Electron Trapping Centers Research Articles

Enhanced Fluorescence Characteristics of SrAl2O4: Eu2+, Dy3+ Phosphor by Co-Doping Gd3+ and Anti-Counterfeiting Application.

A series of long-afterglow luminescent materials (SrAl2O4: Eu2+ (SAOE), SrAl2O4: Eu2+, Dy3+ (SAOED) and SrAl2O4: Eu2+, Dy3+, Gd3+ (SAOEDG)) was synthesized via the combustion method. Temperature and concentration control experiments were conducted on these materials to determine the optimal reaction temperature and ion doping concentration for each sample. The crystal structure and luminescent properties were analyzed via X-ray diffraction (XRD), photoluminescence (PL), and afterglow attenuation curves. The outcomes demonstrate that the kind of crystal structure and the location of the emission peak were unaffected by the addition of ions. The addition of Eu2+ to the matrix's lattice caused a broad green emission with a central wavelength of 508 nm, which was attributed to the characteristic 4f65d1 to 4f7 electronic dipole, which allowed the transition of Eu2+ ions. While acting as sensitizers, Dy3+ and Gd3+ could produce holes to create a trap energy level, which served as an electron trap center to catch some of the electrons produced by the excitation of Eu2+ but did not itself emit light. After excitation ceased, this allowed them to gently transition to the ground state to produce long-afterglow luminescence. It was observed that with the addition of sensitizer ions, the luminous intensity of the sample increased, and the afterglow duration lengthened. The elemental structure and valence states of the doped ions were determined with an X-ray photoelectron spectrometer (XPS). Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to characterize the samples. The results show that the sample was synthesized successfully, and the type and content of ions in the fluorescent powder could be determined. The fluorescence lifetime, quantum yield, bandgap value, afterglow decay time, and coordinate position in the coherent infrared energy (CIE) diagram of the three best sample groups were then analyzed and compared. Combining the prepared phosphor with ink provides a new idea and method for the field of anti-counterfeiting through screen printing.

Specific Features of Formation of Electron and Hole Trapping Centers in Irradiated CaSO4-Mn and BaSO4-Mn

Spectroscopic and thermoactivation methods were used to study the processes of accumulation of electron and hole trapping centers and energy transfer of electronic excitations to impurities in CaSO4-Mn and BaSO4-Mn. It is shown that electronic trapping centers are created during the excitation of an anionic complex as a result of charge transfer from O2−→SO42− to closely spaced anionic complexes SO42− in CaSO4 and BaSO4. In CaSO4 and BaSO4, energy transfer from the host to impurities occurs at the moment of charge transfer from the excited anionic complex to the combined radiative electronic state at 2.95–3.1 eV. This combined state is formed from electronic trapping centers Mn+-SO4− and SO43−-SO4−. It was found that the emerging combined radiative states at 2.95–3.1 eV of sulfates, which are formed as a result of charge transfer from the excited anionic complexes to the excited state of impurities, Tl+,Cu+,and Mn2+, occupy the same energy levels as the intrinsic electronic trapping center SO43− of the host at 2.95–3.17 eV. Experimental results show that during UV photon irradiation, anionic complexes are excited mainly near impurities in sulfates.

Al-doped CuS/Znln2S4 forming Schottky junction induced electron trap centers for photocatalytic overall water splitting

