Controlled Self-Assembly of Nanoscale Superstructures in Phase-Change Ge-Sb-Te Nanowires.

Controlled growth of semiconductor nanowires with atomic precision offers the potential to tune the material properties for integration into scalable functional devices. Despite significant progress in understanding the nanowire growth mechanism, definitive control over atomic positions of its constituents, structure, and morphology via self-assembly remains challenging. Here, we demonstrate an exquisite control over synthesis of cation-ordered nanoscale superstructures in Ge-Sb-Te nanowires with the ability to deterministically vary the nanowire growth direction, crystal facets, and periodicity of cation ordering by tuning the relative precursor flux during synthesis. Furthermore, the role of anisotropy on material properties in cation-ordered nanowire superstructures is illustrated by fabricating phase-change memory (PCM) devices, which show significantly different growth direction dependent amorphization current density. This level of control in synthesizing chemically ordered nanoscale superstructures holds potential to precisely modulate fundamental material properties such as the electronic and thermal transport, which may have implications for PCM, thermoelectrics, and other nanoelectronic devices.

Osteosarcopenia and Mortality in Older Adults Undergoing Transcatheter Aortic Valve Replacement.

Importance: Osteosarcopenia is an emerging geriatric syndrome characterized by age-related deterioration in muscle and bone. Despite the established relevance of frailty and sarcopenia among older adults undergoing transcatheter aortic valve replacement (TAVR), osteosarcopenia has yet to be investigated in this setting. Objective: To determine the association between osteosarcopenia and adverse outcomes following TAVR. Design, Setting, and Participants: This is a post hoc analysis of the Frailty in Aortic Valve Replacement (FRAILTY-AVR) prospective multicenter cohort study and McGill extension that enrolled patients aged 70 years or older undergoing TAVR from 2012 through 2022. FRAILTY-AVR was conducted at 14 centers in Canada, the United States, and France between 2012 and 2016, and patients at the McGill University-affiliated center in Montreal, Québec, Canada, were enrolled on an ongoing basis up to 2022. Exposure: Osteosarcopenia as measured on computed tomography (CT) scans prior to TAVR. Main Outcomes and Measures: Clinically indicated CT scans acquired prior to TAVR were analyzed to quantify psoas muscle area (PMA) and vertebral bone density (VBD). Osteosarcopenia was defined as a combination of low PMA and low VBD according to published cutoffs. The primary outcome was 1-year all-cause mortality. Secondary outcomes were 30-day mortality, hospital length of stay, disposition, and worsening disability. Multivariable logistic regression was used to adjust for potential confounders. Results: Of the 605 patients (271 [45%] female) in this study, 437 (72%) were octogenarian; the mean (SD) age was 82.6 (6.2) years. Mean (SD) PMA was 22.1 (4.5) cm2 in men and 15.4 (3.5) cm2 in women. Mean (SD) VBD was 104.8 (35.5) Hounsfield units (HU) in men and 98.8 (34.1) HU in women. Ninety-one patients (15%) met the criteria for osteosarcopenia and had higher rates of frailty, fractures, and malnutrition at baseline. One-year mortality was highest in patients with osteosarcopenia (29 patients [32%]) followed by those with low PMA alone (18 patients [14%]), low VBD alone (16 patients [11%]), and normal bone and muscle status (21 patients [9%]) (P < .001). Osteosarcopenia, but not low VBD or PMA alone, was independently associated with 1-year mortality (odds ratio [OR], 3.18; 95% CI, 1.54-6.57) and 1-year worsening disability (OR, 2.11; 95% CI, 1.19-3.74). The association persisted in sensitivity analyses adjusting for the Essential Frailty Toolset, Clinical Frailty Scale, and geriatric conditions such as malnutrition and disability. Conclusions and Relevance: The findings suggest that osteosarcopenia detected using clinical CT scans could be used to identify frail patients with a 3-fold increase in 1-year mortality following TAVR. This opportunistic method for osteosarcopenia assessment could be used to improve risk prediction, support decision-making, and trigger rehabilitation interventions in older adults.

ERAS following Gastrectomy for Octo- and Nonagenarians: A Single-Center Retrospective Analysis.

