Generation Of Holes Research Articles

The optimal sintering atmosphere and defect structure of CuO-doped NKN-based ceramic with p/n-type conduction mechanism

The chemical doping and sintering atmosphere have great influence on the defect structure and piezoelectric properties of (Na,K)NbO3 (NKN)-based ceramics. In this work, p/n-type NKN-based ceramics are designed by introducing different CuO doping contents. The defect configuration is analyzed by Rietveld refinement, Hall-effect measurement and impedance spectroscopy. The undoped and 3 mol% CuO-doped ceramics exhibit an n-type conduction mechanism. When n-type ceramics are sintered in air, the electron concentration will decrease, resulting in the better piezoelectric and dielectric properties than that sintered in N2. Nevertheless, 1 mol% CuO-doped ceramics exhibit a p-type conduction mechanism. The generation of holes can be suppressed when p-type ceramics are sintered in N2, which is beneficial to improve their piezoelectric and dielectric properties. The experimental results suggest that the p/n-type behavior can be judged by defect analysis and the optimal sintering atmosphere of NKN-based ceramics can be predicted by analyzing the charge carrier behavior of p/n-type ceramics.

Sub-Pico-Second Hole Generation Lifetime in Thin Film IGZO Sputtered and Annealed on P-Silicon Substrate

Indium-gallium-zinc-oxide (IGZO) sputtered and annealed in the absence of oxygen shows large oxygen vacancy concentration leading to n-type doping of the thin film. However, because of low intrinsic carrier concentration minority carrier (hole) concentration remains weak. Thus, measurement of thermal hole generation lifetime in unipolar IGZO is challenging. In this work, utilizing the charge transient of an appropriately biased depleted HfO2/IGZO thin film MOS capacitor fabricated on a p-silicon substrate, we extracted hole thermal generation lifetime of IGZO. The measured lifetime was found between 0.62–0.064 ps whence IGZO film received 400 °C to 700 °C anneal treatments followed by its direct sputtering on p-silicon substrate. Further, a morphology analysis of the IGZO was presented. Difference in the lifetime which occurred due to amorphous to the nano-crystalline transition of the IGZO thin film with increased anneal temperature was furthermore validated through XRD, SEM and AFM measurements. Hole capture cross-sections as we obtained from surface generation velocities at the IGZO/HfO2 interface and energy distributions of interface state density were found in agreement, which indirectly demonstrates the accuracy of the measured hole generation lifetime employing the transient capacitance extrapolation, since under the steady state condition hole generation through the interface states of IGZO/HfO2 tends to balance its bulk (IGZO) counterpart

Realization of Low-wax Lipstick by Rubber Molding Technology.

Reducing the quantity of wax in lipstick can improve the properties of the lipstick, including the glossiness, moisturizing capability, and longevity. However, lipsticks with less wax tend to break more easily. Therefore, to prevent breakage while reducing the wax content, we focused on the crystal structure of the wax gel and strain generated during the cooling and solidification processes as they are structural factors that affect fragility. Generally, if the crystals and strain are small, the structure is less easily broken. However, because the tip of the lipstick cools more rapidly from below than the root, the strain of the root against the tip increases owing to poor heat transmission. This creates large shrink holes in the root. While reheating from above can suppress the generation of shrink holes, it also causes the crystals to grow larger and the structure to become weak owing to slow cooling. Therefore, we adopted a rubber-molding technology generally used to form logos and complicated shapes as a strategy to mitigate these issues. This successfully reduced the strain generated inside the lipstick during the cooling process, as the rubber mold shrunk along with the lipstick, making it possible to quench the root. Therefore, we were able to realize a small crystal structure and low strain on the root of the lipstick. Our results demonstrate that it is possible to realize a lipstick with excellent features by reducing the quantity of wax.

