标题： 少层石墨烯在SiC(0001)上的电荷溢出和功函数 显示英文标题

标题： Charge spill-out and work function of few-layer graphene on SiC(0001)

摘要： 我们报告了在6H-SiC(0001)上外延的少层石墨烯的电荷溢出和功函数。高分辨率、能量过滤的X射线光电子发射显微镜（XPEEM）实验与使用弛豫界面模型的第一性原理密度泛函理论计算相结合。理论和实验得到的功函数值定性一致，再现了之前观察到的随着每个额外石墨烯层增加而功函数增加的趋势。通过缓冲层在SiC/石墨烯界面发生的电子转移导致界面偶极矩，这是石墨烯功函数调制的起因。总的电荷转移与石墨烯层的数量无关，并且与XPEEM测量的C 1s核心能级中SiC组分的恒定结合能一致。进入真空的电荷泄漏取决于石墨烯层的数量，这解释了为什么实验测得的层依赖性C 1s-石墨烯核心能级结合能位移并不严格遵循功函数的变化。因此，SiC/石墨烯界面的电荷转移和电荷溢出到真空的组合解决了实验测得的功函数与C 1s结合能之间的明显差异。 显示英文摘要

摘要： We report on the charge spill-out and work function of epitaxial few-layer graphene on 6H-SiC(0001). Experiments from high-resolution, energy-filtered X-ray photoelectron emission microscopy (XPEEM) are combined with ab initio Density Functional Theory calculations using a relaxed interface model. Work function values obtained from theory and experiments are in qualitative agreement, reproducing the previously observed trend of increasing work function with each additional graphene plane. Electrons transfer at the SiC/graphene interface through a buffer layer causes an interface dipole moment which is at the origin of the graphene work function modulation. The total charge transfer is independent of the number of graphene layers, and is consistent with the constant binding energy of the SiC component of the C 1s core-level measured by XPEEM. Charge leakage into vacuum depends on the number of graphene layers explaining why the experimental, layer-dependent C 1s-graphene core-level binding energy shift does not rigidly follow that of the work function. Thus, a combination of charge transfer at the SiC/graphene interface and charge spill-out into vacuum resolves the apparent discrepancy between the experimental work function and C1s binding energy.