Rhombohedral stacking-faults in exfoliated highly oriented pyrolytic graphite

IF 3.1 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Carbon Trends Pub Date : 2024-03-20 DOI:10.1016/j.cartre.2024.100345

Filippo Boi , Cheng-Yang Lee , Shanling Wang , Hansong Wu , Lei Li , Lin Zhang , Jiaxin Song , Yixin Dai , Ayoub Taallah , Omololu Odunmbaku , Anna Corrias , Aleksandra Baron-Wiechec , Shuping Zheng , Salvatore Grasso

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Abstract

The recent observation of possible granular superconductivity in highly oriented pyrolytic graphite (HOPG) has attracted significant research interest. Here we report a novel investigation on the structural-properties of exfoliated-HOPG. We investigated two types of exfoliation methods, involving either a full (method-1) or partial (method-2) contact between adhesive tape and the main HOPG. Structural characterization was obtained by employing X-ray diffraction (XRD), Raman spectroscopy and electron microscopy (SEM). In particular, Raman point and mapping spectroscopy revealed significant structural-transitions from ABA (Bernal) to ABC (rhombohedral) stacking (stacking-faults), in those samples obtained with the method-2. Interestingly, strained regions exhibiting structural-deformations with a ridge-like morphology were reproducibly identified. The acquired Raman-spectra revealed a local enhancement of the D and D’ bands-intensity together with contributions arising from Electronic Raman Scattering (ERS) across the band-gap of rhombohedral-graphite, at middle (∼1870 cm⁻¹) and high (∼ 2680 cm⁻¹) frequency. HRTEM of the samples produced with the method-2 allowed also for the identification of local-coexistence of ripplocation-like defects with moiré superlattices, an indicator of non-uniform c-axis configuration.

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剥离高取向热解石墨中的斜方体堆积断层

最近在高取向热解石墨（HOPG）中观察到可能存在粒状超导现象，这引起了研究人员的极大兴趣。在此，我们报告了一项关于剥离型 HOPG 结构特性的新研究。我们研究了两种剥离方法，包括胶带与主 HOPG 之间的完全接触（方法-1）或部分接触（方法-2）。通过使用 X 射线衍射 (XRD)、拉曼光谱和电子显微镜 (SEM) 获得了结构特征。其中，拉曼光谱点和绘图光谱显示，在使用方法-2 获得的样品中，存在从 ABA（贝纳尔）堆叠到 ABC（斜方体）堆叠（堆叠断层）的显著结构转变。有趣的是，呈现出脊状形态结构变形的应变区域被重复识别出来。获得的拉曼光谱显示，D 和 D'波段强度局部增强，同时在中频（∼ 1870 cm-1）和高频（∼ 2680 cm-1），斜方体石墨带隙的电子拉曼散射（ERS）也有贡献。对使用方法-2 制成的样品进行 HRTEM 分析，还能确定局部存在的波纹状缺陷与摩尔超晶格，这是非均匀 c 轴配置的一个指标。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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