Abstract An operando investigation of graphene growth on (100) grains of polycrystalline nickel (Ni) surfaces was performed by means of variable-temperature scanning tunneling microscopy complemented by density functional theory simulations. A clear description of the atomistic mechanisms ruling the graphene expansion process at the stepped regions of the substrate is provided, showing that different routes can be followed, depending on the height of the steps to be crossed. When a growing graphene flake reaches a monoatomic step, it extends jointly with the underlying Ni layer; for higher Ni edges, a different process, involving step retraction and graphene landing, becomes active. At step bunches, the latter mechanism leads to a peculiar ‘staircase formation’ behavior, where terraces of equal width form under the overgrowing graphene, driven by a balance in the energy cost between C–Ni bond formation and stress accumulation in the carbon layer. Our results represent a step towards bridging the material gap in searching new strategies and methods for the optimization of chemical vapor deposition graphene production on polycrystalline metal surfaces.

中文翻译：

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在多晶镍的步骤中石墨烯 CVD 生长的操作原子尺度研究

摘要 通过变温扫描隧道显微镜辅以密度泛函理论模拟，对多晶镍 (Ni) 表面 (100) 晶粒上的石墨烯生长进行了操作研究。提供了对控制基板阶梯区域石墨烯膨胀过程的原子机制的清晰描述，表明可以遵循不同的路线，具体取决于要跨越的台阶的高度。当生长的石墨烯薄片达到单原子步骤时，它与下面的 Ni 层共同延伸；对于更高的 Ni 边缘，一个不同的过程，包括阶梯回缩和石墨烯着陆，变得活跃。在阶梯束中，后一种机制导致一种特殊的“阶梯形成”行为，在过度生长的石墨烯下形成等宽的阶地，由碳层中 C-Ni 键形成和应力积累之间的能量成本平衡驱动。我们的结果代表了在寻找优化多晶金属表面化学气相沉积石墨烯生产的新策略和方法方面弥合材料差距的一步。