Structural, thermal and electronic properties of two-dimensional amorphous graphene, silicene and silicon carbide

In recent times, low dimensional crystalline structures and van-der Waals (vdW) solids have attracted a lot of attention for their huge potential in device applications. However, the exploration of amorphous forms in two-dimension for property tuning is not so commonly found. Here, we present a detailed structural, electronic and thermal analysis of two-dimensional (2D) amorphous graphene(A-Gra), silicene(A-Si) and silicon carbide(A-SiC) by using Classical Molecular Dynamics (CMD) simulations for structure generation, stability tests, thermal conductivity and vibrational analysis while we use first-principles density functional theory (DFT) calculations for electronic structure and charge distributions. A comparison between the structures obtained from large-scale CMD and smaller scale DFT has been made. We find that A-Gra is planar and metallic with a thermal conductivity around 55.30 W/Km. A bilayer of A-Gra shows a vdW character without any chemical bond. On the contrary, A-Si prefers to create covalent bonds in a bilayer structure. It is found that the monolayer A-Si has a much lower thermal conductivity (2.68 W/Km) than A-Gra. Finally, we show that 2D amorphous silicon carbide can be stabilized not only as a single layer but also as a bilayer, where the chemical bonding between Si atoms exist only. Among our studied materials, A-SiC's thermal conductivity is found to be the highest (70.29 W/Km). Our vibrational analysis shows that the heat carriers in A-Si and A-SiC are extendons, especially diffusions in absence of localized vibrational modes. Finally, an observation of uneven charge distributions around the ring structures in these amorphous materials can serve as an interesting ingredient in designing future electronic devices by tuning the local functionalities.