The effect of temperature on the structure of amorphous hydrogenated carbon

The results of a neutron diffraction study on the structure of amorphous hydrogenated carbon a-C:H are presented up to a maximum temperature of 1000 °C. The data show clearly the effect on atomic correlations of elevated temperatures, with the initial room-temperature amorphous network (a mixture of single bonds and olefinic double bonds) becoming progressively aromatic, then graphitic as hydrogen is evolved. Complementary x-ray diffraction and infrared spectroscopy data are also presented, the infrared data enabling a more detailed discussion of the temperature-dependent hydrogen environment, and the x-ray data are used to highlight the change in the carbon network. Comparisons have been made with previous work on similar systems and a brief summary of these results is given.