ION-BEAM MODIFICATION OF TETRAHEDRAL AMORPHOUS-CARBON - THE EFFECT OFIRRADIATION TEMPERATURE

The response of tetrahedral amorphous carbon to irradiation with 200 k eV Xe+ ion irradiation at various temperatures is reported. The struct ure of the tetrahedral amorphous carbon following ion irradiation is m onitored iu-situ by electrical resistance measurements, and ex-situ by Raman spectroscopy, electron energy loss spectroscopy and electron di ffraction. It is found that the irradiation temperature strongly influ ences the final state of the ion irradiated tetrahedral amorphous carb on. For irradiation at room temperature and below, the ion beam transf orms the material into a conducting amorphous carbon with an sp(2) fra ction of about 0.6. The effect of elevated irradiation temperatures is to increase the sp(2) fraction to about 0.8 at the highest doses and to increase the degree of ordering. The ordering is distinctive in tha t there is a high degree of in-plane disorder combined with a regular stacking of the sp(2) bonded planes, The effect of temperature on the ion beam induced transformation of tetrahedral amorphous carbon resemb les that for the ion beam transformation of diamond for which low temp erature irradiations produces a damaged amorphous structure, whereas f or high temperatures a graphitic material is produced. (C) 1997 Elsevi er Science S.A.