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

The properties of ultra-shallow nitrogen layers (<1 nm thick) in diamonds produced by very low energy (200 eV) N-2(+) implantation in polycrystalline diamond films at different doses (1.25x10(14), 3.50x10(14), 7.85x10(14), 1.30x10(15) and 9x10(15) ions<middle dot>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 Cdbnd N/C-N bonding configuration, followed by minor contributions of C equivalent to N and quaternary-N configurations. Annealing (300-1000 degrees C) imparts complex effects that depend on local nitrogen concentration and bonding. The onset of nitrogen thermal desorption increases with ion dose: 300 degrees C for 1.25x10(14) and 3.50x10(14), 400 degrees C for 7.85x10(14), and similar to 650 degrees C for 1.30x10(15) and 9x10(15) ions<middle dot>cm(-2). Upon annealing to 1000 degrees C, the remaining nitrogen concentration in the diamond subsurface region increases with ion dose. The Cdbnd N/C-N configuration was more thermally stable than the C equivalent to N, while the quaternary-N is constant with annealing temperature. The nitrogen ion retention probability increased for 1.25x10(14) and 3.50x10(14) 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.