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Enhanced electronic property of wafer-scale monolayer MoS2 through S/Mo ratio optimization
Monolayer molybdenum disulfide (MoS2), an emergent two-dimensional (2D) semiconductor, represents the ultimate thickness for scaling down channel materials beyond silicon to overcome the limit of semiconductor technology nodes in the sub-1 nm range. However, despite extensive efforts in the growth of monolayer single-crystal MoS2, growth optimization for higher electronic property and reproducible fabrication for satisfying industrial stability still need to be reported. Here, we report an approach to synthesize wafer-scale monolayer single-crystal MoS2 with high carrier mobility and on/off ratio on sapphire by controlled release of S/Mo precursors ratio during the chemical vapor deposition process. We infer that the main cause of the mismatch in the stoichiometric S/Mo ratio is the oxygen doping. It is found that the MoSx film (x = 1.94) has rather high optimization, as confirmed by the relatively high electronic performances of related devices. Specifically, a fabricated field-effect transistor (FET) array based on the single-crystal monolayer MoS1.94 channels demonstrates significant enhancement in room-temperature mobility (up to 122 cm2 V−1 s−1) and an exceptional on/off ratio (over 1010). This work provides an efficient and reliable approach to produce single-crystal monolayer MoS2 for high-performance microelectronics in the future.
Non-hexagonal symmetry-induced QH-graphene as a promising anode material for sodium-ion batteries: Effects of solvent, vacancy defect, and interlayer coupling
Developing two-dimensional (2D) carbon electrode materials with high performance has become an increasingly fascinating pursuit. However, the most popular carbon allotrope, graphene, possesses chemical inertness arising from its delocalized π-electron network. Breaking of the hexagonal symmetry in graphene can disrupt its π-conjugated system, thus increasing the surface reactivity. Here, by employing first-principles calculations, we predict a 2D carbon allotrope (called QH-graphene), which exhibits remarkable stability across the dynamic, thermal, and mechanical aspects. It has several advantages as an anode material for sodium-ion batteries (SIBs), including a high theoretical capacity (1116.7 mA h g−1), a moderate Na migration barrier (0.35–0.60 eV), a suitable average open-circuit voltage (0.55 V), and a small change in lattice parameters (∼3%). When contacted with electrolyte solvents, the Na adsorption and diffusion capabilities are enhanced. Moreover, introducing a monovacancy defect in QH-graphene improves the adsorption strength of Na but reduces its mobility. Compared with single-layer QH-graphene, QH-graphene bilayer has a stronger binding affinity for Na while maintaining rapid ion diffusion on its exterior surface.
Enhancing radiation hardness of microelectronics through stress-relief milling
Single event effects (SEE) in microelectronic devices are predominantly studied from the perspective of electrical charge generation and collection. This study introduces a multi-physics concept by investigating the impact of highly localized mechanical stress in electrically sensitive regions, such as the gate in a transistor. Our hypothesis is that reducing mechanical stress beneath the gate will decrease voltage transients caused by SEE by limiting charge generation and diffusion. To explore this electro-mechanical coupling in relation to SEE, we milled a microscale trench in the substrate beneath a transistor of the LM124 operational amplifier using a focused ion beam, thereby alleviating mechanical stress in the vicinity of the trench. We then perform pulsed laser SEE testing on the stress-relieved transistor and a control specimen without a micro-trench modification. Our experimental results demonstrate a significant decrease in single event transient peak amplitude and collected charge in the stress-relieved device compared to its pristine counterpart under identical pulsed laser conditions. These findings support our hypothesis and suggest that mitigating mechanical stress localizations could inform the design and fabrication of radiation-hardened electronics.
Band structure engineering in 2D BA2PbI4/InSe perovskite heterostructures and superlattices
Periodic stacking of two van der Waals materials enables the realization of superlattice structures with artificial design of band structure. Two-dimensional perovskites offer structural flexibility for engineering of band structure that can result in superlattice structures. Here, InSe/BA2PbI4 perovskite heterostructure and superlattice are explored by first principles calculation. Both the heterostructure and superlattice show a similar direct bandgap structure. As the concentration of VBA defects increases, the bandgap of the heterostructure and superlattices generally increase in different manners due to different interfacial interaction. The introduction of VI defects leads to the formation of a type-I band alignment, contrasting with the type-II band alignment resulting from VBA defects. These findings offer valuable insights into the defect-driven modulation of electronic properties in semiconductor superlattices and heterostructures, providing opportunities to tailor them for various optoelectronic applications.
