Effect of annealing on a Ge thin film on a Si(111)7×7 surface: A study using ARUPS, XPD, and LEED

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Abstract
To study the changes in structure and morphology of a Ge thin film as a function of annealing temperature, we implemented complementary surface analysis techniques such as angle-resolved ultraviolet-photoelectron spectroscopy, x-ray-photoelectron diffraction (XPD), and low-energy electron diffraction. The Ge thin film (≊15 Å) was obtained by exposing a Si(111)7×7 surface to catalytically decomposed germane at room temperature. The amorphous-crystalline transition temperature was found to be close to 400 °C. A 5×5 reconstruction of the Ge surface occurred for a 500 °C annealing temperature and remained stable to 600 °C. This 5×5 surface reconstruction appeared to have an effect on the XPD curve recorded along the Γ¯-M¯ line in the 1×1 surface Brillouin zone. A 2.5° shift of the peak located near 55° was observed along the [1¯21¯] azimuthal direction. Annealing at 700 °C led to the indiffusion of Ge into Si or to Ge islanding: the 5×5 surface reconstruction turned into a 7×7 surface reconstruction.