Three-dimensional morphology and elastic strain revealed in individual photoferroelectric SbSI nanowire

ntimony sulfoiodide (SbSI) exhibits great promise for photovoltaic applications due to it being optically active in its ferroelectric phase. Previous studies on the SbSI system have relied largely on ensemble-averaging techniques and/or computational studies, wherein true volumetric enumeration of atomic displacement has remained ambiguous at the nanoscale. Here, we have mapped strain and the complex Bragg electronic density among the (002) planes in an individual SbSI nanowire using Bragg coherent diffractive imaging in hopes of guiding efforts to strain engineer SbSI nanostructures for photovoltaic and other optoelectronic applications. We have found that the as-grown nanowire showed sharp faceting and high crystallinity, with no evidence of point or line mechanical defects in the (002) atomic displacement map (u 002 ). There is evidence, however, of planar defects in the wire that separate regions of positive and negative shear strain ( _32) where these domain walls are parallel to the (011)-type facets. Increased Bragg electronic density near the center of the nanowire shows that the nanowires could have additional dangling bonds present there, increasing the likelihood that shells could bond to the wire for strain-engineering purposes. Impact statement Bragg coherent diffractive imaging (BCDI) is a lensless imaging technique with promised diffraction-limited spatial resolution. The technique is susceptible to local lattice distortion and structural heterogeneities with quantitative phase information. BCDI is currently widely used in nanotechnology and materials sciences in general. This article demonstrates the application of BCDI on antimony sulfoiodide (SbSI) nanowires that harbor large shear strains due to dangling bonds and crystal-tilting. SbSI is a ferroelectric material with a relatively narrow bandgap, high pyroelectricity, optical activity, and piezoelectricity, making it a promising material for infrared detectors, actuators, and storage devices. Several elastic shear domains in the shear strain component were observed in the SbSl nanowire, leading to the potential formation of ferroelectric domains above room temperature in the nanowire. The likely elastic domains identified in the BCDI reconstructions are the consequences of the strain energy minimization, originating from the global shear present in the SbSl nanowire. Our studies open up a new avenue for local strain mapping and strain-engineering characterization of above room-temperature optoelectronic nanodevices. We envisage that BCDI characterization could be used to learn and develop crucial properties on emergent nanostructure of technological importance. Ultimately, the development and optimization of associated functional devices with real-world applications are attainable. Graphical abstract