Structure of Si atomic chains grown on the Si/Cu(110) <i>c</i> (2×2) surface alloy

The surface atomic structure of Si atomic chains grown on the Si/Cu(110) surface alloy has been investigated by a combination of different experimental techniques. For Si coverages below 0.5 monolayers the low-energy electron diffraction (LEED) pattern shows a c(2×2) reconstruction, corresponding to the formation of a surface alloy. Upon further Si deposition, the LEED pattern evolves toward a (2×2)-like structure with streaks along the [001] direction. Scanning tunneling microscopy (STM) images show the presence of linear atomic Si chains on top of the surface alloy layer. We present an atomic model for the surface termination based on the STM images and on the main atomic directions of the (2×2)-like phase found by a simple analysis of the Si 2<i>p</i> full hemispherical x-ray photoelectron diffraction patterns. This model consists of linear atomic Si chains running along the [1̱10] surface direction formed on top of the surface alloy. The chains present small (2×2) domains, which are not in phase with respect to each other. After heating the (2×2)-like phase up to 250 °C, a quasi-(3×4) structure is developed. This structure consists of similar chains exhibiting a different periodicity. Furthermore, we have used synchrotron radiation photoemission (x-ray and ultraviolet photoemission spectroscopy) to gather information about the electronic structure of the atomic chains.