LEED AND AES STUDIES OF CHEMISORPTION RESULTING FROM LOW EXPOSURES OF C2H4, CO, AND PH3 TO THE (0001) SURFACE OF ZIRCONIUM

Low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES) have been used to study for the first time the chemisorption systems formed on the (000 1 ) surface of zirconium by exposing to C2H4, CO, and pH3 in the one to ten Langmuir regime. The adsorptions are done at room temperature, but there is subsequent heating to optimize the surface ordering. The main observations are as follows: (i) after heating C2H4-covered surfaces to effect hydrogen desorption, the remaining carbon can form two different ordered (1 × 1)-C structures; (ii) CO forms both (2×2)-and (1×1)-type structures; (iii) the temperature at which the bulk diffusion of oxygen becomes significant, as determined by AES, is about 40°C greater on a CO-treated surface than for an O2-treated Zr(000 1) surface; and (iv) heating a pH3-covered surface can yield a weakly-ordered (3×3)-P structure. The observation (iv) contrasts with that for the analogous surface prepared previously with H2S; the poorly developed (3×3)-P surface structure results from the fact that the temperatures required for surface ordering overlap with those which yield a loss of phosphorus from the surface region.