Background: The safety and efficacy of enhanced recovery after surgery (ERAS) following elective gastrectomy for gastric cancer in patients >80 years of age are not well described. The aim of this study was to explore whether an ERAS protocol following gastrectomy in this age group can be safely implemented and reduce postoperative length of stay. Methods: A retrospective, single-center analysis was performed. All patients >80 years of age with gastric cancer undergoing elective subtotal and total gastrectomy between January 2010 and December 2021 were identified. With the implementation of an ERAS protocol in January 2016, patients treated beforehand were allocated to Group A (pre-ERAS) and Group B (ERAS). The length of stay, incidence of postoperative complications and representation/readmission to the hospital were compared between the groups. Results: Of the 221 patients identified, 56 met the inclusion criteria with 22 patients (39.3%) allocated to Group A and 34 patients (60.7%) to Group B. There were no differences with regard to the type of resection and surgical approach. Length of stay was shorter in Group B (5 days, range 2-27 versus 10 days, 3-109, P = .040). A trend toward more discharges by postoperative day 3 was noted among patients in Group B (7/34, 20.6% versus 2/22, 9.1%, P = .253). There were no differences in the incidence of postoperative complications or readmission hospital between the groups. Conclusion: Among patients >80 years of age, ERAS following gastrectomy for cancer is associated with a reduced length of stay and can be safely implemented.

Atomic Layer Deposition of WO3-Doped In2O3 for Reliable and Scalable BEOL-Compatible Transistors.

Tungsten oxide (WO3) doped indium oxide (IWO) field-effect transistors (FET), synthesized using atomic layer deposition (ALD) for three-dimensional integration and back-end-of-line (BEOL) compatibility, are demonstrated. Low-concentration (1∼4 W atom %) WO3-doping in In2O3 films is achieved by adjusting cycle ratios of the indium and tungsten precursors with the oxidant coreactant. Such doping suppresses oxygen deficiency from In2O2.5 to In2O3 stoichiometry with only 1 atom % W, allowing devices to turn off stably and enhancing threshold voltage stability. The ALD IWO FETs exhibit superior performance, including a low subthreshold slope of 67 mV/decade and negligible hysteresis. Strong tunability of the threshold voltage (Vth) is achieved through W concentration tuning, with 2 atom % IWO FETs showing an optimized Vth for enhancement-mode and a high drain current. ALD IWO FETs have remarkable stability under bias stress and nearly ideal performance extending to sub-100 nm channel lengths, making them promising candidates for high-performance monolithic 3D integrated devices.

Enhanced recovery after surgery after radical gastrectomy: Improved compliance over time is associated with a shorter postoperative hospital stay.

BACKGROUND: Changing adherence over time to enhanced recovery after surgery (ERAS) protocols following radical gastrectomy and the impact this has on length of stay (LoS) is not well described. This study aimed to explore the changes in adherence to core ERAS elements over time and the relationship between compliance and LoS. METHODS: A retrospective, single center cohort study was performed between 01/2016-12/2021. An ad hoc analysis revealed the point at which a significant difference in the number of patients being discharge on postoperative day (PoD) 3 was noted allowing allocation of patients to Group A (01/2016-12/2019) or B (01/2020-12/2021). Compliance with core ERAS elements was compared and the relationship between compliance and discharge by (PoD) 3 assessed. Variables significant on univariate analysis were assessed using binary multivariate regression. RESULTS: Of the 268 patients identified, 187 met the inclusion criteria (Group A 112 and Group B 75). More patients in Group B mobilized on PoD 1 (60.0 vs. 31.3%, p = <0.001), tolerated postgastrectomy diet by PoD 3 (84.6 vs. 62.5%, p = 0.049), and were discharged by PoD 3 (34.7 vs. 20.5%, p = 0.002). Protocol compliance of >75% was associated with discharge on PoD 3 (area under the curve, 0.726). Active mobilization on PoD 1 (OR 3.5, p = 0.009), compliance ≥75% (OR 3.3, p = 0.036), and preoperative nutritional consult (OR 0.2, p = 0.002) were independently associated with discharge on PoD 3. Discharge on PoD 3 did not increase readmission or representation to hospital. CONCLUSION: Early mobilization, protocol compliance >75%, and preoperative nutritional consult were associated with discharge on PoD 3 after radical gastrectomy.

Partial gland ablation with high intensity focal ultrasound impact on genito-urinary function and quality of life: our initial experience.

