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Thin films of zinc sulfide (ZnS) with varying thicknesses have been successfully fabricated using radio frequency magnetron sputtering on glass substrates at a temperature of 300 K. Structural analysis via X-ray diffraction and selected area electron diffraction confirmed the presence of nanocrystalline cubic ZnS phases in the films. The crystallite size, determined from X-ray diffraction lines, ranged between 42 and 55 nm. We also explored the morphological attributes of these surfaces and observed significant changes in both grain shape and size. Our atomic force microscopy analyses revealed that the thinner film displayed a topography marked by thinner, elongated rough peaks. As the film thickness increased, these rough peaks gradually transformed into wider, flatter features. Additionally, the films exhibited distinct percolation properties, which were undeniably tied to the alterations in the shape and size of the ZnS grains on their surfaces. Thinner samples demonstrated more pronounced surface percolation (FS > 0.5) compared to thicker samples, which displayed reduced surface percolation. Furthermore, we noted that the 250 nm film predominantly showcased strongly multifractal 3D spatial patterns in contrast to the other films. Spectroscopic measurements in the UV–visible-near infrared region revealed high transparency across the 350–850 nm spectra, with a noticeable blue shift in the absorption edge. Calculations yielded direct allowed band gaps within the range of 3.69–3.85 eV. These results indicate that the optical properties of films can be tailored by their structural and morphological characteristics, thereby offering valuable guidance for their appropriate applications.

The rapid global adoption of solar photovoltaic (PV) modules created the issue of recycling and disposal at their end of life. Several PV modules installed in the late 1980s or early 1990s have reached the end of their 30-year useful life and are now being removed as PV trash. This enormous amount of PV trash acknowledges recycling as a crucial and significant area in the value chain of PV industries. Hence, this study uses an end-of-life perspective to discuss the life cycle evaluation of two market-dominant PV technologies— c-Si and CdTe. This method examines recycling and avoided burden due to recovered material independently in order to determine the overall environmental benefit. The study concludes that recycling glass, metals like copper and aluminium, and semiconductor material from both c-Si and CdTe PV modules has a lower environmental effect than mining, providing, and refining the same components from original sources. © 2023 The Author(s)

The rapid global adoption of solar photovoltaic (PV) modules created the issue of recycling and disposal at their end of life. Several PV modules installed in the late 1980s or early 1990s have reached the end of their 30-year useful life and are now being removed as PV trash. This enormous amount of PV trash acknowledges recycling as a crucial and significant area in the value chain of PV industries. Hence, this study uses an end-of-life perspective to discuss the life cycle evaluation of two market-dominant PV technologies— c-Si and CdTe. This method examines recycling and avoided burden due to recovered material independently in order to determine the overall environmental benefit. The study concludes that recycling glass, metals like copper and aluminium, and semiconductor material from both c-Si and CdTe PV modules has a lower environmental effect than mining, providing, and refining the same components from original sources. © 2023 The Author(s)

Computational efficiency is significantly enhanced using artificial neural network-based computing. A two-terminal memristive device is a powerful electronic device that can mimic the behavior of a biological synapse in addition to storing information and performing logic operations. This work focuses on the fabrication of a memristive device that utilizes a resistive switching layer composed of polyvinyl alcohol infused with ZnO nanoparticles. By incorporating ZnO nanoparticles into the polymer film, the fabricated memristive devices exhibit functionalities that closely resemble those of biological synapses, including short-term and long-term plasticity, paired-pulse facilitation, and spike time-dependent plasticity. These findings establish the ZnO nanoparticle-polymer nanocomposite as a highly promising material for future neuromorphic systems. © 2023 Author(s).

The rapid global adoption of solar photovoltaic (PV) modules created the issue of recycling and disposal at their end of life. Several PV modules installed in the late 1980s or early 1990s have reached the end of their 30-year useful life and are now being removed as PV trash. This enormous amount of PV trash acknowledges recycling as a crucial and significant area in the value chain of PV industries. Hence, this study uses an end-of-life perspective to discuss the life cycle evaluation of two market-dominant PV technologies— c-Si and CdTe. This method examines recycling and avoided burden due to recovered material independently in order to determine the overall environmental benefit. The study concludes that recycling glass, metals like copper and aluminium, and semiconductor material from both c-Si and CdTe PV modules has a lower environmental effect than mining, providing, and refining the same components from original sources. © 2023 The Author(s)

Atmospheric aerosol pollutants are considered for the first time for the durability evaluation of non-metallic photovoltaic materials on the example of pristine and Al2O3-encapsulated Al-doped zinc oxide (AZO) window layers. The AZO samples were exposed to a varied temperature and humidity cycle, completed or not by a daily deposition of (NH4)2SO4 or NaCl aerosols, typical pollutants in rural and marine environments, respectively. The samples exposed with and without the pollutants were compared after 1 and 2 weeks of the test. Optical transmittance and conductivity significantly degraded only for the samples exposed with the pollutants. Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy evidenced localized dissolution of the AZO film and chemical modification of the Al2O3 encapsulation. The most severe degradation was caused by (NH4)2SO4, which was attributed to the high stability of soluble [Zn (NH3)42+] complexes. The Al2O3 encapsulation improved chemical and physical stability of AZO in the presence of (NH4)2SO4 but not in the presence of NaCl. The latter can be explained by pitting corrosion of Al2O3. Optical transmission curves are coherent with the AZO layer thinning in the presence of NaCl and very localized AZO dissolution (most likely grain boundary etching) in the presence of (NH4)2SO4. The enhanced degradation of encapsulated AZO in the presence of atmospheric aerosol pollutants suggests that they cannot be neglected in the evaluation of barrier protection capacities of novel encapsulates and, more generally, in the outdoor durability assessment of novel photovoltaic materials and devices., QC 20220919

Searching for an earth-abundant and environment-friendly absorber for thin-film solar cells that provides similar power conversion efficiency to CdTe and Cu(In,Ga)Se2 is of great importance for large-scale applications. Success would change the world's solar energy supply to an even more sustainable material resource. In this paper, we have studied by first-principles calculations the electronic structure and defect properties of the promising absorber Cu3SbS4. Its electronic properties, like direct band gap, high absorption coefficient, and light carrier effective masses, satisfy the requirements for an absorber except for its somewhat too small band gap energy. Sulfur and copper vacancies are easily formed defects in Cu3SbS4, where the S vacancy shrinks the band gap and degrades the material. This probably explains the experimental findings of a rather poor device performance. The suitable preparation conditions for Cu3SbS4 as an absorber are anticipated to be Cu-poor, Sb-moderate, and S-rich conditions. Herein, isovalent element alloying is demonstrated to be an effective way to increase the gap energy and thereby improve the material properties., QC 20230613