Charge-to-spin conversion at argon ion milled SrTiO3/NiFe hetero-interfaces
Two-dimensional electron gases (2DEGs) at perovskite oxide interfaces, such as strontium titanate (STO), have garnered significant attention due to their induced ferromagnetic (FM), spin–orbit coupling, and superconducting properties. The 2DEG, formed at the interface between STO and either insulating oxides or reactive metals, exhibits efficient charge-to-spin interconversion in STO/NM(non-magnetic)/FM structures. The insulating oxide layer at the STO interface attenuates the spin currents injected into the ferromagnet. In contrast, the metallic layers facilitate efficient spin current injection but suffer from spin current diffusion. Here, we present an approach to overcome these challenges by directly creating a 2DEG at the STO surface through Ar+ ion bombardment. This method enables efficient spin-to-charge conversion without an intermediate NM layer. Our experimental and simulation results demonstrate the generation of unconventional spin currents at the STO(Ar+)/NiFe (Permalloy) interface. Our findings may enable applications of complex oxide and ferromagnet interfaces for efficient charge-to-spin conversion, paving the way for low-power, room-temperature oxide-based spintronic devices.
Analysis of inversion-domain boundaries in four-layer polarity-inverted AlN structure
We have fabricated a four-layer polarity-inverted aluminum nitride (AlN) structure using a combination of sputtering and face-to-face annealing. We investigated the impurity concentrations and structure of the polarity inversion-domain boundaries (IDBs) of the four-layer polarity-inverted AlN structure. Atomic-scale observations revealed that the interface of the IDBs from Al-polar AlN to N-polar AlN consists of three monolayers (MLs) of O-Al-O, while the IDBs from N-polar AlN to Al-polar AlN consist of 8–10 ML of AlxOyNz. Additionally, the positions of the IDBs from N-polar AlN to Al-polar AlN shifted by 20–30 nm from the interface of sputtered AlN toward the surface, whereas those from Al-polar AlN to N-polar AlN remained at the same position as the interface of sputtered AlN. The interface energies of these IDBs were investigated using first-principles calculations, which support the O-Al-O structure for the IDB from Al-polar AlN to N-polar AlN and the AlxOyNz structure for the IDBs from N-polar AlN to Al-polar AlN.
Optical force modulated by the charge transfer plasmons
We have investigated the modulation of the trapping potential and trapping force provided by the graphene charge transfer plasmon (CTP) structure that supports two resonance modes. Both the screened bonding dipolar plasmon mode and the charge transfer plasmon mode greatly provide a strong trapping potential and trapping force. The position of the trapping potential well can be dynamically regulated by modulating the Fermi energy or the geometry of the charge transfer bridge, allowing for the dynamic trapping of the nanoparticles. The restricted Brownian motion trajectory of the nanoparticles near the structure indicates that both modes can achieve stable nanoparticles trapping. These two peculiar resonance modes could potentially open up additional possibilities for optical manipulation and particle sorting.
Stoichiometry effect on the structure and phase of antiperovskite Sr3SnO thin films prepared using combinatorial co-sputtering
The observation of superconductivity in antiperovskite Sr3SnO crystals has sparked significant interest in understanding its underlying mechanism and fabricating them in thin film forms. To date, molecular beam epitaxy has been used to prepare Sr3SnO thin films, but superconductivity has not been observed. Sr deficiency and subsequent hole doping have been suggested as crucial for the emergent superconductivity, but difficulty in sample preparation due to high chemical instability of this material system has posed challenges for systematic and extensive studies. In this study, we report the fabrication of Sr3SnO thin films through co-sputtering of Sr and SnO2 and investigate the stoichiometry effect on the structural properties of Sr3SnO thin films using a combinatorial approach. A single Sr3SnO phase is observed over a wide range of off-stoichiometric Sr/Sn ratio regions, with preferred orientation changing depending on the Sr/Sn ratio. The formation of intermetallic Sr–Sn compounds in highly Sr-deficient regions suggests the need for careful consideration in elucidating the origin of superconductivity. The single orientation along the [002] direction and lattice parameter change due to biaxial strain applied by using a LAO substrate are indicative of the possible epitaxial growth of antiperovskite oxides using sputtering. Our experimental approach and findings pave the way for high-throughput preparation and characterization of antiperovskite oxides, thus encouraging research on antiperovskite oxides as well as other exotic materials involving highly reactive elements.
