GROWTH OF IR OVERLAYERS ON A MO(110) SURFACE

Ir overlayers on a Mo(110) surface were studied by LEED, AES and TPD o f D2. At room temperature, Ir grows layer-by-layer, with LEED indicati ng a distorted Ir(111) layer in the Nishiyama-Wasserman (NW) orientati on for coverages from one to four monolayers when bulk Ir appears. At 880 K, a different growth mode is found, with alloy formation taking p lace when the coverage exceeds one monolayer. Changes in LEED and AES on annealing two monolayers at 900 K indicate formation of a multilaye r of IrMo alloy. TPD of D2 from the annealed layers confirms their all oy character, with a D2 adsorption state intermediate between those fo r pure Ir and Mo.