Contamination of Si surfaces in ultrahigh vacuum and formation of SiC islands

The long-term contamination and carbonization of Si(1 1 1) surfaces in ultr ahigh vacuum (UHV) was investigated by high-resolution electron-energy loss spectroscopy (HREELS), Auger electron spectroscopy (AES), and scanning tun neling microscopy (STM). HREELS measurements show that O-2, carbon-containi ng molecules, H, and OH-containing molecules of the residual gases in UHV g radually absorb on Si surfaces. After 6 days' absorption of residual gases, AES measurements indicate that the coverage of carbon and oxygen on a Si s urface increased up to 18 and 12%, respectively. When the surface is covere d by residual gases in UHV and then flashed to 1250 degreesC for a few time s, islands of SiC are epitaxially grown on the Si(1 1 1)-(7 x 7) surface. H ighly oriented SiC islands in the shape of equilateral triangles are observ ed by STM. The carbonized Si surface in UHV is flat on the atomic scale thr oughout the whole surface. Carbonization of a Si surface in UHV may be an e ffective way to form a perfect interface between epitaxial SiC thin films a nd the Si(I 1 1) substrates. (C) 2001 Elsevier Science B.V. All rights rese rved.