抄録
In this article, we detail the development and application of reflection high-energy positron diffraction (RHEPD). A fine positron beam with a coherence length of approximately 170 Å was obtained by the electrostatic lens system. The beam quality is good enough to observe the RHEPD patterns from a clean Si(111)7×7 and SiC(0001) surfaces. The rocking curve associated with the Si(111)7×7 surface revealed the fact that the vertical position of the adatom layer relative to the first layer is sufficiently relaxed towards the vacuum region than that expected from the electron diffraction experiments. After the high temperature hydrogen etching, the SiC surface became atomically smooth. It was found that Si face is somewhat unstable to the oxygen adsorption as compared to C face. The rocking curves were reproduced assuming the attachment of oxygen atoms at T1 site with a bond length of 1.88Å. Heating the SiC surface in the ultra-high vacuum after the sacrificial oxidation and hydrofluoric etching, an atomically flat carbon rich surface appeared.[DOI: 10.1380/ejssnt.2003.152]