Synergistically tuning electronic states at the atomic level to facilitate photocatalytic overall water splitting is a challenge. However, elucidation of the role of specific electronic states of Znln2S4 (ZIS) in regulating both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is still scarce, making it difficult to accurately predict the actual photocatalytic performance. Here, the substitution of Zn sites with Al atoms was found to modulate the potential difference of the ZIS surface domain heterojunction structure, and electrons were further transferred to CuS to form a built-in field that promotes charge separation. When Al doping is present on the ZIS surface, ZIS exhibits p-type semiconductor properties, which leads to the formation of p-n junctions within Al-CuS/ZIS itself. Due to the large work function and metallic properties of CuS, and Al-CuS/ZIS as a whole tends to form a Schottky heterojunction, and the two heterojunction structures synergistically promote the migration of photogenerated carriers. In addition, the Al doping changes the electronic states around the ZIS, allowing the Al ZIS to promote the adsorption of O* and H* during OWS. The solar-driven photocatalytic overall water splitting efficiency of Al-CuS/ZIS is as high as 153.6 (HER) and 73.1 (OER) μmol/h g−1, which is about 10 times that of ZIS. This work opens the possibility to design efficient photocatalytic materials through tunable composition and electronic structure.

Electron-hole trapping centers in Na2SO4 with a transition metal impurity Mn

The Na 2 SO 4 samples were obtained by slow evaporation method. The mechanisms of the formation of electron and hole trapping centers are investigated by spectroscopic methods. Intrinsic recombination emission of 2.9–3.1 eV and impurity emission of 1.85 eV are excited at 4.0–4.5 eV. Intrinsic SO 3− 4 −SO − 4 and impurity Mn + − SO − 4 trapping centers were revealed. The local levels corresponding between the electron and hole trapping center are 4.0–4.5 eV. The decay of intrinsic and impurity trapping centers was recorded at temperatures of 130–150 K and 280–350 K.

Charge Trapping and Emission Properties in CAAC-IGZO Transistor: A First-Principles Calculations.

The c-axis aligned crystalline indium-gallium-zinc-oxide field-effect transistor (CAAC-IGZO FET), exhibiting an extremely low off-state leakage current (~10-22 A/μm), has promised to be an ideal candidate for Dynamic Random Access Memory (DRAM) applications. However, the instabilities leaded by the drift of the threshold voltage in various stress seriously affect the device application. To better develop high performance CAAC-IGZO FET for DRAM applications, it's essential to uncover the deep physical process of charge transport mechanism in CAAC-IGZO FET. In this work, by combining the first-principles calculations and nonradiative multiphonon theory, the charge trapping and emission properties in CAAC-IGZO FET have been systematically investigated. It is found that under positive bias stress, hydrogen interstitial in Al2O3 gate dielectric is probable effective electron trap center, which has the transition level (ε (+1/-1) = 0.52 eV) above Fermi level. But it has a high capture barrier about 1.4 eV and low capture rate. Under negative bias stress, oxygen vacancy in Al2O3 gate dielectric and CAAC-IGZO active layer are probable effective electron emission centers whose transition level ε (+2/0) distributed at -0.73~-0.98 eV and 0.69 eV below Fermi level. They have a relatively low emission barrier of about 0.5 eV and 0.25 eV and high emission rate. To overcome the instability in CAAC-IGZO FET, some approaches can be taken to control the hydrogen concentration in Al2O3 dielectric layer and the concentration of the oxygen vacancy. This work can help to understand the mechanisms of instability of CAAC-IGZO transistor caused by the charge capture/emission process.

Construction of Z scheme S-g-C3N4/Bi5O7I photocatalysts for enhanced photocatalytic removal of Hg0 and carrier separation

Photocatalysis has demonstrated the potential to solve challenges in various practical application fields such as energy and environmental science due to its environmental friendliness. However, the photocatalytic activity is mainly affected by the weak absorption of visible light and the low separation efficiency of photogenerated carriers. Herein, an S-doped g-C3N4/Bi5O7I heterojunction was designed by the calcination method. It was found that S doping not only reduces the band gap of g-C3N4, which raises the optical absorption boundary of g-C3N4 from 465 nm to 550 nm. At the same time, the introduction of S elements leads to new doping energy levels, which can act as photogenerated electron trapping centers and thus inhibit the complexation of photogenerated carriers. Second, the construction of the heterojunction greatly facilitates the transport of carriers and the separation of electrons and holes driven by the built-in electric field. Finally, the abundant oxygen vacancies in the system result in defective energy levels that not only promote the activation of molecular oxygen, but also act as photogenerated electron traps, which further boost the separation of electron-hole pairs. Benefiting from the optimized performance, the photocatalytic reaction rates of S-doped g-C3N4/Bi5O7I are 5.2 and 2.1 times higher than those of g-C3N4 and Bi5O7I, respectively. This work provides a viable idea for the potential development of non-metal doping combined with heterojunction photocatalytic systems.

