High-resolution AES study of Ar+-irradiated graphite

High-resolution AES (HR-AES) has been used to study the electronic state of Ar+-irradiated graphite in which the increase in the partial charge density caused by the lattice damage has been indicated. At doses of <5 X 10(11) Ar+ cm(-2), which was reported as a maximum value to avoid the overlapping cascades, neither plasmon energies nor the work function in highly oriented pyrolytic graphite (HOPG) was changed. Increase in the work function was observed in Ar+-irradiated graphite with doses in the range of similar to1 X 10(13) to 1 x 10(15) ions cm(-2), and Ar+ at a dosage of 3 X 10(14) ions cm' increased the work function of HOPG by similar to0.2 eV. This implies an increase in the average electron density at the surface or an increase in the local electron density at a torn graphite edge. The pi plasmon energy was decreased by an irradiation of >1 X 10(14) Ar+ cm(-2) and the pi + sigma plasmon energy was decreased slightly at >1 X 10(15) Ar+ cm(-2). The difference in the two energy variations in the range of 1 X 10(14) to 1 x 10(15) Ar+ cm(-2) shows that the possibility of changes in the resonance energy and/or the lattice parameters is present if the pi/sigma electron ratio does not change. Copyright (C) 2003 John Wiley Sons, Ltd.