Research Projects

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are investigated extensively due to their extraordinary performance in various applications like optoelectronics, sensing, catalysis, energy storage, memristor and quantum devices etc. Defect engineering in atomically thin 2D materials and heterostructures would determine their full potential for electronic and optical device applications. At the same time, precise control over defects in 2D materials imposes several scientific and technological challenges and demands newer approaches. For example, many of the conventional lithographic and doping methods are not directly suitable in manipulating defects at atomic scale. In realizing 2D materials-based devices, many challenges arise starting from growth of large area monolayers /heterostructures, control of defects during the growth as well as post growth processing, chemical stability and mechanical reliability issues to final device fabrication and testing. On the other hand, scientific questions such as what is the effect of defects in 2D materials and heterostructures on device performance need to be well addressed. In this proposed work, we would like to focus on WS2 and MoS2 based 2D materials and investigate the defect engineering aspects for memristor devices. We target to explore several approaches to create defects (vacancies, voids, cracks, doping, heterostructures) with the use of CVD growth, post growth chemical methods (chemical treatments, passivation) and few physical methods (ion milling, plasma and microwave). In addition, the actual defect mediated mechanisms (filament formation, vacancy migration, phase transition, charge trapping) responsible for memristor functions will be investigated. One of the objectives will be to use defects as platform to induce multiple functionalities in memristors. Similarly, memristor action triggered by voltage, light, temperature and strain etc will be also investigated. While the fabrication and mechanistic understanding of defect controlled 2D materials are key requirements for developing multifunctional memristor devices, the other engineering aspects such as mechanical failure cannot be neglected in atomically thin 2D materials as they are prone to mechanical failures. Hence important aspects such as the effect on defects on mechanical properties and long-term reliability need to be investigated to optimize defects by comparing the performance and mechanics of 2D materials. One of the main objectives is to establish process-performance map for defect engineered 2D materials (comparison of defect engineered 2D materials by different methods such as ion milling, laser, plasma and microwave with memristor performances) in this important class of 2D materials (MoS2 and WS2).