Construction of NiO/Ag/g-C3N4 nanosheet: Enhanced photocatalytic H2 evolution by the unique structure and synergistic effect of Ag and NiO

In this work, NiO/Ag/g-C3N4 hybrids with unique structure were designed and fabricated by a stepwise photoreduction and thermal treatment method. Herein, under the effect of electrostatic attraction, the NiO was mainly deposited on the surface of Ag quantum dots in the NiO/Ag/g-C3N4 hybrids (denoted as NACN-x, x was the mole ratio of NiO and Ag). Under visible light irradiation, the H2 evolution rate of the optimized hybrid NACN-1 was about 586 μmol•h−1•g−1. However, in the same conditions, the g-C3N4 had negligible H2 evolution property. Furthermore, in comparison with the other contrast materials, the H2 evolution rate of NACN-1 was about 3.5, 2.5 and 1.4 times than that of Ag/g-C3N4, NiO/g-C3N4 and NiO-Ag/g-C3N4 (prepared via one-step photoreduction method). According to the results of the optical-electrical property tests, characterizations of TEM and XPS, and theoretical calculation, the superior H2 evolution property of NACN-1 should profit from the unique structure and synergistic effect of NiO and Ag. Because the Ag quantum dots in NiO/Ag/g-C3N4 hybrid would act as electron trapping center to significantly improve the separation efficiency of photoexcited carriers. Meanwhile, the electrons would be consumed on the reactive sites of the close contacted NiO to produce H2.

Enhancing the removal of the diclofenac contaminant and accelerating the desalinization of seawater by using a biodegradable fibrous support functionalized with Sr2.7Ln0.3Fe1.4Co0.6O7-δ (Ln = La or Nd) perovskites

A biodegradable fibrous support (oak-gall, OG) was functionalized with graphene (G) and Sr2.7Ln0.3Fe1.4Co0.6O7-δ perovskite (named SLFCO and SNFCO when Ln = La and Nd, respectively) to remove the diclofenac (DCF) contaminant from the drinking water by photocatalysis. The photocatalytic experiments revealed that the SNFCO and SLFCO powders produced DCF degradation of 100 % and 94 %, respectively, after 150 min under UV–vis irradiation. This means that making a perovskite with Nd dopant instead of La is more effective to induce the DCF degradation. Later, a composite made of OG + G was evaluated, but only a DCF degradation of 50 % was produced. Subsequently, a floatable composite made with SNFCO particles (OG + G + SNFCO) was tested and produced a complete degradation for DCF after 150 min of UV–vis irradiation, thus, adding the perovskite produced higher DCF degradation. Additionally, scavenger experiments were carried out and confirmed the formation of oxidizing agents such as ∙OH and ∙O2−, which mainly attacked the DCF molecules. Raman, absorbance, and X-ray photoelectron spectroscopy (XPS) measurements demonstrated the presence of oxygen vacancy defects in the biodegradable photocatalytic composites. Such vacancies acted as electron trapping centers, which enhanced the DCF degradation. The OG + G + SNFCO composite was also tested for the evaporation of seawater under natural solar light and produced a maximum evaporation-rate and evaporation-efficiency of 1.67 kg/m2∙h and 95 %, respectively. Adding the OG + G + SNFCO composite to the seawater accelerated its desalination ≈2 times. In fact, the Fourier-transform-infrared (FTIR) technique demonstrated the no presence of NaCl in the condensed water recovered after desalination. Hence, the results of this research indicate that a biodegradable composite functionalized with G + SNFCO is useful for the elimination of pharmaceutical drugs from the water and for seawater desalination.

