Electrochemical properties of graphitized carbonaceous thin films prepared by PACVD

Graphitized carbonaceous thin-film electrodes were prepared by plasma-assisted chemical vapor deposition (PACVD). X-ray diffraction and Raman spectroscopy showed that while the bulk of the film was highly crystallized, its surface was less crystallized, indicating that this surface-modified graphitized thin-film electrode was obtained by a single process. The structures of the surface and bulk of the thin film are influenced by applied radio frequency (rf) powers: the crystallinity of the surface increased with increasing applied rf power, while the crystallinity of the interior bulk decreased with increasing applied rf power. The electrochemical properties of the obtained films were studied in electrolyte consisting of propylene carbonate or ethylene carbonate and diethyl carbonate (1:1 by volume) containing 1 mol dm(-3) LiClO4 by cyclic voltammetry and ac impedance spectroscopy. Because the crystallinity of the surface is low, nearly identical electrochemical properties were seen regardless of the electrolytes used, although the bulk structure is highly graphitized. AC impedance spectroscopy showed that charge transfer resistance decreased with decreasing applied rf power, which suggests that highly graphitized carbonaceous thin films with a less-crystallized surface should be ideal electrodes for the fabrication of thin-film batteries. (C) 2004 The Electrochemical Society.