Ni Graphite Intercalated Compounds in Ohmic Contact Formation on SiC
Ohmic contacts on SiC have been investigated extensively in the past decade. However, the mechanism for ohmic contact formation has been a troublesome issue. The interfacial structures at the atomic scale responsible for forming ohmic contacts have not been revealed. Our previous results have shown that carbon can form ohmic contacts on SiC after thermal annealing, and that an interfacial carbon layer between Ni and the SiC improves the contacts significantly. In this study, we have investigated the interactions between Ni and carbon, and ohmic contact formation on SiC using x-ray diffraction (XRD) and Raman spectroscopy. After annealing, ohmic behavior was observed and Ni graphite intercalated compounds (GICs) were found on Ni/C/SiC structures. Unlike conventional graphite intercalated compounds, the Ni atoms substitute for carbon atoms in the graphitic networks in these Ni-GICs. XRD peaks at 21.6° due to the Ni graphitic intercalation compound (Ni-GIC) and at 26.3° due to graphite have been observed. The distance between graphitic sheets is 0.403nm in the Ni graphite intercalated compounds, whereas it is ~20% larger in the graphite. The thickness of the interfacial carbon layer does not affect the formation of Ni-GIC.
Robert P. Devaty, David J. Larkin and Stephen E. Saddow
W. J. Lu et al., "Ni Graphite Intercalated Compounds in Ohmic Contact Formation on SiC", Materials Science Forum, Vols. 527-529, pp. 863-866, 2006