Investigation of Laser Drilled Pilot Holes and Additively Generated Pilot Holes as Drilling Guides for Single-lip Deep Hole Drilling

Investigation of Laser Drilled Pilot Holes and Additively Generated Pilot Holes as Drilling Guides for Single-lip Deep Hole Drilling

Polarization-dependent hole generation in 222 nm-band AlGaN-based Far-UVC LED: a way forward to the epi-growers of MBE and MOCVD

AGaN-based 222 nm-band Far-ultraviolet-C (Far-UVC) light-emitting-diodes (LEDs) offer a promising technology for the disinfection of surface, air, water, food and airborne disease transmission in occupied spaces, including COVID-19 (SARS-CoV-2) and other viral diseases, when it is meticulously designed, engineered, and applied.

ZnFe2O4 Doped TiO2 Photocatalyst Synthesis and Characterization with Effect of Different Coupling Ratios on Band Gap

In this work the effect of different coupling ratios of ZnFe2O4 and TiO2 on the band gap was investigated, to convert TiO2 as a visible light driven photocatalyst ZnFe2O4. In this work, ZnFe2O4 was synthesized utilizing sol-gel technique and calcining under normal atmosphere at 900 and#176;C. Thereafter, ZnFe2O4 was coupled with TiO2 by mixing in 50 ml water in three different coupling w/w ratios (1:1, 1:2 and 2:1) followed by the calcination of coupled catalyst under nitrogen environment at 500 and#176;C. XRD, XPS, FESEM-EDS imaging, TGA, UV-Vis, and FTIR were performed to characterize the catalyst. Crystal phase identification could be confirmed through XRD analysis with homogenous distribution of metal constituents through color mapping and surface charge transitions from XPS analysis for a better electron hole generation. Thermogravimetric analysis (TGA) confirmed that the pure ZnFe2O4 obtained at 900 and#176;C, while FTIR verified the presence of desired functional group in ZnFe2O4. Moreover, Fourier Transformation Infrared Spectroscopy (FTIR) illustrated two major peaks and no extra major impurity was detected. ZnFe2O4 is visible light driven photocatalyst and TiO2 can work only under UV light. So, the effect of different coupling ratios of ZnFe2O4 with TiO2 was examined by UV-Vis characterization. The band gap is given by 1:1 was 2.8, 2:1 was 3.17 and 1:2 was 3.02. It was observed that the most optimum coupling ratio is 1:1 and the band-gap fall under visible region. The findings of this work could be supportive significantly for the selection of suitable coupling ratio to convert UV-driven photocatalyst into visible region active photocatalyst.

Propagating Fe-N4 active sites with Vitamin C to efficiently drive oxygen electrocatalysis

Free transition metal ions (such as Fe 2+ , Co 2+ ) exposed on the surface of metal organic frameworks (MOFs) would be highly aggregated during the carbonization process, which is not conducive to formation of M-N X active sites, resulting in reduced electrochemically active sites. Accordingly, to effectively suppress the free metal ions on the surface of MOFs and increase Fe-N 4 active sites, Vitamin C (L (+)-ascorbic acid), with an ability to coordinate transition metals, is complexed with ferrous ions. Meanwhile, the acidity of Vitamin C can moderately erode the surface of MOFs materials, further accelerating the generation of holes and defects in the carbonized products. Compared with the control samples without introduction of Vitamin C, the iron-based (VC-MOF-Fe) catalyst, with obviously increased Fe-N 4 active sites, exhibit significantly enhanced oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance. When used in rechargeable zinc-air batteries, the peak power density of VC-MOF-Fe (113 mW cm −2 ) is also better than that of 20% commercial Pt/C + RuO 2 . Interestingly, the function of Vitamin C also applies to the cobalt-based catalyst (VC-MOF-Co), evidencing the universality of this strategy. By introducing Vitamin C, the growth of transition metal (Fe, etc.) particles is suppressed, which significantly increases the amount of Fe-N 4 active sites in MOFs-derived catalysts, leading to a significant improvement in oxygen electrocatalytic performance. • Vitamin C suppresses aggregation of free ferrous ions on MOFs, producing more Fe-N 4 active sites. • The prepared VC-MOF-Fe catalyst exhibit significantly enhanced ORR performance in alkaline and acidic media. • It also shows improved OER performance in alkaline media. • It has high open circuit voltage and power density in the application of zinc-air batteries. • It also applies to VC-MOF-Co catalyst, which provides a new route on increasing M-Nx active sites.

