Generation Of Holes Research Articles

Investigation of the time dependent gate dielectric stability in SiC MOSFETs with planar and trench gate structures

In this work, the time-dependent dielectric breakdown (TDDB) analysis is performed to understand the gate oxide reliability in SiC MOSFETs with two different structures, i.e., planar and trench gate structures. We have discovered different gate leakage current behaviors between the SiC MOSFETs with planar gate (Sample A) and trench gate (Sample B) during the forward gate bias stress. Notably, the slight increase of the gate current during the stress and the negative activation energy (Ea = −0.07 eV) observed in Sample A suggest that the hole generation caused by the impact ionization can be occurred during the forward gate TDDB tests. Furthermore, the SiC MOSFETs with trench gate structure (Sample B) exhibit the operation voltage of 55.7 V (exponential law) and 57.3 V (power law) for the 0.001 % failure of 30 years under 175 °C, indicating that SiC trench gate MOSFETs with enough thick gate dielectric (87.1 nm (bottom) and 77.9 nm (sidewall)) can have the promising forward gate TDDB stability.

An In-Depth Analysis of Variation in Characteristic Performance of OLED with Respect to Position of Charge Generation Layer

In this paper, a high performance blue organic light emitting diode having a charge generation layer (CGL) is proposed and compared with the other five CGL and non-CGL based devices. The utilized CGL layer in the different structure consists of two materials; HAT-CN (hexaazatriphenylene-hexacarbonitrile) and TAPC (1,1-bis[(di-4-tolyamino)phenyl)]cyclohexane,) for electrons and holes generation, correspondingly. In the proposed novel structure, the CGL layer is incorporated outside of the emissive layer (EML) which significantly enhances the device performance in terms of current and luminescence. The device exhibits luminescence and current values as 3636.3 cd m−2 and 0.44 A, respectively. Furthermore, this paper represents in-depth internal analysis of the six devices (D1-D6). This analysis is provided by drawing horizontal and vertical cutlines inside the devices. The proposed device is analysed and compared with other mentioned devices in terms of several parameters such as Langevin recombination rate, electron concentration, hole concentration, band energy, total current density, electron affinity, hole QFL (quasi-Fermi level), conduction current density, potential distribution and electron/hole mobility. In comparison with D1, D2, D3, D4 and D5, the current of the proposed device (D6) is about 16.9, 2.2, 1.7, 3 and 1.6 times improved, correspondingly. Moreover, structural analysis is also included to understand the performance of the devices more precisely.

Photoelectrocatalytic modification of nanofiltration membranes with SrF2/Ti3C2Tx to simultaneously enhance heavy metal ions rejection and permeability

Heavy metal pollution can significantly harm water systems and human health. Combining photoelectrocatalytic (PEC) and nanofiltration (NF) membrane separation technologies can effectively remove heavy metal ions from wastewater. In this study, a water bath method was used to form SrF2/Ti3C2Tx (ST) nanoparticles on the surface of polyvinylidene fluoride (PVDF) membranes and an additional polyamide (PA) functional layer was formed at the interface by crosslinking. ST@PA composite NF membranes (STPP) with good photocatalytic performance were obtained. The separation and catalytic properties of the STPP membranes were controlled by the ST content, which modifies the surface structure and properties of the membranes. The membrane with optimal ST crosslinking exhibited a water contact angle of 50.8°, pure water flux of 24.6 L·m−2·h−1·bar−1, and rejection rates of Mn2+, Ni2+, Cu2+, and Zn2+ of 98.8%, 95.3%, 95.7%, and 97.3%, respectively, under PEC-assisted separation with visible light illumination from a Xe lamp (300 W) and an applied voltage (2 V). The STPP membranes showed improved rejection rates of heavy metal ions under PEC-assisted operation. The mechanism for the improved membrane performance under PEC conditions was preliminarily clarified considering the relationship between the photocatalytic and filtration properties of STPP membranes along with the influence of light irradiation and an external voltage on the heavy metal ions. The generation of electrons, holes, superoxide radicals, and hydroxyl radicals during membrane operation enhances the rejection rates of heavy metal ions. Based on these results, STPP membranes are considered a promising technology for industrial applications in heavy metal removal.

