HALOGEN ADSORPTION ON FE(100) .3. ADSORPTION OF BR2 STUDIED BY AES, LEED, WORK FUNCTION CHANGE AND THERMAL-DESORPTION - COMPARISON OF CL2, BR2 AND I2 ADSORPTION BEHAVIOR

Bromine adsorbs dissociatively on Fe(100) at room temperature. During adsorption it forms a sharp c(2 × 2) which splits into the variable structure III, (2 sin α′ × 2 sin α′)Rα′. A new variable structure, II, designated as ( 1 1 tanα -1 1 tanα then emerges while structure III is still extant. Structure III fades leaving structure II, which evolves into the final form for saturated coverage, a split c(2 × 4). The sticking probability remains constant until structure III begins to form, its value is high and probably close to 1.0. Desorption of bromine is a function of temperature only, the LEED patterns are the same as those observed during adsorption at the same coverage. Coverage changes, as measured by AES, are consistent with the proposed models. The work function change is proportional to coverage and at saturation is 1.06 ± 0.05 eV. Comparisons are drawn between Cl2, Br2 and I2 adsorption on Fe(100) and between halogen adsorption on other metals. © 1979.