FT-IR studies of graphite after keV-energy hydrogen ion irradiation

Fourier-transform infrared absorption spectroscopy (FT-IR) studies were made on vapor-grown carbon fiber (VGCF) after successive irradiations of 6, 3 and 1 keV-H+ to saturation at 373-923 K, and after the irradiations at 623 K followed by a heat-treatment at 893-1150 K. Reference hydrocarbons, cholesterol (C27H45OH) and menthol (C10H19OH), were also measured for C-H stretch band frequencies and relative integrated intensity factors, kappa(-CHx). For the irradiated VGCF, a band was found to be centered at 2892 cm(-1), in between a -CH3 symmetric (2873 cm(-1)) and a >CH2 asymmetric (2924 cm(-1)) stretch band, which was assigned to a >CH- stretch band. Relative densities of the CH, groups, assuming kappa(=CH-): kappa(-CH3): kappa(>CH2): kappa(>CH-) =0.12:2.2:1.1:1.0, showed that >CH2 decreases in density with increasing the irradiation temperature beyond 1000 K, while >CH- reaches maximum at around 823 K and then decreases. The -CH3 group decreases to a minimum from 623 to 823 K, and increases at above 823 K, indicating that methane forms at around 800 K through abstraction of H from >CH- by free CH3. The density ratio of >CH- to >CH2 reached a maximum at 0.4 at around 800 K, indicating that, in the keV-H+ implantation layer, the implanted H atoms are trapped mainly at >CH2, and subsidiarily at >CH-, and -CH3, at defects, below 900 K. (C) 1999 Elsevier Science B.V. All rights reserved.