In Situ Imaging of Ferroelastic Domain Dynamics in CsPbBr3 Perovskite Nanowires by Nanofocused Scanning X-ray Diffraction.

Lucas A B Marçal,Ernesto Joselevich,Alexander Björling,Eva Unger,Amnon Rothman,Susanna Hammarberg,Dmitry Dzhigaev,Eitan Oksenberg,Anders Mikkelsen,Jesper Wallentin

doi:10.1021/acsnano.0c07426

Abstract

The interest in metal halide perovskites has grown as impressive results have been shown in solar cells, light emitting devices, and scintillators, but this class of materials have a complex crystal structure that is only partially understood. In particular, the dynamics of the nanoscale ferroelastic domains in metal halide perovskites remains difficult to study. An ideal in situ imaging method for ferroelastic domains requires a challenging combination of high spatial resolution and long penetration depth. Here, we demonstrate in situ temperature-dependent imaging of ferroelastic domains in a single nanowire of metal halide perovskite, CsPbBr3. Scanning X-ray diffraction with a 60 nm beam was used to retrieve local structural properties for temperatures up to 140 °C. We observed a single Bragg peak at room temperature, but at 80 °C, four new Bragg peaks appeared, originating in different real-space domains. The domains were arranged in periodic stripes in the center and with a hatched pattern close to the edges. Reciprocal space mapping at 80 °C was used to quantify the local strain and lattice tilts, revealing the ferroelastic nature of the domains. The domains display a partial stability to further temperature changes. Our results show the dynamics of nanoscale ferroelastic domain formation within a single-crystal perovskite nanostructure, which is important both for the fundamental understanding of these materials and for the development of perovskite-based devices.

Highlights

The interest in metal halide perovskites has grown as impressive results have been shown in solar cells, light emitting devices, and scintillators, but this class of materials have a complex crystal structure that is only partially understood
During the past few years, metal halide perovskites (MHPs) have attracted the attention of the scientific community owing to their potential applications in photovoltaic and optoelectronic devices.[1−4] Many recent works have revealed the unique optical properties of these materials, and the development of devices based on MHPs has been swift.[5−9] MHPs exhibit several crystal phases with modest transition temperatures, which can be significantly affected by strain.[10]
CsPbBr3 nanowires were grown on a fused silica glass substrate by thermal evaporation at elevated temperatures of >360 °C, analogous to previous reports.[17,54,55]

Summary

Introduction

The interest in metal halide perovskites has grown as impressive results have been shown in solar cells, light emitting devices, and scintillators, but this class of materials have a complex crystal structure that is only partially understood. X-ray diffraction (XRD) can probe deep into samples that have been exposed to minimal preparation prior to the investigation, owing to the long absorption length of X-rays Such characteristics make XRD ideal for studies of in situ processes, including temperature changes.[43] XRD is very sensitive to lattice tilt and can be used to measure domain tilts with extremely high precision.[24,44−47] Traditionally, the real-space resolution of XRD has been poor, but the recent development in X-ray optics has made it possible to focus X-rays down to the nanoscale.[48,49] Scanning XRD using a nanofocused beam has enabled studies of single nanocrystals and nanoscale devices[50−52] as well as static imaging of ferroelectric domains.[53] dynamic in situ studies of ferroelastic or ferroelectric domains, which have a typical size of about 100 nm,[27,33] require a very small and bright X-ray focus. We use the NanoMAX beamline,[48] situated at the first diffraction-limited storage ring MAX IV, to study the dynamics of ferroelastic domains in CsPbBr3 nanowires during temperature variations, and demonstrate how scanning nano-XRD with a 60 nm beam size can be used for high-resolution in situ imaging of nanoscale ferroelastic domains within a single MHP nanowire

Methods

Results

Conclusion