Sacrificial Volume Materials for Small Hole Generation in Low-Temperature Cofired Ceramics

The creation of hole, cavity or channel structures in low-temperature cofired ceramics (LTCCs), using different sacrificial volume materials (SVMs) was tested. The main functionality of the SVMs should be: easy application into the holes; protection of holes during lamination; uninhibited lamination between layers; and, during firing should burn out before the pores of the LTCCs close, to leave the empty holes clear of any residue. Five different materials were tested—hydroxyethyl cellulose (HEC) 2 wt%, HEC 5 wt%, agar-agar, gelatin, and commercial carbon paste—and compared to a reference sample where no SVMs were used. In all cases, lamination parameters were minimised in order to preserve the tested hole structures. Matrixes with holes ranging from 158 to 268 µm, with pitches of 573 µm in a green state, were tested. The agar-agar caused ceramic deformation as a result of thermal burst during firing and the lamination between the layers was compromised. The carbon paste was difficult to handle, requiring extra equipment for hole filling and incomplete filling of the larger holes. Traces of carbon paste were left as a landing pad on top of the holes, inhibiting lamination at these areas. The gelatin and the 2 wt% and 5 wt% hydroxyethylcellulose (HEC 2 wt% and HEC 5 wt%) filled all holes completely, and also worked as adhesive-assisted lamination (AAL) materials with excellent lamination between layers. Excellent lamination was also observed in the no-SVM case. Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) analyses established that, for all SVMs tested, the remaining residue is negligible after firing. As a result, the HEC 2 wt% material was considered ideal for use as an SVM.

Tumor-Targeting Liposomes with Transient Holes Allowing Intact Rituximab Internally.

In this study, the strategy of transient generation of holes in the liposome surface has been shown to enable safe encapsulation of a high-molecular weight antibody (rituximab, Mw ∼140 kDa) within liposomes. These transient holes generated using our magnetoporation method allowed rituximab to safely enter the liposomes, and then the holes were plugged using hyaluronic acid grafted with 3-diethylaminopropylamine (DEAP). In the tumor microenvironment, the resulting liposomal rituximab was destabilized because of the ionization of the DEAP moiety at the acidic pH 6.5, resulting in extensive release of rituximab. Consequently, the rituximab released from the liposomes accumulated at high levels in tumors and bound to the CD20 receptors overexpressed on Burkitt lymphoma Ramos cells. This event led to significant enhancement in tumor cell ablation through rituximab-mediated complement-dependent cytotoxicity and Bcl-2 signaling inhibition-induced cell apoptosis.

Synergistic effects between the S-TiO2 photocatalyst and the Fenton-like reagent: Enhanced contaminant oxidation under visible light illumination

Sulfur-doped TiO2 (S-TiO2) coupled with the Fenton-like reagent (i.e., Fe(III) and H2O2) exhibited photochemical activity under visible-light illumination, resulting in the degradation of over 95 % benzoic acid, 95 % carbamazepine, and 99 % 4-chlorophenol within 30 min. The combined system removed contaminants much faster than its uncombined S-TiO2/visible light and Fe(III)/H2O2 counterparts. The synergistic effect between S-TiO2 and the Fenton-like reagent was found to be due to 1) the generation of conduction band electrons and valence band holes in S-TiO2 under visible light illumination; 2) the reduction of Fe(III) by the conduction band electrons, thereby enhancing Fe(II) generation while minimizing electron-hole recombination; 3) the production of •OH from the reactions between Fe(II) and H2O2, and between H2O2 and conduction band electrons; and 4) the oxidation of contaminants by both valence band holes and •OH. Under the experimental conditions employed in this study, the S-TiO2/visible light/Fe(III)/H2O2 system exhibited a sustainable reactivity over 7 testing cycles, with more than 90 % of BA degraded in each cycle.

