Database of Dopants and Defects in 2D Materials

University Of Florida, Gainesville FL

Investigators

Abstract

NONTECHNICAL SUMMARY This EAGER award supports computational research on two-dimensional materials and the development of a 2D materials data resource that will be made available through the 2-Dimensional Crystal Consortium (2DCC) Materials Innovation Platform at Pennsylvania State University. Graphene is perhaps the most famous of the 2D materials being a one-atom thick mesh of hexagonal "chicken wire" with a carbon atom at each corner. Graphene has exotic electronic properties, including electrons that behave as though they traveled at the speed of light and an ability to conduct electricity some 1,000,000 times better than copper. Other 2D materials that contain atomically thin layers have been developed. These are the focus of this research project and include transition-metal dichalcogenides. A transition-metal dichalcogenide contains a metal atom from the transition metal columns of the periodic table of elements, like tungsten, or molybdenum, and two chalcogen atoms like sulfur or selenium in the primitive unit that upon replication and translation to fill space defines its structure. Transition-metal dichalcogenides differ from graphene in that their electronic properties have some features akin to silicon, which for example is a semiconductor whereas graphene is a semimetal. They also have a host of interesting and more exotic electronic properties. These properties taken together for transition-metal dichalcogenides and related compounds make them promising candidates for the discovery of fundamentally new physical effects and new electronic and optical device technologies, and the subject of much research. The PI will modify software that he has developed for the rapid calculation of the properties of many materials in parallel to enable calculations for 2D materials. Using this software, high quality calculations will be performed for the properties of 2D materials for which the arrangement of the constituent atoms deviates from the structure of a perfect materials because of additional impurity atoms, missing atoms, or other defects in the structural atomic arrangement. This information will be collected and served in a database that is accessible to the broader community, particularly to researchers that use the 2DCC Materials Innovation Platform. Understanding the role of defects and impurities that change the concentration of charged particles that can carry current and otherwise alter the properties of bulk silicon was important in the development of the transistor. Ready access to the data provided under this award may have a similar transformative effect for 2D materials in new fundamental science discoveries and in the invention of new electronic or optoelectronic devices. This project in conjunction with 2DCC would address in a timely way, the growing needs of the community for information on the role defects, dopants, and impurities play in 2D materials to help guide experimental and theoretical efforts. Software, documentation, and data created during the project could be applied in other contexts and will be made freely available to the broader community as part of the materials research community cyberinfrastructure. Data will be made available through the MaterialsWeb database. The project will contribute to the training of the next generation of computational researchers to enable the development of future cyberinfrastructure. Collaboration with researchers in Germany will contribute to the education of the students participating in this project. TECHNICAL SUMMARY This EAGER award supports computational research on two-dimensional materials and cyberinfrastructure development to be made available through 2-Dimensional Crystal Consortium (2DCC) Materials Innovation Platform at Pennsylvania State University. Progress in the synthesis and application of 2D materials as pursued by the 2DCC requires understanding how dopants and defects control the carrier concentration, character, and mobility of 2D materials. Just like in bulk semiconductors, dopants and defects in 2D materials are frequently charged. Understanding their formation energies and charge transition levels is crucial for the design of novel 2D-materials-based electronic and spintronic devices. Developing a database of the properties of defects and dopants in 2D materials has the potential to revolutionize the design of 2D electronic devices, the way analogous data did for bulk semiconductors. Density-functional theory employing accurate hybrid exchange-correlation functionals provides a tool that can predict formation energies and charge transition levels to an accuracy of 0.1 - 0.2 eV, sufficient for electronic device design. However, charged defects in single-layer materials challenge conventional computational approaches such as density-functional theory calculations using plane-wave approaches and lead to the divergence of the energy with vacuum spacing. A correction scheme that employs a generalized dipole approach and restores the appropriate electrostatic boundary conditions for charged 2D materials will be coupled in to the PI's Python-based high-throughput framework MPInterfaces. This will enable the rapid development of the database of defect and dopant properties for widely-used 2D materials, such as graphene, phosphorene, metal dichalcogenides, and monochalcogenides. This approach will then be applied to materials of interest to users of the 2DCC and then to the complete MaterialsWeb database. The results will be made freely available through our MaterialsWeb database. This project in conjunction with 2DCC would address in a timely way, the growing need of the community for information on the role defects, dopants, and impurities play in 2D materials to help guide experimental and theoretical efforts. Software, documentation, and data created during the project could be applied in other contexts and will be made freely available to the broader community as part of the materials research community cyberinfrastructure. Data will be made available through the MaterialsWeb database. The project will contribute to the training of the next generation of computational researchers to enable the development of future cyberinfrastructure. Collaboration with researchers in Germany will contribute to the education of the students participating in this project.