We experimentally studied the formation of vacancy clusters and oxygen related defects in uranium oxide (UO_x) thin films (<70 nm) changing the stoichiometry in the x = 2.2–3.5 range. Films were deposited on Si(0 0 1) by DC magnetron sputtering varying the substrate temperature (room temperature, 400 °C and 600 °C) and different relative O₂ partial pressures in the argon-oxygen mixture. The different species of vacancy-like defects are identified by the combination of depth dependent positron annihilation techniques and by comparison of the experimental data with ab-initio calculations. In samples growth up to 400 °C substrate temperature, di- and tri- vacancies were formed whereas at higher temperature, hexa-vacancies and larger vacancy clusters appear. Film growth at increasing oxygen partial pressure was found not to be correlated with an increase of oxygen defects, but with the formation of more complex vacancy clusters. The presence of oxygen related defects is revealed by identifying preferential positron annihilations with oxygen electrons. Moreover, uranium vacancies inside vacancy clusters are identified by localization of positrons, in agreement with ab-initio calculations.

我们通过实验研究了氧化铀 (UO _x ) 薄膜 (<70 nm)中空位簇和氧相关缺陷的形成，在 x = 2.2-3.5 范围内改变化学计量。通过改变衬底温度（室温、400℃和600℃）和氩-氧混合物中不同的相对O ₂分压，通过DC磁控溅射在Si(0  0  1)上沉积薄膜。不同种类的空位状缺陷通过深度依赖正电子湮灭技术的组合以及实验数据与ab-initio计算的比较来识别。在样品生长高达400℃衬底温度下，二-和三-空缺在较高温度下形成，而，六-出现空缺和更大的空缺群。发现增加氧分压下的薄膜生长与氧缺陷的增加无关，而是与更复杂的空位簇的形成有关。通过识别具有氧电子的优先正电子湮灭，揭示了与氧相关的缺陷的存在。此外，空位簇内的铀空位通过正电子的定位来识别，与ab-initio计算一致。