Trap Levels Research Articles

Abnormal Temperature Dependence of Huang-Rhys Factor and Exciton Recombination Kinetics in CsPbBr3 Perovskite Quantum Dots.

Anomalous thermal behaviors of excitonic luminescence in CsPbBr3 perovskite quantum dots (PQDs) were observed. It is found that the main luminescence peak originated from the excitonic radiative recombination assisted by the longitudinal-optical (LO) phonon, and its integrated intensity first declines as the temperature varies from 10 to 150 K and then turns to increase at ∼160 K, reaching a maximum value at 300 K. A model considering the thermal detrapping and transfer of electrons from a trap level is developed to interpret these abnormal thermal behaviors of the luminescence from the PQDs. On the other hand, the quantum-mechanical multimode Brownian oscillator model was employed to unravel that the Huang-Rhys factor exclusively characterizing the exciton-phonon coupling in the studied CsPbBr3 PQDs decreases from 1.65 at 10 K to 1.31 at 200 K.

Controlling the luminescence of CdSe quantum dots in the fluorinephosphate glass

A series of fluorophosphate glasses with CdSe and CdSe+ZnSe are successfully synthesized. After heat treatment above the glass transition temperature, CdSe quantum dots with sizes 1.5–5.5 nm are formed. The luminescence spectra of CdSe quantum dots are analyzed at various temperatures, excitation energies and chemical composition of glass. The influence of selenium content on the growth features of quantum dots is shown. The size dependence of luminescence quantum yield on the QDs size is found. The 2.0–2.5 nm-sized QDs demonstrate trap emission in the region of 1.7–1.85 eV with a maximum quantum yield of 60 %. It is found that only a broad band due to the transition from the low state of the conduction band and the shallow donor trap states to the deep accepter trap levels is observed. This broad emission band is observed at any selenium cadmium ratio and zinc introduction.

Innovation in Dialysis: Air Trap Level Management

Innovation in Dialysis: Air Trap Level Management

The Photoionization Processes of Deep Trap Levels in n-GaN Films Grown by MOVPE Technique on Ammono-GaN Substrates

In this paper, we present various theoretical models that accurately approximate the spectral density of the optical capture cross-section (σe0) obtained through the analysis of photo-capacitance transients using the deep-level optical spectroscopy (DLOS) technique applied to semi-transparent Ni/Au Schottky barrier diodes (SBDs) fabricated on n-GaN films. The theoretical models examined in this study involved a variety of approaches, from the Lucovsky model that assumes no lattice relaxation to more sophisticated models such as the Chantre–Bois and the Pässler models, which consider the electron–phonon coupling phenomenon. By applying theoretical models to the experimentally determined data, we were able to estimate the photoionization (E0), trap level position (ET), and Franck–Condon (dFC) energy, respectively. In addition, the results of our analysis confirm that the photoionization processes of deep traps in n-GaN grown by the metal–organic vapor-phase epitaxy technique (MOVPE) are strongly coupled to the lattice. Moreover, it was shown that the Pässler model is preferred for the accurate determination of the individual trap parameters of defects present in n-GaN films grown on an Ammono-GaN substrate. Finally, a new trap level, Ec-1.99 eV with dFC = 0.15, that has not been previously reported in n-GaN films grown by MOVPE was found.

Sn2+/Pb2+ Doping‐Induced Highly Transparent Boroaluminate Microcrystalline Glass With Deep Traps for Long‐Term Optical Storage and Time‐Lapse X‐ray Imaging

AbstractThe development of microcrystalline glass‐ceramics with high transparency and deep trap energy levels is crucial for the cost‐effective and large‐scale production of scintillators and optical data storage applications. In this study, the incorporation of highly electronegative divalent tin (Sn2+) plays a key role in modulating the network structure of borate glass. This leads to the successful synthesis of SrAl2O4:Eu2+ microcrystalline glass with high transparency, reaching up to 80%, and excellent crystallinity. Additionally, a series of non‐optically active ions with different valence states is co‐doped with Eu2+ to fine‐tune the trap levels of the SrAl2O4 microcrystals. All samples maintain high crystallinity and exhibit good transparency. In particular, the Pb2+ ion co‐doped samples achieve an increased trap energy level of 1.28 eV, significantly enhancing their capacity to capture X‐rays and ultraviolet light. Density functional theory calculations reveal that this enhancement is due to severe lattice distortion caused by Pb2+ ions occupying interstitial sites in SrAl2O4. Utilizing the SrAl2O4:Eu2+, Pb2+ glass‐ceramics materials, X‐ray imaging with a delay of up to 210 s and optical information storage for >60 d is achieved. This study provides valuable insights into the crystal growth and trap modulation of persistent luminescent materials within a three‐dimensional glass network structure.

