Carbon structural transitions and ohmic contacts on 4H-SiC

The structural properties of sputtered carbon films on SiC are investigated using X-ray photoelectron spectroscopy (YPS) and Raman scattering. The as-deposited films are amorphous with an sp(2)/sp(3) ratio of 1. The sp(2) carbon structures gradually increase with increasing temperatures and consist of amorphous aromatic-like carbon, polyene-like carbon, and nano-size graphite flakes. Schottky contacts on carbon/SiC are converted to ohmic contacts after annealing. The concentration of nano-graphitic flakes relative to the aromatic-like and polyene-like carbon increases nearly linearly with annealing temperature. Stacked graphitic structures are not observed. The specific contact resistivities are at 10(-3)-10(-4)Omegacm(2) on the carbon/SiC after nnnealing from 1050degreesC to 1350degreesC.