Photo-supercapacitor (PSC) devices, which have the ability to convert solar energy into electricity and store it at the same time, are groundbreaking in the field of renewable energy. However, performing energy conversion and storage on the same system with an efficient and compact design is a very challenging task. In this work, novel graphitic carbon nitride (g-C3N4)/zinc oxide nanowire (ZnO NW) composites have been synthesized as photoactive electrode material. All-solid-state two-electrode PSC has been assembled by using the lithiated Nafion® membrane as the electrolyte and separator. Compared to the standard filter paper (FP) separator, the Li+-form Nafion® membrane provided 5-times higher energy density under UV-illumination, at 1.5 V working potential and at 26.7 mAg?1 current density. Moreover, g-C3N4/ZnO NW-based PSC having Li+-form Nafion® membrane showed excellent cycling stability over 25,000 charge/discharge cycles with exceptional capacitance retention and Coulombic efficiency of 90.2 % and 99.9 %, respectively. In addition, UV illumination resulted in prolonged discharge time. In other words, energy density increased 21.5-fold with UV-illumination and reached 11 Wh kg?1 at 1.5 V working voltage and 20 mAg?1 current density. © 2022 Elsevier Ltd, The authors wish to express their sincere thanks to the TEKLAS Company for their support of this research. The authors are grateful to Dr. Francesco Frusteri of CNR-ITAE for his help in the TEM analysis of the samples.

Robust, cost-effective, and scalable solution based chemical bath deposition and ultrasonic spray pyrolysis methods have been applied to fabricate one dimensional (1D) zinc oxide nanowire (ZnO NW) and zinc stannate (ZTO) heterojunction thin films to be employed in photoelectrochemical (PEC) water splitting and UV photodetector (PD) systems. PEC performance evaluation in a three-electrode cell confirmed the positive effect of ZTO on ZnO NW-based photoanode enhancing incident photon-to-current efficiency (IPCE%) two-folds of the pristine ZnO NW at 367 nm wavelength. Responsivity (Rs) and detectivity (D*) values of the pristine ZnO NW-based PD have been increased from 0.5 A.W?1 and 0.5 × 1012 Jones to 1.7 A.W?1 and 1.0 × 1012 Jones with ZTO layer, respectively. © 2022 Elsevier B.V., This research was supported by TUBITAK-BIDEB-2218 Program No.118C551., 118C551

Photo-supercapacitor (PSC) devices, which have the ability to convert solar energy into electricity and store it at the same time, are groundbreaking in the field of renewable energy. However, performing energy conversion and storage on the same system with an efficient and compact design is a very challenging task. In this work, novel graphitic carbon nitride (g-C3N4)/zinc oxide nanowire (ZnO NW) composites have been synthesized as photoactive electrode material. All-solid-state two-electrode PSC has been assembled by using the lithiated Nafion® membrane as the electrolyte and separator. Compared to the standard filter paper (FP) separator, the Li+-form Nafion® membrane provided 5-times higher energy density under UV-illumination, at 1.5 V working potential and at 26.7 mAg?1 current density. Moreover, g-C3N4/ZnO NW-based PSC having Li+-form Nafion® membrane showed excellent cycling stability over 25,000 charge/discharge cycles with exceptional capacitance retention and Coulombic efficiency of 90.2 % and 99.9 %, respectively. In addition, UV illumination resulted in prolonged discharge time. In other words, energy density increased 21.5-fold with UV-illumination and reached 11 Wh kg?1 at 1.5 V working voltage and 20 mAg?1 current density. © 2022 Elsevier Ltd, The authors wish to express their sincere thanks to the TEKLAS Company for their support of this research. The authors are grateful to Dr. Francesco Frusteri of CNR-ITAE for his help in the TEM analysis of the samples.

Robust, cost-effective, and scalable solution based chemical bath deposition and ultrasonic spray pyrolysis methods have been applied to fabricate one dimensional (1D) zinc oxide nanowire (ZnO NW) and zinc stannate (ZTO) heterojunction thin films to be employed in photoelectrochemical (PEC) water splitting and UV photodetector (PD) systems. PEC performance evaluation in a three-electrode cell confirmed the positive effect of ZTO on ZnO NW-based photoanode enhancing incident photon-to-current efficiency (IPCE%) two-folds of the pristine ZnO NW at 367 nm wavelength. Responsivity (Rs) and detectivity (D*) values of the pristine ZnO NW-based PD have been increased from 0.5 A.W?1 and 0.5 × 1012 Jones to 1.7 A.W?1 and 1.0 × 1012 Jones with ZTO layer, respectively. © 2022 Elsevier B.V., This research was supported by TUBITAK-BIDEB-2218 Program No.118C551., 118C551

In this paper, it is shown that the nanoscopic design of combining semiconductors and noble metals has a direct impact on the macroscopic (electrochemical) properties of their assembled, hyperbranched, macroscopic gel networks. Controlled and arbitrary deposition of gold domains on CdSe/CdS nanorods leads to tipped and randomly decorated heteroparticles, respectively. Structural and optical properties of the gel networks depend upon assembling the hybrid particles by means of oxidative or ionic routes. Additionally, the impact of different building block designs on the charge carrier separation processes is investigated from spectroelectrochemical point of view. A more efficient charge carrier separation is revealed in the tipped design manifesting in higher negative photocurrent efficiencies compared to the arbitrary decoration, where the charge recombination processes are more remarkable. This work sheds light on the importance of the nanostructuring on the spectroelectrochemical properties at the macroscale paving the way towards their use in photochemical reactions.