Termination Effects in Aluminosilicate and Aluminogermanate Imogolite Nanotubes: A Density Functional Theory Study

We investigate termination effects in aluminosilicate (AlSi) and aluminogermanate (AlGe) imogolite nanotubes (NTs) by means of semi-local and range-corrected hybrid Density Functional Theory (DFT) simulations. Following screening and identification of the smallest finite model capable of accommodating full relaxation of the NT terminations around an otherwise geometrically and electrostatically unperturbed core region, we quantify and discuss the effects of physical truncation on the structure, relative energy, electrostatics and electronic properties of differently terminated, finite-size models of the NTs. In addition to composition-dependent changes in the valence (VB) and conduction band (CB) edges and resultant band gap (BG), the DFT simulations uncover longitudinal band bending and separation in the finite AlSi and AlGe models. Depending on the given termination of the NTs, such longitudinal effects manifest in conjunction with the radial band separation typical of fully periodic AlSi and AlGe NTs. The strong composition dependence of the longitudinal and radial band bending in AlSi and AlGe NTs suggests different mechanisms for the generation, relaxation and separation of photo-generated holes in AlSi and AlGe NTs, inviting further research in the untapped potential of imogolite compositional and structural flexibility for photo-catalytic applications.

Strongly Reducing (Diarylamino)benzene-Based Covalent Organic Framework for Metal-Free Visible Light Photocatalytic H2O2 Generation.

Photocatalytic reduction of molecular oxygen is a promising route toward sustainable production of hydrogen peroxide (H2O2). This challenging process requires photoactive semiconductors enabling solar energy driven generation and separation of electrons and holes with high charge transfer kinetics. Covalent organic frameworks (COFs) are an emerging class of photoactive semiconductors, tunable at a molecular level for high charge carrier generation and transfer. Herein, we report two newly designed two-dimensional COFs based on a (diarylamino)benzene linker that form a Kagome (kgm) lattice and show strong visible light absorption. Their high crystallinity and large surface areas (up to 1165 m2·g–1) allow efficient charge transfer and diffusion. The diarylamine (donor) unit promotes strong reduction properties, enabling these COFs to efficiently reduce oxygen to form H2O2. Overall, the use of a metal-free, recyclable photocatalytic system allows efficient photocatalytic solar transformations.

High Pressure Effect on Structural and Electrochemical Properties of Anionic Redox-Based Lithium Transition Metal Oxides

Summary The richness of anionic redox chemistry in the solid state offers new opportunities and a possible paradigm shift in energy storage. The excess capacity that goes beyond conventional theoretical values is attributed to the anionic redox in Li-rich transition metal oxide cathodes for Li-ion batteries. Their electrochemical behavior is thermodynamically determined by structural evolution. To better understand the electrochemical dependence on structural factors, we have induced structural modifications in pristine and electrochemically activated Li1.144Ni0.136Co0.136Mn0.544O2 through high-pressure treatment. A unique cyclical change of structural reordering is observed in the anionic redox-activated material during operando pressure sweep, characterized by a periodic evolution of superlattice peak intensity in synchrotron X-ray diffraction patterns. During the structural reordering period, the bulk compressibility of the material decreases, even becoming negative. These insights elucidate the structural flexibility and metastability of anionic redox-based materials, which can undergo large compressions and structural modifications while delivering good electrochemical properties.

