Contaminant-free layer-by-layer annealing to improve the properties of HfO/SiO optical films for the fs laser.

The low laser-induced damage threshold (LIDT) of HfO/SiO films is an important factor in limiting the further development of high repetition rate femtosecond (fs) laser systems. Conventional whole-layer annealing can effectively improve the properties of SiO films, but it is difficult to improve the properties of HfO films located in the intermediate layer and is also prone to introduce contaminants. In this study, an innovative magnetron sputtering-vacuum tube furnace combined system was presented to deposit and anneal the HfO/SiO films without contaminant.

Design of an Oxide Monolayer with High by a Strong Anharmonicity Unit.

In this paper, a new strategy to obtain a transition-metal oxide (TMO) thermoelectric monolayer is demonstrated. We show that the TMO thermoelectric monolayer can be achieved by the replacement of a transition-metal atom with a cluster, which is composed of heavy transition atoms with abundant valence electrons. Specifically, the transition-metal atom in the XO (X = Ti, Zr, Hf) monolayer is replaced by the [Ag] cluster and a stable structure AgO is achieved.

Visualizing Phase Evolution of CoC for Efficient Fischer-Tropsch to Olefins.

Cobalt carbide (CoC) possesses high catalytic efficiency Fischer-Tropsch synthesis (FTS), while the products selectivity appears sensitive to crystallography geometry. Since the Anderson-Schulz-Flory (ASF) distribution in FTS is broken through fabricating facetted CoC nanocrystals, yet the underlying mechanism of CoC crystallization remains unclarified suffering from sophisticated catalyst composition involving promoter agents. Herein, the synthesis of high-purity single-crystal nanoprisms (CoC-p) for highly efficient FTS is reported to lower olefins.

Elastic Properties of Low-Dimensional Single-Crystalline Dielectric Oxides through Controlled Large-Area Wrinkle Generation.

Freestanding single-crystalline SrTiO membranes, as high-κ dielectrics, hold significant promise as the gate dielectric in two-dimensional (2D) flexible electronics. Nevertheless, the mechanical properties of the SrTiO membranes, such as elasticity, remain a critical piece of the puzzle to adequately address the viability of their applications in flexible devices. Here, we report statistical analysis on plane-strain effective Young's modulus of large-area SrTiO membranes (5 × 5 mm) over a series of thicknesses (from 6.

Integration of One-Dimensional (1D) Lead-Free Perovskite Microbelts onto Silicon for Ultraviolet-Visible-Near-Infrared (UV-vis-NIR) Heterojunction Photodetectors.

Lead-free perovskites are considered to be candidates for next-generation photodetectors, because of their excellent charge carrier transport properties and low toxicity. However, their application in integrated circuits is hindered by their inadequate performance and size restrictions. To aim at the development of lead-free perovskite-integrated optoelectronic devices, a CsAgI/silicon (CAI/Si) heterojunction is presented in this work by using a spatial confinement growth method, where the in-plane growth of CAI microbelts with high-quality single-crystal characteristics is primarily dependent on the concentration of surrounding precursor solution.

Efficient degradation of organics by ultrasonic piezoelectric effect on CuO-BTO/AFC composite.

The recombination of photoexcited electron-hole pairs greatly limits the degradation performance of photocatalysts. Ultrasonic cavitation and internal electric field induced by the piezoelectric effect are helpful for the separation of electron-hole pairs and degradation efficiency. The activated foam carbon (AFC) owing to its high surface area is often used as the substrate to grow catalysts to provide more reactive active sites.

The effect of fission products Xe and Cs on the thermal conductivity of the USilattice: a first-principles study.

In the past decades, uranium silicide (USi) as a promising accident tolerant fuel (ATF) has drawn considerable attention in the field of nuclear physics. In comparison with traditional nuclear fuel (UO), the USihas higher thermal conductivity and uranium density, thereby resulting in lower centerline temperatures and better fuel economy. However, during the nuclear fission reaction, some unexpected fission products, such as Xe and Cs, are released and form the defective states.

The effects of point defects on thermal-mechanical properties of BiCuOTe: a first-principles study.

Recently, BiCuOTe as a promising thermoelectric material has attracted extensive interest due to its lower thermal conductivity and higher electrical conductivity. However, little is known about the role of point defects in the growth, processing, and device degradation of this material. Moreover, the elastic properties which provide valuable information about the bonding characteristics, heat conductivity, and their anisotropic characters are investigated for effective design and characterization of new devices.

Critical role of hydrogen for superconductivity in nickelates.

