利用应力调控二维新型SixCy的电子性质

doi:10.15541/jim20250420

摘要/Abstract

摘要： 二维Si_xC_y材料因其独特的结构可调性与优异的物理化学性能成为材料科学领域的研究热点。其中,二维Si₂C₆、Si₆C₁₂、Si₁₂C₂₀被理论预言是一类新型拓扑绝缘体材料,Si₂C₆与Si₁₂C₂₀是具有狄拉克锥的半金属材料,而Si₆C₁₂是具有本征大能隙的高阶拓扑绝缘体材料。目前,应力对二维Si_xC_y (Si₂C₆、Si₆C₁₂、Si₁₂C₂₀)材料电子性质的调控作用尚待研究。本文采用基于密度泛函理论(Density Functional Theory, DFT)的第一性原理方法探究应变对二维Si_xC_y (Si₂C₆、Si₆C₁₂、Si₁₂C₂₀)材料电子性质的调控规律。计算结果表明,在双轴拉伸断裂应变附近,Si₂C₆与Si₁₂C₂₀的狄拉克锥仍保持完整,但较小的双轴压缩应变或单轴应变会破坏Si₂C₆与Si₁₂C₂₀狄拉克点处的简并性,使得Si₂C₆和Si₁₂C₂₀从拓扑绝缘体转变为平庸的直接带隙半导体。此外,双轴应变对高阶拓扑绝缘体Si₆C₁₂的带隙具有调控作用,在0~4%的压缩应变下,Si₆C₁₂的带隙随着压缩应变的增大而减小,在0~10%的拉伸应变下,带隙随着拉伸应变的增大而增大。Si₆C₁₂的带隙对应变变化较为敏感,有望应用在半导体器件中。在断裂应变附近,Si₆C₁₂的价带与导带交叉,体系表现为金属性。在单轴应变下,拉伸或压缩应变会导致Si₆C₁₂在Γ点处的能带发生退简并。此外,通过经典分子动力学(Molecular Dynamics, MD)模拟探究Si₂C₆、Si₆C₁₂、Si₁₂C₂₀的力学性质,发现这类材料的断裂强度随着C/Si比值的减小而降低。Si₂C₆、Si₆C₁₂、Si₁₂C₂₀的断裂应变在0.32~0.37之间,高于单晶石墨烯和无缺陷六方氮化硼,具有良好的延展性。

关键词: 第一性原理计算, 二维Si_xC_y材料, 应力调控, 电子性质, 力学性质

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.

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

中图分类号:

O469

黄奎碎, 王珂馨, 罗万豪, 李飞, 葛一瑶, 高艺璇, 陈克新. 利用应力调控二维新型Si_xC_y的电子性质[J]. 无机材料学报, DOI: 10.15541/jim20250420.

HUANG Kuisui, WANG Kexin, LUO Wanhao, LI Fei, GE Yiyao, GAO Yixuan, CHEN Kexin. Regulating Electronic Properties of Novel Two-dimensional Si_xC_y under External Strain[J]. Journal of Inorganic Materials, DOI: 10.15541/jim20250420.

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