This study presents the advances in the field of ZnO/Ag catalysts from the synthesis of hierarchical ZnO nanowires (NWs) decorated with Ag nanoparticles, prepared by a facile solvothermal method at 120°C. It evaluates the photocatalytic efficiency from studying the time reaction of Ag/Zn concentration ratio and the presence of cetyltrimethylammonium bromide (CTAB) as an organic dispersant. X-ray diffraction, scanning electron microscopy, and analytical/high-resolution transmission electron microscopy results confirmed the presence of homogeneous cylindrical ZnO nanowires and quasi-spherical Ag crystals. ZnO NWs exhibited hexagonal wurtzite structure and cubic FCC symmetry in Ag nanoparticles (NPS). Two types of nanostructures, including homogeneous cylindrical ZnO NWs in the absence of Ag and simultaneous presence of ZnO NWs and Ag NPs, formed depending on experimental conditions. The photocatalytic activity was evaluated by studying methylene blue (MB) degradation time under UV light excitation. Diffuse reflectance UV–Vis spectrophotometry (UV–Vis DRS) allowed identifying the ZnO absorption band at ~393 nm. Crystal size varied depending on the reaction time and the addition of CTAB. Synthesis time increased bandgap values, getting better photocatalytic performance in samples synthesized in intermediate times (6 h), higher Ag+/Zn2+ molar ratio (0.2/1.0), and CTAB. According to HRTEM observations, the presence of silver nanocrystals with high content of defects (twinning, stacking faults) could play an essential role in the photocatalytic response. In this context, the specific synthesis conditions of Ag/ZnO might be more appropriate for their use in organic dyes degradation in water and the potential use in protective treatments against materials biodeterioration processes. © 2022 The Authors

Solar cells with the structure ZnO/CdS/Cu2ZnSnSe4/Mo/glass were studied by photoluminescence (PL) before and after irradiation with a dose of 1.8 × 1015 cm−2 and then 5.4 × 1015 cm−2 of 10 MeV electrons carried out at 77 K in liquid nitrogen bath. The low temperature PL spectra before irradiation revealed two bands, a broad and asymmetrical dominant band at 0.94 eV from the CZTSe layer and a lower intensity high energy band (HEB) at 1.3 eV, generated by defects in the CdS buffer layer. Analysis of the excitation intensity and temperature dependencies suggested that the dominant band is free-to-bound (FB): the recombination of free electrons with holes localised at acceptors whose energy levels are affected by potential fluctuations of the valence band due to high concentrations of randomly distributed charged defects. Irradiation did not induce any new band in the examined spectral range (from 0.5 μm to 1.65 μm) but reduced the intensity of both bands in the PL spectra measured at 77 K without warming the cells. The higher the dose the greater was the reduction. After this the cells were warmed to 300 K and moved to a variable temperature cryostat to measure temperature dependencies of the PL spectra. After irradiation the red shift rate of the FB band with temperature rise was found to increase. Electrons displace atoms in the lattice creating primary defects: interstitials and vacancies. These defects recombine during and shortly after irradiation forming secondary defect complexes which work as deep non-radiative traps of charge carriers reducing the PL intensity and increasing the rate of the temperature red shift. Irradiation did not affect the mean depth of the band tails estimated from the shape of the low energy side of the dominant PL band. © 2020 Elsevier Ltd

Cooperative self-assembly (co-assembly) of diblock copolymers (DBCs) and inorganic precursors that takes inspiration from the rich phase separation behavior of DBCs can enable the realization of a broad spectrum of functional nanostructures with the desired sizes. In a DBC assisted sol–gel chemistry approach with polystyrene-block-poly(ethylene oxide) and ZnO, hybrid films are formed with slot-die coating. Pure DBC films are printed as control. In situ grazing-incidence small-angle X-ray scattering measurements are performed to investigate the self-assembly and co-assembly process during the film formation. Combining complementary ex situ characterizations, several distinct regimes are differentiated to describe the morphological transformations from the initially solvent-dispersed to the ultimately solidified films. The comparison of the assembly pathway evidences that the key step in the establishment of the pure DBC film is the coalescence of spherical micelles toward cylindrical domains. Due to the presence of the phase-selective precursor, the formation of cylindrical aggregates in the solution is crucial for the structural development of the hybrid film. The pre-existing cylinders in the ink impede the domain growth of the hybrid film during the subsequent drying process. The precursor reduces the degree of order, prevents crystallization of the PEO block, and introduces additional length scales in the hybrid films., QC 20220427

Hollow nanostructures have attracted attention because of their unique physiochemical properties and broad potential applications in electronics, optics and photonics. In this study, a facile hydrothermal approach was developed to fabricate hollow ZnO microspheres via self-assembled rod-like nanostructures. The morphology-controlled synthesis was conducted by altering hydrothermal treatment temperature (150, 200 and 250 °C) in solutions containing zinc acetate dihydrate precursor and glycerol as the stabilizing agent. The morphological observations indicated that hydrothermally grown ZnO architectures could be reasonably adjusted by modulating hydrothermal reaction temperature. Possible growth routes are proposed to elucidate the formation process of ZnO microspheres with the rod-like nanostructures. Morphology-dependent absorbance and emission along with red-shifts with improved crystalline qualities were observed with increasing hydrothermal growth temperature. Kerr-type nonlinear optical characteristics examined using single-beam Z-scan technique in the near infrared spectral range under nanosecond Nd-YVO4 laser pulses showed positive values of nonlinear refraction providing an evidence of self-focusing behaviors at the excitation wavelength of 1064 nm in all the samples studied. The highest Kerr-type nonlinear susceptibility was estimated to be 2.31 × 10–6 esu for hollow ZnO microspheres grown at 250 °C, suggesting synergistic effects of surface morphologies on optical nonlinearities., QC 20220425

The electrical properties of an all-oxide core-shell ZnO-Co3O4nanorod heterojunction were studied in the dark and under UV-vis illumination. The contact potential difference and current distribution maps were obtained utilizing new methods in dynamic multifrequency atomic force microscopy (AFM) such as electrostatic and conductive intermodulation AFM. Light irradiation modified the electrical properties of the nanorod heterojunction. The new techniques are able to follow the instantaneous local variation of the photocurrent, giving a two-dimensional (2D) map of the current-voltage curves and correlating the electrical and morphological features of the heterostructured core-shell nanorods., QC 20220426

Solar-driven water splitting is a promising alternative to industrial hydrogen production. This study reports an elaborate design and synthesis of the integration of cadmium sulfide (CdS) quantum dots and cuprous sulfide (Cu2S) nanosheets as three-dimensional (3D) hollow octahedral Cu2S/CdS p–n heterostructured architectures by a versatile template and one-pot sulfidation strategy. 3D hierarchical hollow nanostructures can strengthen multiple reflections of solar light and provide a large specific surface area and abundant reaction sites for photocatalytic water splitting. Owing to the construction of the p–n heterostructure as an ideal catalytic model with highly matched band alignment at Cu2S/CdS interfaces, the emerging internal electric field can facilitate the space separation and transfer of photoexcited charges between CdS and Cu2S and also enhance charge dynamics and prolong charge lifetimes. Notably, the unique hollow Cu2S/CdS architectures deliver a largely enhanced visible-light-driven hydrogen generation rate of 4.76 mmol/(g·h), which is nearly 8.5 and 476 times larger than that of pristine CdS and Cu2S catalysts, respectively. This work not only paves the way for the rational design and fabrication of hollow photocatalysts but also clarifies the crucial role of unique heterostructure in photocatalysis for solar energy conversion., QC 20220314

