The formation of a stable germanium oxide film obtained upon exposure of Ge(0 0 1) surface to atomic oxygen is characterized as a function of the substrate temperature using X-ray photoelectron spectroscopy. Although the atomic oxygen is chemisorbed by forming a mixture of dioxide and sub-stoichiometric oxide species already at room temperature, the best condition to obtain a largely dominant dioxide component is obtained at 300 °C. The evolution of the oxide with temperature is investigated by means of annealing experiments.