Surface and Interface Studies of Si-Rich 4H-SiC and SiO<sub>2</sub>

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A photoemission study of Si-rich polar and nonpolar 4H-SiC surfaces before andafter initial oxidation are presented. Core level and valence band data recorded usingsynchrotron radiation are utilized to explore the properties of these surfaces and of theinterfaces.The Si-rich surfaces showed three prominent surface Si 2p components. These componentsare strongly attenuated upon oxygen exposures and can not be detected after an exposure of3000 L. After exposures of ≥200 L the number of oxidation states, i.e. Si+1, Si+2 and Si+4oxidation states, and also their shifts are found to be the same as after initial oxidation of thesame surfaces prepared by in situ heating.Only one sharp C 1s core level is observed on the Si-rich surfaces. This is quite differentcompared to earlier findings on the same surfaces prepared by in situ heating whereprominent surface shifted C 1s components are found. After oxygen exposure of ~ 200 L theC 1s peak is broadened and an asymmetry is observed on the high binding energy side. Thistogether with the Si 2p results show that oxygen exposures of ~200 L affect not only the Sioverlayers. Layers in the SiC substrate are also affected since the C 1s peak is broadened andthe Si 2p spectrum show the same oxidation states as after large exposures and after oxidationof these surfaces prepared without Si overlayers.