In the current study, promising glass composites based on vanadium pentoxide (V2O5)- doped zinc borate (ZnB) were investigated in terms of their nuclear-radiation-shielding dynamics. The mass and linear attenuation coefficient, half-value layer, mean free path, tenth-value layer, effective atomic number, exposure-buildup factor, and energy-absorption-buildup factor were deeply simulated by using MCNPX code, Phy-X PSD code, and WinXcom to study the validation of ZBV1, ZBV2, ZBV3, and ZBV4 based on (100−x)(0.6ZnO-0.4B2O3)(x)(V2O5) (x = 1, 2, 3, 4 mol%) samples against ionizing radiation. The results showed that attenuation competencies of the studied glasses slightly changed while increasing the V2O5 content from 1 mol% to 4 mol%. The domination of ZnO concentration in the composition compared to B2O3 makes ZnO substitution with V2O5 more dominant, leading to a decrease in density. Since density has a significant role in the attenuation of gamma rays, a negative effect was observed. It can be concluded that the aforementioned substitution can negatively affect the shielding competencies of studied glasses. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

For the first time, ZnO/C composites were synthesized using zinc glycerolate as a precursor through one-step calcination under a nitrogen atmosphere. The effect of the heat treatment conditions on the structure, composition, morphology as well as on the electrochemical properties regarding application in lithium-ion batteries are investigated. The products obtained by calcination of the precursor in nitrogen at 400—800 °C consist of zinc oxide nanoparticles and amorphous carbon that is in-situ generated from organic components of the glycerolate precursor. When used as anode material for lithium-ion batteries, the as-prepared ZnO/C composite synthesized at a calcination temperature of 700 °C delivers initial discharge and charge capacities of 1061 and 671 mAh g−1 at a current rate of 100 mA g−1 and hence 1.5 times more than bare ZnO, which reaches only 749/439 mAh g−1. The native carbon improves the conductivity, allowing efficient electronic conductivity and Li-ion diffusion. By means of ex-situ XRD studies a two-step storage mechanism is proven. © 2021, The Author(s).

Microplastic pollution of water and ecosystem is attracting continued attention worldwide. Due to their small sizes (≤5 mm) microplastic particles can be discharged to the environment from treated wastewater effluents. As microplastics have polluted most of our aquatic ecosystems, often finding its way into drinking water, there is urgent need to find new solutions for tackling the menace of microplastic pollution. In this work, sustainable green photocatalytic removal of microplastics from water activated by visible light is proposed as a tool for the removal of microplastics from water. We propose a novel strategy for the elimination of microplastics using glass fiber substrates to trap low density microplastic particles such as polypropylene (PP) which in parallel support the photocatalyst material. Photocatalytic degradation of PP microplastics spherical particles suspended in water by visible light irradiation of zinc oxide nanorods (ZnO NRs) immobilized onto glass fibers substrates in a flow through system is demonstrated. Upon irradiation of PP microplastics for two weeks under visible light reduced led to a reduction of the average particle volume by 65%. The major photodegradation by-products were identified using GC/MS and found to be molecules that are considered to be mostly nontoxic in the literature., QC 20210720

Dysprosium-doped zinc oxide (ZnO) thin films have been prepared through spray pyrolysis onto glass substrates. Cross-sections of the deposited thin films were assessed through Scanning Electron Microscopy (SEM), showing thicknesses between 200 and 300 nm. The thin film roughness was evaluated using the obtained images from the Atomic Force Microscope (AFM) micrographs. The crystallographic structure of the samples was analyzed by X-ray diffraction (XRD) revealing polycrystalline thin films. However, the slight shift towards a higher 2 theta angle in Dy-doped ZnO films as compared to the pure ones indicates the incorporation of Dy3+ into the ZnO crystal lattice. The analysis of the oxidation state via X-ray photoelectron spectroscopy (XPS) confirms the incorporation of Dy ions in the ZnO matrix. Besides, UV-Vis-NIR spectrophotometry analysis and photoluminescence (PL) spectroscopy showed that bandgap energy values of ZnO decreased when dysprosium doping increased. Therefore, Dy doped ZnO thin films can be potentially used as a solar-light-driven photocatalyst. Among the different doping yields, the ZnO doped with 6% dysprosium provides the highest degradation rate for methylene blue (MB) under solar irradiation. Specifically, 9% of dye degradation was achieved under sunlight irradiation for 120 minutes.

The device operational lifetime and the understanding of the degradation pathways are critical steps for inverted organic solar cells (iOSCs) to enter the energy market. In this work, a combined study of impedance spectroscopy (IS) and photovoltage/photocurrent transient (TPV/TPC) techniques was employed to analyze the degradation of PTB7-Th:PC70BM-based iOSCs in accordance with the ISOS-D1 protocol under ambient conditions without encapsulation. Both techniques provide real information on how devices with different electron transport layers (PFN, TiOx, and ZnO) were degraded, affecting the stability of the active layer. We found that the main cause of degradation is the formation of interface traps in the dark and upon air exposure. The increase of trap density in the active layer upon degradation was revealed by TPV. The change in interface trap density due to the interfacial defect over the shelf-lifetime was further confirmed by the data from IS measurements. Last but not least, modelling dark current-voltage (J-V) using the IS data as well as the morphological changes of each ETL verified our hypothesis.

