通过离子传输中的反冲粒子符合技术对原子级薄材料的成分和污染进行定量分析
Quantitative Analysis of Composition and Contamination of Atomically Thin Materials by Recoil-Projectile Coincidence in Ion Transmission
浏览论文内容
中文总结 AI 辅助
研究通过反冲粒子符合技术对原子级薄材料的成分和污染进行定量分析，以石墨烯为例，比较不同制备工艺的样品，识别主要污染物，展示该方法能实现元素特异性识别和量化，为超薄材料建立定量表征平台。
中文摘要 AI 辅助
表面污染强烈影响纳米级材料的固有特性，可靠识别和量化污染对于准确的实验解释和纳米制造至关重要。扫描透射电子显微镜虽能在纳米区域以原子分辨率分辨污染物，但难以提供定量的大面积污染测量。本文介绍一种用于离子传输实验的微创反冲粒子符合方法，可实现具有同位素分辨率的表面污染物的元素特异性识别和量化。通过比较基于聚甲基丙烯酸甲酯（PMMA）和无PMMA转移工艺制备的自支撑石墨烯样品来证明该方法。碳和氢被确定为主要表面污染物，无PMMA转移的石墨烯原生污染水平最低。在400°C原位热退火1小时后，测量的碳面密度在实验不确定度内接近原子级清洁单层石墨烯的预期值，氢覆盖率大幅降低。与退火后迅速重新污染的PMMA转移石墨烯不同，无PMMA转移的石墨烯在超高真空条件下（$p_{\mathrm{base}} = 2 \times 10^{-8}$ mbar）至少140分钟内几乎保持无污染。该方法为超薄材料建立了定量表征平台，有助于研究此类系统中的表面清洁度、吸附、注入和表面相互作用动力学。
英文摘要
Surface contamination strongly affects the intrinsic properties of nanoscale materials, making its reliable identification and quantification crucial for both accurate experimental interpretation and nanofabrication. Although scanning transmission electron microscopy can resolve contaminants at atomic resolution within nanometer-scale regions, it cannot easily provide a quantitative, large-area contamination measure. Here, we introduce a minimally destructive recoil-projectile coincidence method for ion transmission experiments that enables element-specific identification and quantification of surface contaminants with isotopic resolution. We demonstrate this approach by comparing self-supporting graphene samples prepared using either a polymethylmethacrylate (PMMA)-based or a PMMA-free transfer process. Carbon and hydrogen are identified as the dominant surface contaminants. PMMA-free transferred graphene exhibits the lowest native contamination levels. Following in-situ thermal annealing at 400 °C for 1 h, the measured carbon areal density approaches the value expected for atomically clean single-layer graphene within the experimental uncertainty, while hydrogen coverage is strongly reduced. Unlike PMMA-transferred graphene, which rapidly recontaminates after annealing, PMMA-free transferred graphene remains nearly contamination-free for at least 140 min under ultra-high vacuum conditions ($p_{\mathrm{base}} = 2 \times 10^{-8}$ mbar). Beyond graphene, the presented method establishes a quantitative characterization platform for ultrathin materials, enabling studies of surface cleanliness, adsorption, implantation and surface interaction dynamics in such systems.
