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Layer controlled atomic spalling of van der Waals materials
- Author(s)
- 문지윤
- Advisor
- 이재현
- Department
- 일반대학원 에너지시스템학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2023-08
- Language
- eng
- Alternative Abstract
- Two-dimensional materials (2DMs) have garnered significant attention and research interest as a promising solution to overcome current technological limitations. These materials exhibit diverse physical properties that depend on their type and layer number. Due to quantum effects at the nanoscale, they demonstrate optical, electrical, and physical properties that are not present in conventional bulk materials. In this dissertation, I will discuss a straightforward and efficient method to obtain high-quality 2DMs with precise control over the number of layers on a large scale. Our approach begins with the exfoliation of graphene from graphite, enabling us to obtain a desired number of controllable layers. The interfacial toughness between the metal and graphene varies depending on the metal type, allowing us to exert control over the exfoliated graphene layers. Through experiments, we discovered that the crack depth, representing the thickness of the exfoliated graphene, is directly influenced by the interfacial toughness of the metal. For instance, when utilizing Au stressor films with a binding energy comparable to van der Waals forces, cracks propagate parallel to the surface, selectively delaminating monolayer graphene instead of perpendicular to it. Conversely, metals such as Pd, Ni, and Co, possessing higher binding energies than Au, promote deeper crack propagation, enabling the controlled exfoliation of graphene with layer numbers ranging from bilayer to 40 layers. To achieve precise control over crack depth in 2DMs, we focused on regulating the internal stress of the stressor material. By precisely tuning the internal stress of a metal film on the surface of the 2D crystal, using controlled stress release times, we successfully attained atomic-level control over crack depth. The depth of cracks varied atomically depending on the internal stress level of the film, allowing us to selectively obtain 2DMs with mono-, bi-, and trilayer. Lastly, we made a significant breakthrough by discovering a new stressor material based on semiconductor materials. Unlike conventional metal stressors that require an acid-based solution for removal, this novel material, Ge film, is water-soluble. Consequently, it can be easily removed using water alone, eliminating the need for acid-based processes. This advantage is particularly beneficial when peeling various types of 2DMs, particularly those susceptible to instability.
- Fulltext
- Appears in Collections:
- Graduate School of Ajou University > Department of Energy Systems > 4. Theses(Ph.D)
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