We hereby report detailed structural and morphological studies for an ultrathin NiO/ZnO bilayer structure grown on sapphire (001) substrate using pulsed laser deposition technique. The combined X‐ray reflectivity (XRR) and grazing incidence X‐ray fluorescence (GIXRF) studies revealed formation of a low‐density defective ZnO interfacial layer of thickness ~32 Å at the ZnO/sapphire interface prior to growth of main ZnO layer. Our results further indicate that the variation of electron density across the NiO/ZnO bilayer structure is smooth and we do not observe presence of any interface layer between them. X‐ray diffraction measurements show that deposited ZnO layer is epitaxial in nature whereas NiO is highly oriented along (100) direction. The angle dependent X‐ray absorption near edge fine structure (XANES) measurements at Ni–K edge has been utilized to determine depth‐resolved oxidation state of Ni and the results have been correlated with the depth‐resolved electron density of NiO layer. The method described here offers nondestructive determination of the microstructural parameters as well as depth‐resolved mapping of oxidation state of a thin film‐based heterojunction device. It extends several advantages over destructive methods which are abundantly reported in literature.

中文翻译：

---

超薄脉冲激光沉积NiO / ZnO双层结构的表面界面研究

我们在此报告使用脉冲激光沉积技术在蓝宝石（001）衬底上生长的超薄NiO / ZnO双层结构的详细结构和形态研究。结合X射线反射率（XRR）和掠入射X射线荧光（GIXRF）研究表明，在生长主ZnO之前，会在ZnO /蓝宝石界面处形成厚度约为32Å的低密度缺陷ZnO界面层。我们的结果进一步表明，横跨NiO / ZnO双层结构的电子密度变化是平滑的，并且我们没有观察到它们之间存在任何界面层。X射线衍射测量表明，沉积的ZnO层本质上是外延的，而NiO沿（100）方向高度取向。Ni–K边缘的角度依赖性X射线近边缘精细结构（XANES）吸收测量已用于确定Ni的深度分辨氧化态，并且该结果与NiO层的深度分辨电子密度相关。此处描述的方法提供了基于薄膜的异质结器件的微结构参数的无损确定以及氧化态的深度解析映射。它超越了文献中大量报道的破坏性方法的几个优点。此处描述的方法提供了基于薄膜的异质结器件的微观结构参数的无损确定以及氧化态的深度解析映射。它超越了文献中大量报道的破坏性方法的几个优点。此处描述的方法提供了基于薄膜的异质结器件的微观结构参数的无损确定以及氧化态的深度解析映射。它超越了文献中大量报道的破坏性方法的几个优点。