چكيده به لاتين
Abstract:
MXenes are relatively new family of 2D materials that have received a lot of attention from researchers since the synthesis of their first compounds from MAX phases of transition metal carbides and nitrides. These materials exhibit suitable chemical and physical stability. Additionally, their relatively easy synthesis is another positive aspect that leads to more attention to this family. This family includes three different types of compounds, with the thinnest of them having the chemical formula M_2 XT_2. In this formula, M represents an intermediate metal from groups 3 to 6 of the periodic table, X is either carbon or nitrogen, and T represents one of the elements oxygen, fluorine, or OH.
Until now, these compounds have found numerous applications in various fields, including catalysis, use in lithium batteries, and many other applications. The investigation of the M_2 XT_2 family, which includes 72 different structures, indicates the existence of semiconductor, metallic, semi-metallicand also topological insulator behaviors. Previous studies on these materials, especially those with semiconducting properties, have focused on the examination of their electronic and optical properties using density functional theory methods, but a detailed study of the electron transport behavior of these materials has not been conducted so far.
In this thesis, for the first time, the electronic transport in MXene nanoribbons has been investigated. Here, by using Slater-Koster relations for p orbitals of X atoms and d orbitals of M atoms, a tight-binding Hamiltonian is written, and their band structures are plotted. Then, using the non-equilibrium Green's function method and the Landauer-Buttiker formula, the conductivity properties of the material 〖Zr〗_2 CO_2, as a representative of this family, has been studied.
In this research, it has been observed that by changing the width of the nanoribbon, the energy gap in the system decreases. According to the graphs, increasing the width of the band can reduce the band gap to a certain extent, but alone it will not be able to create conductivity in this compound. Moreover, the creation of various atomic vacancies of carbon and zirconium atoms leads to significant changes in the conductivity magnitude as well as the band gap in the system. The results show that the presence of various carbon vacancies reduces the band gap and also decreases the conductivity magnitude. Additionally, the vacancies of zirconium atoms at the edges reduce the band gap and also decrease the conductivity. However, the vacancy related to the zirconium atom at the bottom of structure, increases the band gap noticeably. These changes in the band gap indicate the potential for engineering the gap of these compounds for use in nanoelectronic devices.
