Beyond Graphene: Unveiling the Structure-Property Relationship of Silicon Carbide (SiC) Through First Principles Calculations

The rising demand for smaller, more compact, and easily portable electronic devices has driven the shift from micro to nanoelectronics. For this progression, researchers need to incorporate low-dimensional nanomaterials, such as nanotubes, nanowires, and quantum dots, into nanoscale devices. These materials not only meet the requirements for device miniaturization but also facilitate the exploration of novel quantum phenomena not exhibited in bulk systems. This evaluation contributes to the fabrication of nanoscale devices, that offer high-performance, energy efficiency, and functional adaptability, which makes it foundational for advancing next-generation electronic devices. A fundamental understanding of the physicochemical properties of low-dimensional materials is crucial for the design of compact, high-performance nanoelectronic devices. However, nanostructures of current benchmark materials such as carbon and silicon, reveals inherent limitations, such as chemical instability, limited bandgap tunability, and compatibility constraints. In this context, silicon carbide-based nanostructures offer a promising alternative due to their physicochemical, and tunable electronic properties. With this motivation, this doctoral thesis employs first principles density functional theory, to conduct a comprehensive investigation of the structural, physicochemical, and electronic properties, of both existing and theoretically proposed SiC based low-dimensional nanostructures. Additionally, the study explores various potential synthesis strategies. The computational findings assist in the possible experimental synthesis approaches for SiC nanostructures and emphasise their potential for various applications. Atomically thin layered 2D SiC nanosheets are wide band gap semiconductors with excellent thermal stability, making them promising candidates for flexible nanoelectronic devices. However, due to the strong covalent bonding in bulk SiC, exfoliating monolayer 2D SiC remain experimentally challenging. In Chapter 3, we demonstrate that exfoliation of ultrathin SiC layers from bulk wurtzite SiC through a defect engineering approach may be feasible. Further, we explain the effect of defects on the structural and electronic properties of monolayer to tri-layer SiC nanosheets. Chapter 4 focuses on an approach to form single walled SiC nanotubes. While, experimental synthesis has commonly achieved the formation of multi-walled SiC nanotubes, the formation of single walled SiCNTs remains a significant challenge. In this chapter we used dangling edge bonds to control the technique as a novel alternative approach to the traditional method (i.e. cutting a 2D SiC nanosheet along its Bravais direction and rolling it into a single walled SiC nanotubes). Specifically, it is demonstrated that stacking of bilayer SiC nanoribbons can lead to the formation of single walled SiC nanotube via bond formation at the nanoribbon edges. Notably, this self-formation processes does not require any external energy. Further, the critical threshold diameter for successful tube formation was determined to be ~1.2 nm. Beyond that diameter, the nanotubes underwent radial deformation, limiting their structural stability. Chapter 5.1 addresses the radial deformation of larger diameter defective SiC nanotubes, utilizing a charge injection approach to mitigate this reconstruction. The injection of holes (electron) leads to an expansion (contraction) of the nanotube diameter. This results in an electromechanical strain that can reached up to 10.6%, which is significantly higher than conventional nanotubes such as CNTs or SiNTs. This strain response highlights the suitability of 1D SiC allotropes for applications in nanoelectromechanics. Chapter 5.2 demonstrates that defective SiC nanotubes are promising candidates for anode materials in alkali-metal ion batteries. The chapter provides detailed insights into their structural stability, bonding nature, and electrochemical behaviour. Furthermore, the anodic performance of defective SiCNTs is evaluated by analyzing their average intercalation voltage (AIV) profiles, confirming their suitability for energy storage applications. Finally, Chapter 6 investigates the influence of quantum confinement on the structural and electronic properties of SiC nanoflakes. A detailed analysis of edge geometry and flakes size reveals that physicochemical properties are highly sensitive to these factors. The tunability of these properties make potential for nanoelectronic applications. Overall, the findings presented in this thesis range from the structural and physicochemical properties to novel synthesis strategies for SiC based nanostructures, all highlighting their potential in nanoelectronic and energy storage applications. We believe these insights will encourage further research in the field of nanoelectronics and support experimental efforts towards the synthesis of SiC based nanostructures.