INTRODUCTION:   Partial gland ablation (PGA) using high intensity focal ultrasound (HIFU) is an alternative to active surveillance for low to intermediate risk localized prostate cancer.  This pilot study assessed quality of life (QoL) outcomes during the implementation of PGA-HIFU at our institution. MATERIALS AND METHODS:   We prospectively enrolled 25 men with a diagnosis of localized low/intermediate risk prostate cancer who elected to undergo PGA-HIFU in a pilot study at our institution between 2013 and 2016.  Patients underwent pre-treatment mpMRI and transrectal ultrasound-guided biopsies.  The primary endpoints were impact on patient-reported functional outcomes (erectile, urinary function, QoL) assessed at 1, 3, 6- and 12-months. RESULTS:   The median age was 64 years old (IQR 59.5-67).  Baseline median International Index of Erectile Function-15 score was 50, which decreased to 18 at 1 month (p < 0.0005), returned to baseline by 3 months and thereafter. International Prostate Symptom Score median at baseline was 8, which worsened to 12 at 1 month (p = 0.0088), and subsequently improved to baseline thereafter.  On the UCLA-Expanded Prostate Cancer Index Composite urinary function, there was a decrease in median score from 92.7 at baseline to 76.0 at 1 month (p < 0.0001), which improved to or above baseline afterwards.  QoL remained similar to baseline at each follow up period as assessed by EQ-5D and the Functional Cancer Therapy-Prostate score. CONCLUSIONS:   In this initial cohort of PGA-HIFU men at our institution, patients demonstrated a slight, but transient, deterioration in urinary and erectile function at 1 month prior to normalization.  All QoL metrics showed no impact upon 1 year of follow up post-treatment.

Observation of Sub-10 nm Transition Metal Dichalcogenide Nanocrystals in Rapidly Heated van der Waals Heterostructures.

Two-dimensional materials, such as transition metal dichalcogenides (TMDCs), have the potential to revolutionize the field of electronics and photonics due to their unique physical and structural properties. This research presents a novel method for synthesizing crystalline TMDCs crystals with <10 nm size using ultrafast migration of vacancies at elevated temperatures. Through in situ and ex situ processing and using atomic-level characterization techniques, we analyzed the shape, size, crystallinity, composition, and strain distribution of these nanocrystals. These nanocrystals exhibit electronic structure signatures that differ from the 2D bulk: i.e., uniform mono- and multilayers. Further, our in situ, vacuum-based synthesis technique allows observation and comparison of defect and phase evolution in these crystals formed under van der Waals heterostructure confinement versus unconfined conditions. Overall, this research demonstrates a solid-state route to synthesizing uniform nanocrystals of TMDCs and lays the foundation for materials science in confined 2D spaces under extreme conditions.

Enhanced Switching Reliability of Hf0.5Zr0.5O2 Ferroelectric Films Induced by Interface Engineering.

Ferroelectric materials have been widely researched for applications in memory and energy storage. Among these materials and benefiting from their excellent chemical compatibility with complementary metal-oxide-semiconductor (CMOS) devices, hafnia-based ferroelectric thin films hold great promise for highly scaled semiconductor memories, including nonvolatile ferroelectric capacitors and transistors. However, variation in the switched polarization of this material during field cycling and a limited understanding of the responsible mechanisms have impeded their implementation in technology. Here, we show that ferroelectric Hf0.5Zr0.5O2 (HZO) capacitors that are nearly free of polarization "wake-up"─a gradual increase in switched polarization as a function of the number of switching cycles─can be achieved by introducing ultrathin HfO2 buffer layers at the HZO/electrodes interface. High-resolution transmission electron microscopy (HRTEM) reveals crystallite sizes substantially greater than the film thickness for the buffer layer capacitors, indicating that the presence of the buffer layers influences the crystallization of the film (e.g., a lower ratio of nucleation rate to growth rate) during postdeposition annealing. This evidently promotes the formation of a polar orthorhombic (O) phase in the as-fabricated buffer layer samples. Synchrotron X-ray diffraction (XRD) reveals the conversion of the nonpolar tetragonal (T) phase to the polar orthorhombic (O) phase during electric field cycling in the control (no buffer) devices, consistent with the polarization wake-up observed for these capacitors. The extent of T-O transformation in the nonbuffer samples is directly dependent on the duration over which the field is applied. These results provide insight into the role of the HZO/electrodes interface in the performance of hafnia-based ferroelectrics and the mechanisms driving the polarization wake-up effect.

Transabdominal Management of Epiphrenic Diverticula in the Setting of Achalasia: A Single-center Review.

