Structure and Electrochemical Properties of Carbon Films Prepared by a Electron Cyclotron Resonance Sputtering Method

摘要

This paper describes the characterization, electrochemical properties, and applications of carbon films prepared by the electron cyclotron resonance (ECR) sputtering method. The ECR-sputtered carbon film was deposited within several minutes at room temperature. The optimized sputtering conditions significantly change the film structure, which includes many more sp~(3) bonds (sp~(3)/sp~(2) velence 0.702) than previously reported film (sp~(3)/sp~(2) velence 0.274)~(1) with an extremely flat surface (0.7 A). The ECR-sputtered carbon films exhibit excellent electrochemical properties. For example, they have nearly the same potential window in the positive direction as that of high-quality, borondoped diamond (moderately doped, 10~(19)-10~(20) boron atoms/cm~(3))~(2) and an even wider potential window in the negative direction with a low background current, high stability, and suppression of fouling by electroactive species without pretreatment. The electron-transfer rates at ECR-sputtered carbon films are similar to those of glassy carbon (GC) for Ru(NH_(3))_(6)~(2+/3+) and Fe(CN)_(6)~(3-/4-), whereas they are much slower than those of GC for Fe~(2+/3+), dopamine oxidation, and O_(2) reduction due to weak interactions between electroactive species and the ECR-sputtered carbon film surface. Such a response can be attributed to the ultraflat surface and low surface O/C ratios of ECR-sputtered carbon films. ECR-sputtered carbon film is advantageous for measuring biochemicals with high oxidation potentials because of its wide potential window and high stability. Highly reproducible and well-defined cyclic voltammograms were obtained for histamine and azide ions with a peak potential at 1.25 and 1.12 V vs Ag/AgCl, respectively. The film is very stable for continuous voltammetry measurements in 10 (mu)M bisphenol A, which usually fouls the electrode surface with oxidation products.