[6] Effect of hydrogen on carbon diffusion on Ni(111)

In the chemical vapor deposition process for carbon nanotube growth using catalytic particles, many carbon atoms as well as hydrogen atoms coexist on actual surfaces of catalysts and their mutual interaction may change the adsorption and diffusion properties of carbon atoms. To investigate the effect of hydrogen on carbon diffusion on the Ni(111) surface we have performed pseudopotential density-functional calculations. The diffusion barriers of CH_x (x=1, 2, 3) on Ni(111) are obtained and compared with that of a single carbon atom. The diffusion barrier decreases with the presence of attached hydrogens, which implies that such adsorbates with more hydrogen are likely to diffuse more easily.