Regulation of Electronic Properties of Novel Two-dimensional SixCy under External Strain

doi:10.15541/jim20250420

Abstract

Abstract:

Two-dimensional (2D) Si_xC_y materials have become a research hotspot in materials science due to their unique structural tunability and outstanding physicochemical properties. Among these, 2D Si₂C₆, Si₆C₁₂ and Si₁₂C₂₀ are theoretically predicted to represent a novel class of topological insulator materials. Si₂C₆ and Si₁₂C₂₀ are semimetallic materials exhibiting Dirac cones, while Si₆C₁₂ is a high-order topological insulator with an intrinsic large bandgap. Currently, the regulation of electronic properties in two-dimensional Si_xC_y (Si₂C₆, Si₆C₁₂ and Si₁₂C₂₀) materials by stress remains to be investigated. In this study, first-principles density functional theory (DFT) was employed to investigate the strain-induced electronic properties of 2D Si_xC_y (Si₂C₆, Si₆C₁₂ and Si₁₂C₂₀) materials. Computational results reveal that near the biaxial tensile fracture strain, the Dirac cones of Si₂C₆ and Si₁₂C₂₀ remain intact. However, even small biaxial compressive strains or uniaxial strains disrupt the degeneracy at the Dirac points of Si₂C₆ and Si₁₂C₂₀, transforming them from topological insulators into trivial direct-bandgap semiconductors. Furthermore, biaxial strain modulates bandgap of the higher-order topological insulator Si₆C₁₂. Under 0-4% compressive strain, the bandgap decreases with increasing compressive strain. Under 0-10% tensile strain, the bandgap increases with increasing biaxial tensile strain. The bandgap of Si₆C₁₂ exhibits significant sensitivity to strain variations, making it a promising candidate for semiconductor devices. Near fracture strain, the valence and conduction bands of Si₆C₁₂ intersect, resulting in metallic behavior. Under uniaxial strain, tensile or compressive deformation induces band delocalization at the Γ point. Additionally, classical molecular dynamics (MD) simulations were employed to investigate the mechanical properties of Si₂C₆, Si₆C₁₂, and Si₁₂C₂₀. Results indicate that the fracture strengths of these materials decrease as the C/Si ratio reduces. The fracture strains of Si₂C₆, Si₆C₁₂, and Si₁₂C₂₀ range from 0.32 to 0.37, exceeding those of single-crystal graphene and defect-free hexagonal boron nitride, and demonstrating excellent ductility. The datasets in this article are listed in Science Data Bank at http://doi.org/10.57760/sciencedb.jim.00065.

Key words: first-principles calculation, two-dimensional Si_xC_y material, strain regulation, electronic property, mechanical property

CLC Number:

O469

HUANG Kuisui, WANG Kexin, LUO Wanhao, LI Fei, GE Yiyao, GAO Yixuan, CHEN Kexin. Regulation of Electronic Properties of Novel Two-dimensional Si_xC_y under External Strain[J]. Journal of Inorganic Materials, 2026, 41(7): 993-1000.

Figures/Tables 18

Fig. 1 (a-e) Optimized atomic structures and (f-j) band structures of 2D Si2C6 under −8%, −5%, 0, +5%, and +10% biaxial strains

Fig. 2 (a-e) Optimized atomic structures and (f-j) band structures of 2D Si6C12 under −4%, −3%, 0, +5%, and +10% biaxial strains

Fig. 3 Bandgap evolution of Si6C12 with external strain

Fig. 4 Structural evolution of Si2C6 under uniaxial tensile along (a-c) x and (d-f) y directions in MD simulations

Fig. 5 COHP of C-C and C-Si bonds in Si2C6 (a) Schematic of selected C-C and C-Si bonds in Si2C6; (b, c) COHP of (b) C-C and (c) C-Si bonds

Fig. 6 Tensile curves and stress analysis diagrams of Si2C6 (a) Atomic structure of Si2C6; (b) Stress-strain curves of Si2C6 stretched along x and y directions, respectively; (c, d) Force analysis diagrams for tensile loading along (c) x and (d) y directions

Fig. S1 Schematic of coordinate transformation (a) Real space (blue) and reciprocal space (orange) of the hexagonal unit cell; (b) Real space (blue) and reciprocal space (orange) of the orthorhombic unit cell

Fig. S2 (a-c) Optimized atomic structures and (d-f) band structures of 2D Si2C6 under -7%, +15% and +20% biaxial strains

Fig. S3 Band structures calculated by first-principles (red lines) and Wannier (blue circles) for (a) Si2C6 at -8% biaxial strain and (b) Si12C20 at -2% biaxial strain

Fig. S4 Optimized atomic structures of Si2C6, Si6C12, and Si12C20 at biaxial strains of (a) +26%, (b) +25%, and (c) +17%, respectively, showing structural failure

Fig. S5 (a-e) Optimized atomic structures and (f-j) band structures of 2D Si12C20 under −2%, −1%, 0, +5%, and +10% biaxial strains

Fig. S6 (a, b) Optimized atomic structures and (c, d) band structures of 2D Si12C20 under +12% and +15% biaxial strains

Fig. S7 (a-e) Optimized atomic structures and (f-j) band structure of Si2C6 under -1%, 0, and +1% uniaxial strains along x and y directions (a, b) Optimized atomic structures and (f, g) band structures of Si2C6 under -1% and +1% uniaxial strains along x direction; (c) Optimized atomic structure and (h) band structure of unstrained Si2C6; (d, e) Optimized atomic structures and (i, j) band structures of Si2C6 under -1% and +1% uniaxial strains along y direction

Fig. S8 (a-e) Optimized atomic structures and (f-j) band structure of Si12C20 under -1%, 0, and +1% uniaxial strains along x and y directions (a, b) Optimized atomic structures and (f, g) band structures of Si12C20 under -1% and +1% uniaxial strains along x direction; (c) Optimized atomic structure and (h) band structure of unstrained Si12C20; (d, e) Optimized atomic structures and (i, j) band structures of Si12C20 under -1% and +1% uniaxial strains along y direction

Fig. S9 Band structures of 2D Si6C12 under -4%, -3%, 0, +5%, and +10% biaxial strains based on the HSE06 hybrid functional

Fig. S10 (a, b) Optimized atomic structures and (c, d) band structures of 2D Si6C12 under +15% and +20% biaxial strains

Fig. S11 (a-e), (k-o) Optimized atomic structures and (f-j), (p-t) band structures of Si6C12 under -4%, -3%, 0, +5% and +10% uniaxial strains along x and y directions (a-e) Optimized atomic structures and (f-j) band structures of Si6C12 under -4%, -3%, 0, +5% and +10% uniaxial strains along x direction;(k-o) Optimized atomic structures and (p-t) band structures of Si6C12 under -4%, -3%, 0, +5% and +10% uniaxial strains along y direction

Fig. S12 (a, c) Atomic structural models and (b, d) stress-strain curves of (a, b) Si6C12 and (c, d) Si12C20 during tensile loading

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