Diamond-Metal Adhesion Enhancement

The poor adhesion of diamond films to metal substrates has been a long-standing issue that prevents practical applications of the excellent properties of synthetic diamond. Analysis [97] of Ni surface chemisorption indicated that the C-Ni(OOl) bond experiences strong compression and the surface is covered with Ni and Ni , while the N-Ni(OOl) bond undergoes slight tension and the surface comprises Ni and Ni P alternatives. XRD measurement [15] has confirmed the prediction that carbon turns the tensile stress of Ti surface to be compressive. Comparison of the surface morphology of TiC with that of TiN indicates that the surface stresses are different in nature [98]. 

The success of this approach evidences that the extension of the sp hybrid bonding of oxygen to carbon and nitrogen is on an essentially correct track. The sp hybrid bonding of nitrogen helps to understand why it is more difihcult to form the crystalline carbon nitride than the hexagonal SiCN crystallite [99] and that overdose ( 75 % partial pressure) of nitrogen in diamond deposition could turn the diamond to SiCN [100]. 

---

N creates tensile but C compressive stress at a surface. A combination of both enhances diamond—metal adhesion. 

---