The role of hydrogen in nitrogen-containing diamondlike films studied by photoelectron spectroscopy

Abstract

The influence of H on the local structure of N-containing amorphous diamondlike films $\mathrm{(a-}{\mathrm{CN}}_x:\mathrm{H})$ is reported. The samples were prepared by rf sputtering of graphite in a ${\mathrm{N}}_{\mathrm{2}},$ Ar, and ${\mathrm{H}}_{\mathrm{2}}$ atmosphere. The chemical bonding of C and N atoms was inferred by analyzing the $\mathrm{C\hspace{0.17em}1}s$ and $\mathrm{N\hspace{0.17em}1}s$ electronic core-level by x-ray photoelectron spectroscopy. Hydrogen free films present $\mathrm{N\hspace{0.17em}1}s$ peaks with a “doublet”, located at 398.2–400.5 eV. When H is introduced in the preparation chamber, the doublet evolves to a single wider band located at 399.1 eV. This new band becomes dominant when increasing ${\mathrm{H}}_{\mathrm{2}}$ partial pressure, completely hiding the original structure. High ${\mathrm{H}}_{\mathrm{2}}$ partial pressure interrupts the growing network formed by N and C due to the attachment of H to N and/or C. Furthermore, the experimental results suggest that the possibility of formation of the ${\mathrm{C}}_{\mathrm{3}}{\mathrm{N}}_{\mathrm{4}}$ phaselike is inhibited by the presence of hydrogen.