Experimental and theoretical studies of the Si(001)-2 X 1 reconstructi
on are reviewed. The review indicates that a technique, which is sensi
tive and fast enough to detect the basic symmetry of the Si(001)-2 X 1
surface, seems still unavailable and the local density approximation
(LDA) adopted in calculations makes it difficult to determine the basi
c electronic property of the surface: metallic or semiconducting. The
review of the distinct features of the reflection high-energy electron
diffraction (RHEED) technique shows that it dearly has a role in reso
lving the controversies over the Si(001)-2 X 1 reconstruction. The mul
tislice formalism of Cowley and Moodie with a recently developed edge-
patching method has been applied to the analyses of several experiment
al RHEED patterns from the Si(001)-2 X 1 surface. The calculation resu
lts reject the static buckled model for the surface. The analyses also
show that the information to determine which one of three possible sy
mmetrical models for the surface (namely 'inherent symmetry', 'individ
ual-dimer-random-symmetry' and 'domain-random-symmetry') is closest to
the true structure can be found in the experimental RHEED patterns. T
he results indicate that the intensity symmetry (symmetry regarding th
e intensities rather than geometrical locations of spots) of a RHEED p
attern from the Si(001)-2 X 1 surface is very sensitive to the structu
re variations of the surface.