The newly discovered nickelate superconductors so far only exist in epitaxial thin films synthesized by a topotactic reaction with metal hydrides. This method changes the nickelates from the perovskite to an infinite-layer structure by deintercalation of apical oxygens. Such a chemical reaction may introduce hydrogen (H), influencing the physical properties of the end materials.

Boosting thermoelectric performance of HfSe monolayer by selectivity chemical adsorption.

In this work, a strategy to boosting thermoelectric (TE) performance of 2D materials is explored. We find that, appropriate chemical adsorption of atoms can effectively increase the TE performance of HfSe monolayer. Our results show that the adsorption of Ni atom on HfSe monolayer (Ni-HfSe) can improve the optimal power factor PF and ZT at 300 K, increased by more than ∼67% and ∼340%, respectively.

CuO nanorod arrays by gas-phase cation exchange for efficient photoelectrochemical water splitting.

CuO has been considered a promising candidate for photoelectrochemical water splitting electrodes owing to its suitable bandgap, favorable band alignments, and earth-abundant nature. In this paper, a novel gas-phase cation exchange method was developed to synthesize CuO nanorod arrays by using ZnO nanorod arrays as the template. ZnO nanorods were fully converted to CuO nanorods with aspect ratios of 10-20 at the temperature range from 350 to 600 °C.

Strain Tunable Thermoelectric Material: Janus ZrSSe Monolayer.

Thermoelectric (TE) performance of the Janus ZrSSe monolayer under biaxial strain is systematically explored by the first-principles approach and Boltzmann transport theory. Our results show that the Janus ZrSSe monolayer has excellent chemical, dynamical, thermal, and mechanical stabilities, which provide a reliable platform for strain tuning. The electronic structure and TE transport parameters of the Janus ZrSSe monolayer can be obviously tuned by biaxial strain.

First-principles study of the stability and migration of Xe and Cs in USi.

In the past several years, the USi has been suggested as an alternative nuclear fuel for light water reactors due to its high uranium density and outstanding thermal conductivity. In order to gain fundamental insights into the behavior of fission products in USi, the trapping and migration behaviors of the fission products Xe and Cs in USi are investigated using density functional theory calculations in this work. Under-rich and Si-rich conditions, both the Xe and Cs atoms prefer to substitute for Si andatoms, respectively.

First-principle study of neutron irradiation induced performance degradation of amorphous porous silica.

Neutron irradiation induced degradation of porous silica film is studied by Molecular Dynamics and Density-Functional theory-based methods. The degradation of microscopic structure, thermal property, and optical property of porous silica film are systematically investigated. Low-energy recoil is used to simulate the neutron irradiation effect.

Highly Sensitive and Selective Surface Acoustic Wave Ammonia Sensor Operated at Room Temperature with a Polyacrylic Acid Sensing Layer.

In this study, polyacrylic acid (PAA) films were deposited onto a quartz surface acoustic wave (SAW) resonator using a spin-coating technique for ammonia sensing operated at room temperature, and the sensing mechanisms and performance were systematically studied. The oxygen-containing functional groups on the surfaces of the PAA film make it sensitive and selective to ammonia molecules, even when tested at room temperature. The ammonia molecules adsorbed by the oxygen-containing functional groups of PAA (e.

High-κ perovskite membranes as insulators for two-dimensional transistors.

The scaling of silicon metal-oxide-semiconductor field-effect transistors has followed Moore's law for decades, but the physical thinning of silicon at sub-ten-nanometre technology nodes introduces issues such as leakage currents. Two-dimensional (2D) layered semiconductors, with an atomic thickness that allows superior gate-field penetration, are of interest as channel materials for future transistors. However, the integration of high-dielectric-constant (κ) materials with 2D materials, while scaling their capacitance equivalent thickness (CET), has proved challenging.

Ultrahigh oxygen evolution reaction activity in Au doped co-based nanosheets.

Oxygen evolution reaction (OER) has attracted enormous interest as a key process for water electrolysis over the past years. The advance of this process relies on an effective catalyst. Herein, we employed single-atom Au doped Co-based nanosheets (NSs) to theoretically and experimentally evaluate the OER activity and also the interaction between Co and Au.

First-principles study of fission products Xe and Cs behaviors in USi.

In the past several decades, the USihas received much attention for the development of accident tolerant fuel in light water reactors because of its superior thermal conductivity and higher uranium density. In this study, density functional theory calculations have been carried out to study the occupation and diffusion behaviors of fission products Xe and Cs in USi. It is revealed that the occupation sites of Xe and Cs depend on the chemical environment, and both of Xe and Cs are favorable to substitute for U or Si sites.

