| The effect of substrate surface conditions on the growth of a Ni graphite intercalation compound (Ni-GIC) by the method of Ni deposition onto SiC followed by high vacuum annealing was examined. Single crystal 6H-SiC(0001) substrates were prepared with an ambient oxide layer, a thermally induced 3 x 3 reconstructed surface, and a pristine surface (no oxide, bulk 1 x 1 surface ordering). Ni films approximately 7 nm thick were deposited onto the SiC substrates at 600°C under ultrahigh-vacuum, and then annealed to between 800°C and 900°C. After annealing, ex situ analysis using atomic force microscopy (AFM), scanning electron microscopy (SEM), and x-ray diffraction powder and texture scan analysis showed Ni-GIC islands readily formed on the pristine surface. There were indications Ni-GIC formation occurred to a lesser extent on the oxidized surface but this could not be confirmed. And finally, no evidence of Ni-GIC formation was present on the reconstructed surface. Examination of nickel silicide formation showed Ni-GIC growth was accompanied by an increase in the presence of Ni2Si relative to Ni32Si12. The nickel silicide phase formation/transformation may therefore play a role in the Ni-GIC growth mechanism, however this was not confirmed. The only previous observation of pure Ni-GIC formation reported growth of GIC islands approximately 300 nm across, 30 nm high and separated by 5 mum from each other. In this study, Ni-GIC islands nearly 1 mum across, 60 nm high and with approximately 40% substrate surface area coverage has been achieved. Finally, this study reports the first ever observation by x-ray diffraction of the Ni-GIC structure. |