We report on the results of comparative study of the photocatalytic performances of the wide band gap semiconductor catalysts titania (TiO2), zinc oxide (ZnO) and mixed phase of ZnO-ZnS (zinc sulfide). The mixed phase structures show better photodegradation properties under UV and visible light illumination compared to its analogous forms. Rutile phase TiO2 nanotubes showed the highest catalytic activity, resulting in 70% decay of dye concentration within 85 min with visible light irradiation, while the rutile-anatase mixture of TiO2 degrade 75% of the test contaminant within 10 min under UV illumination. Microparticles and assemblies of nanostructures used in the experiments can be recycled effectively and subsequently reused., QC 20210330

This contribution concerns the effect of the Ag content in wide-gap AgwCu1-wIn1-xGaxSe2 (ACIGS) absorber films and its impact on solar cell performance. First-principles calculations are conducted, predicting trends in absorber band gap energy (Eg) and band structure across the entire compositional range (w and x). It is revealed that a detrimental negative conduction band offset (CBO) with a CdS buffer can be avoided for all possible absorber band gap values (Eg = 1.0–1.8 eV) by adjusting the Ag alloying level. This opens a new path to reduce interface recombination in wide-gap chalcopyrite solar cells. Indeed, corresponding samples show a clear increase in open-circuit voltage (VOC) if a positive CBO is created by sufficient Ag addition. A further extension of the beneficial compositional range (positive CBO at buffer/ACIGS interface) is possible when exchanging CdS with Zn1-ySnyOz, because of its lower electron affinity (χ). Nevertheless, the experimental results strongly suggest that at present, residual interface recombination still limits the performance of solar cells with optimized CBO, which show an efficiency of up to 15.1% for an absorber band gap of Eg = 1.45 eV., QC 20200626

Highly efficient gamma shielding of BZBB glasses with various Bi2O3 concentrations in the xBi2O3-30B2O3-(65-x)ZnO-5BaO, (5 ≤ x ≤ 25 mol%) were evaluated for their radiation shielding properties. The m results have been evaluated via the NISTXCOM database and simulated via FLUKA code. The simulation values by Monte Carlo code (FLUKA) have been shown to converge and correlate with XCOM values. Shielding properties like HVL, MFP, Zeff, EBF, and EABF values have been computed. The values observed that μm and Zeff increase with increasing Bi2O3. 47.09, 48.91, 50.73, 52.54 and 54.36 (cm2/g) are the μm values for BZBB1, BZBB2, BZBB3, BZBB4 and BZBB5 glasses at 15 keV. Also, the μm values decrease with increasing photon energy for all glass samples. Moreover, BZBB5 sample had the lowest HVL, MFP, EBF, and EABF values. That indicates to the addition of Bi2O3 improves the radiation shielding properties of BZBB glasses. The obtained results were compared with the most commonly shielding materials such as lead and concretes. It was concluded that the improved BZBB glasses with the addition of Bi2O3 showed excellent shielding properties comparing with shielding materials. These results could be highly beneficial for fields such as medical treatment facilities. © 2020 The Authors.

Recently introduced model for quantitative analysis of in-depth non-uniform surfaces is applied to reexamine the X-ray Photoelectron Spectroscopy (XPS) data of Cd0.99Fe0.01Te0.97Se0.03 and Zn0.98Fe0.02Te0.91Se0.09 crystalline samples. Special attention is paid to the precise identification of phases which form the bulk-like near-surface region and the surface overlayers (the oxide layer and the layer of organic impurities), as well as the influence of surface morphology on the measurements. The obtained results fully support earlier qualitative estimations, but also provide new quantitative insight into the composition of the three investigated regions. The near-surface region of Cd0.99Fe0.01Te0.97Se0.03 and Zn0.98Fe0.02Te0.91Se0.09 samples is slightly electropositive, with cation/anion ratio 52:48 and 53:47, respectively. Model surface structures, which are fully compatible with the experimental results, comprise 0.76 nm thick CdTeO3 layer at the surface of Cd0.99Fe0.01Te0.97Se0.03 and 0.33 nm thick mixed ZnO/TeO2 oxide layer on Zn0.98Fe0.02Te0.91Se0.09. In both samples the oxide layer is only a few atomic layers thick, implying that it suppresses further rapid migration of oxygen into the bulk.

The present work reports the realisation of high-quality crystalline CdS/Mn3O4(CM) nanocomposites by a simple cost-effective chemical method in air atmosphere. The authors have performed theoretical calculations and experimental analysis in order to understand the synthesised nanocomposites. X-ray diffraction results showed that the CM nanocomposites were cubic and orthorhombic mixed structure which is in good agreement with the theoretical studies. Field emission scanning electron microscopy images of CM confirmed the formation of well distributed nanocomposites. The outcomes of DFT calculations provide results for the bandgap calculation of pure CdS, Mn3O4and the CM nanocomposites. Photoluminescence studies with interesting visible light absorption demonstrated the great potentiality of the as-synthesised nanocomposites towards photocatalytic applications that could be a detailed research scope for the authors' future studies. © 2020 Institution of Engineering and Technology. All rights reserved.

In this work, a series of tellurite glass combined with various concentrations of germanium oxide was fabricated according to the formula of (70-x)TeO2-xGeO2–20ZnO-10Li2O where x = 5, 10, 15 and 20 mol% via utilizing the melt-quench method for possible use in a radiation shielding applications. X-ray diffraction and Attenuated Total Reflectance Fourier Transform Infrared was employed to investigate the structure of the synthesized glasses. The density and Poisson's ratio for current samples reduced gradually from 5.221–5.008 g.cm−3 and 0.134–0.131, respectively, while the enhancement in bandgap values from 3.700–3.872 eV with addition of GeO2 is observed. The linear attenuation coefficient values at 0.015 MeV are 230.123 and 236.832 cm−1 for samples TG1 and TG4, respectively. Moreover, the lowest half-value layer attained via TG1 and raises from 0.0030 to 3.6684 cm while the highest HVL attained by TG4 and raises from 0.0029 to 3.9696 cm. © 2020 Elsevier B.V.

In this article, high dense glasses based heavy metal former and modifier have been synthesized. The glass system with composition formula of (60-x)TeO2–10GeO2 -20ZnO–10BaO - xBi2O3 (where x = 2.5, 5, 7.5, and 10 mol. %). The glasses have been produced using the usual melt, quenching, and annealing process. Many physical features were investigated. To confirm the amorphous nature of theses glasses, we examined the samples with X-ray diffraction in the range of between 10° and 80°. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) transmission spectrum for the current glass samples within the range of 400–1500 cm−1 has been recorded to study the behavior of the obtained glasses that is mixed between tellurium and germanium glass phase. To study the transparency and cut-off wavelength and other optical properties, Ultraviolet–Visible spectrometer (UV–Vis) was utilized between 200 and 800 nm. Radiation shielding ability of the (60-x) TeO2–10GeO2-20ZnO–10BaO-xBi2O3 glasses was examined. Monte Carlo simulation method was applied to estimate the shielding parameters for gamma photons with various energies varied in rang from 0.015 to 15 MeV. © 2020 Elsevier B.V.

