Reconstruction of the CoGa(100) surface studied by thermal-energy helium-atom scattering, LEED, and AES

The surface structure of CoGa(100) has been studied by means of thermal-energy helium-atom scattering (TEAS), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES). A c(4x2) surface reconstruction is revealed by LEED and TEAS measurements. Sometimes this reconstruction is mixed with a (√(5)x√(5)) reconstruction, which is found to be due to a very minor contamination with oxygen. Only double-layer steps are found on the surface. Above 500 K, the reconstructed layer starts to disorder, but short-range ordering in this layer is still observed until 700 K. Near 900 K, segregation of Co is observed with AES. The increase of the cobalt concentration is consistent with filling up the 0.25 ML, necessary for the c(4x2) reconstruction, to a completed monolayer at 900 K. This interpretation implies that the surface is always terminated by Co