סמינר כימיה פיסיקלית ואנליטית: Interaction of low-energy nitrogen ions with diamond surfaces
November 29nd
חדר סמינרים
15:30
Miri Fischer Horowitz Supervisor: Prof. Alon Hoffman
Interaction of low-energy nitrogen ions with diamond surfaces
Miri Fischer Horowitz
Supervisor: Prof. Alon Hoffman
The interaction of nitrogen with diamond surfaces is interesting from a scientific perspective as well due to its importance in the bio-functionalization of diamond surfaces and emerging quantum technologies like quantum information processing. In particular, nitrogen-associated color centers in diamond, NV‒, are very attractive as a single photon source at room temperature and when localized in the near-surface region, they may be potentially utilized for quantum sensing applications.
The population of near-surface NV‒ centers in diamond is strongly affected by the chemical composition of the surface and structural defects. Structural defects may result in preferred centers for charge trapping resulting in the destabilization of NV‒ in the near-surface region.
The incorporation of nitrogen in the near-surface region of diamond with minimal defects for the formation of NV‒ centers can be achieved by low energy ion implantation in the sub-keV range. Therefore, the aim of this work is to investigate the fundamental interaction of low-energy nitrogen ion beam with the diamond surface, near-surface and subsurface regions and their properties.
Modification of the diamond surface as a result of the interaction of nitrogen with the diamond surface can be by a physical process associated with structural damage and by a chemical process associated with the reactivity of the activated nitrogen with the diamond lattice. Therefore, to examine the physical effects, first, the interaction of chemically inert Ar+ ions (700 and 5000 eV) with diamond was investigated. The results are very surprising. Based on SRIM modeling, the implanted Ar and defects distributions do not fully overlap within the modified diamond volume. Therefore, Ar can be incorporated into different local carbon phases (sp3 and sp2) with distinct properties depending on implantation energy, ion dose and substrate temperature. For hot implantation, Ar entrapped in a local high crystalline diamond environment possesses a very high thermal stability.
The chemical processes associated with nitrogen ion implantation are investigated by studying the sub-surface bonding, retention and thermal stability of nitrogen in polycrystalline diamond implanted with low energy (200, 500 and 800 eV) N2+ at room temperature (RT) and 600 °C at an ion dose of 3.4×1014 ions/cm2. The same element, nitrogen, in a particular bonding configuration in the diamond acts as an NV‒ source, whereas a properly nitrogen-terminated diamond surface enhances the population of NV centers in the near surface region of diamond. It is believed that the optimal energy for NV center formation is achieved when there are sufficient vacancies to create NV centers, but not too many, to maintain the diamond structure, which would likely occur at an intermediate energy of 500 eV at 600 °C. Considering the very low ion energy and dose applied in the present work, 200 eV N2+, no physical damage to diamond by the implantation is expected as the ion energy is not sufficient to displace the carbon atom in the diamond structure. Interestingly, it is observed that sp2 partially hybridized carbon is formed near the incorporated nitrogen, which is attributed to a chemical effect rather than a physical effect of the implantation process. Due to this, enhancement of shallow NV centers through termination by very low nitrogen implantation should take into consideration the chemical effect, which is probably less significant at a very low dose of up to 5×1013 ions/cm2.