Abstract
The nanomaterials often have a single crystalline structure; their mechanical properties exhibit both size and orientation dependence. Recently, we developed a Microscopic Nanomechanical Measurement Method (MNMM) that allows us to precisely obtain the equivalent spring constants (force gradients) of nanomaterials while observing their atomic structures [1]. However, Young's modulus can vary locally depending on the cross-sectional area, meaning that the overall shape and size can only provide an average Young's modulus for the entire system, not a size-dependent one. In a previous study, Zhang et al. found that a {111} layer was introduced at the narrowest constriction every ca. 0.24 nm elongation; from the stiffness difference before and after the introduction, Young’s modulus was estimated for the introduced {111} layer [2]. In this study, we propose a method to determine the local Young's modulus of nanomaterials by measuring the initial interval and displacement of a specific region in TEM images during stretching (Fig. 1): the local Young's modulus can be estimated when the ratio of the displacement of the local region with respect to the overall elongation is calculated. In contrast to the previous study, the present method can measure the local Young's modulus at various positions within the same nanocontact. This enables us to demonstrate the size dependence of local Young's modulus within the same nanocontact. Our estimated local Young’s modulus for gold [111] nanocontacts exhibited a similar size dependence to the previous findings for each introduced {111} layer [2].
[1] J Zhang, K Ishizuka, M Tomitori, T Arai and Y Oshima, Nanotechnology 31 205706 (2020)
[2] J Zhang, K Ishizuka, M Tomitori, T Arai and Y Oshima, PHYSICAL REVIEW LETTERS 7 (2022)