Multi-field inflation with large scalar fluctuations: non-Gaussianity and perturbativity

Recently multi-field inflation models that can produce large scalar fluctuations on small scales have drawn a lot of attention, primarily because they could lead to primordial black hole production and generation of large second-order gravitational waves. In this work, we focus on models where the scalar fields responsible for inflation live on a hyperbolic field space. In this case, geometrical destabilisation and non-geodesic motion are responsible for the peak in the scalar power spectrum. We present new results for scalar non-Gaussianity and discuss its dependence on the model's parameters. On scales around the peak, we typically find that the non-Gaussianity is large and close to local in form. We validate our results by employing two different numerical techniques, utilising the transport approach, based on full cosmological perturbation theory, and the δN formalism, based on the separate universe approximation. We discuss implications of our results for the perturbativity of the underlying theory, focusing in particular on versions of these models with potentially relevant phenomenology at interferometer scales.

A swarm of helical photocatalysts with controlled catalytic inhibition and acceleration by magneto-optical stimuli

Highly persistent and toxic organic pollutants increasingly accumulate in freshwater resources, exacerbating the human water scarcity crisis. Developing novel microrobots with high catalytic performance, high mobility, and recycling capability integrated to harness energy from the surrounding environment to degrade pollutants effectively remains a challenge. Here, we report a kind of Spirulina (SP)-based magnetic photocatalytic microrobots with a substantially decreased band gap than that of pure photocatalysts, facilitating the generation of stable holes and electrons. Under sunlight irradiation, the degradation rate of rhodamine B (RhB) by the microrobots could be increased by 7.85 times compared with that of pure BiOCl, indicating its excellent photocatalytic performance. In addition, the microrobots can swarm in a highly controllable manner to the targeted regions and perform selective catalytic degradation of organic pollutants in specific areas by coupling effect of light and magnetic field. Importantly, the catalytic capability of the swarming microrobots can be activated by light stimulus whereas inhibited by magneto-optical stimuli, with a rate constant 2.15 times lower than that of pure light stimulation. The biohybrid and magneto-optical responsive microrobots offer a potential platform for selective pollutants catalysis at assigned regions in wastewater treatment plants.

Enhanced plasmonic photocatalytic performance of C doped TiN nanocrystals through ultrathin carbon layers

Carbon-doped TiN nanoparticles on an ultrathin carbon layer, were successfully used for photocatalytic dye degradation synthesised by a simple calcination process. The resulting catalyst exhibited remarkable plasmonic photocatalytic performance under visible light irradiation. In comparison with benchmark rutile TiO2 and g-C3N4/TiO2 heterostructure catalysts, the first-order reaction rate constant of the developed catalyst improved approximately 34.2 and 6.5 times, respectively. The doping concentration of carbon and the crystal size of TiN nanoparticles, predominantly influenced by the amount of urea and calcination temperature, were identified as crucial factors governing the plasmonic photocatalytic activity. Density functional theory (DFT) calculations indicated that the introduction of carbon-sp bands into the TiN band structure promoted interband excitation of electrons and facilitated the generation of hotter holes, thereby enhancing the degradation of dyes and ultimately contributing to the superior photocatalytic activity observed.

ZnS/CuFe2O4/MXene ternary heterostructure photocatalyst for efficient adsorption and photocatalytic degradation of azo dyes under visible light: Synergistic effect, mechanism, and application