Designing LiTaO3:Ln3+,Eu3+ (Ln = Tb or Pr) perovskite dosimeter with excellent charge carrier storage capacity and stability for anti-counterfeiting and flexible X-ray imaging

Developing X-ray charged dosimeters with excellent charge carrier storage capacity and stability is challenging. Such energy storage dosimeters have fascinating use in developing novel applications, for instance, in radiation detection, advanced multimode anti-counterfeiting, and flexible X-ray imaging of curved objects. Herein, novel LiTaO3:Ln3+,Eu3+ (Ln = Tb or Pr) perovskite dosimeters are reported by combining the vacuum referred binding energy (VRBE) diagram of LiTaO3 and the optimization of dopant’s concentration and compound synthesis condition. Based on the VRBE diagram prediction, charge carrier capturing and de-trapping processes in Eu3+ and/or Ln3+ (Ln = Tb or Pr) doped LiTaO3 will be studied to unravel the role of Eu3+ as a good electron trapping centre and to discover a record storage phosphor. The ratios of the thermoluminescence intensity of the optimized LiTaO3:0.005Tb3+,0.001Eu3+ to that of the state-of-the-art BaFBr(I):Eu2+, Al2O3:C, or NaLuF4:Tb3+ are 5.2, 8.8, or 2.8, respectively. The charge carriers can be stored more than 1000 h in LiTaO3:0.005Tb3+,0.001Eu3+. Proof-of-concept anti-counterfeiting application will be demonstrated by combining the colour-tailorable photoluminescence, afterglow, thermally, or optically stimulated luminescence in LiTaO3:0.005Tb3+,xEu3+ and LiTaO3:0.005Pr3+,0.001Eu3+. Multimode anti-counterfeiting application will be proposed by combining a high absolute X-ray scintillation light yield of 19000 ± 1800 ph/MeV of LiTaO3:0.005Tb3+,0.001Eu3+. Proof-of-concept flexible X-ray imaging application will be demonstrated by using the optimized LiTaO3:0.005Tb3+, 0.001Eu3+ dispersed in a silicone gel film.

Experimental and theoretical divulging of electronic structure and optical properties of Zn-doped SnSe thermoelectric materials

Electron momentum densities (EMDs) of undoped and Zn-doped SnSe are measured using a 100 mCi 241Am Compton spectrometer. Various density functional theories and hybrid exchange and correlation potentials (LDA, PBE, PBEsol, PBE0, and B3LYP) within the linear combinations of atomic orbitals (LCAO) calculations have been attempted to compute Compton profiles (CPs) and electronic structure of the doped and undoped SnSe. Among all the Compton line shapes predicted using first principles, B3LYP approximation-based EMDs are found to be in a better reconciliation with the CP measurements. Experimental data is also analyzed in terms of localization of Zn-d states. Going beyond the LCAO method, the density of state (DOS), energy bands, reflectance, dielectric constant, and absorption coefficient for Zn-doped (Sn0.97Zn0.03Se and Sn0.95Zn0.05Se) and undoped SnSe are computed using the FP-LAPW-mBJ method. It is seen that Sn-5s and Se-4p orbitals are responsible for the formation of the indirect band gap. Interestingly, Zn doping in SnSe (Sn0.97Zn0.03Se and Sn0.95Zn0.05Se) leads to interstitial bands in the low energy side of the conduction region leading to electron trapping centres and reduction of band gap (from 0.816 to 0.508eV in case of FP-LAPW-mBJ scheme and 1.152 to 0.510 eV in case of LCAO-B3LYP scheme). Our works evidently support the positive effect of Zn doping in enhancing the electronic and thermoelectric properties of the SnSe by forming interstitial bands. Apart from this, undoped and Zn-doped SnSe can also be used for solar cells as an absorber material and detection of ultraviolet (B and C) rays. Due to the formation of interstitial bands induced trapping centres, Zn-doped SnSe can also be uniquely employed in thermoluminescence devices (TLDs).

