Lund University

报告摘要:

Metal halide perovskites (MHPs) have shown impressive results in solar cells, light emitting devices, and scintillator applications, but basic questions regarding its complex structure are still open. The low symmetry of MHP crystal structures allows the formation of ferroelastic domains, whose ferroelectric nature is debated. Ferroelastic and ferroelectric materials show nanoscale domains with typical sizes ranging from 10 to 1000nm. Imaging dynamics of ferroic domains require an experimentally challenging combination of high spatial resolution, strain sensitivity and long penetration depth. We have developed nanoscale X-ray diffraction methods to study the dynamics of ferroelastic domains within MHP nanostructures, made available by recent developments in X-ray optics and synchrotron sources. CsPbBr₃ nanowires were imaged across the orthorhombic to tetragonal crystal phase transition using in situ temperature-dependent nanofocused scanning X-ray diffraction, with the 60 nm beam at the NanoMAX beamline, MAX IV. The formation of highly organized domain pattern near 80 °C revealed the ferroelastic nature of the domains. To achieve improved temporal resolution, we used the newly developed Full-Field Diffraction X-ray Microscopy technique, available at the ID01 beamline, ESRF, France, to probe the domain evolution at 6 s time resolutions. Twinned ferroelastic domains in single 500 nm CsPbBr₃ particles were studied with 3D Bragg coherent x-ray diffraction imaging. These results demonstrate that X-ray methods now offer sufficient spatial resolution to image ferroic domains, allowing for in situ studies of their formation and dynamics in realistic conditions. Finally, I will give an update of the status of the 4th-generation synchrotron MAX IV in Lund, Sweden (https://www.maxiv.lu.se/).

报告人简介:

Jesper Wallentin is Professor at the division for Synchrotron Radiation Research at Lund University, Sweden. He was previously a postdoctoral fellow at the University of Göttingen, Germany. His research concerns the intersection of nanoscience and X-ray science, both developing X-ray methods to investigate nanostructured devices, and developing nanostructured X-ray detectors. His group has a strong collaboration with the Nanomax beamline at MAX IV in Lund, but also visits many other synchrotrons for experiments.

邀请人：王刚 研究员（82649182）