However, the disappearance of oscillations in LNO-Vo' oscillation means that the H2 treatment results in the film having lost its epitaxial relation to the substrate. It can be seen that the peak position of LNO shifted to lower angles when oxygen vacancies were introduced. The corresponding lattice constants are displayed in Figure . The lattice constants of LNO are 3.802 Å, while the lattice constants of LNO-Vo and LNO-Vo' are 3.810 Å and 3.815 Å. It can be observed that the lattice constant increases when oxygen vacancies are introduced in LNO, a phenomenon also observed for other perovskites such asBaTiO3. The increase in lattice constant can be attributed to the introduction of oxygen defects resulting in the reduction of Ni 3+ to Ni 2+ , and the ionic radius of Ni is larger than that of Ni 3+ , which in turn leads to an increase in lattice constant. In addition, we also noticed that the peak intensity of both LNO-Vo and LNO-Vo' decreases, indicating that the introduction of oxygen vacancies leads to a decrease in the crystallinity of the sample. The decrease in crystallinity of LNO-Vo' is particularly pronounced, suggesting that the H2 treatment resulted in a severe alteration of the film surface, which is further confirmed by the following AFM results.