MAE Seminar: Understanding the Mechanical Behavior of Small-scale Materials: Small for the Sake of Big

Abstract: Thin films are widely used as functional and structural elements in micro-electronic devices, large-scale integrated circuits, thin-film solar cells, electrical sensors and electronic textiles. Understanding the mechanical behavior of thin films at different length scales and environmental conditions is essential for the design of reliable devices. However, it is difficult to precisely measure the properties of small-scale materials with the methods that are employed for bulk materials; probing micro/nano-scale samples is challenged by the inherent difficulties associated with fabricating and handling of extremely small specimens. Advanced instrumentation and manufacturing techniques with enhanced characterization capabilities are required to better understand the properties and deformation mechanisms of technologically relevant materials.

In this presentation, I will introduce experimental studies utilizing micro/nano-scale manufacturing to understand the mechanical behavior of small-scale materials and to develop advanced metallic alloys for use in extreme environments. Specifically, the effect of temperature, carbon addition, and passivation layer on the microstructure and mechanical behavior of freestanding metallic thin films will be discussed. Tensile specimens with sub-micron thickness are fabricated via sputter deposition followed by standard silicon-based microfabrication techniques. Mechanical characterization at elevated temperatures are performed through use of a custom-built in-situ SEM mechanical tester and two silicon-based micro heaters that support the sample and allow us to study the mechanical behavior of metallic thin films at temperatures up to 740°C. Ongoing efforts in our laboratory utilizing high-throughput combinatorial experiments to identify the effect of carbon content and addition of an ultra-thin (< 10 nm) passivation layer on the mechanical behavior of metallic thin films will be presented. Finally, I will discuss how these techniques are being used to develop advanced metallic alloys such as nanotwinned Ni-Mo-W thin films and NiTi shape memory alloy thin films.

Bio: Gi-Dong Sim is an assistant professor at Korea Advanced Institute of Science and Technology (KAIST) where he leads the in-situ characterization and reliability evaluation (iCaRE) laboratory in the department of mechanical engineering. Prior to joining KAIST in 2018, he conducted research at Johns Hopkins University, Harvard University and KAIST. His group research is focused on developing experimental techniques to test the mechanical behavior of metallic materials at various length-scales and in different environments, on the development of advanced metallic alloys and devices that can reliably operate in extreme environments, and on elucidating deformation mechanisms of materials in extreme environments