Development and application of reflection high-energy positron diffraction

Reflection high-energy positron diffraction (RHEPD) has been utilized using a 20 keV positron beam generated by an electrostatic beam apparatus. The s tructure of a hydrogen-terminated Si(1 1 1) surface has been analyzed from the rocking curves with dynamical calculation. Residual surface roughness o bserved after the hydrogen-termination was explained as the presence of SiH 3 molecule on monohydride surface. Reflectivities of positrons at Au, Ni an d Ir(0 0 1) surfaces have been measured as a function of positron energy no rmal to surface. Abrupt decreases in the reflectivities were observed in th e total reflection region of positrons, which are possibly associated with the surface dipole barriers. (C) 2000 Elsevier Science B.V. All rights rese rved.