ZnS/CuFe2O4/MXene (ZSCFOM) composite with ternary heterostructures was prepared by solvothermal methods for the first time to effectively adsorb and photodegrade the azo dyes. ZSCFOM mainly adsorbed azo dyes through the hydrogen bonding and electrostatic interactions, with saturated adsorption capacities of 377 mg g−1 for direct brown M and 390 mg g−1 for direct black RN. ZSCFOM exhibited both characteristics of Schott heterostructure and p-n heterostructure, but it is not a simple superposition of the two heterostructures, but rather achieves better photocatalytic property. ZSCFOM performed a higher separation efficiency of electrons and holes than pure CuFe2O4 and pure ZnS. Under visible light, ZSCFOM was more effective in removing the azo dyes than MXene, CuFe2O4, ZnS, CuFe2O4/MXene, ZnS/MXene, and ZnS/CuFe2O4. The migration pathways of photogenerated carriers in ZSCFOM were inferred as that the electrons were concentrated in MXene and conduction band of ZnS, and holes were gathered in valence band of CuFe2O4. MXene served as a cocatalyst to accelerate the separation of electrons and holes. ZSCFOM mainly degraded DBM and DBRN by catalyzing the generation of holes, superoxide radicals, and hydroxyl radicals. The 100% of 0.05 g L−1 azo dyes were removed by ZSCFOM within 30 min from the environmental water systems.

Plasmon-Enhanced Photocatalysis Based on Plasmonic Nanoparticles for Energy and Environmental Solutions: A Review

Plasmonic nanoparticles are able to enhance the photocatalytic performance of semiconductor nanoparticles using four main mechanisms of light scattering, light concentration, hot electron injections, and plasmon-induced resonance energy transfer. Pushing the semiconductor nanoparticles’ absorption range to the visible and near-infrared and boosting the electron–hole generation quantum yield are the major effects. However, most of the reviewed papers lack a systematic design for conjugation of plasmonic nanoparticles with semiconductor nanoparticles, and they mainly benefited from the general enhancement because of the generated localized surface plasmon resonances. In this Review, we have systematically showed the importance of rational optical design of plasmonic-semiconductor nanoparticle conjugation for an efficient photocatalytic activity. The application of plasmon-enhanced phenomenon for the environmental remediation and green energy production was thoroughly reviewed. The degradation of organic dyes, air pollutants, volatile organic compounds, pesticides, and pharmaceutical compounds were the major reviewed works in environmental applications, while the green energy productions were limited to the role of plasmonic nanoparticles for the enhancement of H2/O2 production, water splitting, and CO2 reduction. This review can be a useful guideline for researchers working on enhancing the photocatalytic activity of the semiconductor nanoparticles and those interested in plasmon-enhanced phenomena by emphasizing the underlying mechanisms.

Hot hole multiplication from silver plasmon-resonated gold interband transitions for enhanced photoelectrochemical sensing

Compared with the widespread exploitation of hot electrons in plasmonic nanoparticles (NPs), hot holes generated from plasmonic metal interband transitions, are often overlooked in photoelectrochemistry, including photoelectrochemical sensing. Motivated by the subtle spectral overlap between the characteristic plasmonic bands of Ag NPs and interband transitions of Au, herein, we construct unusual core-shell Ag@Au NPs via an anti-galvanic reaction to promote the generation of hot holes. Benefiting from the unique plasmon resonances of Ag cores in specific wavelength regimes, Ag@Au can excite multiplied hot holes while Au cannot under the same conditions. With satisfactory accuracy and good practicability, the photoelectrochemical sensing platform based on Ag@Au NPs possesses a detection limit of 77 nmol/L for glucose, exhibiting significantly higher sensitivity compared to that using Au NPs. This work exemplifies the applications of interband hot-hole accumulation initiated by plasmons and may inspire more strategies to explore the utilization of hot holes in photoelectrochemistry.

Remarkably enhanced light and Ultrasonic-Boosting Peroxidase-like activity of g-C3N4-Cu-TCPP for antimicrobial applications

