Surface structure of ZnTe (110) as determined from dynamical analysis of low-energy-electron diffraction intensities

Abstract

Dynamical calculations of the intensities of normally incident low-energy electrons diffracted from ZnTe (110), performed using a matrix-inversion method, are compared for structures resulting from (i) a kinematical search, (ii) a dynamical search, and (iii) energy-minimization calculations. Second-layer structural distortions as well as top-layer reconstructions are examined in our structural search. Our analysis leads to the selection of the most probable surface structure for ZnTe (110) as one in which the top layer Te moves outward 0.20 Å and the top layer Zn moves inward 0.55 Å, corresponding to a surface bond angle of 33.2°. No convincing evidence is obtained for second-layer reconstruction. The structure is different from zinc-blende (110) surface structures previously examined, e.g., GaAs (110) and InSb (110), in that the in-plane anion displacement in the surface layer is only half that characteristic of a rigid bond rotation, and the second atomic layer beneath the surface appears to be undistorted to within the accuracy of our analysis. The difference between ZnTe and more covalent zinc-blende materials is attributed to a dependence of the structure of (110) surfaces of zinc-blende-compound semiconductors on the bulk bonding ionicity.