关键词: Effect; Small; Size; Stress; Localization

This award supports an investigation of the failure behavior of silicon at small scales. Most micro-nano mechanical systems use silicon beams as their structural components. These beams are typically subjected to bending during operation. But silicon is brittle at room temperature. This limits the design space of silicon devices. Bending, however, localizes high stresses near the surface of the beams close to the anchors. In addition, the stresses decrease from the surface towards the middle plane of the beam, giving rise to stress gradients. The effects of small size, stress localization and stress gradient on the failure mechanisms of silicon remain elusive to date. Recent evidence suggests that silicon at small scale can be ductile (i.e., not brittle) at very high yield stresses. If so, then small size, stress localization and stress gradients together may offer the virtues of both ductility and high strength to silicon. Such failure resistance would present a yet untapped paradigm to the design space of silicon devices. A detailed understanding of the failure and deformation mechanisms of silicon at small scale under bending would be transformative for both semiconductor physics and industry, and will be a fundamental advance for the field of mechanics. The goal of this project is to explore the mechanics and mechanisms of deformation and failure in small silicon samples under bending by combining theory and experiments. The working hypothesis of the project is that dislocation is the primary mechanism of deformation in silicon under bending at small scale. Small samples are dislocation free. Small size and stress localization in bending offer high flaw tolerance against fracture. This is due to the low probability of flaw incidence in the small stressed region. Bending results in dislocation nucleation from the surface before any flaw induced fracture. These dislocations enter the bulk yielding the silicon. But the yield stress increases with decreasing size due to stress gradient. This hypothesis will be tested by undertaking three tasks: (1) mechanistic modeling and molecular dynamics simulations of silicon samples under bending, (2) bending experiments on micro-nano fabricated single crystal silicon samples with various sizes and at different temperatures, and (3) in situ bending experiments in transmission electron microscopes (TEM) to reveal the mechanisms of deformation (in collaboration with Max Planck Institute at Dusseldorf, Germany). A novel micro mechanical stage will be developed for tasks 2 and 3. The research will be integrated with education and outreach activities involving K-12 to graduate students.

该奖项支持对硅在小尺度上的故障行为的调查。大多数微纳米机械系统都使用硅束作为结构组件。这些梁通常在操作过程中弯曲。但是硅在室温下易碎。这限制了硅设备的设计空间。然而，弯曲将靠近锚的梁表面附近的高应力定位。另外，应力从表面降低到梁的中间平面，从而产生应力梯度。较小的大小，应力定位和应力梯度对硅失败机理的影响仍然难以捉摸。最近的证据表明，小规模的硅可以在非常高的屈服应力下是延展性的（即不是脆性）。如果是这样，那么小尺寸，压力定位和应力梯度在一起可能会提供延展性和高强度对硅的优点。这种抗故障的能力将为硅设备的设计空间带来尚未开发的范式。对弯曲下的硅在小规模下的故障和变形机制的详细理解对于半导体物理和工业都会进行变化，这将是机械领域的基本进步。该项目的目的是通过结合理论和实验来探索小型硅样品的变形和故障的机制和机制。该项目的工作假设是，脱位是小规模弯曲下硅变形的主要机制。小样品不含错位。弯曲中的小尺寸和应力定位可对裂缝具有很高的缺陷耐受性。这是由于小压力区域中缺陷发生率的可能性低。弯曲会导致在任何缺陷引起的裂缝之前，会导致表面脱位成核。这些位错进入散装，产生硅。但是由于应力梯度，屈服应力随着尺寸的减小而增加。该假设将通过执行三个任务来检验：（1）弯曲下的硅样品的机理建模和分子动力学模拟，（2）（2）在微纳米制造的弯曲实验，具有各种尺寸和不同温度下的单晶硅样品，以及（3）与原位弯曲实验（3）与弯曲的机制（TEMISINIS）（TELENIS）（TELENIS）（TELESISIS）（TELESIS）（TELESIS）（TELESIS）（TELESIS）（TELESIS）德国杜塞尔多夫的研究所）。将为任务2和3开发一个新型的微型机械阶段。该研究将与涉及K-12的教育和外展活动集成到研究生。