Two-dimensional silicon carbide (SiC) is an important semiconducting material that can offer unprecedented properties. It has a stable, planar structure and is known to have a wide range of electronic and magnetic properties. However, its structural differences from bulk SiC make it difficult to isolate. The potential for 2D SiC is immense. As an alloy, it offers a range of capabilities and functionalities that are not possible in bulk materials. Unlike graphene, SiC can be synthesized in a variety of different compositions.
Several theoretical studies have investigated the electronic properties of 2D SiC. For example, simulations show that the ground state of 2D SiC is completely planar. This is due to the fact that there is an all-electron density between layers. Another reason for this is the electronic confinement perpendicular to the c axis. Consequently, the band structure of few layer SiC is expected to be slightly different from that of bulk SiC.
Unlike bulk SiC, which is a covalently bonded material, 2D SiC is a heteroatomic material. Therefore, there is a strong dependence on the ratio of carbon to silicon. Since the atomic ratio of C and Si in 2D SiC can be varied, the electronic properties of the material are highly dependent on the amount of the two elements present. Moreover, the number of layers is also expected to influence the band structure of the material.
The electronic properties of SiC can be influenced by substituents on the Si=C double bond. When the Si=C bond is weakened, the positive charge density at carbon becomes lower. In addition, the bond angle increases from 109 to 120 degrees. Ultimately, this affects the electronic polarity of the SiC. This can cause the SiC to behave as a topological insulator.
Silicon carbide is commonly used in high-temperature applications. One of its main advantages is its hardness. Although the bulk SiC is chemically stable, it has a poor thermal expansion coefficient. It is therefore suitable for use in aerospace, energy, and high-temperature applications. Other properties of the material include its ability to withstand heavy flux usage. Increasing interest in this material is particularly evident in its use as a catalyst support in combustion engines.
While bulk SiC is stable and does not undergo significant change in temperature, it cannot be isolated from two-dimensional SiC. Moreover, the crystalline structures of bulk SiC can vary greatly, from hexagonal to three-dimensional. These variations can result in a variety of interlayer distances. So, the synthesis of single-layer SiC requires a thorough understanding of the composition and crystal structure of the bulk material.
To produce monolayer SiC, the phase transformation from sp3 to sp2 is required. During this process, the crystalline structure is strongly affected, making it unstable in bilayers. Fortunately, it is possible to achieve direct bonding between the two layers at temperatures in the range of 2400 degC. Because of the increased bonding distance, the p-p overlap is limited.
Monolayer SiC is relatively stable, and can be doped with nitrogen to create a metallic conductor. It is also possible to obtain a sp2 silicon carbide, or semimet, by doping a p-type silicon atom with aluminum. Moreover, the metal boron has been used in heavy doping to improve its metallic conductivity.
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