Investigation of the properties of elements doped graphene structures by density functional theory (DFT)

Graphene with extremely high crystal and electronic quality is a new class of materials with only one atomic thickness. The Graphene name is given to the sheet monolayer of carbon atoms tightly packed into a two-dimensional honeycomb lattice. The superior properties of graphene such as high thermal and electrical conductivity, high mechanical strength, large specific surface area, thermal stability and chemical resistance change as the number of layers changes and other elements are added to its structure. Thus, the properties of the newly formed graphene are very different and it can be used for many different purposes. Graphene with this new structure and these new properties is expected to be used in many areas, for example in the manufacture of fast, flexible and robust consumer electronics products such as microelectronic devices, lithium-ion batteries, solar cells, transistors, biosensors and bioelectronics, nanoelectronics, electronic paper and flexible communication devices. However, it is very difficult to determine experimentally why these properties of the newly formed graphene change, and thus quantum chemical methods are used for this purpose. Some elements are doped on the graphene structure in the literature. This doping process has been done in binary form for some elements and in triple form for a few elements. The aim of this study is to determine the basic properties of graphene surfaces doped with Ga, Ge, P, Si, Al using DFT (Density Functional Theory), one of the quantum chemical calculation methods highly valued by many universities and industrial organizations around the world. Despite the widespread use of this method in the world, there are not lots of studies on quantum chemical methods of materials modeling and properties in our country so this study with the effect of the doping of various elements on the graphene structure will contribute to the scientific world and literature of our country and it has been expected it can lead to possible experimental studies. The method of WB97XD / 6-31G (d, p) was used for these quantum chemical calculations in this study. By comparing the property data such as structural, electrical, chemical and optical properties obtained by quantum chemical methods by doping elements on the graphene structures, which are laid out as a single layer, it was determined how the structure of the graphene changes. With these data, the goal of investigating the basic properties (structural, chemical, mechanical, electronic, optical, magnetic) of graphenes with the help of quantum chemical calculations was achieved. Quantum chemical methods were used to determine the reason for the change in the graphene structure and the element doping, which is difficult to determine experimentally. With the data obtained in this way, a prediction could be made about the possible areas of application of element-doped graphene structures such as sensors, transistors and conductors. Compared to the studies with single doping, the investigations carried out with triple doping have greatly changed the properties of graphene and made the use of the structure in devices more effective. Except for the graphene structure doped with Ga-P-Ga combination, in all other combinations (Ga-Ga-Ga, Ge-Ge-Ge, PPP, Si-Si-Si, Al-Al-Al, Ga-Ga-Ge, Ga-Ga- Si, GaGaAl-GaAl-Ga, GeGeGa-GeGaGe, GeGeP-GePGe, GeGeSi, GeGeAl-GeAlGe, PP-Ga, PP-Ge, PP-Si, PP-Al, SiSiGa-SiGaSi, Si-Ge-Si, Si- P-Si, Si-Si-Al, AlAlGa-AlGaAl, Al-Al-Ge, Al-Al-P, Al-Al-Si, Ga-P-Ge, Ga-Ge-Si, Ge-Ga-Al, Ga-P-Si, P-Ga-Al, Ga-Al-Si, Ge-P-Si, Ge-P-Al, Si-Ge-Al, Si-P-Al) HLG value, which expresses its chemical hardness, decreased. Increased stiffness in doped graphene structures, increased movement of the system towards a more stable configuration, higher stability of the electronic structure, high chemical reactivity, high chemical potential, low electronegativity value, and high electrical conductivity. Electron density increased due to the increase in Fermi level Si-Si-Si, Ga-Ga-Ge, Ga-Ga-Si, Ge-Ge-Si, PP-Ga, PP-Ge, PP-Si, PP-Al, Si -Ge-Si, Si-P-Si, Si-Si-Al, Al-Al-Ge, Ga-Ge-Si, Ge-Ga-Al, Ga-Al-Si, Ge-P-Si, Si-Ge we see it in all combinations. Thanks to these results and doped elements with different properties, element doped graphenes can be used for new multi-purpose device use.