Subsurface nitrogen bonding, thermal stability, and retention of 200 eV N2+ implanted polycrystalline diamond studied by in situ X-ray photoelectron spectroscopy

Abstract

The properties of ultra-shallow nitrogen layers (<1 nm thick) in diamonds produced by very low energy (200 eV) N2+ implantation in polycrystalline diamond films at different doses (1.25×1014, 3.50×1014, 7.85×1014, 1.30×1015 and 9×1015 ions·cm−2), followed by thermal annealing, are investigated by in situ X-ray photoelectron spectroscopy. Spectral analyses of C(1s) and N(1s) peaks reveal that a chemical effect occurs depending on nitrogen local concentration and annealing temperature. Nitrogen exists in a predominant CN/C–N bonding configuration, followed by minor contributions of C≡N and quaternary-N configurations. Annealing (300–1000 °C) imparts complex effects that depend on local nitrogen concentration and bonding. The onset of nitrogen thermal desorption increases with ion dose: 300 °C for 1.25×1014 and 3.50×1014, 400 °C for 7.85×1014, and ∼650 °C for 1.30×1015 and 9×1015 ions·cm−2. Upon annealing to 1000 °C, the remaining nitrogen concentration in the diamond subsurface region increases with ion dose. The CN/C–N configuration was more thermally stable than the C≡N, while the quaternary-N is constant with annealing temperature. The nitrogen ion retention probability increased for 1.25×1014 and 3.50×1014 and decreased for the higher doses due to recombination-assisted desorption. This study may have important implications for stabilizing near-surface NV- centers for quantum sensing applications.