Figure 4
Atomically resolved HAADF STEM of pure Au hcp phase (a) together with FFT of that region. Au intergrowth region (b) made of two Au domains fcc and hcp. A black guide line is added following the stacking of the horizontal layers. The stacking sequence is labeled with the letters A, B and C in order to define the stacking sequence. Results of the EELS spectroscopy measurements of the Au islands: ADF-STEM of the examined area (c) and corresponding EELS Ge L2,3 (green) and Au M4,5 (red) map (d). In (e) EELS spectrum is presented from area 1 (the Au island) and area 2 (germanium). It is seen that within the precision of the EELS spectroscopy the Au island is free of any germanium. (f) Change of the RHEED intensity, recorded during sample cooling, after post annealing of 6 ML Au/Ge(001) to temperature higher then Au/Ge eutectic. Monotonic increase of the intensities is seen for all type of surface reconstruction spots. In the temperature range of 470 K–423 K a drop of the intensity occurs, which takes ~8 min, later the intensities increase monotonically in the same way. The observed drop of RHEED intensity is assigned to the decay of the beta-Au-Ge metastable phase leading to formation of Au hcp and pure germanium.
