Abstract
The structures of the (001) surface of potassium tantalate doped with nominally 2, 4 and 7%
lithium have been investigated using high resolution helium atom scattering. The surfaces were prepared
by cleaving single crystal samples in situ under UHV conditions. Di raction measurements in
the region around the He specular re
ection angle soon after cleaving yielded specular peaks initially
with broad shoulders. However, over a period of about an hour, the widths of these specular peaks
decreased markedly as the shoulders diminished into the background. Drift spectra measurements of
the stabilized surfaces revealed that the step heights separating surface terraces were predominantly
multiples of the cubic unit cell dimension, about 4A, rather than multiples of a half unit cell, 2A,
expected from the cleaving of these crystals. Together these results suggest that after cleaving these
surfaces are rapidly modi ed by migration of ions to the surface from the near-surface. Further,
half-order di raction peaks were observed in the <100> azimuth a short time after cleaving samples
at room temperature, indicating that domains with (21) structure had formed.