Bacterial infections therapy based on reactive oxygen species (ROS) remains challenging due to the limited efficacy of ROS generation. Herein, sonosensitizer molecules meso-tetra (4-carboxyphenyl) porphyrin (TCPP) -modified graphitic carbon nitride (g-C3N4) (g-C3N4-Cu-TCPP) was linked by Cu. The obtained g-C3N4-Cu-TCPP exhibited highly efficient photoacoustic-augmented catalytic activities. Moreover, the peroxidase-like (POD-like) activity of g-C3N4-Cu-TCPP was enhanced by ultrasound-visible light stimulation to enhance ROS production (i.e., superoxide radicals (∙O2–) and hydroxyl radicals (∙OH)) to achieve effective antimicrobial activities against both gram-negative and gram-positive bacteria with killing efficiency up to nearly 99.99%. Furthermore, in vitro antibacterial experiments results indicated that g-C3N4-Cu-TCPP exerted a synergistic effect for antimicrobial through disrupting cell integrity and producing ROS. Another possible reason is that a large amount of generation of holes (h+) and electrons (e-) under the photoacoustic-augmented caused charge transfer made a great contribution to the strong antibacterial capacity of the g-C3N4-Cu-TCPP. The developed photoacoustic nanozyme system provides a promising strategy for eradication of bacterial infection.

Enhancement of weak magnetism of 3C–SiC by 3d-transition metal doping

Defects seem to play a very decisive role in setting up long-range magnetic order in 3C–SiC. The feeble ferromagnetic response exhibited by SiC at room temperature, known as d0 magnetism, has been attributed to defects in the system. We present the strengthening of d0 magnetism through hole doping by 3d-transition metal (TM) substitution at the Si site. The valence state of the Mn, Co, and Ni has been found to be 2+ while Cr takes a 3+ valence state. The Mn-doped system exhibits the highest Curie temperature, saturation magnetization, and spontaneous magnetization value as compared to samples with other dopants. Detailed quantitative analysis of magnetization data and electron spin resonance spectra suggests the enhancement of the d0 magnetism due to the generation of holes caused by the TM doping at the Si site. The room temperature ferromagnetic response observed in the doped samples could be explained using modified Bound Magnetic Polaron (BMP) model.

Photocatalytic degradation of ciprofloxacin by MMT/CuFe2O4 nanocomposite: characteristics, response surface methodology, and toxicity analyses.

The photocatalytic degradation of ciprofloxacin (CIP) was examined by loading spinel ferrite copper (CuFe2O4) nanoparticles onto montmorillonite (MMT) under irradiation using UV light. The laboratory parameters were optimized using response surface methodology (RSM), and maximum efficiency (83.75%) was achieved at a pH of 3, CIP concentration of 32.5 mg/L, MMT/CuFe2O4 dose of 0.78 g/L, and irradiation time of 47.50 min. During the photocatalysis process, the experiments on radical trapping demonstrated the generation of hydroxyls (•OH), superoxide (•O2-) radical, electrons (e-), and holes (h+). A low rate drop (below 10%) in the CIP degradation during the six consecutive reaction cycles corroborated the remarkable recyclability and stability of the MMT/CuFe2O4. The acute toxicity of the treated solution was determined using Daphnia Magna, by applying photocatalysis, which was indicative of a marked decline in the toxicity. Comparing the findings of the degradation using UV and the degradation process using visible light represented results with close resemblance to each other at the end of the reaction time. Besides, under UV and visible light, the particles in reactor are easily activated when the pollutant mineralization exceeded 80%.

A novel Cr-doped CdS/ZnO nanocomposite for efficient photocatalytic hydroxylation of benzene to phenol

In this study, Cr-doped CdS/ZnO (Cr-CdS/ZnO) nanocomposites were synthesized for the first time and systematically characterized using different physicochemical methods, such as XRD, SEM, HRTEM, UV-Vis DRS, XPS, PL, EIS and EPR, etc. The photocatalytic activity of the Cr-CdS/ZnO nanocomposites was evaluated for the hydroxylation of benzene to phenol using H2O2 as the oxidant under visible-light irradiation. The impacts of various reaction conditions, including the role of catalyst dosage, solvents and volume ratio of benzene to H2O2 were specifically investigated. Owing to the similar lattice structure and well-matched band positions of CdS and ZnO, generation of electrons and holes by CdS-captured photons, as well as separation and imigration of electrons to ZnO were all realized. Furthermore, Cr-doping favored the formation of a new trapping level in the band gap of the Cr-CdS/ZnO composite, which would not only enhance visible-light absorption capacity, but also inhibit the rapid recombination of photo-generated electron-hole pairs. As a result, an excellent phenol selectivity of 98% with a phenol yield of 11.1% was achieved, which was higher than those of the pristine Cr-CdS, Cr-ZnO and CdS/ZnO. In the end, a rational mechanism for enhanced photocatalytic activity of the synthesized composites under visible-light irradiation was also proposed. The visible-light absorption and remarkably improved photocatalytic performance for benzene hydroxylation enable the potential of Cr-CdS/ZnO nanocomposites for the application of photocatalytic green synthesis of fine chemicals.

