Exploring Size Dependent Brittle-to-Ductile Transition in Single Crystal Silicon Using High Temperature MEMS

本计划的目标是(a)测量广泛用于微/纳米级器件的单晶硅（SCS）的脆性到延性（BDT）温度作为尺寸的函数，以及(b)揭示BDT的尺寸依赖机制。材料从脆性变为延展性的温度称为BDT温度。在宏观尺度上，BDT与尺寸无关。有新的证据表明，在纳米尺度上，BDT温度变得依赖于尺寸，尽管潜在的机制尚不清楚，这是本计划寻求探索。该研究将通过开发一种新型碳化硅微机械平台来进行，该平台可以在室温至1000℃的温度下测试微/纳米尺度的样品，同时在扫描或透射电子显微镜下观察其微观结构。智力上的优点是该项目探索了一个基本问题：BDT温度如何变得依赖于尺寸。它的工作假设是，BDT是由位错等晶体缺陷的密度和迁移率突然增加引起的。从表面激活位错所需的能量比从本体激活的能量要小得多。因此BDT温度随尺寸减小。更广泛的影响：研究将通过开发动手教学模块和招募来自不同背景的REU学生，与教育和推广相结合。由于与维也纳大学和奥地利莱奥本大学的合作，参与者将获得国际经验。如果该研究表明BDT在纯SCS中依赖于大小及其潜在机制，那么该研究可能具有变革性。该研究可能为理解SCS提供一个新的范式。

The objectives of this program are to (a) measure brittle-to-ductile (BDT) temperature in Single Crystal Silicon (SCS), widely used in micro/nano scale devices, as a function of size, and (b) unravel the mechanisms of size dependence of BDT. The temperature at which materials become ductile from brittle is known as BDT temperature. At macro scale, BDT is independent of size. There is emerging evidence suggesting that at nano scale, BDT temperature becomes size dependent, although the underlying mechanism is unclear, which this program seeks to explore. The research will be conducted by developing a novel SiC micro mechanical stage that allows testing micro/nanometer scale specimens at room to 1000C while visualizing their microstructure in scanning or transmission electron microscopes.The intellectual merit is that the project explores a fundamental question: how BDT temperature becomes size dependent. Its working hypothesis is, BDT is caused by a sudden increase in density and mobility of crystalline defects such as dislocations. The energy required to activate dislocations from the surface is substantially smaller than that from the bulk. Hence BDT temperature decreases with size. Broader impact: Research will be integrated with education and outreach by developing a hands-on instructional module, and recruiting REU students from diverse backgrounds. Due to collaborations with the Universities of Vienna and of Leoben, Austria, the participants will gain international experience.The study could be transformative if it shows that BDT is size dependent in pure SCS, and its underlying mechanism. The study may offer a new paradigm in the understanding of SCS.