Stress-driven self-assembly on Ir(1 1 0): stripes, droplets, and missing-row-type reconstructions

We present a scanning tunneling microscopy (STM) study of the Ir(1 1 0) surface between 300 and 1020 K. The structural transformation from the {3 3 1} faceted surface, which is stable at room temperature, to a flatter (1×2) missing row (MR) reconstruction at about 800 K is discussed as a function of temperature. In an intermediate temperature range pyramid-like droplets form with preferential orientation along [1 1̄ 2] and [1 1̄ 0]. They coexist with (1×3) MR reconstructed as well as faceted areas. At 875 K these droplets become more rounded while the reconstruction changes to (1×2) MR. Above 900 K the preferential orientation of surface structures disappears. At 1020 K rapid kink diffusion eventually gives rise to fringy step edges in the STM images indicating undersampling. In addition, a long-range periodic surface modulation is observed in the entire temperature range.