Let's play with graphene (stacking graphene Lego blocks)

• Main Author: Rajdave Singh
• Other Authors: Sanghoon Chae
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/168306
• Institution: Nanyang Technological University

Graphene, a two-dimensional material consisting of carbon atoms arranged in a honeycomb lattice, has unique electronic and mechanical properties A lot of research has been done on graphene because of its exceptional mechanical and electronic characteristics. However, because it lacks an intrinsic bandgap, its use is restricted in some fields, including optoelectronics. In order to get around this restriction, scientists have looked into stacking graphene with other two-dimensional substances like tungsten diselenide (WSe2), molybdenum disulfide (MoS2), and molybdenum diselenide (MoSe2) to produce hybrid materials with special characteristics. With a change in temperature between 80 to 140 degrees Celsius, it enable the development of a link between the layers, enabling the stacking of these two-dimensional blocks. This makes it possible for the layers to be precisely aligned, creating a distinctive electrical structure that is highly reliant on the stacking arrangement. These structures are very attractive for a variety of applications, including electronics, optoelectronics, and energy harvesting, because the heterostructure's usage of diverse two-dimensional materials enables the tuning of the electrical and optical properties. The ability to adjust the electronic properties of hybrid materials built on graphene is one of their main benefits. Other 2D materials with various band structures can be used to modify the electronic characteristics of graphene. A bandgap may emerge in graphene, for instance, when it is stacked with WSe2, a semiconductor with a bandgap of about 1.3 eV, as a result of the electronic state hybridization between the two substances. This makes it possible to create high-performance graphene-based field-effect transistors and other electronic systems. Hybrid materials built on graphene are also very interesting in terms of their mechanical characteristics. While WSe2 and MoS2 have strong fracture strengths and ductility, graphene is renowned for its extraordinary strength and stiffness. These materials can be combined to create hybrid materials with improved mechanical characteristics. For instance, it was discovered that a hybrid material made of graphene and WSe2 had better fracture durability than either material by itself. Graphene-based hybrid materials have mechanical and electronic properties as well as possible uses in optoelectronics. Enhancements in light-matter interactions, like the link between excitons in WSe2 and plasmons in graphene, can result from combining graphene with other 2D materials. Due to this, highly responsive and detectable hybrid photodetectors built on graphene have been developed. The order in which the graphene-based composite materials are stacked can also have a big impact on how they behave. For instance, when graphene and molybdenum disulfide are layered on top of each other, a heterostructure with a type-II band alignment results, with graphene's conduction band minimum being lower than molybdenum disulfide's valence band maximum. Due to the strong electric field that is created at the interface as a consequence, charge separation and transfer may be improved. Due to this, high responsive and low dark current graphene/MoS2-based photodetectors have been developed. Additionally, graphene-based hybrid materials present new possibilities for fundamental studies of charge and energy transfer at the interfaces between various 2D materials. For instance, the strong coupling between the two materials at the interface allows for the generation of a valley-dependent photocurrent when graphene and MoSe2 are layered. This makes it possible to create valleytronics devices, which make use of the 2D materials' valley degree of freedom. Overall, the ability to create and engineer novel materials with distinctive features that can be customized for particular applications has increased thanks to the stacking of graphene with other two-dimensional materials.