Subsurface nitrogen bonding and thermal stability of low-energy nitrogen implanted H-Diamond (100) surfaces studied by XPS and HREELS

Abstract

We investigate the surface/subsurface bonding, retention, and thermal stability of nitrogen in H-Diamond (100) implanted with 200 eV N2+ at a dose of 1×1014 ions/cm2 (D1) in comparison to a dose of 3-4×1014 ions/cm2 (D2) and to nitrogen adsorbed on the surface (by MW(N2) exposure) by electron spectroscopy. For D1, the N(1s) XP line displays a single symmetric peak associated with C‒N/C=N species, concurrently observing a minor C=C/C(def) component in C(1s). The N(1s) line intensity decreases linearly with annealing temperature without changes in line shape. This could be due to competition of diffusion of trapped nitrogen from interstitial positions followed by desorption and recombination of the implanted nitrogen with carbon vacancies, resulting in very thermally stable nitrogen species. The latter process is dominant at ∼700 °C where the onset of vacancies diffusion in diamond occurs. For D2, an additional component associated with CN(nitrile-like) bonds is observed. From vibrational spectroscopy, the H-Diamond surface implanted with a D1 dose displays features associated with nitrogen bonding to carbon atoms and hydrogen bonding to the diamond surface and defects. Unlike the MW(N2) plasma case, no NHx(ads) bonds are identified upon implantation. High-temperature annealing shows that for the D1 dose, partial surface structural recovery occurs.