A characteristic of obtaining metal powders by direct current electrolysis is changes in the morphology of particles over the loose deposit layer thickness up to the formation of large spherulites. Deposits should be periodically removed from the cathode in order to obtain a powder with homogeneous composition. This paper justifies the choice of the parameter describing the change in loose deposit properties and proposes a method for determining the periodicity of its removal from the cathode. Loose zinc deposits were obtained at 25°C from zincate electrolyte containing 0.3 mol L–1 of ZnO and 4 mol L–1 of NaOH at a current setpoint exceeding six times the limiting diffusion current calculated using the smooth electrode. Electrode potential, deposit thickness and evolved hydrogen volume were measured directly in the process of electrolysis. Current redistribution between the metal reduction and hydrogen evolution leads to a change in the structure of loose deposit particles. It is shown that the differential current efficiency of zinc is the parameter describing the change in the loose zinc deposit density. Its value should not exceed 0.96, in order to ensure deposition of loose deposit with homogeneous properties. A further increase in current efficiency will lead to the formation of aggregates at the deposit growth front. It is proposed to determine the periodicity of loose deposit removal from the cathode using the empirical equation for the time dependency of differential current efficiency of zinc. The mathematical and statistical analysis of the data obtained in six replicates was carried out. The interval approach made it possible to significantly narrow the range of permissible differential current efficiency values and, as a consequence, to determine empirical equation coefficients with acceptable accuracy and calculate the growth time period of a deposit with homogeneous structure. The obtained approach can be used to estimate the time period of l

Cadmium chalcogenide nanoplatelets (NPLs) have gained tremendous attention in the past decade due to their extremely narrow optical features and their special electronic properties. For the application of the NPLs as optical emitters, in (photo) catalysis or sensing, further modification of the pristine (core) NPLs can be required. Therefore, many procedures for the synthesis of crowns (lateral extension of the core NPLs), shells and particle domains on the NPLs have already been developed. CdSe/CdS core/crown NPLs are characterised by extremely short photoluminescence (PL) lifetimes and high PL quantum yields (PLQYs) and might therefore be ideal candidates for lighting applications. In this work, we show how the optical properties of CdSe/CdS core/crown NPLs, especially their PLQYs, can be strongly improved by applying a sulphur precursor with a low reactivity. Under optimised conditions, the new procedure allows the growth of uniform CdS crowns around CdSe core NPLs with various lateral sizes, thicknesses and shapes. In addition, the modified growth kinetics was investigated by various methods, including UV/vis and PL spectroscopy as well as transmission electron microscopy. This journal is © The Royal Society of Chemistry.

Recently introduced model for quantitative analysis of in-depth non-uniform surfaces is applied to reexamine the X-ray Photoelectron Spectroscopy (XPS) data of Cd0.99Fe0.01Te0.97Se0.03 and Zn0.98Fe0.02Te0.91Se0.09 crystalline samples. Special attention is paid to the precise identification of phases which form the bulk-like near-surface region and the surface overlayers (the oxide layer and the layer of organic impurities), as well as the influence of surface morphology on the measurements. The obtained results fully support earlier qualitative estimations, but also provide new quantitative insight into the composition of the three investigated regions. The near-surface region of Cd0.99Fe0.01Te0.97Se0.03 and Zn0.98Fe0.02Te0.91Se0.09 samples is slightly electropositive, with cation/anion ratio 52:48 and 53:47, respectively. Model surface structures, which are fully compatible with the experimental results, comprise 0.76 nm thick CdTeO3 layer at the surface of Cd0.99Fe0.01Te0.97Se0.03 and 0.33 nm thick mixed ZnO/TeO2 oxide layer on Zn0.98Fe0.02Te0.91Se0.09. In both samples the oxide layer is only a few atomic layers thick, implying that it suppresses further rapid migration of oxygen into the bulk.

Nanostructured thin films of Co-doped zinc sulfide were synthesized through femtosecond pulsed laser deposition. The scheme involved ablation of physically mixed Co and ZnS with pairs of ultrashort pulses separated in time in the 0–300 ps range. In situ monitorization of the deposition process was carried out through a simultaneous reflectivity measurement. The crystallinity of generated nanoparticles and the inclusion of Co in the ZnS lattice is demonstrated by transmission electron microscopy and energy dispersive X-ray microanalysis (TEM-EDX) characterization. Surface morphology, Raman response, and photoluminescence of the films have also been assessed. The role of interpulse temporal separation is most visible in the thickness of the films obtained at the same total fluence, with much thicker films deposited with short delays than with individual uncoupled pulses. The proportion of Co in the synthesized doped ZnS nanoparticles is found to be substantially lower than the original proportion, and practically independent on interpulse delay.

In this paper the results of the study of optical absorption, photo-EPR signals and magnetic measurements of hydrothermal single crystals of zinc oxide doped with manganese were presented. Several lines were detected in optical absorption spectra at the temperature of 4.2 K and 77.3 K for σ- and π- polarizations of light in a 1.72-2.3 eV spectral range. These lines are attributed to a donor exciton [(d5 + h)e] that emerges as a result of the Coulomb binding of a free s electron and a hole, which is localized on p-d hybridized states. Properties of these lines are significantly different from the properties of lines of donor and acceptor excitons in II-VI:3d compounds. In EPR-spectra of Zn1-xMnxO crystals the intensity of allowed and forbidden EPR-signals of Mn2+ (d 5)-ions does not change under the illumination while the intensity of EPR-signals of unintentional Fe3+ (d 5)-ions decreases by 70 %. The value of the magnetic susceptibility of Zn1-xMnxO (x = 0.0009) is in linear dependence with temperature, which agrees with the Curie equation. Temperature dependence of the inverse value of the Mn2+ magnetic susceptibility indicates that the exchange interaction in ZnO:Mn crystals is absent. New experimental results allow us to assume that investigated Zn1-xMnxO (x = 0.0009) samples are semiconductors in the forbidden gap of which the donor level of d5/d4 does not exist. The hybridization of d5 states of Mn2+ and p states of the nearest four oxygen ions O2- leads to pushing out the antibonding DBH-states (d 5 + p) into the forbidden gap. The transitions of electrons from DBH-states to the conduction band provide a broad band of the impurity absorption in ZnO:Mn. Below this band we observed a, b, c and d lines, which are called dbh-donor excitons [(d5+h)e]. © Published under licence by IOP Publishing Ltd.

