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This study reports on the influence of nitrogen plasma exposure of H‐diamond (100) on the adsorption of adventitious oxygen, nitrogen bonding, and thermal stability studied by X‐ray photoelectron spectroscopy. The nitrogen‐plasma exposures include microwave (MW) and radio frequency (RF) (at pressures: 3 × 10−2 (damaging) and 7 × 10−2 Torr (nondamaging)) nitrogen plasmas. The largest amount of oxygen ambient adsorption occurs on the damaging RF(N2) (O = 2.8 at%) exposed surface, whereas for MW(N2) (O = 0.8 at%) and nondamaging RF(N2) (O = 1.3 at%) exposed surfaces, a lower oxygen concentration is observed. Also, the highest level of structural damage to the upper atomic layers of the diamond is induced by exposure to the damaging RF(N2), followed by nondamaging RF(N2) and MW(N2). Thus, the near‐surface damage induced by the plasma interaction promotes adventitious oxygen adsorption (in various bonding configurations, including COx and C–NOx). For ambient‐exposed MW(N2)‐processed surface, nitrogen is adsorbed mainly in C–N/C=N state. Whereas for ambient‐exposed nondamaging‐ and damaging RF(N2)‐treated surfaces, nitrogen is bonded in mixed C–N/C=N and C≡N states alongside a small C–NOx component depending on the degree of surface defects. The damaging RF(N2)‐exposed surface exhibits a lower oxygen and nitrogen thermal stability than the other cases. [ABSTRACT FROM AUTHOR]

[Display omitted] • A model for energy-dependent XPS for depth profiling of chemical bonding. • N-Terminated diamonds obtained by Microwave Plasma show no sp2 defects. • A ∼5 % coverage of graphene-like islands is present atop the diamond surface. • The energy level of N surface states is determined within the diamond bandgap. • The high energy of the unoccupied surface states could help to stabilize NV- centers. Nitrogen-terminated diamonds hold promise for stabilizing near-surface NV− centers, which is essential for reliable quantum sensing. Among various surface preparation methods, microwave (MW) nitrogen plasma, known for its minimal surface damage, appears as the most effective choice. In this investigation, we explore the nature of nitrogen bonding of polycrystalline diamond (PCD) surfaces exposed to MW nitrogen plasma using X-ray Photoelectron Spectroscopy (XPS) depth profiling and Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy at the C K - and N K -edges. XPS depth profiling with atomic resolution, achieved by varying the probing photon energy using synchrotron radiation and supported by a physical model considering the associated inelastic mean free path, suggests a surface of almost fully saturated nitrogen in two main bonding configurations of similar contribution and a low coverage of ∼5 % of graphene-like islands residing atop the nitrogen-terminated diamond surface. The thermal stability of these surface groups is monitored by in situ annealing up to 700 °C. The depth profiles reveal that nitrogen atoms do not diffuse in the diamond crystal, resulting in excellent diamond crystallinity in the first atomic planes below the surface. C K -edge NEXAFS analysis reveals the position of unoccupied surface states within the diamond bandgap, opening new perspective on the stabilization of near-surface NV− centers. [ABSTRACT FROM AUTHOR]

• Nitrogen exists in a single bonding configuration associated to C‒N/C=N. • N desorption may occur by interstitial and/or vacancy-assisted diffusion. • No NH x (ads) species populated upon implantation in contrast to MW(N 2) exposure. • Partial surface structural recovery occurs. We investigate the surface/subsurface bonding, retention, and thermal stability of nitrogen in H-Diamond (100) implanted with 200 eV N 2 + 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(N 2) 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 C N(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(N 2) plasma case, no NH x (ads) bonds are identified upon implantation. High-temperature annealing shows that for the D1 dose, partial surface structural recovery occurs. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Ar entrapped in a local high crystalline diamond environment possesses a very high thermal stability. • Ar thermal desorption occurs via diffusion between local defects, greatly enhanced between 600 and 700 °C. • Implantation at 400 °C results in two distinct regions: graphitic and diamond. • Retained amount of Ar upon 700 eV implantation at RT is about 100 times lower than that upon 5000 eV. • Ar entrapped in a high crystalline diamond matrix is under higher compressive stress than in graphitic/amorphous carbon. The retention and thermal stability of Ar implanted into polycrystalline diamond surfaces with 700 and 5000 eV Ar ions, with high dose (HD) and low dose (LD) of 1016 and 1014 ions/cm2 at room temperature (RT) and 400 °C were investigated. Upon implantation at 400 °C, the thermal stability of the retained Ar is very high and can exceed 1000 °C, whereas, upon RT implantation at the same energy, it is below ∼800 °C. Ar entrapped in a local high crystalline diamond environment possesses a very high thermal stability compared to when it is entrapped in a graphite/amorphous local carbon environment. Ar thermal desorption occurs via diffusion between local defects, greatly enhanced between 600 and 700 °C. Implantation at 400 °C (at HD) results in two distinct regions: graphitic and highly crystalline diamond with low defect density due to dynamic annealing and direct desorption of Ar entrapped within the graphitic/damaged region during the implantation. Ar entrapped in a high crystalline diamond matrix is under higher compressive stress than in graphitic/amorphous carbon. [ABSTRACT FROM AUTHOR]