Substrate stoichiometry changes during pulsed laser deposition: a case study on SrTiO[formula omitted

The influence of UV illumination by the plasma plume on the substrate stoichiometry during pulsed laser deposition (PLD) was examined on the model perovskite SrTiO3 (STO) by the means of in situ impedance spectroscopy during pulsed laser deposition (IPLD). In this manner, the evolution of the STO bulk conductivity was tracked at 300 ∘C during STO thin film deposition and during deposition on a quartz cover to isolate illumination effects from deposition effects. These measurements revealed an increasing bulk conductivity during covered measurements. Impedance spectroscopy under applied bias voltages indicates that these changes are not caused by photovoltages but by an enhanced oxygen incorporation compensated by electron hole generation under UV illumination. This enhanced conductivity persists after illumination. The combination of across-plane and in-plane measurements further indicates the formation of a layered system, allowing to estimate conductivity and thickness of the newly formed oxygen vacancy deficient layer. This results in a ∼30 times more conductive top layer with a thickness of ∼40 μm. The driving force induced by the UV illumination which is responsible for this stoichiometry change corresponds to a p(O2) difference of around six orders of magnitude. Results of in situ measurements show that the real deposition of a thin film leads to a more complex layered system where the growing film interacts with the illuminated top layer of the substrate and possibly introduces additional oxygen vacancies. These changes have a strong influence on any grown thin film either by oxidation/reduction potential or lattice parameter changes.

CMOS-compatible all-dielectric metalens for improving pixel photodetector arrays

Metasurfaces and, in particular, metalenses have attracted large interest and enabled various applications in the near-infrared and THz regions of the spectrum. However, the metalens design in the visible range stays quite challenging due to the smaller nanostructuring scale and the limited choice of lossless CMOS-compatible materials. We develop a simple yet efficient design of a polarization-independent, broadband metalens suitable for many CMOS-compatible fabrication techniques and materials and implement it for the visible spectral range using niobium pentoxide (Nb2O5). The produced metalens demonstrates high transmittance and focusing ability as well as a large depth of focus, which makes it a promising solution for a new generation of silicon photomultiplier photodetectors with reduced fill factor impact on the performance and reduced electron–hole generation regions, which altogether potentially leads to improved photodetection efficiency and other characteristics.

Carbon quantum dots decorated heteroatom co-doped core-shell Fe0@POCN for degradation of tetracycline via multiply synergistic mechanisms

In this study, novel core-shell catalyst with a new ternary heterostructure was synthesized (Fe0@POCN/CQDs) for the degradation of tetracycline (TC). The TEM results showed that the Fe0 particles were wrapped in POCN material and many nano CQDs were uniformly dispersed in the material. The new ternary nanocomposite exhibits excellent photocatalytic activity for the removal of TC, which was approximately 4.76 times higher than that of GCN. The enhancement of photocatalytic activity was attributed to the effective heterojunction as well as the multiply synergistic effects of POCN combined with Fe0 and CQDs, which was beneficial for retardation of recombination rate of photogenerated electron–hole pairs and generation of more free radicals for the oxidation of TC. Besides, the reactive oxygen species (ROS) of h+, •O2− and •OH played pivotal roles in the degradation of TC by Fe0@POCN/CQDs during the photocatalytic reaction. At the same times, sulfate radical (SO4•-) and hydroxyl radical (•OH) highlighted the dominant role in the degradation process compared with other free radicals under persulfate hybrid mixture system (PS system), which was further confirmed by radical scavenger experiments and electron spin resonance (ESR) analysis. The response surface methodology (RSM) study indicated that the optimal removal parameters of tetracycline could reach 97.57% within 30 min under PS system. In addition, the possible degradation pathway intermediates of TC were studied by HPLC-MS and the reaction catalytic activity mechanism of Fe0@POCN/CQDs/persulfate system was discussed.

