XI Jinyang , NAKAMURA Yuma , ZHAO Tianqi , WANG Dong , SHUAI Zhigang ,＊ Materials Genome Institute, Shanghai University, Shanghai 00444, P. R. China.

2 MOE Key Laboratory of Organic OptoElectronics and Molecular Engineering, Department of Chemistry, Tsinghua University,Beijing 100084, P. R. China.

Abstract: The electronic structures, deformation potential, electron-phonon couplings (EPCs), and intrinsic charge transport of layered systems — the sp + sp2 hybridized carbon allotropes, graphynes (GYs) and graphdiynes(GDYs), as well as sp2 + sp3 hybridized structure with buckling, such as stanine — have been investigated theoretically. Computational studies showed that, similar to graphene, some GYs can possess Dirac cones (such as α-, β-, and 6,6,12-GYs), and that the electronic properties of GYs and GDYs can be tuned by cutting into nanoribbons with different widths and edge morphologies. Focusing on the features of Dirac cones, band structure engineering can provide a clue for tuning electronic transport in 2D carbon-based materials. Based on the Boltzmann transport equation and the deformation potential approximation (DPA), the charge carrier mobilities in GYs and GDYs were predicted to be as high as 104–105 cm2∙V−1∙s−1 at room temperature. Interestingly, due to lower EPC strength and longer relaxation time, the charge carrier mobility in 6,6,12-GY with double Dirac cones structure was found to be even larger than that of graphene at room temperature. The unique electronic properties and high mobilities of GYs and GDYs make them highly promising candidates for applications in next generation nanoelectronics. Additionally, through the full evaluation of the EPC by density functional perturbation theory (DFPT) and Wannier interpolation, the EPCs with different phonon branches and wave-vectors as well as charge carrier mobilities for graphene, GYs and stanene have been discussed. This showed that the longitudinal acoustic (LA) phonon scattering in the long wavelength limit is the main scattering mechanism for GYs and graphene, and thus the DPA is applicable. Due to stronger LA phonon scattering, the electron mobilities (～104 cm2∙V−1∙s−1) of α-GYs and γ-GYs were predicted to be one order of magnitude smaller than that of graphene at room temperature by full evaluation of the EPC. However, the DPA would fail if there was buckling in the honeycomb structure and the planar symmetry was broken (absence of σh), such as in stanene, where the inter-valley scatterings from the out-of-plane acoustic (ZA) and transverse acoustic (TA) phonons dominate the carrier transport process and limit the electron mobilities to be (2–3) × 103 cm2∙V−1∙s−1 at room temperature. In addition to our calculations, others have also found that the main scattering mechanisms in layered systems with buckling, such as silicene and germanene, are ZA and TA phonons. Thus, these results give us new insights into the role of EPCs and the limitation of the DPA for carrier transport in layered systems. They also indicate that the carrier mobilities of systems without σh-symmetry can be improved by suppressing the out-of-plane vibrations, for example by clamping by a substrate.

Key Words: Graphyne; Stanene; Electronic structure; Deformation potential; Electron-phonon coupling;Mobility

1 引言

纳米材料尤其是低维纳米材料由于其尺寸受限效应，带来了很多不同于传统三维材料的量子现象，成为电子学、材料学、光电子学等诸多领域中炙手可热的材料。在低维材料中，碳原子形成的键都比较稳定，且具有高度的灵活多样性，不同碳碳键(如 sp3、sp2和 sp杂化)形成的碳材料具有差异非常大的结构和性质，使得碳材料种类丰富多样。随着几十年来各种研究手段的不断突破和创新，人们已经能够制备出各种特点的低维碳材料，如零维富勒烯1、一维碳纳米管2、二维石墨烯3等，它们展现了优良的电子性能、电化学性能和机械性能，是能够应用于纳米电子学、化学传感器和能源存储等领域的潜在低维材料4–6。以上几类碳材料都具备sp3和sp2的杂化，然而在碳碳键中还有一种有趣的sp杂化，以sp杂化形成的碳碳三键具有线性结构、无顺反异构体和高共轭等特点，所以多年来人们也一直渴望和尝试能够获得含有sp杂化的新型碳的同素异形体。直到1987年，Baughman等7通过计算认为将炔键(C≡C)引入到苯环中形成共轭大碳环的二维平面网状结

帅志刚，1962年出生。1989年博士毕业于复旦大学。现为清华大学化学系长江特聘教授、博士生导师。主要研究领域为理论化学、材料的功能理论计算与模拟。构是可以稳定存在的，并将这类以sp和sp2杂化形成的二维碳的同素异形体称之为石墨炔，例如三种典型的含单炔键的石墨炔结构：α-，β-和 γ-石墨一炔(图1a–c)；之后国际上的理论学家以及功能分子研究组都开始了相关的研究并探索制备石墨炔8–11，其中在1997年 Haley等10首次制备出了含双炔键的一种石墨炔片段，我们称之为石墨二炔(图1d)；……