“…Oxygen non-stoichiometry is common in oxide thin films and plays an important role in the properties of many cuprates, such as oxygen ordering in the ortho phases of YBa 2 Cu 3 O 7−δ and oxygen staging in La 2 CuO 4+δ [40][41][42][43], as well as other oxides such as brownmillerites and SrTiO 3 [44,45]. In T cuprates, a reduction process has been seen to be essential to achieving superconductivity [3,4], and it is believed that this annealing process may remove excess apical oxygen [46,47] as well as possibly dope additional electron carriers [48,49].…”