The effect of growth conditions on the thermal stability and chemical composition of iridium-oxide thin films fabricated by annealing Lr films in O-2 is presented. The oxide growth as a function of anneal temperature was studied by x-ray photoelectron spectroscopy depth profile analysis and the thermal stability was determined using temperature programmed desorption spectroscopy. We observed that with increasing anneal temperature, the surface oxidized to IrO2 (110) and the thermal stability of the resulting oxide increased. X-ray photoelectron spectroscopy depth profiles showed that IrO2 starts to form at 600 degrees C simultaneous with an increase in the surface roughness of the film.