Title: Your Clean Graphene is Still Not Clean Show Chinese title

Title: 你的干净石墨烯仍然不干净

Abstract: Efforts aimed at scaling fabrication processes to the level of single atoms, dubbed atom-by-atom fabrication or atomic fabrication, invariably encounter the obstacle of atomic scale cleanliness. When considering atomic fabrication, cleanliness of the base material and purity of the source reservoir from which atomic structures will be built are invariable constraints imposed by laws of physics and chemistry. As obvious as such statements may be, and regardless of the inevitable consequences for successful atomic fabrication, there is a poignant lack of understanding of the "dirt" (contamination/impurities). Here, we examine hydrocarbon contamination on graphene. Graphene has formed the base substrate for many e-beam-based atomic fabrication studies and many strategies for cleaning graphene have been presented in the literature. One popular method is heating to high temperatures (>500 {\deg}C). It is usually inferred that volatile hydrocarbons evaporate into the microscope vacuum system leaving behind pristine graphene. Here, we show through direct image intensity analysis that what appears to be clean graphene can be coated with a thin layer of dynamically diffusing hydrocarbons. This result holds significant implications for approaches to e-beam based atomic fabrication, updates the conceptual model of e-beam induced hydrocarbon deposition, and may extend to hot surfaces generally. Show Chinese abstract

Abstract: 旨在将制造工艺扩展到单个原子水平的努力，被称为逐原子制造或原子制造，总会遇到原子尺度清洁度的障碍。 在考虑原子制造时，基材的清洁度和用于构建原子结构的源库的纯度是物理和化学定律不可避免的约束。 尽管这些陈述显而易见，并且无论对成功的原子制造有何不可避免的后果，但对“污垢”（污染/杂质）的理解仍存在深刻的不足。 在此，我们研究了石墨烯上的碳氢化合物污染。 石墨烯已成为许多基于电子束的原子制造研究的基础基底，并且文献中已经提出了许多清洁石墨烯的策略。 一种流行的方法是加热至高温（>500{\deg }C）。 通常推断挥发性碳氢化合物会蒸发到显微镜真空系统中，留下纯净的石墨烯。 在这里，我们通过直接图像强度分析表明，看似干净的石墨烯可能被一层动态扩散的碳氢化合物覆盖。 这一结果对基于电子束的原子制造方法具有重要意义，更新了电子束诱导碳氢化合物沉积的概念模型，并可能适用于一般加热表面。