Direct method of surface structure determination by Patterson analysis of correlated thermal diffuse scattering for Si(001)2X1

A simple oscillatory intensity variation in medium-energy electron diffract ion found recently [Abukawa ei al., Phys. Rev. Lett. 82, 335 (1999)] was te rmed correlated thermal diffuse scattering (CTDS). The potential of CTDS as a direct surface structural tool has been fully explored for the Si(001)2 X 1 surface at 300 K in a very-grazing-incidence condition. Nearly 2 pi sol id-angle, three-dimensional (3D) CTDS patterns were measured for an energy range of 500-2000 eV. The 3D Patterson functions obtained by Fourier invers ion of the measured CTDS patterns clearly revealed the building blocks of t he Si(001)2 X 1 surface, i.e., the bond orientations and lengths of the buc kled Si dimers, within an accuracy of 1 degrees and 0.1 Angstrom, respectiv ely.