BACKGROUND: The perioperative and functional outcomes of patients with epiphrenic diverticula (ED) on a background of achalasia managed via a minimally invasive transabdominal approach are under-reported. We describe our center's experience over 10 years of treating such patients. METHODS: A single-center, retrospective chart of a prospectively maintained hospital database was performed. All patients with a diagnosis of ED and manometrically proven achalasia were identified. Demographic, clinical, and surgical data were extracted from the institution's medical records. Patients were stratified by whether they underwent myotomy only or myotomy plus diverticulectomy and compared in a univariate manner. RESULTS: There were 18 patients who met the inclusion criteria. The median age of the cohort was 67.1 years (range 53.1 to 77.8), the maximal size of the diverticula was 3.5 cm (range 2.0 to 7.0), and the distance of the proximal lip of the diverticulum to the incisors was 33.5 cm (range 28.0 to 38.0). In terms of surgical intervention, 14 patients (77.8%) underwent myotomy plus diverticulectomy, and 4 (22.2%) underwent myotomy alone. The duration of surgery was significantly longer in the former (177.5 vs. 75.0 min, P =0.031). In total, 9/18 (50.0%) of patients were discharged on the day of surgery. There was a trend to more major postoperative complications following diverticulectomy plus myotomy, with 2/13 (15.4%) patients suffering staple line leaks. Excellent long-term functional outcomes were achieved, with 81.3% of patients having sustained resolution of their symptoms. CONCLUSIONS: Laparoscopic transabdominal approach for the treatment of ED offers an acceptable risk profile and favorable functional outcomes in patients with underlying achalasia.

Chemical potential gradient induced formation of Kirkendall voids at the epitaxial TiN/MgO interface.

We report the observation of Kirkendall voids at the epitaxial titanium nitride (TiN)/magnesium oxide(MgO)(001) interface. While epitaxial growth of TiN on MgO has been known for years, many reports show a perfectly sharp epitaxial interface. Because TiN is a prototypical diffusion barrier material, observing the consequence of rapid diffusion at a TiN interface is interesting. Structural characterization of the interface using X-ray diffraction and electron microscopy confirms the diffuse nature of the interface. Rectangular voids that form at the TiN/MgO(001) interface and extend into both TiN and MgO result from a large chemical potential gradient at the interface, which contributes a strong chemical driving force for diffusion. The spatial localization of the observed voids is limited to within ∼10 nm from the interface, consistent with a chemical potential gradient driving force. A composition gradient on the nanometer scale is also observed. Observation of Kirkendall voids at this nitride/oxide interface suggests possibilities for engineering oxygen and nitrogen vacancies at thin film interfaces.

Nanoscale compositional segregation in epitaxial AlScN on Si (111).

We report the growth of epitaxial wurtzite AlScN thin films on Si (111) substrates with a wide range of Sc concentrations using ultra-high vacuum reactive sputtering. Sc alloying in AlN enhances piezoelectricity and induces ferroelectricity, and epitaxial thin films facilitate systematic structure-based investigations of this important and emerging class of materials. Two main effects are observed as a function of increasing Sc concentration. First, increasing crystalline disorder is observed together with a structural transition from wurtzite to rocksalt at ∼30 at% Sc. Second, nanoscale compositional segregation consistent with spinodal decomposition occurs at intermediate compositions, before the wurtzite to rocksalt phase boundary is reached. Lamellar features arising from composition fluctuations are correlated with polarization domains in AlScN, suggesting that composition segregation can influence ferroelectric properties. The present results provide a route to the creation of single crystal AlScN films on Si (111), as well as a means for self-assembled composition modulation.

Interfacial Reaction and Diffusion at the One-Dimensional Interface of Two-Dimensional PtSe2.

Two-dimensional (2D) PtSe2 has potential applications in near-infrared optoelectronics because its band gap can be tuned by varying the layer thickness. There are several different platinum-selenide phases with different stoichiometries that result from high-temperature processing. In this report, we use in situ scanning/transmission electron microscopy (STEM) to investigate high-temperature phase transitions in 2D PtSe2 and observe interfacial reactions as well as the Kirkendall effect. The 2D nature of PtSe2 plays a key role in the unique one-dimensional interfaces that result during the formation of Se-poor phases (PtSe and PtSe1-x) at the edges of the PtSe2 crystals. The activation energy extracted for this formation suggests that the process is mediated by Se vacancies, as evidenced by the large strain variations in the material made via 4D STEM measurements. The observation of the Kirkendall effect in a 2D material suggests routes to engineer 1D edge chemistry for contact engineering in device applications.

Traumatic Birth Injury in a Term Neonate.

