Development of edge state on graphite surface induced by Ar+ irradiation studied using near-edge X-ray absorption fine structure spectroscopy

作者：Kudo Yasuhiko; Kiguchi Manabu^*; Takashiro Jun ichi; Takai Kazuyuki; Enoki Toshiaki

来源：Carbon, 2014, 72: 152-159.

DOI：10.1016/j.carbon.2014.01.067

We have studied the electronic structure of the surface of graphite irradiated by Ar+ ions with various kinetic energies using in situ near-edge X-ray absorption fine structure spectroscopy in order to verify the appearance of an edge state over a macroscopic area and the variation of the edge state feature by severely damaging a sample. The disruption of the pi bonding network of graphite is manifested by the reduction of the intensity of the pi* peak upon Ar+ irradiation. The increase of the lower energy shoulder of the pi* peak can be clearly attributed to the edge state of pi-electron origin at vacancies. High energy Ar+ irradiation strongly induces an amorphous-like structure at the surface where carbon atoms have a random coordination. As a consequence, sp(3)-hybridized carbon atoms become involved in bonding, resulting in the mixing of pi and sigma states that then broadens the observed pi* peak. In addition, the reduction in concentration of pi electrons that screen core holes results in a blue shift of the central pi* peak energy. Moreover, the edge state, which is the signature of pi conjugation, survives even at the severely damaged Ar+ irradiated graphite surface having an amorphous-like structure.

• 出版日期2014-6