Pushing the Limits of Photoconductivity via Hot Electrons in Deep Trap States in Plasmonic Architectures.

Although extensive research on the mechanisms of photoconductivity enhancement in plasmonic Schottky structures has been conducted, the photoconductive interplay between hot electrons and trapping states remains elusive. In this study, we explored the photoconductive relationship between plasmonic hot-carriers and defect sites present in plasmonic architectures consisting of N-face n-GaN and Au nanoprisms. Our experimental results clearly verified that the plasmonic hot-electrons generated by interband transitions preferentially occupied deep trap levels in n-GaN, thereby considerably enhancing the photoconductivity through the combination of photogating and photovoltaic effects. Our quantitative evaluation demonstrated that a mere 63% increase in hot-electron trapping leads to a 1.7-fold increased photocurrent under localized surface plasmon resonance (LSPR) excitation compared to the figure of photocurrent under non-LSPR stimulus. Our findings provide novel insights into the mechanisms of photoconductive enhancement for advanced plasmonic applications.

Thermoluminescence properties of β-ray irradiated LuAGG:Ce nanophosphors prepared by sol-gel method for potential applications in dosimetry

In this paper, Lu2.97Al5–xGaxO12:Ce0.03 (x = 0, 1, 2, 3) nanophosphors were synthesized using sol-gel method and calcined at 1100 °C for 3 h. The effect of Ga content on the structural, photoluminescence (PL), and notably thermoluminescence (TL) glow curve, dose response, repeatability and fading properties were investigated. X-ray diffraction (XRD) results indicated that all synthesized samples were crystallized in a pure garnet phase. The PL emission spectra exhibited a broad emission band corresponding to the 5 d → 4f (2F5/2, 2F7/2) transition of Ce3+ ions in the garnet lattice. Furthermore, a significant decrease in emission intensity was observed upon increasing Ga content. The TL characteristics of nanopowders irradiated with β-rays revealed a significant effect of Ga content on the peak position, shape and intensities of TL Glow curves, which can be explained by the reduction of the energy gap and the distribution of trap levels. The dose response linearity in the range of 0.125–100 Gy was examined for different Ga content, revealing a good linear behavior for x = 0 and 1 Ga. Additionally, samples prepared with x = 0, 1, and 2 Ga exhibited a high level of repeatability across a batch of 10 samples. Also, fading studies were performed for 128 h and revealed strong fading in samples synthesized with x = 0 and 1 Ga. These results suggest potential applications of Lu3Al5O12:Ce and Lu3Al4Ga1O12:Ce in ionizing radiation dosimetry.

An investigation on thermoluminescence properties and kinetic parameters of Çankırı rock salt

This study investigates the thermoluminescence (TL) dosimetric properties and kinetic parameters of natural salt samples sourced from the Çankırı rock salt cave in Turkey using β irradiation. Obvious effective TL maximum observed at around 85 and 230°C. A preheat condition was determined to apply a thermal cleaning for the lower temperature side of TL spectrum. Dose sensitivity, linearity and reusability characteristics were investigated for effective TL maximum on the high temperature side of the spectrum. TL kinetic parameters were determined via various heating rates (VHR) experiment, and whole TL glow curve was studied via Tm−Tstop experiment and glow curve deconvolution. General order kinetics approach was utilized for glow curve deconvolution analysis. Kinetic parameters were determined for at least eight electron trap levels which has activation energies in the range of 0.8–1.53 eV.

Al–O–Al defect complexes as possible candidates for channel electron mobility reducing trapping centers in 4H-SiC metal–oxide–semiconductor field-effect transistors

The deep-level drain current transient spectroscopy (Id-DLTS) measurements of Al-doped SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) strongly suggest that the reduction in the channel mobility at low temperatures is related to a shallow trap detectable at 70 K. Using the Shockley–Reed–Hall (SRH) theory, the level of this trap has been extracted to be around 0.15 eV below the conduction band minimum of SiC. Density functional theory (DFT) calculations of AlSiNCAlSi and AlSiOCAlSi defect complexes have found one configuration of the AlSiOCAlSi complex, which has a charge transition level within the SRH extracted trap level range. Therefore, we suggest that these AlSiOCAlSi defects are likely candidates for traps responsible for the channel mobility reduction.

