Superior B-Doped SiC Nanowire Flexible Field Emitters: Ultra-Low Turn-On Fields and Robust Stabilities against Harsh Environments

Influence of Silane Coupling Agent and Anionic Dispersant on the Dispersion Effect of Silicon Carbide Particles

Silicon carbide (SiC), as a widely used material, has great properties. To improve the flowability of ultrafine silicon carbide slurry, this study used sodium humate, tetramethylammonium hydroxide (TMAH), and N-(β-monoaminoethyl)-γ-aminopropyltrimethyl(ethoxysilane) (KH792) to modify the ultrafine silicon carbide powder produced by Qingzhou Micro Powder Company. The effects of different modifiers on improving the flowability of ultrafine silicon carbide slurry were investigated by means of viscosity tests, sedimentation experiments, and SEM observations. Their modification mechanisms were investigated by means of zeta potential tests, XPS tests, and so on. In this paper, the initial modification of SiC was carried out with KH792, followed by the secondary modification with anionic and cationic modifiers (tetramethylammonium hydroxide and sodium humate), and the optimal modification conditions were investigated by means of a viscosity test, which showed that the lowest viscosity of the modified SiC reached 0.076 Pa·s and that the absolute maximum value of the zeta potential increased from 47.5 at the time of no modification to 63.7 (maximum values) at the time of modification. This means it has an improved surface charge, which improves dispersion. The adsorption results of the modifier on the silicon carbide surface were also demonstrated by the XPS test results.

Erbium Single Atom Composite Photocatalysts for Reduction of CO2 under Visible Light: CO2 Molecular Activation and 4f Levels as an Electron Transport Bridge

It is still challenging to design a stable and efficient catalyst for visible-light CO₂ reduction. Here, Er³⁺ single atom composite photocatalysts are successfully constructed based on both the special role of Er³⁺ and the special advantages of Zn₂ GeO₄ /g-C₃ N₄ heterojunction in the photocatalysis reduction of CO₂ . Especially, Zn₂ GeO₄ :Er³⁺ /g-C₃ N₄ obtained by in situ synthesis is not only more conducive to the tight junction of Zn₂ GeO₄ and g-C₃ N₄ , but also more favorable for g-C₃ N₄ to anchor rare-earth atoms. Under visible-light irradiation, Zn₂ GeO₄ :Er³⁺ /g-C₃ N₄ shows more than five times enhancement in the catalytic efficiency compared to that of pure g-C₃ N₄ without any sacrificial agent in the photocatalytic reaction system. A series of theoretical and experimental results show that the charge density around Er, Ge, Zn, and O increases compared with Zn₂ GeO₄ :Er³⁺ , while the charge density around C decreases compared with g-C₃ N₄ . These results show that an efficient way of electron transfer is provided to promote charge separation, and the dual functions of CO₂ molecular activation of Er³⁺ single atom and 4f levels as electron transport bridge are fully exploited. The pattern of combining single-atom catalysis and heterojunction opens up new methods for enhancing photocatalytic activity.

High-Performance Field Emitters Based on SiC Nanowires with Designed Electron Emission Sites

Making field emitters with both low turn-on field (E_to) and high current emission stability is one of the keys to push forward their practical applications. In the present work, we report the exploration of high-performance field emitters with designed sharp corners around SiC nanowires for fundamentally enhanced electron emission sites. The sharp corners with tailored densities are rationally created based on a facile etching technique. Accordingly, the emission sites and nanowires are integrated into a single-crystalline configuration without interfaces, which could offer the emitters with a robust structure to avoid the structural damage induced by the generated Joule heat and electrostatic forces over long-term field emission (FE) operation. Consequently, the E_to of the as-fabricated SiC field emitter is low down to 0.52 V/μm, which is comparable to the state-of-the-art one ever reported. Moreover, they have high electron emission stability with a current fluctuation of just 2% over 10 h, representing their promising applications in FE-based electronic units.

Giant Piezoresistance in B-Doped SiC Nanobelts with a Gauge Factor of -1800

The giant piezoresistance effect (PRE) of semiconductors as featured by a high gauge factor (GF) is recognized as the prerequisite for realizing optimal pressure sensors with desired high sensitivity. In this work, we report the discovery of giant PRE in SiC nanobelts with a record GF measured using an atomic force microscope. The transverse piezoresistance coefficient along the [111] direction reaches as high as -312.51 × 10^-11 pa^-1 with a corresponding GF up to -1875.1, which is twice more than the highest value ever reported on SiC nanomaterials. The first-principles calculations reveal that B doping turns the acceptor states in the bandgap into deeper impurity levels, which makes the major contribution to the observed giant piezoresistance behavior. Our result provides new insights on designing pressure sensors based on SiC nanomaterials.

Enhanced Piezoresistive Behavior of SiC Nanowire by Coupling with Piezoelectric Effect

Improving the sensitivity of the piezoresistive behavior of semiconductor nanostructures is critically important because it is one of the keys to explore advanced pressure sensors with desired sensitivity. Herein, we reported a strategy for improving the piezoresistive behavior of SiC nanowire by coupling with the piezoelectric effect of ZnO nanolayers, which were grown by an atomic layer deposition approach. As a result, the detected current of the as-constructed ZnO/SiC heterojunction nanowires is 6 times more than SiC nanowires, suggesting its substantially improved sensitivity. Moreover, the measured ΔR/R₀ value and gauge factor (GF) of the ZnO/SiC heterojunction nanowires could be up to 0.82 and 50.93, respectively, which was profoundly higher than those of the SiC counterpart and most of reported positive piezoresistive SiC sensors.

Effect of Piezoresistive Behavior on Electron Emission from Individual Silicon Carbide Nanowire

The excellent properties of silicon carbide (SiC) make it widely applied in high-voltage, high-power, and high-temperature electronic devices. SiC nanowires combine the excellent physical properties of SiC material and the advantages of nanoscale structures, thus attracting significant attention from researchers. Herein, the electron vacuum tunneling emission characteristics of an individual SiC nanowire affected by the piezoresistive effect are investigated using in situ electric measurement in a scanning electron microscope (SEM) chamber. The results demonstrate that the piezoresistive effect caused by the electrostatic force has a significant impact on the electronic transport properties of the nanowire, and the excellent electron emission characteristics can be achieved in the pulse voltage driving mode, including lower turn-on voltage and higher maximum current. Furthermore, a physical model about the piezoresistive effect of SiC nanowire is proposed to explain the transformation of electronic transport under the action of electrostatic force in DC voltage and pulsed voltage driving modes. The findings can provide a way to obtain excellent electron emission characteristics from SiC nanowires.

Effect of heat preservation time on the micro morphology and field emission properties of La-doped SiC nanowires

Lanthanum doped SiC nanowires (La-doped SiC NWs) were prepared using the chemical vapor reaction technique at different heat preservation times.