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Deposition of Ge on Si(001) 2 ¡Ñ 1 surface was done in an UHV-CVD reaction system using GeH4 as the reactant. The growth kinetics of the Ge, especially in the wetting layer stage, was investigated by using an in-situ XPS technique to count the Ge signal at the very beginning of the deposition process. It was found that at 773 K a flat and well-crystallized Ge wetting layer is observed even after 6 min deposition at a GeH4 pressure of 1.0 ¡Ñ 10-5 Torr. A kinetic analysis of the Ge deposition rate at temperatures ranging from 698 to 823 K showed an activation energy of 30.7 kcal/mol. Density functional theory calculations have been performed on the possible surface reaction pathways of GeH4 on Si(001) 2 ¡Ñ 1. The result indicated that dimer-opening, which is the rate-determining step for Ge deposition from GeH4 on Si(001) 2 ¡Ñ 1 surfaces, has the energy barrier of 33.8 kcal/mol, consistent with the prediction based on experimental analysis. |