ION-IMPLANTATION IN TETRAHEDRAL AMORPHOUS-CARBON

Tetrahedral amorphous carbon (ta-C) is a dense form of amorphous carbo n with a structure consisting of a highly tetrahedral bonding network. Approximately 20% of the atoms in ta-C are sp(2) hybridized and the p resence of these sites plays an important role in the electrical and o ptical properties of the material. In the present investigation, we us e 50 keV C+ and 200 keV Xe+ ion implantation to damage the structure i n a controlled manner. The structure of the ta-C following ion irradia tion is monitored using the dose dependence of the electrical conducti vity, Raman spectroscopy, electron diffraction, and electron energy-lo ss spectroscopy. It is shown that the damage is predominantly reflecte d in an increased concentration of sp(2)-bonded sites. With increasing dose, the structure is observed to change from an essentially tetrahe dral network containing sp(2) sites as ''defects'' to an essentially s p(2)-bonded structure in which there is a high degree of in-plane diso rder combined with a regular stacking of the planes.