Cation doped approach for photodegradation of 4-chlorophenol by highly efficient solar active NiS photocatalyst: The case of Cu2+ doping

This study reports an efficient photodegradation of 4-chlorophenol using Cu2+ doped nickel sulfide (NiS) nanoparticles. Our study provides a facile method to synthesize Cu2+ doped NiS nanoparticles by partial polyol method and structurally validates the formation of single phased random-shaped particles. Cu2+ doping in NiS matrix results in a red shift of the absorption band edge, thus lowering the band gap from 3.62 to 2.98 eV and creating electron trapping centers that prevent electron-hole recombination. The presence of such electron trapping centers was attributed to oxygen vacancies which were justified from the appearance of g-signal in electron paramagnetic resonance analysis. Photodegradation study of 4-chlorophenol by Cu2+ doped NiS nanoparticles under ambient solar light showed significant improvement in degradation efficiency up to 90 % as compared to 19 % for undoped NiS nanoparticles. Furthermore, increased degradation efficiency was also backed by total organic carbon (TOC) analysis of the mineralization ability of Cu2+ doped NiS nanoparticles. Moreover, scavenging trapping analysis showed holes, ⋅OH and superoxide radicals as reactive oxidative species (ROS) primarily responsible for increased photodegradation efficiency. Thus, the synthesized Cu doped NiS nanoparticles proved to be an efficient catalyst, which could be used as a potential candidate for industrial photocatalytic applications under ambient solar light.

Enhanced photocatalytic degradation of cationic dye using Cu-doped ZnSe

The persistence of organic contaminants in an aqueous system adversely influences the ecosystems. To alleviate this ruinous issue, Cu doped ZnSe nanostructure is investigated for its catalytic performance assisted with hydrogen peroxide (H2O2) where cationic Methylene Blue (MB) is employed as a model contaminant. The Cu-doped ZnSe nanocatalysts are synthesized by a solvothermal approach and are characterized by XRD, FTIR, XPS, FE-SEM-EDX, BET, UV-VIS Spectroscopy, and PL. Enhancement in Cu doping improves the degradation performance of H2O2 assisted MB degradation, where with 5% of Cu-doping achieved 95.69% and 15% of Cu doping attains 98.09% of MB degradation across 180 min under visible light illumination. The proficient exculsion of MB dye by using Cu-doped ZnSe is attributed to Cu dopant, which decreases ZnSe bandgap and serves as an electron trapping center that inhibits the recombination of charge carriers. Among all, 15% Cu-doped ZnSe when assisted with H2O2 exhibits the highest degradation efficiency under visible light illumination is a repercussion to the synergetic effect of high surface area, tunable bandgap, and enhanced charge carriers separation owning to electron scavenging effects of H2O2. Thus, offering a promising strategy in fulfilling the upcoming environmental issues concerned with the removal of organic dyes from water reservoirs.

Key Role Effect of Samarium in Realizing Zero Thermal Quenching and Achieving a Moisture-Resistant Reddish-Orange Emission in Ba3LaNb3O12:Sm3.

