THE EFFECT OF ANNEALING AND IMPLANTATION TEMPERATURE ON THE STRUCTUREOF C ION-BEAM-IRRADIATED GLASSY-CARBON

Raman spectroscopy has been used to investigate the effects of dynamic and postimplantation annealing on glassy carbon implanted with 50 keV C ions to a dose of 5X10(16) ions/cm(2). The postimplantation anneali ng of damage in the ion-beam modified material was found to occur in t wo stages as a function of postimplantation annealing temperature T-a. These occur for 500<T-a<800 K and T-a>1300 K and correspond to the th ermal energy required to activate C interstitials and vacancies, respe ctively Once mobile these defects diffuse through the implanted layer, reducing bond angle disorder which leads to an increase in graphitic order as interstitial-vacancy recombination occurs, The effects of the ion-beam irradiation on the find structure of glassy carbon were foun d to be a strong function of the temperature of the sample during the irradiation, T-i. This dependence is interpreted in terms of dynamic a nnealing and radiation-enhanced diffusion. Three temperature regimes w ere found to be important. For T-i<300 K defect motion during irradiat ion is suppressed. For 300<T-i<600 K, the mobility of C interstitials during irradiation results in dynamic annealing which prevents amorphi zation, with the result that the ion irradiation creates a highly diso rdered, but essentially graphitically bonded carbon. For T-i>600 K, va cancy mobilities are sufficiently high such that most ion-beam-induced defects are dynamically annealed and, for T-i>800 K the unimplanted g lassy carbon microstructure is retained following the ion-beam irradia tion. Finally, activation energies for interstitial and vacancy mobili ties were determined and found to compare favorably with those found i n other forms of carbon. (C) 1995 American Institute of Physics.