Near-surface microstructure of Pt-Rh(110) and (111) surfaces

Abstract

Diffuse x-ray scattering under grazing incidence was measured of Pt-47 at. % Rh(110) and (111) surfaces at 1000 K. The elastic scattering contributions of short-range order scattering and displacement scattering were separated from the inelastic scattering contributions that served for data calibration. The modulations in short-range order scattering are small and indicate differences in the near-surface microstructure of the two surfaces: a global maximum at 1¹/₂0 (as for the bulk microstructure) for the (110) surface and at ¹/₂¹/₂¹/₂ positions for the (111) surface. The dominant nearest-neighbor configuration of both surfaces is reminiscent of the segregation profile of a (111) surface. A tendency towards the bulk "40" structure is only noted for the (110) surface.