Control of Chemical Bonding and Surface Modification of Nitrogen-Implanted Glassy Carbon by Doping of Different Kinds of Elements

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1. In this work, I have characterized Si doped carbon nitride layer formed by N implantation to investigate effects of Si doping on the chemical bonding in the nitride layer. It is found that the carbon nitride layer with Si concentration of 5-8 at. % is amorphous and has predominantly an sp^2 bonded carbon structure with a small amount of C≡N bonds. The examination of chemical shifts in XPS spectra suggests the existence of local C=N-Si(C_nN_<3-n>) arrangements in the nitride layer in Si-preimplanted GC. The formation of the C=N-Si(C_nN_<3-n>) structures in the carbon nitride layer increases the number of possible bonding sites for N atoms and may result in the higher saturation level for the implanted N atoms ; the N concentration in the nitride layer increased from 26 at. % to 35 at. % by the Si-preimplantation. In addition, Si atoms in the nitride layer play a role in the prevention of oxygen incorporation during N implantation, although the mechanism is not yet known.2. It was demonstrated that the hydrogen doping (〜30 at. %) was an effective method to obtain a smooth surface of N-implanted GC. A part of the doped hydrogen atoms is released by N implantation, but hydrogen incorporation occurs simultaneously. Consequently, concentration of hydrogen in the N-implanted layer exceeds 20 at. % at any N implantation doses. XPS and Raman analysis reveals that chemical bonding in the N-implanted layer for the D-doped GC is quite similar to that for the undoped, GC, but the size of graphitic layers containing N atoms is different. The smaller size of the graphitic layers can relax the strain introduced at polishing scratches, which may maintain the surface smooth.