Degradation of Sliding Ferroelectricity Induced by Environmental Gas Molecules: Case of Bilayer WS.

Emerging sliding ferroelectricity (SF) holds great potential for the development of low-energy-cost and high-endurance ferroelectric devices. In the van der Waals (vdWs) stacking of SF, atomic vacancies inevitably exist and gas molecules commonly stay in the interlayer, but their impact on SF is unclear. In this work, the bilayer WS is taken as an example and demonstrate their effect on the SF polarization and switching barrier.

Atomic-Scale Insights into Surface Instability in Halide Perovskites.

The pathway of surface structure evolution plays a vital role in determining the stability of the halide perovskites. Understanding the mechanism of surface instability and how external stimuli interact with the surface is essential for developing strategies to mitigate the degradation of halide perovskites. Here, we directly observed structural evolutions on the surface of CsPbBr via an integrated differential phase contrast scanning transmission electron microscope.

SiX (X = S, Se) Nanowire Gate-All-Around MOSFETs for Sub-5 nm Applications.

The gate-all-around (GAA) field-effect transistor (FET) holds great potential to support next-generation integrated circuits. Nanowires such as carbon nanotubes (CNTs) are one important category of channel materials in GAA FETs. Based on first-principles investigations, we propose that SiX (X = S, Se) nanowires are promising channel materials that can significantly elevate the performance of GAA FETs.

Amorphous Transparent Cu(S,I) Thin Films with Very High Hole Conductivity.

Amorphous transparent conductors (a-TCs) are key materials for flexible and transparent electronics but still suffer from poor p-type conductivity. By developing an amorphous Cu(S,I) material system, record high hole conductivities of 10-10 S cm have been achieved in p-type a-TCs. These high conductivities are comparable with commercial n-type TCs made of indium tin oxide and are 100 times greater than any previously reported p-type a-TCs.

Robust Thermal Neutron Detection by LiInP Se Bulk Single Crystals.

Direct neutron detection based on semiconductor crystals holds promise to transform current neutron detector technologies and further boosts their widespread applications. It is, however, long impeded by the dearth of suitable materials in the form of sizeable bulk crystals. Here, high-quality centimeter-sized LiInP Se single crystals are developed using the Bridgman method and their structure and property characteristics are systematically investigated.

Defect Mo Misidentified as Mo in Monolayer MoS by Scanning Transmission Electron Microscopy: A First-Principles Prediction.

The defect types in layered semiconductors can be identified by matching the scanning transmission electron microscopy (STEM) images with the structures from first-principles simulations. In a PVD-grown MoS monolayer, the Mo antisite (one Mo replaces two S) is recognized as being dominant, because its calculated structure matches the distortive structure in STEM images. Therefore, Mo has received much attention in MoS-related defect engineering.

Sliding ferroelectricity in van der Waals layered γ-InSe semiconductor.

Two-dimensional (2D) van-der-Waals (vdW) layered ferroelectric semiconductors are highly desired for in-memory computing and ferroelectric photovoltaics or detectors. Beneficial from the weak interlayer vdW-force, controlling the structure by interlayer twist/translation or doping is an effective strategy to manipulate the fundamental properties of 2D-vdW semiconductors, which has contributed to the newly-emerging sliding ferroelectricity. Here, we report unconventional room-temperature ferroelectricity, both out-of-plane and in-plane, in vdW-layered γ-InSe semiconductor triggered by yttrium-doping (InSe:Y).

Effective lifetime of non-equilibrium carriers in semiconductors from non-adiabatic molecular dynamics simulations.

The lifetimes of non-equilibrium charge carriers in semiconductors calculated using non-adiabatic molecular dynamics often differ from experimental results by orders of magnitude. By revisiting the definition of carrier lifetime, we report a systematic procedure for calculating the effective carrier lifetime in semiconductor crystals under realistic conditions. The consideration of all recombination mechanisms and the use of appropriate carrier and defect densities are crucial to bridging the gap between modeling and measurements.

Aluminum (Al) causes a delayed suppression of nucleotide excision repair (NER) capacity in zebrafish (Danio rerio) embryos via disturbance of DNA lesion detection.

Aluminum (Al) is extensively used for making cooking utensils and its presence in the aquatic environment may occur through acid mine drainage and wastewater discharge. Al is known to induce genotoxicity in human cells, rodents, and fish. Nucleotide excision repair (NER) eliminates helix-twisting DNA lesions such as UV-induced dipyrimidine photoproducts.

First-principles identification of V + Cudefect cluster in cuprous iodide: origin of red light photoluminescence.

The-phase cuprous iodide (CuI) emerges as a promising transparent p-type semiconductor for next-generation display technology because of its wide direct band gap, intrinsic p-type conductivity, and high carrier mobility. Two main peaks are observed in its photoluminescence (PL). One is short wavelength (410-430 nm) emission, which is well attributed to the electronic transitions at Cu vacancy, whereas the other long wavelength emission (680-720 nm) has not been fully understood.

Temperature-dependent electronic structure of γ-phase CuI: first-principles insights.

