X-ray crystal truncation rod (CTR) scattering and reciprocal space mapping (RSM) are widely used to characterize the structure of thin films. The methods can provide the structural information, such as the atomic structure, shape and size of crystalline domain, and strain distribution, in any ambient conditions without destructing the specimen. The use of the methods is often limited in the static structure analysis, because the acquisitions of CTR scattering profile and RSM dataset are often time consuming (mins to hrs).

Our group has developed a method that can measure a wide range of CTR profile and RSM in a single acquisition by using an energy-dispersive converging X-rays [1]. The technique allows the in-operando observation of atomic scale processes of photo-induced surface phenomenon [2] and electrochemical processes at the solid-liquid interface [2] with a time resolution of 1 s. The time frame is also reasonable to study the thin film growth processes.

In this contribution talk, we show the atomic scale growth processes of ultra thin films, Bi and Bi₂Se₃, as reveled by the energy-dispersive surface X-ray diffraction. In the growth of Bi film, we observed: the formation of wetting atomic layer at the interface, the growth of black phosphorous phase, which does not exists in bulk, below the thickness of ~2 nm, and the growth of bulk Bi structure in the upper layer. In the growth of Bi₂Se₃ film, we observed a strained Bi₂Se₃ structure in the first a few Bi₂Se₃ layers. The relationships between the growth behaviors and the electronic properties, namely, the quantum confinement effect in Bi and the topological phase transition of Bi₂Se₃, are discussed.

[1] T. Matsushita, T. Takahashi, T. Shirasawa, E. Arakawa, H. Toyokawa, and H. Tajiri, J. Appl. Phys. 110, 102209 (2011).

[2] T. Shirasawa, W. Voegeli, E. Arakawa, T. Takahashi, and T. Matsushita, J. Phys. Chem. C 120, 29107 (2016).

[3] T. Shirasawa, T. Masuda, W. Voegeli, E. Arakawa, C. Kamezawa, T. Takahashi, K. Uosaki, and T. Matsushita, J. Phys. Chem. C 121, 24726 (2017).