On March 23, Associate Professor Yue Lu from BJUT's Faculty of Materials and Manufacturing, and Professors Linxing Zhang and Jianjun Tian from the University of Science and Technology Beijing, as the joint corresponding authors, had published a research report online in the leading international journal Science. Their research paper, titled Ferroelectricity in layered bismuth oxide down to one nanometer, that BJUT as one of its affiliates. Its first authors are Qianqian Yang , a doctoral candidate from the University of Science and Technology Beijing, Jingcong Hu, a doctoral candidate from BJUT, and Yue-wen Fang, a postdoctoral researcher from the University of San Sebastián.

This research relied on high-end characterization techniques made possible by the electron microscopy platform in the Beijing Key Laboratory of the Microstructure and Properties of Solids, of BJUT's Faculty of Materials and Manufacturing. It accurately identified the atomic occupation of the new structure of Bi₆O₉ ferroelectric thin film, through integrated Differential Phase Contrast Scanning Transmission Electron Microscopy (iDPC-STEM), Synchrotron Radiation X-ray Diffraction, and Density Functional Calculation Theory Calculations (DFT). By accurately characterizing the occupation sites of Bi and O atoms as well as those of Sm, the researchers discovered that Sm occupies lattice points otherwise occupied by Bi as a doping element. In addition, due to the epitaxial growth relationship, it was discovered that there was a large stress between the substrate and the film. When the thickness of the film is reduced to 1nm, the c-axis direction of the unit cell is stretched. This research points out that this may be one of the important reasons why the film still has a maximum remanent polarization of 17μC∙cm^-2 when the film thickness is 1 nm.

Link to the research: https://www.science.org/doi/10.1126/science.abm5134