Study of the Micromechanical Properties of Synthetic Mica under Various Stress Angles via Nanoindentation

Ying-Hao Chu^1,2, Yu Hao Tu^1*, Shou-Yi Chang²

¹College of Semiconductor Research, National Tsing Hua University, Hsinchu, Taiwan
²Material Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Yu Hao Tu, email:dennistu1223@gmail.com

Crystal slip is the primary mechanism of crystal deformation under an applied stress. Over the past decades, slip behavior in crystals has been extensively studied by numerous researchers. However, these studies have mainly focused on materials with metallic, covalent, and ionic bonds. Since the discovery of graphene in 2004, 2D materials have become a popular research field worldwide. Unlike conventional materials such as metals or ceramics, the interlayer bonding in a 2D material is van der Waals, which is much weaker than other bonds. Because of this unique feature, the slip behavior of a 2D material must differ significantly from that of conventional crystals. In this study, we chose the 2D material, synthetic mica, as our research target. To investigate the slip behavior of mica, we used a focused ion beam to fabricate micron-scale mica pillars. The stress-strain curve was obtained by nanoindentation under compressive stress at different angles, aiming to provide more insights into the slip behavior of mica in the van der Waals bonding plane. In the meantime, we used not only pristine mica but also hydrothermally treated mica. Compared to pristine mica, hydrothermally treated mica is more easily exfoliated, which indicates that its interlayer bonding is weaker than that of the pristine one. After the nanoindentation test, the remainder was sent for further analysis by a transmission electron microscope. The slip direction was confirmed to be along the mica [100] direction. Moreover, a computer simulation was conducted to gain a deeper understanding of mica slip behavior.

Keywords: synthetic mica, mechanical property, nanoindentation