The effect of annealing and implantation temperature on the structure of C ion-beam-irradiated glassy carbon

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Abstract
Raman spectroscopy has been used to investigate the effects of dynamic and postimplantation annealing on glassy carbonimplanted with 50 keV C ions to a dose of 5×1016 ions/cm2. The postimplantation annealing of damage in the ion‐beam modified material was found to occur in two 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 thermal energy required to activate C interstitials and vacancies, respectively. 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 final structure of glassy carbon were found to be a strong function of the temperature of the sample during the irradiation,T i . This dependence is interpreted in terms of dynamic annealing and radiation‐enhanced diffusion. Three temperature regimes were found to be important. For T i <300 K defect motion during irradiation is suppressed. For 300<T i <600 K, the mobility of C interstitials during irradiation results in dynamic annealing which prevents amorphization, with the result that the ion irradiation creates a highly disordered, but essentially graphitically bonded carbon. For T i ≳600 K, vacancymobilities are sufficiently high such that most ion‐beam‐induced defects are dynamically annealed and, for T i ≳800 K the unimplanted glassy carbon microstructure is retained following the ion‐beam irradiation. Finally, activation energies for interstitial and vacancymobilities were determined and found to compare favorably with those found in other forms of carbon.

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