Spectral computed tomography (CT) allows optimizing image quality by combining the data in several energy channels with optimal weighting factors. In an improvement of this technique, the weighting factors are made dependent on spatial frequency, and previous work has shown that this can improve detectability for a simple detector model. In this work, we investigate the achievable detectability improvement from frequency-dependentweighting for realistic models of photon-counting detectors. We use a Monte-Carlo based simulation model to obtain point-spread functions and autocovariances for two detector models with 0.5 × 0.5 mm2 pixels, one CdTe-based with five energy bins and one silicon-based with eight energy bins. We generated noise-only images for two different energy weighting schemes: one where optimal weights were selected individually for each spatial frequency, and one where the weights optimal for zero frequency were applied to all frequencies. The modulation transfer function was set equal in both schemes. Results show that frequency-based weighting can decrease noise variance by 11 % for Si and by 38 % for CdTe, for an edge-enhancing MTF, demonstrating that optimal frequency-dependent weighting has the capability of reducing noise in high-resolution CT images., QC 20200505

Sub-wavelength THz imaging has previously been demonstrated by the optical rectification method, i.e. generating THz waves in the sample [1]. We have rendered the initial experimental setup more practical by using a simple fs laser oscillator and an efficient photo-conducting detector. We thus recorded images, at different THz frequencies with a 41-μm lateral resolution, of a sample made of ZnTe grains, and generated THz peak magnitudes with a 33 μm and 12 μm lateral resolution of a periodically poled KTP crystal., QC 20200427

Knowledge on relations between particle properties and dissolution/transformation characteristics of metal and metal oxide nanoparticles (NPs) in freshwater is important for risk assessment and product development. This critical review aims to elucidate nanospecific effects on dissolution of metallic NPs in freshwater and similar media. Dissolution rate constants are compiled and analyzed for NPs of silver (Ag), copper (Cu), copper oxide/hydroxide (CuO, Cu(OH) 2 ), zinc oxide (ZnO), manganese (Mn), and aluminum (Al), showing largely varying (orders of magnitude) constants when modeled using first order kinetics. An effect of small primary sizes (<15 nm) was observed, leading to increased dissolution rate constants and solubility in some cases. However, the often extensive particle agglomeration can result in reduced nanospecific effects on dissolution and also an increased uncertainty related to the surface area, a parameter that largely influence the extent of dissolution. Promising ways to model surface areas of NPs in solution using fractal dimensions and size distributions are discussed in addition to nanospecific aspects related to other processes such as corrosion, adsorption of natural organic matter (NOM), presence of capping agents, and existence of surface defects. The importance of the experimental design on the results of dissolution experiments of metal and metal oxide NPs is moreover highlighted, including the influence of ionic metal solubility and choice of particle dispersion methodology., QC 20190821

Cu2ZnSnSe4 (CZTSe) is one of the leading candidates for the absorber layer in sustainable solar cells. Thin films of CZTSe with a near stoichiometric [Cu]/[Zn + Sn] were used to produce solar cells with conversion efficiency η = 6.4% by a standard solar cell processing including KCN etching and the deposition of CdS and ZnO. Both CZTSe films and solar cells were examined using photoluminescence (PL) to analyse the nature of radiative recombination and photoluminescence excitation (PLE) at 4.2 K to determine the bandgap (E g). Low temperature PL spectra of the films reveal an intense band P1 at 0.81 eV and a low intensity band P2 at 0.93 eV. Their temperature and excitation intensity dependencies suggest that they both involve recombinations of free electrons with holes localised at acceptors with the energy level influenced by potential fluctuations in the valence band. We associate P1 and P2 with different fractions of CZTSe: with a lower and higher degree of order of Cu and Zn on the cation sub-lattice, respectively. Device processing reduced the intensity of P1 by 2.5 whereas the intensity of P2 increased by a 1.5. We assign this to a low temperature annealing due to CdS and ZnO deposition which increased the fraction of CZTSe with high degree of Cu/Zn order and decreased the fraction with low degree of Cu/Zn order. Device processing increased E g, blue shifted P1, decreased its width, j-shift and the mean depth of potential fluctuations. These can also be related to the annealing and/or KCN etching and the chemical effect of Cd, due to CdS replacing copper at the CdS-CZTSe interface layer. Processing induced a new broad band P3 at 1.3 eV (quenching with E a = 200 meV) which we attributed to defects in the CdS layer. © 2018 IOP Publishing Ltd.

Dielectric properties of nanocomposites based on opal matrices with ZnO particles are studied. Microwave measurements are carried out in the frequency range from 26 to 38 GHz. Frequency dependences of transmittance and reflection coefficients are obtained. The values of the real and imaginary parts of the complex dielectric permeability are obtained. The X-ray phase analysis of nanocomposites is carried out and their structure is studied. Low temperature magnetic properties of artificial crystals with ZnO particles doped with Mn and Gd in magnetic fields up to 30 kOe are discussed. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Local structural and electronic properties around Fe in multi-component Cd0.99Fe0.01Te0.97S0.03 system were studied by means of X-ray absorption fine structure (XAFS). Composition of non-polar (110) surfaces of Cd0.97Fe0.03Te and Cd0.99Fe0.01Te0.97S0.03 systems and mechanism of their oxidation in ambient conditions were studied by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). It has been found that Fe preferentially substitutes Cd, but due to much smaller covalent radius and preferences for paring with S, it causes local distortion of the host CdTe lattice. The distortion is confined to the Fe-immediate surrounding and the second and third coordination shell atoms are (inside experimental uncertainties) placed at distances expected in CdTe. Although local structure around Fe is well defined in the bulk of both samples, their near-surface region is completely depleted from Fe, and in case of Cd0.99Fe0.01Te0.97S0.03 somewhat enriched in S. Special attention is, therefore, paid to characterization of the near-surface region and evaluation of its composition and structure. To that end we have introduced a general standard-free algorithm for XPS data analysis of the two-layer surface structure (bulk, oxide layer, and the impurity layer). Results of the in-depth composition analysis revealed that despite different bulk composition and impurity layer thickness, underneath the topmost impurity layer lays approximately one monolayer of CdTeO3 which passivates the surface. © 2018 Elsevier B.V.

