Hydrogen Treatment Effects of a-C Films for C60/a-C Superlattice Solar Cells

The film quality improvement of amorphous carbon (a-C) layers for C₆₀/a-C superlattice solar cells has been intended. a-C:N films were deposited by C₆₀-cage breaking, and the layer-by-layer hydrogen treatment method was applied to the a-C:N films for the improvement of the film quality, and the structural change by the hydrogen treatment was investigated. Hydrogen radicals reconstruct carbon bonding structure of a-C:N film surface by etching the weak carbon bonds. Such structural change causes reducing the optical gap and changing the peak intensity ratio of Raman scattering spectra, which is concerned with sp² cluster size. The spin defect density much depends on the hydrogen treatment time. It is clear that the spin defect density has minimum at the particular time of the hydrogen treatment, so that hydrogen radicals also affect to cut the carbon bonds and induce defects. It is necessary to optimize hydrogen treatment time to improve film quality