RAMAN INVESTIGATION ON THIN-FILM ELECTRODES OF A-C-LI

Amorphous carbon films, deposited via radio frequency magnetron sputte ring, have been electrochemically intercalated with lithium to study t heir possible application as anodes for rechargeable Li microbatteries . Various concentrations of intercalated lithium have been obtained by using galvanostatic and potentiostatic methods. After preliminary exa minations by optical microscopy and by optical absorption measurement, a comparative Raman spectroscopy characterization of the films has be en performed with excitation wavelengths ranging from 676.4 to 457.9 n m, to follow resonance effects. A study is made on the Raman spectral shape and its excitation wavelength dependence for the film samples wi th different Li concentrations. A moderate graphitization process of a -C films after intercalation results from this analysis, The Raman spe ctral changes induced by Li insertion iio not reverse after further de intercalation cycles, and this fact is discussed in connection to the observed electrochemical reversibility of the a-C:Li electrodes. (C) 1 996 American Institute of Physics.