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Oxygen vacancy defects have been widely studied for fundamental research and industrial applications, because they significantly influence the physical properties of oxides. Precise and systematic control over oxygen deficiency is a prerequisite for qualitative and quantitative studies on the effect of oxygen defects. In this paper, we report a novel approach to accurately control the oxygen deficiency of oxide thin films using high-throughput reactive sputtering (HTRS). SiOx combinatorial libraries consisting of 110 × 130 cells (cell area of 1 cm2) were fabricated on a large-scale glass substrate (110 × 130 cm2). These libraries allow for macroscopic analysis tools that are not amenable to the existing combinatorial methods, such as optical and x-ray spectroscopies. The cells exhibit spatial gradients in optical constants and optical transmission depending on the oxygen deficiency, indicating a gradual transition from Si to SiO2. X-ray photoelectron spectroscopy analysis reveals that the libraries consisting of silicon oxides with diverse oxidation states are in good accordance with the continuous compositional variation. The HTRS method demonstrates the controllability of oxygen deficiency by 0.5% (Δδ ≈ 0.01) and provides potential controllability of 0.05% (Δδ ≈ 0.001). Our approach provides the systematic control of oxygen deficiency and makes a step toward discovering the emerging properties of non-stoichiometric oxides. [ABSTRACT FROM AUTHOR]

We have fabricated high-quality polycrystalline Fe1−xRhx composition-spread thin films by cosputtering Fe and Rh, and investigated their structural and magnetic transformations as a systematic function of composition. With increasing Rh concentration, Fe1−xRhx thin film undergoes from an α׳ phase to a disordered γ phase and also shows a magnetic transition from a ferromagnetic phase to a paramagnetic phase. Vibrating-sample magnetometry and x-ray magnetic circular dichroism measurements show an antiferromagnetic-ferromagnetic transition in the range of 0.52 < x < 0.58 in the Fe1−xRhx composition gradient at room temperature. Based on our structural and magnetic property mapping, we construct a thin-film phase diagram of Fe1-xRhx. Compared to reported results in bulk alloys, the antiferromagnetic-ferromagnetic transition in the Fe1−xRhx thin films was found to occur at slightly higher Rh concentrations, while the boundary between the pure γ phase and the α׳/γ mixed phase region is shifted to the lower concentration Rh. [ABSTRACT FROM AUTHOR]

An approach for the analysis of atomically resolved scanning transmission electron microscopy data with multiple ferroic variants in the presence of imaging non-idealities and chemical variabilities based on a rotationally invariant variational autoencoder (rVAE) is presented. We show that an optimal local descriptor for the analysis is a sub-image centered at specific atomic units, since materials and microscope distortions preclude the use of an ideal lattice as a reference point. The applicability of unsupervised clustering and dimensionality reduction methods is explored and is shown to produce clusters dominated by chemical and microscope effects, with a large number of classes required to establish the presence of rotational variants. Comparatively, the rVAE allows extraction of the angle corresponding to the orientation of ferroic variants explicitly, enabling straightforward identification of the ferroic variants as regions with constant or smoothly changing latent variables and sharp orientational changes. This approach allows further exploration of the chemical variability by separating the rotational degrees of freedom via rVAE and searching for remaining variability in the system. The code used in this article is available at https://github.com/saimani5/ferroelectric_domains_rVAE. [ABSTRACT FROM AUTHOR]

The predictability of a certain effect or phenomenon is often equated with the knowledge of relevant physical laws, typically understood as a functional or numerically derived relationship between the observations and known states of the system. Correspondingly, observations inconsistent with prior knowledge can be used to derive new knowledge on the nature of the system or indicate the presence of yet unknown mechanisms. Here, we explore the applicability of Gaussian processes (GP) to establish predictability and uncertainty of local behaviors from multimodal observations, providing an alternative to this classical paradigm. Using atomic resolution scanning transmission electron microscopy (STEM) of multiferroic Sm-doped BiFeO3 across a broad composition range, we directly visualize the atomic structure and structural, physical, and chemical order parameter fields for the material. GP regression is used to establish the predictability of the local polarization field from different groups of parameters, including the adjacent polarization values and several combinations of physical and chemical descriptors, including lattice parameters, column intensities, etc. We observe that certain elements of microstructure, including charged and uncharged domain walls and interfaces with the substrate, are best predicted with specific combinations of descriptors, and this predictability and associated uncertainties are consistent across the composition series. The associated generative physical mechanisms are discussed. It is also found that certain parameter combinations tend to predict the orthorhombic phase in the cases where rhombohedral phase is observed, suggesting a potential role of clamping and confinement phenomena in phase equilibrium in Sm-BiFeO3 system close to morphotropic phase boundary. We argue that predictability and uncertainty in observational data offer a new pathway to probe the physics of condensed matter systems from multimodal local observations. [ABSTRACT FROM AUTHOR]

We present a joint experimental and theoretical study on the desolvation of Ba(+) cations in (4)He nanodroplets excited via the 6p ← 6s transition. The experiments reveal an efficient desolvation process yielding mainly bare Ba(+) cations and Ba(+)Hen exciplexes with n = 1 and 2. The speed distributions of the ions are well described by Maxwell-Boltzmann distributions with temperatures ranging from 60 to 178 K depending on the excitation frequency and Ba(+) Hen exciplex size. These results have been analyzed by calculations based on a time-dependent density functional description for the helium droplet combined with classical dynamics for the Ba(+). In agreement with experiment, the calculations reveal the dynamical formation of exciplexes following excitation of the Ba(+) cation. In contrast to experimental observation, the calculations do not reveal desolvation of excited Ba(+) cations or exciplexes, even when relaxation pathways to lower lying states are included.