On October 23, 2024, in the building of the Institute of Fundamental Technological Problems of the Polish Academy of Sciences in Warsaw, the public defense of the doctoral thesis entitled. “Design and Optimization of 2D Nanostructures based on Molybdenum”. The author of the thesis is Mohammed Javeed Akhter, M.Sc . , while the thesis supervisor is Prof. Wacław Kuś, M.Sc. The reviewers in the doctoral dissertation were Prof. Anna Kucaba-Piętal from the Rzeszów University of Technology, Prof. Łukasz Rauch from the AGH University of Science and Technology in Krakow, and Prof. Wojciech Sumelka, from the Poznan University of Technology.
Summary of the dissertation:
In the realm of next-generation electronics, a material of extraordinary promise has emerged: two-dimensional molybdenum disulfide, or MoS2, a single layer of the mineral molybdenite. While its electromechanical properties have garnered significant attention, unlocking its full potential hinges on a thorough understanding of its mechanical behavior. This understanding is particularly crucial in the context of MoS2 application in both nanodevices, such as sensors and transistors, and composite materials, where its potential to replace silicon as a reinforcement material arises due to the ever-present challenge of miniaturization in conventional electronics. However, a critical barrier exists in the form of mechanically weak interfaces that form when MoS2 comes into contact with adjoining materials. To bridge this gap and pave the way for reliable MoS2-based systems, this thesis delves into the fundamental mechanics of 2D MoS2 using the powerful tools of molecular statics and dynamics simulations. The first part of this thesis embarks on an exploration of the mechanical properties of MoS2, specifically focusing on the impact of structural defects on its monolayer form. The overarching goal is to unravel the strengthening mechanisms at play within free-standing MoS2 and decipher how defects influence its mechanical response. Through meticulous simulations involving randomly distributed defects at varying concentrations, ranging from 0% to 25%, the study sheds light on the detrimental effect of these imperfections on the material’s elastic properties, with a particularly noticeable decline observed at the highest concentration. These valuable insights pave the way for informed design principles in the development of 2D MoS2-based devices. Building upon these foundational findings, the second part of the thesis embarks on a quest to optimize the nanostructure of MoS2. Leveraging the power of an evolutionary algorithm (EA), the study sets out to design monolayer 2D MoS2 nanostructures with precisely tailored elastic properties. This innovative approach, where the EA works hand-in-hand with molecular dynamics simulations, identifies the optimal size of elliptical voids required to achieve the desired mechanical characteristics. The success of this methodology underscores its potential in tailoring the mechanical properties of MoS2 nanostructures.