The strategy to enhance phosphor stability against thermal quenching and moisture conditions will contribute to controlling the feature of phosphor-converted white-light-emitting diodes (pc-WLEDs). Herein, an effective strategy is achieved with the incorporation of Sm3+ ions, and a robust reddish-orange emission (no thermal quenching up to 498 K) is obtained based on Ba3LaNb3O12 as a host. In light of excitation by near-ultraviolet irradiation at 408 nm, Ba3LaNb3O12:Sm3+ gives rise to a typical signal ascribed to the 4G5/2 → 6HJ/2 (J = 5, 7, 9, and 11) transitions of Sm3+ ions. The concentration quenching effect is observed when the Sm3+ content exceeds 10%, and the quenching mechanism is caused by electronic dipole-dipole interactions. Based on the narrow emission curves, a very high color purity (92.4%) could be recorded. The Sm3+ substitution at the Ba2+/La3+ site leads to a rigid structural lattice and abundant electron-trapping centers for the Sm3+ ions, which will be responsible for the zero-thermal-quenching phenomenon. In addition, oleic acid (OA) is selected to form a hydrophobic covering surface structure to protect Ba3LaNb3O12:Sm3+, which can assist in improving the moisture resistance. The most favorable parameters concerning the warm-light emission (a high general color rendering index, Ra, of 85.7 and a low correlated color temperature, CCT, of 4965 K) can be achieved in pc-WLEDs containing an OA-modified sample. Moreover, its luminous efficiency, LE, can maintain 82.9% of its initial value after 120 h under controlled environmental conditions of 85 °C and 85% humidity. These results pave a new way to optimize the sample as a potential candidate for red-emitting materials.

Enhancement in photocatalytic H2 evolution utilizing the synergistic effect between dual cocatalysts and heterojunctions

Expediting electrons-holes separation and surface reaction kinetics is deemed to be pivotal factor to determine the photocatalytic performance. Decoration of reductive and oxidative cocatalysts on semiconductors is a resultful approach for motivating electrons-holes separation and surface reaction kinetics. In this work, a ternary 2.4%-(CoSe2@NiS-1)/CdS photocatalyst was developed. Among this compound, reductive cocatalyst CoSe2 not only acted as electron trapping center by extracting photogenerated electrons, but also constructed Schottky junction with CdS to accelerate migration of photogenerated carriers and inhibit the backflow. Meanwhile, oxidative cocatalyst NiS forming p-n type heterojunction with CdS served as hole-trap center to boost transport and consumption of photoinduced holes. Integrating of dual cocatalysts and heterojunctions played synergistic effect in promoting the photocatalytic performance and photo-corrosion stability. 2.4%-(CoSe2@NiS-1)/CdS achieved H2 evolution of 1413.9 μmol and maintained at 85.47% after six cycles. It's expected that this work can provide an insight into designing high active solar energy conversion system.

Thermally stimulated luminescence properties of MgTa2O6 prepared by solid-state chemical reaction

Persistent luminescent (PLUM) materials have been developed for a variety of applications in road marking, toys decoration, safety and bio-imaging. Such materials are set to answer the need for energy conservation. In this work, Magnesium Tantalate (MgTa2O6) compound was synthesized by a conventional solid-state chemical reaction route at 800 °C for 8 h, after ball milling the mixed precursors. The MgTa2O6 compound was confirmed with only minor impurities of Ta2O5, as identified by X-ray diffraction (XRD). The scanning electron microscopy (SEM) images of MgTa2O6 showed a surface morphology with different shapes and sizes, which are bound to each other. The energy band gap of the material was approximated to 4.34 eV using the Kubelka-Munk relation. The photoluminescence (PL) spectrum displayed a broad emission between 360 and 780 nm, when the sample was excited with a 295 nm beam, as observed from the photoluminescence excitation (PLE) spectrum. Upon investigating the thermoluminescence (TL) properties of the compound, the glow curves revealed the presence of at least three prominent electron trapping centres at ∼108, ∼258, and ∼315 °C. The competition between electron trapping centres, pre-heating effects, stability of the electron trapping centres and TL fading were examined. In addition, the depth of the electron trapping centres was determined. From the TL analysis, the prominent electron trapping centres were approximated to 0.75 ± 0.04 eV, 1.28 ± 0.07 and 1.55 ± 0.02 eV. Additionally, from the stable electron trapping centres and TL signal fading study, results indicated that MgTa2O6 is a promising material for energy storage applications.

