While a linear growth behavior is one of the fingerprints of textbook atomic layer deposition processes, the growth often deviates from that behavior in the initial regime, i.e. the first few cycles of a process. To properly understand the growth behavior in the initial regime is particularly important for applications that rely on the exact thickness of very thin films. The determination of the thicknesses of the initial regime, however, often requires special equipment and techniques that are not always available. We propose a thickness determination method that is based on X-ray reflectivity (XRR) measurements on double layer structures, i.e. substrate/base layer/top layer. XRR is a standard thin film characterization method. Utilizing the inherent properties of fast Fourier transformation in combination with a multi-Gaussian fitting routine permits the determination of thicknesses down to $t \approx 2$ nm. We evaluate the boundaries of our model, which are given by the separation and full width at half maximum of the individual Gaussians. Finally, we compare our results from two layer stacks with data from X-ray fluorescence spectroscopy, which is a standard method for measuring ultra thin films.

中文翻译：

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XRR 数据的快速傅立叶变换和多高斯拟合，以确定初始生长范围内 ALD 生长薄膜的厚度

虽然线性生长行为是教科书原子层沉积工艺的特征之一，但生长通常偏离初始状态中的行为，即工艺的前几个循环。正确理解初始状态下的生长行为对于依赖于非常薄的薄膜的精确厚度的应用尤为重要。然而，确定初始状态的厚度通常需要特殊的设备和技术，而这些设备和技术并不总是可用的。我们提出了一种基于对双层结构（即基板/基层/顶层）进行 X 射线反射率 (XRR) 测量的厚度确定方法。XRR 是标准的薄膜表征方法。利用快速傅立叶变换的固有特性与多高斯拟合例程相结合，可以确定低至 $t\大约 2$ nm 的厚度。我们评估模型的边界，这些边界由单个高斯分布的分离和半高全宽给出。最后，我们将两层堆叠的结果与 X 射线荧光光谱的数据进行比较，这是测量超薄膜的标准方法。