The structure of clean crystalline surfaces and chemisorbed overlayers

Abstract

Low-energy electron diffraction (LEED) is being successfully applied to the determination of atomic arrangements in the surface region of crystalline solids. Some recent work in this field is presented. Partial results are discussed for the structure analyses of: (1) the clean Mo{001} surface, which is found to be contracted by approximately 11 % with respect to the bulk; (2) the clean Ti(0001) surface, which is only very slightly contracted (by about 2 %) with respect to the bulk; (3) the 1 × 1 structure of an overlayer of silicon on Mo{001}; and (4) the c(2 × 2) structure of an overlayer of nitrogen on Mo{001}. The confidence level for the latter is considerably lower than that for the former structures. Possible reasons for situations of this kind are discussed, and an assessment of the status quo in surface crystallography is given.