Wang Le, Yang Zhenzhong, Yin Xinmao, Taylor Sandra D, He Xu, Tang Chi Sin, Bowden Mark E, Zhao Jiali, Wang Jiaou, Liu Jishan, Perea Daniel E, Wangoh Linda, Wee Andrew T S, Zhou Hua, Chambers Scott A, Du Yingge
Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99354, USA.
Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542, Singapore.
Sci Adv. 2021 Mar 5;7(10). doi: 10.1126/sciadv.abe2866. Print 2021 Mar.
Recent discovery of superconductivity in NdSrNiO motivates the synthesis of other nickelates for providing insights into the origin of high-temperature superconductivity. However, the synthesis of stoichiometric Sr NiO thin films over a range of has proven challenging. Moreover, little is known about the structures and properties of the end member SrNiO Here, we show that spontaneous phase segregation occurs while depositing SrNiO thin films on perovskite oxide substrates by molecular beam epitaxy. Two coexisting oxygen-deficient Ruddlesden-Popper phases, SrNiO and SrNiO, are formed to balance the stoichiometry and stabilize the energetically preferred Ni cation. Our study sheds light on an unusual oxide thin-film nucleation process driven by the instability in perovskite structured SrNiO and the tendency of transition metal cations to form their most stable valence (i.e., Ni in this case). The resulting metastable reduced Ruddlesden-Popper structures offer a testbed for further studying emerging phenomena in nickel-based oxides.
近期在钕锶镍氧化物中发现超导性，这推动了对其他镍酸盐的合成，以便深入了解高温超导的起源。然而，在一定范围内合成化学计量比的锶镍氧化物薄膜已被证明具有挑战性。此外，对于端成员锶镍氧化物的结构和性质知之甚少。在此，我们表明，通过分子束外延在钙钛矿氧化物衬底上沉积锶镍氧化物薄膜时会发生自发相分离。形成了两种共存的缺氧的鲁德尔斯登-波珀相，即Sr₂NiO₃和Sr₃Ni₂O₅，以平衡化学计量并稳定能量上更有利的镍阳离子。我们的研究揭示了一种由钙钛矿结构的锶镍氧化物中的不稳定性以及过渡金属阳离子形成其最稳定价态（在这种情况下为镍）的趋势所驱动的不寻常的氧化物薄膜成核过程。由此产生的亚稳还原型鲁德尔斯登-波珀结构为进一步研究镍基氧化物中出现的现象提供了一个试验平台。
