Igari Tomoya, Tsuruta Ryohei, Nishiyama Yuji, Adachi Manabu, Myojin Takuma, Asanagi Ken, Sasaki Masahiro, Kobayashi Nobuhiko, Yamada Yoichi
Institute of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan.
R&D Center for Innovative Material Characterization, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan.
Sci Rep. 2025 Jul 28;15(1):27456. doi: 10.1038/s41598-025-11895-x.
We demonstrated a stable and efficient field electron emission from vertically aligned graphene edges at the apex of the graphitized pencil lead (PL). We found that the electron emission pattern from PL observed with Field Emission Microscope (FEM) was dominated by the "dragonfly patterns" that are characteristic of the graphene edge, clearly suggesting the presence of the graphene edges with nearly vertical alignment at the apex of PL. A large enough emission current was found at the relatively small macroscopic electric field of several V/µm, showing the efficient field enhancement at each graphene flake. The energy spectrum of the emitted electron from PL was slightly broader than that of metals, reflecting the characteristic DOS shape of the π-bands of graphene, and this result is also supported by the recursion-transfer-matrix (RTM) simulations of field emission. A large amount of chemically stable emission sites due to graphene at the apex of PL leads to a large and stable emission current, which was also stable even at high-pressure environments up to 10 Pa of N. Therefore, the graphitized PL can be utilized as a low-cost electron emitter with high performance. At the same time, it can also be used for specimens for fundamental investigations of graphene edges.
我们展示了在石墨化铅笔芯（PL）顶端垂直排列的石墨烯边缘具有稳定且高效的场电子发射。我们发现，用场发射显微镜（FEM）观察到的PL的电子发射图案主要由石墨烯边缘特有的“蜻蜓图案”主导，这清楚地表明在PL顶端存在几乎垂直排列的石墨烯边缘。在几V/µm的相对较小宏观电场下发现了足够大的发射电流，这表明每个石墨烯薄片都有高效的场增强。从PL发射的电子的能谱比金属的能谱略宽，这反映了石墨烯π带的特征态密度形状，并且这个结果也得到了场发射的递归转移矩阵（RTM）模拟的支持。由于PL顶端的石墨烯而产生的大量化学稳定发射位点导致了大且稳定的发射电流，即使在高达10 Pa的氮气高压环境下该电流也很稳定。因此，石墨化的PL可以用作高性能的低成本电子发射器。同时，它也可用于石墨烯边缘基础研究的样本。