Surface sulphur vacancies of CdS/MIL-68(In)–NH2 for Boosting Visible-Light photocatalytic hydrogen evolution

The incorporation of sulfur vacancies (SVs) during the synthesis of CdS represents an essential approach for enhancing its photocatalytic hydrogen production performance. The CdS/MIL-68(In)–NH2 photocatalytic material with SVs was successfully synthesized via a facile two-step method and employed for visible light photocatalytic hydrogen evolution. Among various loading ratios, the CdS(30)/MIL-68(In)–NH2 composite exhibited remarkable photocatalytic performance, demonstrating hydrogen evolution rates 3.7 times and 7.3 times higher than those of pure CdS and mechanically mixed CdS with MIL-68(In)–NH2, respectively, while maintaining significant photocatalytic stability. The incorporation of MIL-68(In)–NH2 effectively enhanced the dispersion of CdS particles, thereby increasing the availability of active sites for efficient photocatalytic reactions. Moreover, the presence of SVs on the surface of CdS served as electron trapping levels, significantly improving charge separation efficiency. This study not only provides novel insights into fabricating composite photocatalysts but also explores a defect engineering regulation strategy.

Prognostic Significance of Plasma Neutrophil Extracellular Trap Levels in Patients with Non-Small Cell Lung Cancer Treated with Immune Checkpoint Inhibitors.

Neutrophil extracellular traps (NETs) released from neutrophils are related to cancer progression. However, the relationship between the therapeutic effects of immune checkpoint inhibitors (ICIs) such as anti-PD-1 and anti-PD-L1 antibodies and plasma NET concentration in patients with non-small cell lung cancer (NSCLC) is poorly understood. In this study, concentrations of citrullinated histone H3 (CitH3), a surrogate marker of NETs, in plasma before/after treatment were examined in patients with advanced or recurrent NSCLC undergoing ICI treatment (n = 185). The clinical significances of NET levels before/after treatment and posttreatment changes were statistically evaluated. As a result, multivariate Cox analysis showed that high NET levels before treatment were statistically significant predictors of unfavorable overall survival (OS; p < 0.001, HR 1.702, 95% CI 1.356-2.137) and progression-free survival (PFS; p < 0.001, HR 1.566, 95% CI 1.323-1.855). The Kaplan-Meier curves showed significant separation between the high- and low-NET groups in OS (p = 0.002) and PFS (p < 0.001). Additionally, high NET levels after treatment were also significantly associated with worse OS (p < 0.001) and PFS (p < 0.001) by multivariate Cox analysis. Notably, the pretreatment NET levels were significantly correlated with the plasma levels of NET-related inflammatory cytokines, such as IL-6 and IL-8, and with NET-related gene expression and immune-suppressive profile in peripheral blood mononuclear cells. Our findings suggest that NETs released from activated neutrophils might reduce the clinical efficacy of ICIs in patients with NSCLC.

Beta radiation-induced thermoluminescence in pure and rare earth doped ZrO2 prepared by pechini-type sol-gel

Thermoluminescence properties of ZrO2, ZrO2:Gd3+, ZrO2:Gd3+–Dy3+, ZrO2:Gd3+–Yb3+, ZrO2:Gd3+–Er3+ and ZrO2:Gd3+–Sm3+ phosphors synthesized by Pechini method were investigated. XRD measurement suggested that all the samples are monoclinic and tetragonal multiphase. Crystallite size measured using SEM is around 200 nm–250 nm. The Tmax–TSTOP, variable dose and glow curve fitting methods were applied to the phosphors and reusability, dose responses and fading characteristics were examined. The phosphors exhibit a natural TL emission which disappeared after heat treatment. The glow curves of the pure ZrO2 have thirteen individual glow peaks, which include the peaks reported for the monoclinic and tetragonal phases. Although some peaks emerge at low irradiation doses, others can only be observed at high doses. Moreover, although the dopes blanched some of the peaks of pure ZrO2, they made others more intense. These peaks can be interpreted as if they emerged caused by the rare earth doping into the matrix material. On the other hand, Gd3+, Dy3+, Yb3+, Er3+ and Sm3+ dopes did not alter the peak temperatures of the matrix material. As a result, the individual peak intensities are very sensitive to the dopes. Fundamental trapping parameters of the trap levels were calculated, and the results are in good agreement with the given values of activation energies in the literature. Fading experiments show the materials have both normal and abnormal fading characteristics in long and short-term storage.

Methyl Syringate: A Primary Driving Factor in Manuka Honeys Ability to Ameliorate Neutrophil Intracellular ROS Activity and NETosis.

