Applicability of coherent x-ray diffractive imaging to ferroelectric, ferromagnetic, and phase change materials

Abstract

Rapid development in the field of ferroelectric and magnetic materials has attracted much interest in the past decade. The underlying mechanisms of the fundamental phenomenon of phase transitions in these materials are extremely important in understanding their physical properties and their potential technological applications. Therefore, it is vital for the advancement of high-resolution versatile imaging techniques that enable high-throughput and nano-scale characterization in the nano-crystals and electronic devices. X-ray based imaging techniques such as Bragg coherent x-ray diffractive imaging (CXDI) has been one of the dominant nondestructive imaging tools with high-resolution and refraction sensitivities that provide quantitative information in bulk and nano-scale crystals and their associated nano-devices. In this review, we will focus on the recent developments of using Bragg CXDI at the state-of-art endstations in synchrotron radiation facilities worldwide to understand the structures of ferroelectric and magnetic materials and the structural phase transition of complex materials. We will also present our perspectives on the opportunities and challenges in using Bragg CXDI techniques for materials characterization.

Dark-field X-ray microscopy visualization

“…Advances in X-ray brilliance and optics have recently led to the development of Bragg scanning probe X-ray microscopy (Chahine et al, 2014), Bragg coherent diffraction imaging (Shi et al, 2022), Bragg X-ray ptychography (Pfeiffer, 2018) and dark-field X-ray microscopy (DF-XRM) (Simons et al, 2015). Bragg diffraction is scattering from crystallographic planes, and Bragg diffraction occurs due to interference along specific directions, requiring precise alignment of the sample.…”

Imaging the electric field with x-ray diffraction microscopy

“…Imaging with Bragg-diffracted x rays may provide a new route to mapping the electric field in bulk materials. Several new quantitative diffraction-based imaging techniques have emerged in the past decade, such as dark-field x-ray microscopy (DF-XRM) [6] and x-ray Bragg coherent diffraction imaging (Bragg-CDI) [7], Bragg scanning probe x-ray microscopy (Bragg-SPM) [8], and Bragg x-ray ptychography [9], which now allow us to obtain images of the scattering function inside materials. Typically, this scattering function is used to map the local distribution of strain inside a single crystal or a single grain in a polycrystalline matrix [7,10], since the location of the intensity maxima in reciprocal space can be directly related to the strain.…”

“…Several new quantitative diffraction-based imaging techniques have emerged in the past decade, such as dark-field x-ray microscopy (DF-XRM) [6] and x-ray Bragg coherent diffraction imaging (Bragg-CDI) [7], Bragg scanning probe x-ray microscopy (Bragg-SPM) [8], and Bragg x-ray ptychography [9], which now allow us to obtain images of the scattering function inside materials. Typically, this scattering function is used to map the local distribution of strain inside a single crystal or a single grain in a polycrystalline matrix [7,10], since the location of the intensity maxima in reciprocal space can be directly related to the strain. However, since the x-ray scattering function also depends on the position of atomic sublattices in the material and thus the electric polarization of the lattice, it is conceivable that DF-XRM, Bragg-CDI, -SPM, or -ptychography could image the electric field within bulk materials directly and in situ.…”

“…As the electric field drives a smaller sublattice shift than that associated with ferroelectric switching, this would require a low noise level in the instrumentation to provide quantitative data. Additionally, a homogeneous strain state was assumed in [13], and for a 2469-9950/2023/108(10)/104314 (7) 104314-1 ©2023 American Physical Society general case where both the polarization and strain varies, the strain and polarization information will be convoluted in the phase of the scattered x-ray beam. Shablin et al [14] suggested a method for separating the strain and polarization information contained in the phase of the scattered beam by choosing two x-ray energies on either side of an absorption edge.…”