Kwoka M, Lyson-Sypien B, Comini E, Krzywiecki M, Waczynski K, Szuber J
Department of Cybernetics, Nanotechnology and Data Processing, Faculty of Automatic Control, Electronics and Computer Science, Silesian University of Technology, 44-100 Gliwice, Poland.
Nanotechnology. 2020 Jul 31;31(31):315714. doi: 10.1088/1361-6528/ab7586. Epub 2020 Feb 12.
In this work, comparative studies of the surface morphology and surface chemistry of SnO nanolayers prepared by spin coating with subsequent thermal oxidation (SCTO) in the temperature range of 400-700 °C using scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS) methods, are presented. The SEM images show that SCTO SnO nanolayers contain partly connected irregular structures strongly dependent on the final oxidation temperature, with interconnected single grains of longitudinal shape and size, resulting in a flatter surface morphology with respect to the commonly used three-dimensional (3D) SnO thin films. In turn, AFM studies additionally confirm that SCTO SnO nanolayers after post-oxidation annealing at higher temperatures contain isolated grains of average lateral dimensions in the range of 20-50 nm having a rather flat surface morphology of average surface roughness defined by the root mean square factor at the level of ∼2 nm. From the XPS experimental research it can be concluded that, for our SCTO SnO samples, a slight surface nonstoichiometry defined by the relative [O]/[Sn] concentration at the level of 1.8-1.9 is observed, also depending on the final post-oxidation temperature, being an evident contradiction to recently published literature using x-ray diffraction data. Moreover, XPS experiments show that there is also a permanent small amount of carbon contamination present at the surface of internal grains of our SCTO SnO nanolayers, creating an undesired potential barrier for interactions with gaseous species when they are used as the active materials for gas sensing devices.
在这项工作中，我们使用扫描电子显微镜（SEM）、原子力显微镜（AFM）和X射线光电子能谱（XPS）方法，对通过旋涂随后在400-700°C温度范围内进行热氧化（SCTO）制备的SnO纳米层的表面形态和表面化学进行了比较研究。SEM图像表明，SCTO SnO纳米层包含部分相连的不规则结构，这些结构强烈依赖于最终氧化温度，具有纵向形状和尺寸相互连接的单个晶粒，与常用的三维（3D）SnO薄膜相比，其表面形态更平坦。反过来，AFM研究进一步证实，在较高温度下进行后氧化退火后的SCTO SnO纳米层包含平均横向尺寸在20-50 nm范围内的孤立晶粒，其表面形态相当平坦，平均表面粗糙度由均方根因子定义，在约2 nm的水平。从XPS实验研究可以得出结论，对于我们的SCTO SnO样品，观察到由相对[O]/[Sn]浓度在1.8-1.9水平定义的轻微表面非化学计量，这也取决于最终的后氧化温度，这与最近使用X射线衍射数据发表的文献明显矛盾。此外，XPS实验表明，在我们的SCTO SnO纳米层内部晶粒的表面也存在少量永久性碳污染，当它们用作气体传感装置的活性材料时，会对与气态物质的相互作用产生不希望的势垒。
