Surface Structure of Lithium Doped Potassium Tantalate (KLT) using Helium Atom Scattering.

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. Diraction 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 modied by migration of ions to the surface from the near-surface. Further, half-order diraction peaks were observed in the azimuth a short time after cleaving samples at room temperature, indicating that domains with (21) structure had formed.