Neutrophils use both the production of reactive oxygen species (ROS) and a specialized process called NETosis to defend the body from material deemed foreign. While these neutrophil behaviors are critical in preventing infection, a dysregulated response can lead to tissue damage and fibrosis at host-biomaterial interfaces. It was hypothesized that applying the flavonoids found in Manuka honey: chrysin, pinocembrin, and pinobanksin, and the phenolic compound methyl syringate to neutrophils exhibiting pro-inflammatory behavior will reduce ROS activity and prevent NETosis in primary human neutrophils. Using primary human neutrophils isolated from donor (n = 5) peripheral blood, concentrations between 1 nM and 10 µM of each flavonoid, 10 µM and 2 mM of methyl syringate, 0.1% v/v and 10% v/v Manuka honey, and combinations of both 1 nM-10 µM of each flavonoid and 10 µM-2 mM of methyl syringate were assayed for reductions in NETosis using Sytox orange extracellular DNA staining and reduction in intracellular ROS activity via standard dichloro-dihydro-fluorescein diacetate (DCFH-DA) oxidation assay. Compared to positive control levels, individual flavonoids showed moderate effect sizes. Higher concentrations of flavonoids, especially in combination, stimulated ROS activity by up to 105%. Whole Manuka honey reduced neutrophil extracellular trap (NET) levels by up to 91% but only reduced ROS activity by 36%. However, methyl syringate reduced NET levels by up to 68% and ROS activity by 66%. Methyl syringate and whole Manuka honey are potent inhibitors of neutrophil intracellular ROS activity and NET formation. Methyl syringate potentially drives the anti-inflammatory capabilities of Manuka honey demonstrated by previous studies.

A Multiscale Simulation on Aluminum Ion Implantation-Induced Defects in 4H-SiC MOSFETs

Aluminum (Al) ion implantation is one of the most important technologies in SiC device manufacturing processes due to its ability to produce the p-type doping effect, which is essential to building p–n junctions and blocking high voltages. However, besides the doping effect, defects are also probably induced by the implantation. Here, the impacts of Al ion implantation-induced defects on 4H-SiC MOSFET channel transport behaviors are studied using a multiscale simulation flow, including the molecular dynamics (MD) simulation, density functional theory (DFT) calculation, and tight-binding (TB) model-based quantum transport simulation. The simulation results show that an Al ion can not only replace a Si lattice site to realize the p-doping effect, but it can also replace the C lattice site to induce mid-gap trap levels or become an interstitial to induce the n-doping effect. Moreover, the implantation tends to bring additional point defects to the 4H-SiC body region near the Al ions, which will lead to more complicated coupling effects between them, such as degrading the p-type doping effect by trapping free hole carriers and inducing new trap states at the 4H-SiC bandgap. The quantum transport simulations indicate that these coupling effects will impede local electron transports, compensating for the doping effect and increasing the leakage current of the 4H-SiC MOSFET. In this study, the complicated coupling effects between the implanted Al ions and the implantation-induced point defects are revealed, which provides new references for experiments to increase the accepter activation rate and restrain the defect effect in SiC devices.

Investigation of the efficacy of Zn/Ce-CuO nanoparticles for enhanced photocatalytic, antibacterial, and antioxidant activities.

The world is dealing with unprecedented environmental challenges, leading to a growing urgency to limit environmental damage. So, this study focuses on the synthesis of pure CuO, Zn, Ce, and Zn/Ce dual-doped CuO nanoparticles (NPs)using extract of Citrus limon leaves as reductant via simple co-precipitation method. The X-ray diffraction (XRD) characterization was employed to analyze structural characteristics of synthesized samples which confirm influence of Zn or Ce doping on crystallite size, dislocation density, and strain. The role of functional groups, changes in force constant, and bond length on addition of dopants was indicated by FTIR results. The SEM and TEM results showed variation in morphology from irregular to spherical. The zeta-potential and BET analysis confirmed surface potential as well as surface area characteristics. The change in energy gap values from 1.81 to 1.45eV of Zn/Ce-doped CuO NPscomputed from UV-vis analysis elevated its photocatalytic performance and reduced the chances of recombination of electron-hole pair due to presence of trapping levels between valence and conduction bands. The enhanced photo-degradation of Congo red (CR) and rhodamine B (RhB) with 91 and 94%, respectively, for Zn/Ce-doped CuO NPswas observed. The so-obtained samples have also exhibited good antibacterial and antioxidant activities.

The Effects of Acute and Chronic Alcohol Administration and Withdrawal on Bone Microstructure, Mechanical Strength, and Remodeling Protein Expression and Their Relation to an Antioxidant and FGF23 In Vivo.

