Photoemission study of clean and oxidized nonpolar 4H-SiC surfaces
2003 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, Vol. 68, no 12Article in journal (Refereed) Published
The results of a photoemission study of clean and oxidized nonpolar (10 (1) over bar0) and (11 (2) over bar0) surfaces of 4H-SiC crystals are reported. For the clean surfaces prominent surface shifted components are revealed in the C 1s spectra, although with different relative strengths for the two surfaces. In the Si 2p spectra only one weak surface related feature is observed. These observations suggest carbon enrichment on both surfaces. Valence band spectra show a semiconducting behavior for both surfaces but also distinct differences. The lower lying subband, originating mainly from C 2s states, is for example found to be considerably weaker on the (10 (1) over bar0) than on the (11 (2) over bar0) surface. Observed differences are suggested to originate from differences in surface carbon arrangement and bonding. It is concluded, from the absence of a graphitelike C 1s peak, that the clean surfaces are not graphitized. The effects induced in the core levels and valence bands upon initial oxidation were investigated. The surfaces were oxidized gradually from 1 to 10(6) L while keeping the substrate at a temperature of 800 degreesC. Recorded Si 2p spectra show three oxidation states for both surfaces, and these are interpreted to originate from Si+1, Si+2, and Si+4, respectively. This is quite different compared to earlier results for the polar surfaces where only Si+4 and one suboxide were revealed on each surface. It is concluded that the Si+4 oxide (SiO2) grow as a layer on top of the Si+1 and Si+2 suboxides that are located at the interface. The surface/interface related carbon is found to decrease dramatically, but not to be totally eliminated, after the large oxygen exposures made.
Place, publisher, year, edition, pages
2003. Vol. 68, no 12
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-47751DOI: 10.1103/PhysRevB.68.125314OAI: oai:DiVA.org:liu-47751DiVA: diva2:268647