High linearity and low hysteresis LMPs/MXene/AgNWs strain sensor for human motion detection
Resistive strain sensors show great potential in motion detection, medicine and healthcare, and human–machine interaction owing to their ease of fabrication, simple structure, and adjustable electrical performance. However, developing high-performance flexible resistive strain sensors with high sensitivity, high linearity, and low hysteresis remains a challenge. In this work, we report an LMPs (liquid metal particles)/MXene/AgNWs strain sensor (LMA strain sensor) with high sensitivity (GF = 6.339), high linearity (R2 = 0.982 24), and low hysteresis (0.452%). In this process, AgNWs act as a bridge between the MXene nanosheets, and the change in contact area of the MXene nanosheets under stretching endows the sensor with high sensitivity. The aggregated LMPs function as a structural framework, capitalizing on their intrinsic fluidic characteristics to serve as an adhesive between silver nanowires (AgNWs) and MXene nanosheets. This approach effectively minimizes the interstitial spaces between AgNWs and MXene. The formation of Ti-O → Ga3+ coordination bonds between MXene nanosheets and LMPs has strengthened the interfacial interactions. Consequently, the sensor demonstrates superior linearity and low hysteresis. In addition, a sensitive layer with a buckled structure is obtained by stretch-release. The buckled structure inhibits inhomogeneous and irreversible connection losses of the sensitive material, further improving the sensor's mechanical durability. LMA strain sensors can accurately detect various human activities such as breathing detection, motion detection, and expression detection. This work will provide an avenue for developing high-performance strain sensors.
‘Publish or perish’ culture blamed for reproducibility crisis
Paralysed man flies virtual drone using brain implant
Nomogram models for predicting outcomes in thyroid cancer patients with distant metastasis receiving 131iodine therapy
Abstract This study aimed to establish and validate prognostic nomogram models for patients who underwent 131I therapy for thyroid cancer with distant metastases. The cohort was divided into training (70%) and validation (30%) sets for nomogram development. Univariate and multivariate Cox regression analyses were used to identify independent predictors for overall survival (OS) and progression-free survival (PFS). Nomograms were developed based on these predictors, and Kaplan-Meier curves were constructed for validation. Among 451 patients who were screened, 412 met the inclusion criteria and were followed-up for a median duration of 65.2 months. The training and validation sets included 288 and 124 patients, respectively. Pathological type, first 131I administrated activity, and lesion 131I uptake in lesions were independent predictors for PFS. For OS, predictors included gender, age, metastasis site, first 131I administrated activity, 131I uptake, pulmonary lesion size, and stimulated thyroglobulin levels. These predictors were used to construct nomograms for predicting PFS and OS. Low-risk patients had significantly longer PFS and OS compared to high-risk patients, with 10-year PFS rates of 81.1% vs. 51.9% and 10-year OS rates of 86.2% vs. 37.4%. These may aid individualized prognostic assessment and clinical decision-making, especially in determining the prescribed activity for the first 131I treatment.
Daily briefing: Who are Trump’s science advisers
Analysing the effect of physical exercise on social anxiety in college students using a chained mediation model
Calcium carbonate sediment corrosion and formation investigation in drinking water distribution network in Sough City, Iran
Performance and emissions of diesel engine combustion lubricated with Jatropha bio-lubricant and MWCNT additive
Abstract Vegetable oil-based lubricants, modified through transesterification and epoxidation, present a sustainable alternative to mineral lubricants for transport and industrial use. This study evaluates epoxidized jatropha oil (EJA) enhanced with multi-walled carbon nanotubes (MWCNT) as a bio-lubricant for compression ignition engines. MWCNT, dispersed in EJA using an ultrasonic probe sonicator with Triton X-100 as a surfactant, was tested at nanoparticle concentrations from 0.5 to 2 wt%. Engine performance and emission characteristics were assessed using SAE 20W40, EJA, and EJA-MWCNT in a four-stroke diesel engine. Results showed that EJA with 2 wt% MWCNT reduced friction power by 39.13% compared to SAE 20W40 and decreased brake specific energy consumption by 6.11%, while lowering emissions of hydrocarbons, carbon monoxide, and smoke. These findings highlight EJA-MWCNT as a promising lubricant for diesel engines, enhancing efficiency and reducing pollutants, making it a viable eco-friendly substitute for diminishing petroleum resources.
Subliminal visual stimulation produces behavioural oscillations in multiple frequencies in a visual integration task
Abstract We perceive our surrounding as a continuous stream of information. Yet, it is under debate, whether our brain processes the incoming information continuously or rather in a discontinuous way. In recent years, the idea of rhythmic perception has regained popularity, assuming that parieto-occipital alpha oscillations are the neural mechanism defining the rhythmicity of visual perception. Consequently, behavioural response should also fluctuate in the rhythm of alpha oscillations (i.e., at ~ 10 Hz). To test this hypothesis, we employed a visual integration task. Crucially we investigated if a subliminal stimulus preceding the target stimulus modulates behaviour. Our results show that behaviour fluctuates as a function of delay between subliminal and target stimuli. These fluctuations were found in the range of theta, alpha and beta oscillations. Our results further support the idea, that alpha oscillations are a functional rhythm for visual perception, leading to rhythmic fluctuations of perception and behaviour. In addition, other frequencies seem to play a role for temporal perception.