插入剂诱导的凯克勒有序和准自由-standing石墨烯中能隙的打开
Intercalant-induced Kekule ordering and gap opening in quasi-free-standing graphene
AI总结：
Sn插入通过解耦缓冲层并引入局部晶格畸变，诱导石墨烯中凯克勒有序和能隙打开，揭示了插入剂均匀性和应变对石墨烯性质的调控作用。
摘要：
我们通过低温扫描隧道显微镜和光谱（LT-STM/STS）、点分析低能电子衍射（SPA-LEED）以及密度泛函理论（DFT）计算，全面研究了Sn插入的缓冲层在SiC（0001）上的结构和电子性质。Sn插入有效解耦了缓冲层，产生准自由-standing单层石墨烯（QFMLG），同时引入局部晶格畸变。偏压依赖的STM成像揭示了传统和凯克勒有序石墨烯域的共存，由SiC界面下的Sn（1×1）重构控制。测得的STS光谱与DFT结果有良好一致性。然而，实现均匀的Sn（1×1）域仍然具有挑战性，显然由于Sn单层中的应变，驱动了凯克勒畸变的出现以及在石墨烯中相关的电子能隙的均匀打开。这些发现突显了插入剂的均匀性和应变在调节石墨烯的结构和电子性质中的关键作用。
英文摘要：
We present a comprehensive investigation of the structural and electronic properties of Sn intercalated buffer layers on SiC(0001) using low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS), spot-profile analysis low-energy electron diffraction (SPA-LEED), and density functional theory (DFT) calculations. Sn intercalation effectively decouples the buffer layer, yielding quasi-free-standing monolayer graphene (QFMLG) while introducing local lattice distortions. Bias-dependent STM imaging revealed the coexistence of conventional and Kekule-ordered graphene domains, governed by the underlying Sn(1x1) reconstruction at the SiC interface. The measured STS spectra exhibit good agreement with DFT results. However, achieving homogeneous Sn(1x1) domains remains challenging, apparently, due to strain within the Sn monolayer, which drives the emergence of Kekule distortions and the associated electronic band-gap opening omogeneously in graphene. These findings highlight the crucial role of intercalant homogeneity and strain in tuning graphene`s structural and electronic properties.
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