Cephalohematoma is among the most common forms of birth trauma. It is described as a benign collection of blood above the skull and is associated with prolonged or difficult deliveries. We present the case of a term male born at 39 weeks of gestation with a large cephalohematoma and additional features of caput succedaneum. The patient's condition was successfully treated with minimal intervention and close observation. This case report is aimed at illustrating an atypical presentation of cephalohematoma and discussing the potential sequelae of extracranial birth trauma.

Bending and precipitate formation mechanisms in epitaxial Ge-core/GeSn-shell nanowires.

Core-shell Ge/GeSn nanowires provide a route to dislocation-free single crystal germanium-tin alloys with desirable light emission properties because the Ge core acts as an elastically compliant substrate during misfitting GeSn shell growth. However, the uniformity of tin incorporation during reduced pressure chemical vapor deposition may be limited by the kinetics of mass transfer to the shell during GeSn growth. The balance between Sn precursor flux and available surfaces for GeSn nucleation and growth determines whether defects are formed and their type. On the one hand, when the Sn precursor delivery is insufficient, local variations in Sn arrival rate at the nanowire surfaces during GeSn growth produce asymmetries in shell growth that induce wire bending. This inhomogeneous elastic dilatation due to the varying composition occurs via deposition of Sn-poor regions on some of the {112} sidewall facets of the nanowires. On the other hand, when the available nanowire surface area is insufficient to accommodate the arriving Sn precursor flux, Sn-rich precipitate formation results. Between these two extremes, there exists a regime of growth conditions and nanowire densities that permits defect-free GeSn shell growth.

Anomalous metal vaporization from Pt/Pd/Al2O3 under redox conditions.

Al2O3-supported Pt/Pd bimetallic catalysts were studied using in situ atmospheric pressure and ex situ transmission electron microscopy. Real-time observation during separate oxidation and reduction processes provides nanometer-scale structural details - both morphology and chemistry - of supported Pt/Pd particles at intermediate states not observable through typical ex situ experiments. Significant metal vaporization was observed at temperatures above 600 °C, both in pure oxygen and in air. This behavior implies that material transport through the vapor during typical catalyst aging processes for oxidation can play a more significant role in catalyst structural evolution than previously thought. Concomitantly, Pd diffusion away from metallic nanoparticles on the surface of Al2O3 can also contribute to the disappearance of metal particles. Electron micrographs from in situ oxidation experiments were mined for data, including particle number, size, and aspect ratio using machine learning image segmentation. Under oxidizing conditions, we observe not only a decrease in the number of metal particles but also a decrease in the surface area to volume ratio. Some of the metal that diffuses away from particles on the oxide support can be regenerated and reappears back on the catalyst support surface under reducing conditions. These observations provide insight on how rapid cycling between oxidative and reductive catalytic operating conditions affects catalyst structure.

Nanoscale Chemical and Structural Analysis during In Situ Scanning/Transmission Electron Microscopy in Liquids.

Liquid-cell scanning/transmission electron microscopy (S/TEM) has impacted our understanding of multiple areas of science, most notably nanostructure nucleation and growth and electrochemistry and corrosion. In the case of electrochemistry, the incorporation of electrodes requires the use of silicon nitride membranes to confine the liquid. The combined thickness of the liquid layer and the confining membranes prevents routine atomic-resolution characterization. Here, we show that by performing electrochemical water splitting in situ to generate a gas bubble, we can reduce the thickness of the liquid to a film approximately 30 nm thick that remains covering the sample. The reduced thickness of the liquid allows the acquisition of atomic-scale S/TEM images with chemical and valence analysis through electron energy loss spectroscopy (EELS) and structural analysis through selected area electron diffraction (SAED). This contrasts with a specimen cell entirely filled with liquid, where the broad plasmon peak from the liquid obscures the EELS signal from the sample and induces beam incoherence that impedes SAED analysis. The gas bubble generation is fully reversible, which allows alternating between a full cell and thin-film condition to obtain optimal experimental and analytical conditions, respectively. The methodology developed here can be applied to other scientific techniques, such as X-ray scattering, Raman spectroscopy, and X-ray photoelectron spectroscopy, allowing for a multi-modal, nanoscale understanding of solid-state samples in liquid media.

Surface Facet Engineering in Nanoporous Gold for Low-Loading Catalysts in Aluminum-Air Batteries.