[Display omitted] • Annealing of highly-damaged surfaces promotes nitrogen incorporation into graphitic sites. • Surface damage enhances hydrogen incorporation into the N delta layer. • Etching of the disordered layer occurs during the initial stages of diamond overgrowth. • NRR efficiency depends on the crystallinity of the nitrogen terminated surface and bonding. We investigate the influence of surface chemical and structural properties of initial nitrogen terminated diamond surfaces on the nitrogen and hydrogen distribution in the N delta layers fabricated onto diamond (100) surfaces by different surface nitridation methods followed by a diamond layer overgrowth. Surface analysis shows that annealing of highly-damaged surfaces results in graphitization and promotes nitrogen incorporation into graphitic sites whereas lower damaged surfaces result in recovery of the near surface diamond structure alongside with nitrogen bonded mostly in a single configuration. Surface damage enhances hydrogen incorporation into the N delta layer. The etching of the disordered layer (formed during the nitrogen termination) occurs during the initial stages of diamond over growth. The nitrogen retention ratio efficiency in the delta layer depends on the crystallinity of the nitrogen terminated surface and bonding: is higher when nitrogen is bonded in the sub-surface region. Hydrogen diffusion into the N delta layer occurs following the nitrogen distribution most likely bonding to nitrogen and defects. At optimal conditions, the FWHM of N delta layer in diamond (100) is ~3 nm with a maximum nitrogen and hydrogen concentration of ~1.2×1020 atoms.cm−3 and ~2.0×1021 atoms.cm−3, respectively. The overgrown layers possess high crystallinity. [ABSTRACT FROM AUTHOR]

• Developed N-diamond (111) surface with little or no defects by RF(N2) plasma exposure. • N-diamond (111) shows (1 × 1) low-energy electron diffraction pattern. • Thermal stability of non-damaged N-diamond is lower than 700°C. • •Nitrogen coverage on N-diamond (111) is less than that of N-diamond (100). Nitrogen terminated diamond (111) (N-diamond) is suggested to have benefits to near-surface negative nitrogen vacancy (NV−) centers in diamond. To this end, better understanding of defects formation and nitrogen bonding on N-diamond (111) is important. However, there are no studies of N-diamond (111) surface. In this study, we report preparation of N-diamond (111) surface, and evaluation of its thermal stability, chemical states and structural properties. The N-diamond was produced by exposing diamond (111) to radio frequency (RF) nitrogen plasma at two different conditions expected to result in different levels of near surface damage due to the interaction of the activated nitrogen with the diamond surface. X-ray photoelectron spectroscopy (XPS) shows that the amount of incorporated nitrogen on diamond (111) surface differs for these two plasma conditions and is lower than obtained on diamond (100) for the same exposure conditions. Moreover, the thermal stability of nitrogen on non-damaged N-diamond is lower than 700°C as determined by low energy electron diffraction and XPS. The N-diamond (111) surface prepared by non-damaging plasma conditions exhibits a low defects density and well-defined structure, which may pave the way to control the shallow NV− charge state and magnetic spin properties in the near surface region of (111) oriented diamond. Image, graphical abstract [ABSTRACT FROM AUTHOR]