Oriented growth of diamond on metals and compounds

Diamond CVD on group VIII transition metals (Cr, Mn, Fe, Co, and Ni) has been investigated in search of relevant substrates for diamond heteroepitaxy. The material properties are listed in Table 9.1 [166]. See Appendix E for more information. These transition metals can dissolve carbon and hydrogen to form a surface layer of metal (M)-C-H complex. This seems to be common to many metal substrates, including Pt and Ir, as will be seen later. 

Material Crystal structure Lattice constant (at 20 °C, A) Melting point (°C) Thermal expansion coefficient at 20°C (X 10 % C) 

After the work of Zhu et al. [166], oriented growth of diamond on Ni(lOO) was studied extensively by Glass and Sitar s groups at North Carolina State University (NCSU), and a three-step process was established to suppress graphite formation by HFCVD [170-172]  

Step 1 (pretreatment)-. The method of seeding for diamond nucleation centers on Ni surface has been optimized as the research was developed. In Ref. [170], the Ni surface was scratched with diamond powder of 0.25 pm in size. In their successive experiments, instead of scratching, diamond powder was sprinkled on the 

Ni surface [171], Fullerene (Ceo) powder of 0-25 pm and graphite powder of 10-15 pm were also used [172]. In Refs. [173, 174], diamond powder of 0.5 pm in size, which was suspended in acetone, was apphed on the Ni surface. For heteroepitaxial growth of diamond on Ni, the seeding step is very important to make oriented diamond nuclei and suppress the graphitization of diamond simultaneously. 

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