Surface structure of niobium-doped potassium tantalate KTa1 − xNbxO3 obtained from helium atom scattering studies

Helium atom scattering experiments have been carried out on the (001) surface of KTaO3 doped with 6, 10 and 15% Nb, produced by cleaving in situ single crystal samples. Several phenomena were observed through He atom diffraction measurements, including metastable behavior immediately after cleaving, reconstruction of a fraction of the surface to (2 X 1) domains after thermally cycling the surface temperatures, and the distribution of step heights of terraces at the surface as multiples of the unit cell dimension of ~ 4 A. In addition, a large hysteresis effect was found in the 100 azimuth in the variation of surface reflectivity with surface temperature; a much smaller hysteresis effect was found in the 110 azimuth. The hysteresis effects appear for all Nb doping concentrations. Finally, small oscillations in the specular and Bragg diffraction intensities near the surface temperature 80 K were also observed.