Heavy Primordial Black Holes from Strongly Clustered Light Black Holes.

We show that heavy primordial black holes may originate from much lighter ones if the latter are strongly clustered at the time of their formation. While this population is subject to the usual constraints from late-time universe observations, its relation to the initial conditions is different from the standard scenario and provides a new mechanism to generate massive primordial black holes even in the absence of efficient accretion, opening new scenarios, e.g., for the generation of supermassive black holes.

Selective photocatalytic oxidation of aromatic alcohols using B-g-C3N4/Bi2WO6 composites

In this work, B-g-C3N4/Bi2WO6 composites were synthesized by simple hydrothermal reaction and calcination, and their morphology, composition and physicochemical properties were characterized. The results show that the composite can selectively oxidize aromatic alcohols to aromatic aldehydes under visible light. The conversion rate of benzyl alcohol can reach 98.9% and the selectivity can reach 99% in 4 h, which are 1.59 times and 5.03 times that of Bi2WO6 alone, respectively. Further photoelectric performance investigation revealed that the recombination of B-g-C3N4 with Bi2WO6 effectively enhanced the separation of photogenerated carriers of B-g-C3N4 and suppressed the generation of holes on Bi2WO6, thereby improving the photocatalytic activity and the selectivity of the catalytic reaction of p-benzyl alcohol. In addition, the electronic effect and steric hindrance effect of substituents on the benzene ring on the selective catalytic oxidation of aromatic alcohols were also explored. Our work also reveals that the bandgap structure of the composites and the efficient separation of photogenerated electron transport are key factors to improve the photocatalytic reactivity and selectivity of organic reactions.

Generation of primordial black holes from an inflation model with modified dispersion relation

A primordial black hole (PBH) is interesting to people for its ability of explaining dark matter as well as supermassive astrophysical objects. In the normal inflation scenario, the generation of PBHs usually requires an enhanced power spectrum of scalar perturbation at the end of inflation era, which is expected when the dispersion relation of the inflaton field gets modified. In this work, we study a kind of inflation model called the Dirac-Born-Infeld-inspired nonminimal kinetic coupling (DINKIC) model, where the dispersion relation is modified by a square root existing in the field Lagrangian. We discuss the enhancement of scalar power spectrum due to the modified dispersion relation, as well as the abundance of PBHs produced by the Press-Schechter collapse mechanism. We also discuss the formation of scalar-induced gravitational waves by linear scalar perturbations.

Impact Generation of Holes in the Early Lunar Crust: Scaling Relations

AbstractAfter its formation, the Moon is widely believed to have possessed a deep, global magma ocean. As it cooled, an anorthositic crust formed, floating atop this magma ocean and acting as an insulating blanket. As well as forming the Moon, the Moon‐forming giant impact also released more than a lunar mass of debris into heliocentric orbit. Reimpacting debris subjected the newly formed Moon to an extremely intense bombardment. We have conducted a suite of impact simulations for a range of conditions representative of this early period. We find that impact outcomes can be divided into four regimes and construct scaling relations for the transitions between these regimes and size of impact features. Exposure of liquid magma to the surface is generally more efficient than previously assumed, implying significant shortening of the solidification time of the Lunar Magma Ocean. Comparison with work on icy satellites also suggests that penetration of a solid crust overlying liquid is a relatively universal process with weak dependence on target material properties.