Performance improvement of ultra-thin CIGS solar cells with decrease in light loss by surface texturing

The main objective of the present study is to present a solution for downsizing the promising CIGS solar cells in order to be more flexible, economic and environmentally friendly. To avoid possible degradations due to downsizing, a series of optimizations were performed. ATLAS and DEVEDIT of SILVACO tool were used for simulations. After verification of the accuracy of simulation process, surface texturing was used to reduce light reflections and enhance the light trapping of an ultra-thin CIGS solar cell (thickness = 0.5 µm). Compared with the results of non-textured solar cells all output parameters showed a notable improvement. Replacement of CdS buffer by ZnO layer led to further enhancement of the output parameters. In the following step, a dual-grading profile was used to increase the electron–hole generation. Successful combination of the performed optimizations resulted in high conversion efficiency of 18.62% for an ultra-thin CIGS solar cell.

Surface oxygen vacancies on WO3 nanoplate arrays induced by Ar plasma treatment for efficient photoelectrochemical water oxidation

The construction of surface defects on semiconductor oxide photoanodes has been identified as a promising route for attaining improved photoelectrochemical (PEC) performance. Here, Ar plasma treatment has been used to etch the surface of hydrothermally synthesized WO3 nanoplate array films, which generated surface oxygen vacancies (Ovs) with the concomitant reduction of surface W6+ to W5+/W4+. As a result, the visible-light absorption and photogenerated charge separation of WO3 was enhanced, as evidenced by X-ray photoelectron spectroscopy (XPS), UV/Vis diffuse-reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. A WO3 photoanode subjected to Ar plasma treatment for 120 s exhibited a photocurrent density of 1.32 mA cm−2 and an O2 evolution rate of 1.0 μmol cm−2·min−1 under simulated solar light irradiation at a bias potential of 1.23 V vs. reversible hydrogen electrode, approximately 1.7- and 5-times higher, respectively, than those of a pristine sample. This improvement is mainly attributed to the facilitative effect of surface oxygen vacancy defects, which promote electron–hole generation and separation rates and decrease the interfacial charge-transfer resistance between the WO3 photoanode and electrolyte. Our Ar plasma surface modification also has potential for developing other photoanodes for efficient PEC performance.

Analogue Hawking radiation from black hole solitons in quantum Josephson transmission lines

The nonlinear LC circuit dual to the Toda lattice (voltage) soliton is studied using the reductive perturbation method. It is found that the current flowing through the circuit obeys the defocusing modified Korteweg--de Vries equation with shock-wave-type (current) solitons. The current soliton spatially modulates the nonlinear inductance, equivalently the spatial modulations of electromagnetic wave velocity in the circuit, resulting in the generation of analogue black holes. Hawking radiation from the black holes is also discussed based on the tunneling models.

Effects of Zn Ratio Tuning on the Structural and Transport Properties of Amorphous Indium Zinc Tin Oxide Thin Films

In this study, various indium zinc tin oxide (IZTO) films were fabricated using co-sputtering to explore amorphous transparent conducting oxides as alternatives to crystalline indium tin oxide (ITO). Various Zn ratios were tuned to study their effects on the structural evolution of IZTO. Amorphous IZTO (aIZTO) films were obtained when the Zn concentration was higher than approximately 17 at.%. X-ray diffraction and transmission electron microscopy analyses indicated that amorphous structures were formed due to the high crystallization temperatures of IZTO and nanocrystalline In2Zn5O8, which also caused aIZTO to exhibit small band gaps. On average, 87% transmittance was achieved in the visible light range. The aIZTO films had substantially higher transmittance in the infrared region than the ITO films did. Samples with Zn ratios between approximately 17 at.% and 27 at.% exhibited resistivity (approximately 3 × 10−4 Ω-cm), mobility (7 cm2 V−1 s−1), and carrier concentrations (4 × 1021 cm−3) comparable to those of crystalline ITO. Thus, the aIZTO films are promising alternative TCO materials. The mechanisms of competition between the crystallinity, oxygen deficiency, high-mobility In2Zn5O8, and electron and hole generation rates were applied to shed light on the excellent electrical and transport properties of aIZTO films.