To deepen the understanding of CuI that emerges as a promising next-generation transparent display material, we investigate the temperature effect on the electronic structures of its room-temperature phase γ-CuI. Using density-functional-theory-based approaches, we investigate the bandgap renormalization, which is contributed by the electron-phonon (el-ph) interaction and lattice thermal expansion. Different from most semiconductors, the bandgap widens as temperature increases, although it only widens by 88.

First-principles exploration of oxygen vacancy impact on electronic and optical properties of ABO (A = La, Sr; B = Cr, Mn) perovskites.

ABO3-δ perovskites are utilized in many applications including optical gas sensing for energy systems. Understanding the opto-electronic properties allows rational selection of the perovskite-based sensors from a diverse family of ABO3-δ perovskites, associated with the choices of A and B cations and range of oxygen concentrations. Herein, we assess the impact of oxygen vacancies on the electronic structure and optical response of pristine and oxygen-vacant ABO3-δ (A = La, Sr; B = Cr, Mn) perovskites via first-principles calculations.

Theoretical and experimental study of temperature effect on electronic and optical properties of TiO: comparing rutile and anatase.

To gain fundamental understanding of the high-temperature optical gas-sensing and light-energy conversion materials, we comparatively investigate the temperature effects on the band gap and optical properties of rutile and anatase TiOexperimentally and theoretically. Given that the electronic structures of rutile and anatase are fundamentally different, i.e.

Anharmonicity Explains Temperature Renormalization Effects of the Band Gap in SrTiO.

Soft phonon modes in strongly anharmonic crystals are often neglected in calculations of phonon-related properties. Herein, we experimentally measure the temperature effects on the band gap of cubic SrTiO, and compare with first-principles calculations by accounting for electron-phonon coupling using harmonic and anharmonic phonon modes. The harmonic phonon modes show an increase in the band gap with temperature using either Allen-Heine-Cardona theory or finite-displacement approach, and with semilocal or hybrid exchange-correlation functionals.

High carrier mobility in monolayer CVD-grown MoS through phonon suppression.

Mobility engineering is one of the most important challenges that determine the optoelectronic performance of two-dimensional (2D) materials. So far, charged-impurity scattering and electrical-contact barriers have been suppressed through high-κ dielectrics and seamless contact engineering, giving rise to carrier-mobility improvement in exfoliated 2D semiconducting MoS2. Here we demonstrate a facile and scalable technique to effectively suppress both Coulomb scattering and electron-phonon scattering via the HfO2 overlayer, resulting in a large mobility improvement in CVD-grown monolayer MoS2, in excess of 60 cm2 V-1 s-1.

Curative effect and mechanism of radiofrequency ablation nucleoplasty in the treatment of cervical vertigo.

Objective: This study aims to investigate the curative effects and mechanism of radiofrequency ablation nucleoplasty in the treatment of cervical vertigo.

Methods: A total of 27 patients diagnosed with cervical vertigo from January 2012 to October 2014 received treatment of radiofrequency ablation nucleoplasty. The narrow-side vertebral artery diameters were examined by using Philips 1.

Psychometric Properties of the Modified Personal Diabetes Questionnaire Among Chinese Patients With Type 2 Diabetes.

This study examined the psychometric properties of the Chinese version of the Personal Diabetes Questionnaire (C-PDQ). The PDQ was translated into Chinese using a forward and backward translation approach. After being reviewed by an expert panel, the C-PDQ was administered to a convenience sample of 346 adults with Type 2 diabetes.

Factors associated with diet barriers in patients with poorly controlled type 2 diabetes.

Background: The study was conducted to investigate the diet barriers perceived by patients with poorly controlled type 2 diabetes and examine the associations between diet barriers and sociodemographic characteristics, medical condition, and patient-centered variables.

Methods: Secondary subgroup analyses were conducted based on the responses of 246 adults with poorly controlled type 2 diabetes from a multicenter, cross-sectional study. Diet barriers were captured by the Diet Barriers subscale of the Personal Diabetes Questionnaire.

Giant molecular magnetocapacitance.

Through investigating the spin-dependent charging energy of nanoscale systems, we introduce a new concept of intrinsic molecular magnetocapacitance (MC). In molecules and nanosize quantum dots that undergo a spin state transition, the MC can be as high as 12%. First-principles calculations demonstrate that in a number of nanoscale systems, the quantum capacitance is highly sensitive to the system spin and charge states.

Enhancement of Ag cluster mobility on Ag surfaces by chloridation.

To understand the role of chlorine in the stability and the observed fragmentation of Ag dendritic nanostructures, we have studied computationally two model systems using density functional theory. The first one relates to diffusion of Ag(n) and Ag(n)Cl(m) (n = 1-4) clusters on an Ag(111) surface, and the second demonstrates interaction strength of (Ag(55))(2) dimers with and without chloridation. Based on our calculated energy barriers, Ag(n)Cl(m) clusters are more mobile than Ag(n) clusters for n = 1-4.

Adsorption of small molecules on silver clusters.

We report investigations of adsorption of N(2) and O(2) molecules on silver cluster cations. We have first revisited structures of small silver clusters based on first-principles calculations within the framework of density functional theory with hybrid functional. The 2D to 3D transition for the neutral clusters occurs from n = 6 to 7 and for cations, in agreement with experiments, from n = 4 to 5.