Dynamical analysis of low-energy-electron diffraction intensities from InP (110)

Dynamical calculations of the intensities of normally incident low-energy electrons diffracted from InP (110), performed using a matrix-inversion method, are reported for structures resulting from (1) a kinematical search, (2) a dynamical search, and (3) energy-minimization calculations. The model structures considered in all three cases embody distortions of the uppermost three atomic layers of InP from their truncated bulk geometries. The dynamical calculations are compared with elastic low-energy-electron-diffraction intensities measured for fourteen beams with a sample temperature of T=150 K. This comparison leads to the selection of the most probable surface structure for InP (110) as one in which the top layer undergoes both a rotation of 30.4°and a 0.11- relaxation toward the substrate. The P atoms in the top layer move outward and the In atoms inward, giving a relative vertical shear of 0.69. In the second layer, the In species move outward 0.03 and the P inward 0.03. This surface atomic geometry is similar to that which we reported earlier for GaAs (110) and InSb (110), differing from it in that the uppermost layer exhibits greater relaxation inward toward the substrate and the second-layer distortion is decreased. Evidence for reconstruction of the second atomic layer is weaker than for GaAs (110) and InSb (110).