Owing to oxygen vacancies, the as-prepared ZnO normally shows n-type semiconducting characteristic. This has restricted the preparation of high-quality p-type ZnO and the application of ZnO optoelectronic devices. Therefore, we studied a method of using H2O2 as an oxygen source to passivate oxygen vacancies (V-o) in ZnO films via atomic layer deposition (ALD). The temperature range for the self-limited growth of crystalline ZnO thin films by ALD using diethylzinc and H2O2 was found to be in the range of 80 to 150 degrees C. Our results show that the use of H2O2 as an oxygen source can provide an O-rich condition (instead of H2O) for the growth of ZnO film, with a total preferential (002) orientation of the growth plane and decreased grain size. Further, the O-rich growth environment can suppress the formation of V-o and zinc interstitials and decrease the carrier concentration in ZnO (from 2.525 x 10(19) cm(-3) to 1.695 x 10(12) cm(-3)). This can lead to an increase in the film resistivity from 1.717 x 10(-2) Omega.cm for a ZnO film prepared using H2O to 1.348 x 10(4) Omega.cm for a ZnO film prepared using H2O2. Thus, H2O2 could be used to passivate V-o in ZnO at a low temperature, and it could be beneficial for the preparation of p-type ZnO films.