Abstract
Graphite-related materials play an important role in various kinds of devices and catalysts. Controlling the properties of such materials is of great significance to widen the potential applications and improve the performance of such applications as field emission devices and catalyst for fuel cells. In particular, the work function strongly affects the performance, and thus development of methods to tune the work function widely is urgently required. Here, we achieved wide-range control of the work function of graphite by nitrogen and hydrogen plasma treatments. The time of hydrogen plasma treatment and the amount of nitrogen atoms doped beforehand could control the work function of graphite from 2.9 to 5.0 eV. The formation of a surface dipole layer and the nitrogen-derived electron donation contributed to such lowering of the work function, which is advantageous for applications in various fields.
Highlights
Two-dimensional materials consisting of sp[2] carbon atoms have been considered as promising materials for various applications such as transparent electrodes[1,2] and field emission devices.[3,4] Engineering of the structural and electronic properties of graphite sheets is essential for these applications, and controlling the work function of these materials has a great significance
We investigated the effect of plasma treatment on the work function of highly oriented pyrolytic graphite (HOPG)
The σ peak around the binding energy of 13.7 eV22 in pristine HOPG (p-HOPG) weakened after plasma treatment, reflecting the disorder induced in the honeycomb lattice
Summary
Two-dimensional materials consisting of sp[2] carbon atoms (e.g., graphite, graphene, and graphene oxide) have been considered as promising materials for various applications such as transparent electrodes[1,2] and field emission devices.[3,4] Engineering of the structural and electronic properties of graphite sheets is essential for these applications, and controlling the work function of these materials has a great significance. In the previous reports on graphite materials, a dipole layer was formed with Cs and O atoms on the graphene surface, which decreased the work function to 3.4 eV by solution process[17] and to 1.3 eV by vacuum evaporation.[18] the latter method drastically decreased the work function, the surface was unstable in the atmosphere. Another way to decrease the work function of carbon-based materials is by hydrogenation of the surface. The analysis by electron spectroscopies indicated that the electron donation from nitrogen atoms assisted the decrease of the work function of graphite in addition to the formation of the surface dipole layer
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