The performance of metal-air batteries and fuel cells depends on the speed and efficiency of electrochemical oxygen reduction reactions at the cathode, which can be improved by engineering the atomic arrangement of cathode catalysts. It is, however, difficult to improve upon the performance of platinum nanoparticles in alkaline electrolytes with low-loading catalysts that can be manufactured at scale. Here, the authors synthesized nanoporous gold catalysts with increased (100) surface facets using electrochemical dealloying in sodium citrate surfactant electrolytes. These modified nanoporous gold catalysts achieved an 8% higher operating voltage and 30% greater power density in aluminum-air batteries over traditionally prepared nanoporous gold, and their performance was superior to commercial platinum nanoparticle electrodes at a 10 times lower mass loading. The authors used rotation disc electrode studies, backscattering of electrons, and underpotential deposition to show that the increased (100) facets improved the catalytic activity of citrate dealloyed nanoporous gold compared to conventional nanoporous gold. The citrate dealloyed samples also had the highest stability and least concentration of steps and kinks. The developed synthesis and characterization techniques will enable the design and synthesis of metal nanostructured catalysts with controlled facets for low-cost and mass production of metal-air battery cathodes.

In utero exposure to genistein decreased intranasal house dust mite-induced respiratory allergy in middle-aged male B6C3F1 offspring.

Despite many hypothesized benefits of dietary isoflavone genistein (GEN) deriving from soy-based products, questions surrounding GEN's developmental effects are increasing. To understand if in utero GEN exposure modulated postnatal respiratory allergies in the middle age, we conducted a time course study in the B6C3F1 offspring (PND 240-330) using a common household allergen (house dust mites: HDM; 10 µg/mouse for PND 240 and 290, and 50 µg/mouse for PND 330, a middle age in mice) following intranasal instillation, a physiological route of allergen exposure. GEN was administered to dams by gavage from gestational day 14 to parturition at a physiologically relevant dose (20 mg/kg body weight). Female and male offspring were sensitized with HDM allergens beginning about one month prior to sacrifice followed by challenges with three weekly dosings of HDM extracts, and they were euthanized at day 3 following the final HDM exposure. In utero exposure to GEN decreased HDM allergen-induced respiratory allergy in male B6C3F1 offspring at PND 330 as reflected by decreases in airway hyperresponsiveness (e.g., Penh value), HDM-specific IgG1 (a Th2 type Ab) and the activity of eosinophil peroxidase in the lung (an indication of eosinophil recruitment to the lungs). However, in utero exposure to GEN had minimal effects on HDM allergen-induced respiratory allergy in the middle-aged female offspring. Changes in serum total IgE, HDM-specific IgE, and lung histopathology scores in both male and female offspring were not biologically significant. Overall, in utero GEN exposure exerted a protective effect on respiratory allergy in the middle-aged male, but not female, B6C3F1 offspring following later-life HDM exposures.

Phase-field investigation of the stages in radial growth of core-shell Ge/Ge1-xSnx nanowires.

Core-shell Ge/Ge1-xSnx nanowires are considered promising silicon-compatible nanomaterials with the potential to achieve a direct band-gap for optoelectronic applications. In this study, we systematically investigated the formation of this heterostructure in the radial direction by the phase field method coupled with elasticity. Our model simulated the shell growth of the wire, capturing the evolution of both the sidewall morphology and the strain distribution. We predicted the minimum chemical potential driving forces required for initiating the Ge1-xSnx shell growth at given tin concentrations. In addition, we studied the dependences of the shell growth rate on the chemical potential, the tin concentration, the sidewall interface kinetics and the mass transport rate respectively. From these analyses, we identified three sequential stages of the growth: the Stage 1 growth at an accelerated rate, the Stage 2 growth at a constant rate, and finally the Stage 3 growth at a reduced rate scaling with . This research improves our current understanding on the growth mechanisms of heterogeneous core-shell nanowires, and provides useful guidelines for optimizing nanowire synthesis pathways.

Thermal Stability of Mixed Cation Metal Halide Perovskites in Air.

We study the thermal stability in air of the mixed cation organic-inorganic lead halide perovskites Cs0.17FA0.83Pb(I0.83Br0.17)3 and Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3. For the latter compound, containing both MA+ and FA+ ions, thermal decomposition of the perovskite phase was observed to occur in two stages. The first stage of decomposition occurs at a faster rate compared to the second stage and is only observed at relatively low temperatures (T < 150 °C). For the second stage, we find that both decomposition rate and the activation energy have similar values for Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3 and Cs0.17FA0.83Pb(I0.83Br0.17)3, which suggests that the first stage mainly involves reaction of MA+ and the second stage mainly FA+.