OXYGEN-CHEMISORPTION ON A STEPPED RU (APPROXIMATELY 001) CRYSTAL

The 300 K chemisorption of oxygen on a stepped Ru (∼001) single crystal [17(001)×(100)] gives 2×2 complete half-order, 1×2 complete or incomplete half-order, and 1×1 integral-order LEED patterns depending on oxygen exposure and sample annealing. The corresponding relative AES oxygen signals are 0.25, 0.50, and 1.0, respectively. Under certain surface conditions, the presence of the steps is seen to break the threefold degenerate growth habit of 1×2 domains. The 1×1 pattern forms at 300 K only after lengthy exposure at relatively high pressure (10-5 Torr) and is stable to 600 K. Prolonged exposure gives rise to relative AES oxygen signals greater than unity suggesting penetration into the subsurface region. © 1979 American Institute of Physics.