Alcohol's detrimental effects on bone health are well established, yet some literature suggests moderate consumption may offer benefits. With alcohol use on the rise, we investigate the impact of acute and chronic alcohol administration, along with withdrawal, on male Wistar rat femurs. We observed a transient cortical thickness increase with acute alcohol (AA) compared to chronic exposure (CA) but no significant changes in trabecular parameters or mechanical properties. High osteocalcin and osteopontin expression levels were noted in AA, alongside elevated RANKL expression. Conversely, CA showed low TRAP levels. FGF23 expression significantly increased during alcohol withdrawal (AW), while GPX decreased after chronic exposure but rose during withdrawal. Although mechanical strength changes were insignificant, biochemical shifts suggest alcohol exposure promotes bone resorption, reduces antioxidant protection, and potentially hampers active vitamin D and phosphate reabsorption via FGF23 upregulation.

Discrete trapping levels of localized states in amorphous silicon nitride

The spectrum of localized hole states (traps) in amorphous silicon nitride, a-Si3N4, is experimentally studied using the method of thermally stimulated depolarization. The experiment is compared with theoretical calculations using three models of the energy spectrum of traps: discrete spectrum (monoenergetic trap), continuous spectrum, and Gaussian trap distribution. The experiment is quantitatively described by a model of a discrete spectrum of traps with an energy of 1.15 eV and a width of no more than 0.01 eV. In the case of a continuous and Gaussian spectrum of traps, the contribution to depolarization is made by the deepest traps. The blurring of the trap energy level in a-Si3N4 due to the absence of long-range order (fluctuations in the Si–N bond length and fluctuations in the N–Si–N and Si–N–Si angles) does not exceed 0.01 eV.

Effect of Acceptor Traps in GaN Buffer Layer on Source/Drain Contact Resistance in AlGaN/GaN High Electron Mobility Transistors

As‐grown GaN buffer layers have a significant electron concentration, which causes an increase in leakage current and a decrease in the breakdown voltage, VBR, of GaN High Electron Mobility Transistors (HEMTs). To prevent this, deep acceptor traps of density, NAT, are added to the GaN layer during growth. While a study on the effect of NAT on VBR is available in the literature, that on the effect of NAT on contact resistance, Rc, of source/drain contacts is lacking. Herein, the following is established using technology computer‐aided design simulations calibrated with measured current–voltage characteristics of ungated AlGaN/GaN structures: 1) Rc increases significantly with NAT and with the depth of the trap level from the conduction band. For trap level 2.5 eV below the conduction band, Rc doubles for an increase in NAT from 1 × 1016 to 5 × 1017 cm−3. 2) The variation of Rc with temperature is non‐monotonic. Over a temperature range of 300–450 K, Rc is nearly constant with temperature for NAT = 1 × 1016 cm−3 and decreases by 20% for NAT = 5 × 1017 cm−3, when traps are 2.5 eV below the conduction band. Also, the degradation of the transfer and output characteristics of GaN HEMTs due to a notable increase in Rc due to NAT is investigated.

Spectral characterization of a Cryo-Cooled CO laser operating with CO2 laser gas mixture

This study explores the emission spectra and performance characteristics of a cryo-cooled CO laser system operating with CO2 laser gas mixture under various operating conditions, viz., N2 free gas mixture, different coolant temperatures and in grating tuned configuration. The narrow operational window in case of N2 free gas mixture, increased output power and richer emission spectrum obtained with the addition of N2 gas indicates enhanced discharge stability and efficient excitation in presence of Nitrogen. The emission spectrum revealed shifting of the trapping levels towards lower vibrational quantum number with reducing coolant temperature and the same was also corroborated by theoretical calculations. No lasing was observed for vibrational levels V>15 which is attributed to the higher partial pressure of oxygen inherently present in the gain medium formed due to dissociation of CO2. The system lased on more than 20 transitions in grating tuned configuration with power exceeding 100mW on several lines. The presence of higher concentration of O2 in the discharge prevents carbon deposition − a common issue in CO lasers. This study underscores the significance of this unconventional CO laser system offering reliable operation in the 5 µm wavelength region without the usage of extraneous CO gas.

Blue-emitting perovskite nanocrystals with enhanced optical properties through using NaBH4

APbX3-type [A = CH3NH3 + (MA+), NH2CH=NH2 + (FA+), X = Cl–, Br–, I–] organic–inorganic perovskite nanocrystals (PeNCs) have superior optical properties, such as emission with a narrow full width at half maximum and emission color tunability over the entire visible range. However, blue-emitting PeNCs [APb(Br/Cl)3] exhibit low photoluminescence quantum yields owing to Cl defects, hindering their practical applications. The Cl defects induce nonradiative recombination caused by the trap levels formed deep in the band gap. Herein, we report the preparation of blue-emitting PeNCs that exhibit excellent optical properties by using NaBH4 to decrease the number of Cl defects.