Analysis of the atomic geometries of the (101^-0) and (112 ^-0) surfaces of CdSe by low-energy-electron diffraction and low-energy-positron diffraction

The relaxed atomic geometries of the low-index cleavage surfaces of wurtzite-structure CdSe are determined via comparison of dynamical scattering calculations with measured low-energy-electron-diffraction (LEED) and low-energy-positron-diffraction (LEPD) intensities. Both surfaces are found to be relaxed in accordance with recently proposed geometries deduced from total-energy-minimization calculations. Since this analysis represents the use of LEPD for quantitative surface-structure determination, we discuss the experimental technique, the differences observed between LEPD and LEED, and the complementary nature of the two spectroscopies.