Effects of Group-I Elements on Output Voltage Generation of ZnO Nanowires Based Nanogenerator; Degradation of Screening Effects by Oxidation of Nanowires.

Here, we report the successful incorporation of group I elements (K, Na, Li) to ZnO nanowires. Three distinct (2, 4, and 6 wt.%) doping concentrations of group I elements have been used to generate high piezoelectric voltage by employing a vertically integrated nanowire generator (VING) structure. X-ray photoelectron spectra (XPS) indicated the seepage of dopants in ZnO nanowires by substitution of Zn. Shallow acceptor levels (LiZn, NaZn, KZn) worked as electron trapping centers for intrinsically n-type ZnO nanowires. Free moving electrons caused a leakage current through the nanowires and depleted their piezoelectric potential. Reverse leakage current is a negative factor for piezoelectric nanogenerators. A reduction in reverse leakage current signifies the rise in output voltage. A gradual rise in output voltage has been witnessed which was in accordance with various doping concentrations. K-doped ZnO nanowires have generated voltages of 0.85 V, 1.48 V, and 1.95 V. For Na-doped ZnO nanowires, the voltages were 1.23 V, 1.73 V, and 2.34 V and the voltages yeilded for Li-doped ZnO nanowires were 1.87 V, 2.63 V, and 3.54 V, respectively. Maximum voltage range has been further enhanced by the surface enrichment (oxidized with O2 molecules) of ZnO nanowires. Technique has been opted to mitigate the screening effect during an external stress. After 5 h of oxidation in a sealed chamber at 100 ppm, maximum voltage peaks were pronounced to 2.48 V, 3.19 V, and 4.57 V for K, Na, and Li, respectively. A low-cost, high performance mechanical transducer is proposed for self-powered devices.

Tuning the local electronic structure of oxygen vacancies over copper-doped zinc oxide for efficient CO2 electroreduction

Oxygen vacancies in metal oxides can serve as electron trap centers to capture CO2 and lower energy barriers for the electrochemical CO2 reduction reaction (CO2RR). Under aqueous electrolytes, however, such charge-enriched active sites can be occupied by adsorbed hydrogen (H∗) and lose their effectiveness for the CO2RR. Here, we develop an efficient catalyst consisting of Cu-doped, defect-rich ZnO (Cu–ZnO) for the CO2RR, which exhibits enhanced CO Faradaic efficiency and current density compared to pristine ZnO. The introduced Cu dopants simultaneously stabilize neighboring oxygen vacancies and modulate their local electronic structure, achieving inhibition of hydrogen evolution and acceleration of the CO2RR. In a flow cell test, a current density of more than 45 ​mA ​cm−2 and a CO Faradaic efficiency of > 80% is obtained for a Cu–ZnO electrocatalyst in the wide potential range of −0.76 ​V to −1.06 ​V vs. Reversible Hydrogen Electrode (RHE). This work opens up great opportunities for dopant-modulated metal oxide catalysts for the CO2RR.

Bismuth oxychloride photocatalytic wide band gap adjustment through oxygen vacancy regulation using a hybrid intelligent computational method

Bismuth oxychloride is a lamellar semiconductor with fascinating features in photocatalysis due to its excellent charge storage capacity, sufficient reduction/oxidation potentials, stable chemical properties, wide distribution of elements, and low toxicity. The wider application of this semiconductor for many technological and industrial applications is hindered by the resistive factors of wide band gap and the ease of recombination of photo-generated electrons and holes. Oxygen vacancy creation in bismuth oxychloride semiconductor controls and adjusts the band gap to the desired spectrum region and subsequently acts like electron trapping centers for the prevention of carrier's re-union. The formation of oxygen vacancy peaks for the lattice and adsorbed oxygen species in the de-convoluted O 1s spectra of x-ray photoelectron spectroscopy (XPS) at a particular value of binding energy experimentally confirms oxygen vacancy creation for photocatalytic activity enhancement. This work focuses on modeling the energy gap (Eg) of bismuth oxychloride semiconductor with oxygen vacancies using the binding energy (BE) of the de-convoluted O 1s lattice oxygen and oxygen vacancy as descriptors through hybrid particle swarm-based support vector regression (PSVR) model as well as stepwise regression (STR) model. The developed PSVR-Eg model shows performance improvement of 23.38%, 55.96%, and 66.54% over the STR-Eg model on the basis of the coefficient of correlation, root means square error, and mean absolute error. The developed PSVR-Eg further predicts the influence of lattice oxygen and oxygen vacancy on the energy gap of the semiconductor. The characteristic precision, accuracy, and quickness of the developed models are highly meritorious in determining the level of oxygen vacancy that adjusts the semiconductor energy gap to the desired value for photocatalytic activity enhancement at a reduced cost and without experimental stress.