Low-order wavefront control using a Zernike sensor through Lyot coronagraphs for exoplanet imaging

Context. Wavefront sensing and control (WFSC) will play a key role in improving the stability of future large segmented space telescopes while relaxing the thermo-mechanical constraints on the observatory structure. Coupled with a coronagraph to reject the light of an observed bright star, WFSC enables the generation and stabilisation of a dark hole (DH) in the star image to perform planet observations. Aims. While WFSC traditionally relies on a single wavefront sensor (WFS) input to measure wavefront errors, the next generation of instruments will require several WFSs to address aberrations with different sets of spatial and temporal frequency contents. The multiple measurements produced in such a way will then have to be combined and converted to commands for deformable mirrors to modify the wavefront subsequently. Methods. We asynchronously operate a loop controlling the high-order modes digging a DH and a control loop that uses the rejected light by a Lyot coronagraph with a Zernike wavefront sensor to stabilize the low-order aberrations. Using the HiCAT testbed with a segmented telescope aperture, we implement concurrent operations and quantify the expected cross-talk between the two controllers. We then present experiments that alternate high-order and low-order control loops to identify and estimate their respective contributions. Results. We show an efficient combination of the high-order and low-order control loops, keeping a DH contrast better than 5 × 10−8 over a 30 min experiment and stability improvement by a factor of 1.5. In particular, we show a contrast gain of 1.5 at separations close to the DH inner working angle, thanks to the low-order controller contribution. Conclusions. Concurrently digging a DH and using the light rejected by a Lyot coronagraph to stabilize the wavefront is a promising path towards exoplanet imaging and spectroscopy with future large space observatories.

Hole Depth Prediction in a Femtosecond Laser Drilling Process Using Deep Learning.

In high-aspect ratio laser drilling, many laser and optical parameters can be controlled, including the high-laser beam fluence and number of drilling process cycles. Measurement of the drilled hole depth is occasionally difficult or time consuming, especially during machining processes. This study aimed to estimate the drilled hole depth in high-aspect ratio laser drilling by using captured two-dimensional (2D) hole images. The measuring conditions included light brightness, light exposure time, and gamma value. In this study, a method for predicting the depth of a machined hole by using a deep learning methodology was devised. Adjusting the laser power and the number of processing cycles for blind hole generation and image analysis yielded optimal conditions. Furthermore, to forecast the form of the machined hole, we identified the best circumstances based on changes in the exposure duration and gamma value of the microscope, which is a 2D image measurement instrument. After extracting the data frame by detecting the contrast data of the hole by using an interferometer, the hole depth was predicted using a deep neural network with a precision of within 5 μm for a hole within 100 μm.

Photocatalytic degradation of tetracycline by N-CQDs modified S-g-C3N4 nanotubes and its product toxicity evaluation

In this study, to improve the electron-hole pairs separation rate and enhance the antibiotic wastewater treatment efficiency, the sulfur doped g-C3N4 (SCN) nanotubes were modified with nitrogen-doped carbon quantum dots (N-CQDs) derived from pig manure by a simple solvothermal method, and SCN/N-CQDs composite photocatalyst was synthesized. SCN with hexagonal tubular structure has strong light scattering ability and abundant active sites. At the same time, the modification of N-CQDs extended the visible light response range, accelerated the separation of electron-hole pairs, and realized the efficient photocatalytic degradation of tetracycline (TC). The SCN/N-CQDs-1 showed the best photocatalytic performance, and degradation rate of TC could reach to 79.11% after 90 min of visible light irradiation, much higher than the degradation efficiency of pure SCN (58.33%). Among them, the generation of hole, hydroxyl radicals and superoxide radicals play an important role in the efficient degradation of TC. Furthermore, the intermediates produced during the degradation process were detected by ultra-performance liquid chromatography-mass spectrometry (HPLC − MS), and the possible TC degradation pathways were investigated. The repeatability and practicability of SCN/N-CQDs are proved by five cycle experiments. In addition, compared with the original toxicity, the inhibition rate of Escherichia coli (E. coli) colony growth was reduced by 91.315% after 90 min photodegradation. The results of biotoxicity analysis showed that SCN/N-CQDs leaching solution and its photodegradation wastewater did not produce biotoxicity to E. coli.