A. Verdini et al., Determination of TiO2(110) surface relaxation by variable polarization photoelectron diffraction, SURF REV L, 6(6), 1999, pp. 1201-1206
A new method to determine the surface relaxation by means of photoelectron
diffraction (PED) from an s-core level has been applied to the (1x1)-TiO2(1
10) surface. Complete 2 pi solid angle FED patterns for both oxygen Is and
titanium 3s core level peak intensities have been measured at the ALOISA be
amline (Elettra Synchrotron, Italy) in two different photon polarization/el
ectron detection geometrical configurations: one with the photon polarizati
on vector parallel to the surface normal (TM polarization) and the other wi
th the photon polarization vector perpendicular to the surface normal (TE p
olarization). In the latter case the FED sensitivity to the vertical spacin
g is enhanced. Because forward scattering is suppressed on the node of the
primary wave along the surface normal, the relative weight of the distance-
sensitive higher order interference fringes is enhanced. The opposite occur
s for the TM polarization, which enhances the FED sensitivity to lateral sp
acing at grazing emission angles. The experimental FED patterns are compare
d with the theoretical simulations calculated for the relaxed and unrelaxed
TiO2(110) surface. The results prove the feasibility of the method and the
adequacy of the FED technique to the studies of relaxation phenomena at cr
ystal surfaces.