Co on Mo(1 1 0) studied by scanning tunneling microscopy

We have studied the interface formation of thin films of Co on a Mo(1 1 0) surface by the use of scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and auger electron spectroscopy (AES). Below a coverage of about 0.4 monolayers (ML) we find that Co grows in small islands which are pesudomorphic with the Mo substrate. At a Co coverage above 0.4 ML, the Co atoms condense into larger islands and forms a close-packed Co layer close to that of the Co(0 0 0 1) plane resulting in a coincidence structure with the underlying Mo(1 1 0) substrate. Increasing the Co coverage, we observe that the film grows in a layer-by-layer fashion up to 2 ML at room temperature, however by annealing such a film to 670 K the Co forms 3D islands. STM images displaying atomic resolution, reveal the atomic arrangement and corrugation of the close-packed Co film formed at Co coverages above 0.4 ML at room temperature. In particular, the STM data directly demonstrate the appearance of the coincidence lattice between the Nishiyama–Wasserman orientated Co film and the Mo(1 1 0) substrate. We show how this appearance may change due to subtle changes of the registry between the Co film and the Mo(1 1 0) surface. This behavior can be explained by partial dislocations relaxing the strained close-packed Co layer by a small rigid translation.