本研究中，导电原子力显微镜在未扭转的、生长于碳化硅上的外延石墨烯中，惊人地发现了具有不同电导率的条纹状区域，这种对比度表明存在ABA和ABC堆叠区域，因为它与在扭转剥离石墨烯中观察到的ABA/ABC区域的电导率差异完全吻合，并且这一差异也通过密度泛函理论得到了计算验证。
堆叠区域的大小和几何形状取决于应变、孤子交叉以及三层区域形状之间的相互作用。有趣的是，研究人员展示了三层区域的生长过程，其中ABA/ABC堆叠区域自发组织成稳定且宽度为几十纳米的条纹。
这种可控制生长的孤立且条纹状的ABA/ABC区域，为在这些区域上制造量子器件开辟了道路。这些关于在碳化硅上自组装形成ABA/ABC外延石墨烯条纹的发现，无需耗时且难以规模化的石墨烯剥离、对齐和扭转过程，为石墨烯在电子器件中的不同潜在应用提供了可能。
据悉，在范德华材料通过堆叠和扭转原子层所形成的区域中，已观察到从超导性到铁电性、磁性以及相关多体带隙等一系列涌现的电子现象。在石墨烯中，人们已通过剥离后由专业机械扭转并与所需方向对齐的过程，获得了ABC堆叠区域，并在这些区域中观察到了涌现的特性。然而，这一过程极具挑战性且难以规模化。
附：英文原文
Title: Spontaneous emergence of straintronics effects and striped stacking domains in untwisted three-layer epitaxial graphene
Author: Rejhon, Martin, Parashar, Nitika, Schellack, Lorenzo, Shestopalov, Mykhailo, Kunc, Jan, Riedo, Elisa
Issue&Volume: 2024-12-4
Abstract: Emergent electronic phenomena, from superconductivity to ferroelectricity, magnetism, and correlated many-body band gaps, have been observed in domains created by stacking and twisting atomic layers of Van der Waals materials. In graphene, emergent properties have been observed in ABC stacking domains obtained by exfoliation followed by expert mechanical twisting and alignment with the desired orientation, a process very challenging and nonscalable. Here, conductive atomic force microscopy shows in untwisted epitaxial graphene grown on SiC the surprising presence of striped domains with dissimilar conductance, a contrast that demonstrates the presence of ABA and ABC domains since it matches exactly the conductivity difference observed in ABA/ABC domains in twisted exfoliated graphene and calculated by density functional theory. The size and geometry of the stacking domains depend on the interplay between strain, solitons crossing, and shape of the three-layer regions. Interestingly, we demonstrate the growth of three-layer regions in which the ABA/ABC stacking domains self-organize in stable stripes of a few tens of nanometers. The growth-controlled production of isolated and stripe-shaped ABA/ABC domains open the path to fabricate quantum devices on these domains. These findings on self-assembly formation of ABA/ABC epitaxial graphene stripes on SiC without the need of time-consuming and nonscalable graphene exfoliation, alignment, and twisting provide different potential applications of graphene in electronic devices.
DOI: 10.1073/pnas.2408496121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2408496121