Deterministic dual control of phase competition in strained BiFeO3 : a multiparametric structural lithography approach

UK Research and Innovation, MR/T043172/1, Raymond G. P. McQuaid; Department for Employment and Learning, Northern Ireland, USI-082, Amit Kumar; Engineering and Physical Sciences Research Council, EP/S037179/1, Amit Kumar; EP/L015323/01, Nathan Black.The realization of a mixed-phase microstructure in strained BiFeO3 (BFO) thin films has led to numerous novel effects derived from the coexistence of the tetragonal-like monoclinic phase (T phase) and rhombohedral-like monoclinic phase (R phase). Strong strain and polarization differences between the phases should result in a high level of transformation plasticity, which enables the continuous alteration of the relative proportion of R and T states in response to external forces. Although the potential for utilizing such plasticity to control mixed-phase populations under external stimuli is evident, direct experimental evidence backed by equilibrium predictions has not yet been fully demonstrated. Here we demonstrate deterministic control of mixed-phase populations in an epitaxially strained BFO thin film through the application of localized stresses and electric fields in a reversible manner. The results illustrate and rationalize deterministic control of mixed phases in strained BFO films, which could be crucial in tuning their functional properties. The findings also highlight a new multiparametric technique in the scanning probe lithography toolbox based on tip-assisted electric and strain field manipulation of functional properties that might find application beyond the ferroelectric domain and structural phase lithography.Publisher PDFPeer reviewe

The contribution of X-linked coding variation to severe developmental disorders

Over 130 X-linked genes have been robustly associated with developmental disorders, and X-linked causes have been hypothesised to underlie the higher developmental disorder rates in males. Here, we evaluate the burden of X-linked coding variation in 11,044 developmental disorder patients, and find a similar rate of X-linked causes in males and females (6.0% and 6.9%, respectively), indicating that such variants do not account for the 1.4-fold male bias. We develop an improved strategy to detect X-linked developmental disorders and identify 23 significant genes, all of which were previously known, consistent with our inference that the vast majority of the X-linked burden is in known developmental disorder-associated genes. Importantly, we estimate that, in male probands, only 13% of inherited rare missense variants in known developmental disorder-associated genes are likely to be pathogenic. Our results demonstrate that statistical analysis of large datasets can refine our understanding of modes of inheritance for individual X-linked disorders

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

High resolution spatial mapping of the electrocaloric effect in a multilayer ceramic capacitor using Scanning Thermal Microscopy

Scanning thermal microscopy (SThM) is emerging as a powerful atomic force microscope based platform for mapping dynamic temperature distributions on the nanoscale. To date, however, spatial imaging of temperature changes in electrocaloric (EC) materials using this technique has been very limited. We build on the prior works of Kar-Narayan et al (2013 Appl. Phys. Lett. 102 032903) and Shan et al (2020 Nano Energy 67 104203) to show that SThM can be used to spatially map EC temperature changes on microscopic length scales, here demonstrated in a commercially obtained multilayer ceramic capacitor. In our approach, the EC response is measured at discrete locations with point-to-point separation as small as 125 nm, allowing for reconstruction of spatial maps of heating and cooling, as well as their temporal evolution. This technique offers a means to investigate EC responses at sub-micron length scales, which cannot easily be accessed by the more commonly used infrared thermal imaging approaches

Fundamental aspects of conduction in charged ErMnO 3 domain walls

It is now well‐established that ferroelectric domain walls, at which there are discontinuities in polarization, are usually electrically conducting. Yet, there is a dearth of rather basic information on the physics underpinning conductivity. Here, Kelvin Probe Force Microscopy (KPFM)‐based experiments are reported, which allow significant new insights regarding charge transport at domain walls in ErMnO3. In one set of experiments, KPFM is used to spatially map the Hall potential, developed at the surface of polished single crystals. These maps provide direct experimental evidence that n‐type head‐to‐head domain walls arise in otherwise p‐type material. In another set of experiments, the geometry for current flow is restricted, by cutting sub‐micron thick lamellar slices of ErMnO3 (using a Focused Ion Beam microscope). Separate contacts are made to n and p‐type walls and the potential profiles, when driving source‐drain currents, are measured (again using KPFM). Current‐electric field functions showed Ohmic behaviour for p‐type walls, with an intrinsic room temperature conductivity value of ≈0.4Sm−1. The n‐type walls showed non‐Ohmic behaviour and a significantly lower conductivity, supporting the prediction that electrons are in a polaronic state; an upper bound for the room temperature conductivity of the domains themselves is ≈6 × 10−6Sm−1 at 0.1 MVm−1