Hydride evolution in annealing the Si(001) surface after adsorption of silane/germane at room temperature has been investigated by using multiple-internal-reflection IR absorption spectroscopy. For both silane and germane adsorptions, it was found that major species existing above 300^oC are Si-Si doubly occupied dimers (DOD) and step-edge SiH. For further annealings above 300^oC, the DOD kept its original intensity or even evolved until 370−400^oC, but eventually decayed at 450^oC with the hydrogen desorption. The onset of the DOD decay was concurrent with depletion of the step-edge SiH, which suggests a role of the step-edge SiH as being a “reservoir” for DOD states. Possible transfer of hydrogen atoms from the step-edge SiH to DOD can be related to adatom migrations, which include exchange between adatoms and substrate atoms. It is highly probable that low-temperature hydrogen desorption from germane-adsorbed Si surface is rate-limited by diffusion of Ge adatoms.