Wide Range X‐Ray to Infrared Photon Detection and Energy Storage in LiTaO3:Bi3+,Dy3+ Perovskite

AbstractIt is challenging to obtain a material that can detect photons ranging from X‐rays to infrared light. Such materials have promising use to develop advanced applications like in information storage, anticounterfeiting, or X‐ray imaging. This article reports on such a material; LiTaO3:xBi3+,yDy3+ perovskite phosphor. Experimental spectroscopy, thermoluminescence, and vacuum referred binding energy diagram (VRBE) construction are combined to study the trapping processes of charge carriers. The VRBEs in the ground or excited states of Bi3+ and Bi2+ are discussed. Bi3+ emerges to act as a ≈1.3 eV deep hole capturing center and it may possibly also act as a 0.80 ± 0.5 eV deep electron trapping center. A linear relation between the amount of stored charge carriers and a photochromic phenomenon both induced by X‐rays or 254 nm UV‐light charging appears. The stored charge carriers in LiTaO3:xBi3+,yDy3+ are removed by heating or with an optically stimulated process with 365 nm UV light to 850 nm infrared laser. More than 3 or 40 h of Bi3+ and Dy3+ based white afterglow is measurable in LiTaO3:0.005Bi3+,0.004Dy3+ after exposure to X‐rays or 254 nm UV light. Proof‐of‐concept light detection applications like 2D information storage and anticounterfeiting or X‐ray imaging are demonstrated by using the phtotochromic and white afterglow LiTaO3:xBi3+,yDy3+ phosphors.

Enhancement of radiation detection performance with reduction of EH6/7 deep levels in n-type 4H–SiC through thermal oxidation

We report the effect of EH6/7 electron trap centers alone on the performance of high-resolution radiation detectors fabricated on n-type 4H–SiC epitaxial layers. A Schottky barrier detector (SBD) and a metal-oxide-semiconductor (MOS) capacitor detector fabricated using two sister samples derived from the same 50 μm 4H–SiC parent wafer exhibited widely different energy resolutions of 0.4% and 0.9% for 5486 keV alpha particles. An equivalent noise charge model analysis ruled out the effect of the detector capacitance and the leakage current on the resolution of the detectors. Deep level transient spectroscopic studies revealed the presence of two trapping centers in each detector within the temperature scan range 240–800 K. The Z1/2 center, a potential electron trap, was detected in both the detectors in equal concentration, which suggested that the observed difference in the energy resolution is due to the presence of the other defect, the EH6/7 center, in the SBD. The capture cross section of the EH6/7 center was calculated to be three orders of magnitude higher than the second defect [a carbon antisite vacancy (CAV) center] observed in the MOS detector with an activation energy of 1.10 eV, which accounted for the enhanced electronic trapping in the SBD leading to its poor energy resolution. It has been proposed that the EH6/7 centers in the SBD have likely been reconfigured to CAV pairs during the thermal growth of the silicon dioxide layer in the MOS detector. The proposed formation mechanism of CAV, a stable qubit state for quantum information processing, addresses the outstanding questions related to the role of defect dynamics in their formation.