High resolution photoemission study of the 6H-SiC/SiO2 interface

Core and valence band photo mission measurements with a spatial resolution of 150 mu m mere used to probe the SiO2/6H-SiC(0001) interface. To this end a thermally grown 100nm thick oxide was etched back in the form of a wedge with a slope of 65 Angstrom/mm down to the SiC substrate. From an analysis of the energies and intensities of Si2p and Cls core levels as a function of position on the sample a 22 Angstrom thick interface layer has been identified which consists of silicon suboxide (SiO1.5) interspersed in a carbon matrix. The ratio of C:Si is 3:1 in this interface layer. The valence band offset between 6H-SiC and SiO2 was determined to be 2.9(1) eV.