First-principles study of point defects in USi: effects on the mechanical and electronic properties.

In recent years, USi has been proposed as an alternative nuclear fuel material to uranium dioxide (UO) because of its intrinsically high uranium density and thermal conductivity. However, the operation environment in the nuclear reactor is complex and extreme, such as in-pile neutron irradiation, and thus it is necessary to explore the radiation response behavior of USi and the physical properties of its damaged states. In the present study, first-principles calculations based on density functional theory were carried out to investigate the mechanical and electronic properties of defective USi.

Nickel-Based Selenides with a Fractal Structure as an Excellent Bifunctional Electrocatalyst for Water Splitting.

Nickel-based selenides are believed to be promising non-precious metal electrocatalysts, and have been widely used for both oxygen evolution reactions (OER) and hydrogen evolution reactions (HER). Here, we control the aging time to prepare NiSe with different fractal structures as a bifunctional catalyst. An obtained sample with an aging time of 80 min shows outstanding electrocatalytic performance for hydrogen evolution reactions (HER) with an overpotential of 225 mV (η@10 mA/cm) and for oxygen evolution reactions (OER) with an overpotential of 309 mV (η@50 mA/cm).

Exceptional Photocatalytic Activities of rGO Modified (B,N) Co-Doped WO , Coupled with CdSe QDs for One Photon Z-Scheme System: A Joint Experimental and DFT Study.

Artificial Z-scheme, a tandem structure with two-step excitation process, has gained significant attention in energy production and environmental remediation. By effectively connecting and matching the band-gaps of two different photosystems, it is significant to utilize more photons for excellent photoactivity. Herein, a novel one-photon (same energy-two-photon) Z-scheme system is constructed between rGO modified boron-nitrogen co-doped-WO , and coupled CdSe quantum dots-(QDs).

Promoting the Oxygen Evolution Activity of Perovskite Nickelates through Phase Engineering.

Perovskite oxides have emerged as promising candidates for the oxygen evolution reaction (OER) electrocatalyst due to their flexible lattice structure, tunable electronic structure, superior stability, and cost-effectiveness. Recent research studies have mostly focused on the traditional methods to tune the OER performance, such as cation/anion doping, A-/B-site ordering, epitaxial strain, oxygen vacancy, and so forth, leading to reasonable yet still limited activity enhancement. Here, we report a novel strategy for promoting the OER activity for perovskite LaNiO by crystal phase engineering, which is realized by breaking long-range chemical bonding through amorphization.

Effect of Copper Doping on Electronic Structure and Optical Absorption of CdSe Quantum Dots.

The photophysical properties of Cu-doped CdSe quantum dots (QDs) can be affected by the oxidation state of Cu impurity, but disagreement still exists on the Cu oxidation state (+1 or +2) in these QDs, which is debated and poorly understood for many years. In this work, by using density functional theory (DFT)-based calculations with the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid functional, we clearly demonstrate that the incorporation of Cu dopants into the surface of the magic sized CdSe QD leads to non-magnetic Cu 3d orbitals distribution and Cu oxidation state, while doping Cu atoms in the core region of QDs can lead to both Cu and Cu oxidation states, depending on the local environment of Cu atoms in the QDs. In addition, it is found that the optical absorption of the Cu-doped CdSe QD in the visible region is mainly affected by Cu concentration, while the absorption in the infrared regime is closely related to the oxidation state of Cu.

Strong UV laser absorption source near 355 nm in fused silica and its origination.

As a high-performance optical material, fused silica is widely applied in high-power laser and photoelectric systems. However, laser induced damage (LID) of fused silica severely limits the output power and performance of these systems. Due to the values in strong field physics and improving the load capacity and performance of high power systems at UV laser, LID at 355 nm of fused silica has attracted much attention.

Growth of High-Quality Monolayer Transition Metal Dichalcogenide Nanocrystals by Chemical Vapor Deposition and Their Photoluminescence and Electrocatalytic Properties.

Two-dimensional transition metal dichalcogenide (TMDC) nanocrystals (NCs) exhibit unique optical and electrocatalytic properties. However, the growth of uniform and high-quality NCs of monolayer TMDC remains a challenge. Until now, most of them are synthesized via a solution-based hydrothermal process or ultrasonic exfoliation method, in which the capping ligands introduced from organic solution often quench the optical and electrocatalytic properties of TMDC NCs.