Morphology and chemical composition of cobalt germanide islands on   Ge(001): in-situ nanoscale insights into contact formation for Ge-based   device technology
  The reactive growth of cobalt germanide on Ge(001) was investigated by means of in-situ x-ray absorption spectroscopy photoemission electron microscopy (XAS-PEEM), micro-illumination low-energy electron diffraction ($\mu$-LEED), and ex-situ atomic force microscopy (AFM). At a Co deposition temperature of 670{\deg}C, a rich morphology with different island shapes and dimensions is observed, and a correlation between island morphology and stoichiometry is found. Combining XAS-PEEM and $\mu$-LEED, we were able to identify a large part of the islands to consist of CoGe$_2$, with many of them having an unusual epitaxial relationship: CoGe$_2$[$\bar110$](111) $\parallel$ Ge[$\bar110$](001). Side facets with (112) and (113) orientation have been found for such islands. However, two additional phases were observed, most likely Co$_5$Ge$_7$ and CoGe. The occurrence of these intermediate phases is promoted by defects, as revealed by comparing growth on Ge(001) single crystals and on Ge(001)/Si(001) epilayer substrates. 
M. Ewert, Th. Schmidt, J. I. Flege, I. Heidmann, T. Grzela, W. M.   Klesse, M. Foerster, L. Aballe, T. Schroeder and J. Falta
cond-mat.mtrl-sci