Professor Ji Young Jo's research team observes real-time atomic behavior with applied external stimuli

□ Professor Ji Young Jo of the School of Material Science and Engineering at the Gwangju Institute of Science and Engineering (GIST, President Seung Hyeon Moon) has observed in real time how movement in atomic materials depends on the electric field and external physical forces, providing a better understanding of the polarization phenomenon occurring in the ferroelectricity * film at the atomic level.

* Ferroelectric: A state where an electric field is formed in the surroundings by separating into positive and negative ions in a natural state without applying an electric field.

□ The physical properties of electromechanical devices, such as ferroelectric and piezoelectric, are largely dependent on the position of the atoms making up the material. It is very important to study the change of physical properties and position of the thin film device according to the atomic movement under the actual physical condition of the thin film device.

∘ However, it is very difficult to observe the movement of the constituent atoms in real time. Indeed, most of the work in changing atomic positions in materials has been limited to ex situ experiments involving several external variables, such as shifting to different places to infer results and changing experimental conditions.

□ Therefore, it is necessary to design an experimental method that can detect the change of atomic position under the physical conditions of the device, such as electric field application. In this study, the movement of atoms in the ferroelectric thin film was measured in real time and has identified ferroelectric principles according to atomic positions.

□ Atomic movement observations were possible while applying a very short (10 μs) electric field with no current leakage through a very fast X-ray diffraction analysis (time-resolved fine X-ray diffraction) developed by the researchers. The results show that the oxygen atoms in the thin film move 1.4 times more than the chelate atoms, and this result is consistent with calculations made by Professor Jae-kwang Lee of Pusan National University.

* BiFeO3 (bismuth iron oxide): substance that has the property of an electrode and magnet

∘ Therefore, the researchers found that the ferroelectricity of the BiFeO3 thin film is due to the distance between the oxygen atom and the iron atom.

□ Professor Ji Young Jo said, "We have confirmed that time-resolved X-ray can be used to measure the movement of atoms constituting the material according to external stimuli. From a methodological point of view, the team's approach is expected to open new methods for simultaneously applying and observing atoms under various stimuli, including magnetostriction and light strain."

□ This research was supported by the National Research Foundation of Korea funded by the Korean government, the GIST Research Institute at GIST, the TJ Park Science Fellowship of the POSCO TJ Park Foundation, MSIO & PAL, Korea, and Creative Materials Discovery Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT. "In situ observation of atomic movement in a ferroelectric film under an external electric field and stress" was published in Nano Research on December 28, 2017.