Transparent carbon film prepared by mass-separated negative-carbon-ion-beam deposition

Abstract

A carbon film was deposited by mass-separated negative-carbon-ion-beam deposition in the energy range of 25–1000 eV. The carbon film deposited by a C− ion beam was optically transparent (the maximum optical gap was 0.96 eV) and served as an electrical insulator (the maximum electrical resistivity was 1.5×108 Ω cm). The film property strongly depended on the ion-beam energy for deposition and, the film obtained at the deposition energy of 115–215 eV was the most transparent and the best insulator. Its atomic density was also the highest and was almost the same as that of diamond. The carbon film deposited at room temperature was amorphous and showed no IR absorption. On the other hand, the film deposited at a substrate temperature of 800 °C showed graphitelike rings in reflection high-energy electron-diffraction patterns and an IR absorption such as graphite. Its electrical resistivity was much lower. The property of the film deposited by a C−2 ion beam was more strongly dependent on the ion-beam energy than that of the film deposited by the C− ion beam (the maximum optical gap was 1.44 eV, and the maximum electrical resistivity 1.8×1010 Ω cm). The surface of the film deposited by the C− or the C−2 ion beam was smooth and chemically inert.