The effect of solar cell processing (including etching in KCN along with deposition of CdS and ZnO) on photoluminescence (PL) spectra and bandgap E g (measured at 4.2 K by photoluminescence excitation) of Cu 2 ZnSnSe 4 films, produced by selenising metallic precursors at 450 °C, 500 °C and 550 °C, was studied. Temperature and excitation intensity analysis of the P1 dominant band in the PL spectra of solar cells suggests that after processing this band still can be assigned to the free-to-bound recombination of free electrons with holes bound at deep acceptor levels influenced by valence band-tails. However processing increased the intensity of P1 and blue shifted it. The strongest effect was observed for the film selenised at 500 °C. For the film selenised at 450 °C the blue shift and increase in the intensity were smaller and only a slight intensity rise was found for the film selenised at 550 °C. The intensity increase we assign to a reduction in the concentration of non-radiative recombination centers on the surface because of the etching and changes in doping due to inter-diffusion of Cd, S, Se and Zn after the deposition of CdS. Such an inter-diffusion depends on the elemental composition of the films defining the chemistry of defects and influencing E g which increased in the film selenised at 500 °C but decreased in the other films. Processing increased the P1 shift rate (j-shift) with excitation power change in all the films demonstrating a higher compensation degree in the solar cells which is consistent with the formation of an interface layer containing new donors Cd Cu . © 2019 Elsevier B.V.

The priority direction of thermal energy on solid fuels is to increase efficiency and environmental safety, approaching zero emissions of harmful substances. To achieve these goals, they are currently creating new schemes for combined cycle gas turbine units with intra-cycle gasification (IGCC). To improve the efficiency of the IGCC cycle, hot dry desulfurization (HGC) technologies are being developed. HGC uses regenerable sorbents that allow the repeated adsorption of hydrogen sulfide from synthesis gas, among which the most acceptable thermodynamic and operational characteristics are based on ZnO sorbents. The article uses the method of thermogravimetric analysis (TGA) to investigate the development of target reaction capture hydrogen sulfide ZnO-containing sorbent and sorbent reactions with components of synthesis gas in the temperature range up to 1000°C. The sorbent calcined at 900°C shows thermal stability in an inert atmosphere over the entire temperature range studied. Uncalcined sorbents at temperatures of 200 and 600°C emit carbon dioxide in an amount of 1.5-4.5% by weight of the sorbent. At temperatures up to 550°C, the target reaction is basic, and side reactions practically do not develop. The maximum rate of absorption of hydrogen sulfide by the sorbent is observed at a temperature of 600°C. At 500-550°C reactions of a sorbent begin with H2 and CO, at 750-800°C-with carbon, at 850°C-with CH4. The intensity of effect of reagents is defined on degradation of a sorbent by reactionary ability of gases more than temperature. © Published under licence by IOP Publishing Ltd.

Hot gas clean-up (HGC) technology uses special zinc oxide based sorbents. Sorbent attrition is one of the negative factors that should be improved. The current study has determined that one of the main reasons of sorbent reduction is interaction with syngas components, namely, carbon monoxide, hydrogen, methane and carbon (side reactions). In this study, kinetics of main reaction (h2s adsorption by zinc oxide) and side reactions were considered and compared. Models of chemical processes and mechanisms were considered as well. Complicated nature of HGC process was researched. It is stated that the process can run in three different phases (gas, solid, dust). Methods of TGA data calculation are presented and compared with literature. In syngas where hydrogen sulphide concentration is much lower than concentration of hydrogen and carbon monoxide, main reaction is dominant at temperatures near 300-500 °C. At 650 °C main reaction takes the second place after H2 reduction, and at 850°C it is the third after CO reduction (with diffusion resistance of product shell). Hydrogen reduction is more active than carbon monoxide reduction, that is why CO/H2 ratio in syngas should be increased for rising the HGC operation temperature. A wide range of processes (main and side reactions) was considered with the use of the same materials, equipment and methods. © Published under licence by IOP Publishing Ltd.

The IGCC technology serves to efficiently produce thermal and electrical energy with minimal impact on the environment. In operating IGCC, wet desulphurization is used at temperatures below 200°C. The use of hot desulphurization at temperatures around 500°C will significantly improve IGCC efficiency. The preferred sorbent for hot gas cleaning is ZnO. At temperature of 450-500°C, ZnO begins decomposing because of reactions with syngas components (primarily hydrogen). Steam impedes reaction of ZnO with H2 and increases ZnO thermal stability. Syngas H2/H2O ratio is determined by gasifier operation mode. The purpose of this work is to determine maximum temperature of hot gas cleaning depending on condition of ZnO-sorbent thermal stability and steam-air-blown mechanically activated coal gasifier operation mode. To determine the effect of steam supply to syngas composition, experiments were performed on entrained-flow gasifier (1 MW). Experimental results were processed using thermodynamic analysis to determine idealized syngas composition and CFD-modeling to determine real experiment process parameters. Syngas H2O content was determined by CFD-modeling results. Study of ZnO-sorbent thermal stability depending on H2 concentration and syngas H2/H2O ratio was performed by TGA. As a result of experimentally confirmed thermodynamic calculations, ZnO-sorbent thermal stability was found to increase to 815°C due to steam dilution. © Published under licence by IOP Publishing Ltd.

Extraction of zinc from sulphide forms by pyrometallurgical methods is difficult due to the high energy of the "zinc-sulfur" bond. Theoretically justified and experimentally confirmed the possible methods of extracting zinc from such compounds by changing of raw material phase composition. The zinc oxide obtained by this way has high purity and does not require additional purification by hydrochemical methods. © The Authors, published by EDP Sciences.

We investigated effects of chemical stoichiometry of ZnO channel, controlled by oxygen partial pressure during deposition, on bias instability for ZnO thin-film transistors. Parallel threshold voltage shifts were mainly enhanced under gate bias stresses due to charge trapping when O-rich ZnO was used for channel layer. On the contrary, negative threshold voltage shifts were observed under both gate and drain bias stresses when Zn-rich ZnO was used for channel layer. This degradation was enhanced regardless of the bias polarity and the direction, attributing to electrically activated trap generations.

Stability is the most crucial issue in the fabrication of oxide thin-film transistors (TFTs) for next-generation displays. We have investigated the thermal distribution of an InSnZnO TFT under various gate and drain voltages by using an infrared imaging system. An asymmetrical thermal distribution was observed at a local drain region in a TFT depending on bias stress. These phenomena were decelerated or accelerated with stress time. We discussed the degradation mechanism by analyzing the electrical properties and thermal distribution. We concluded that the degradation phenomena are caused by a combination of Joule heating and the hot carrier effect.

We analyzed the photoleakage current (Ileak) in ZnO thin-film transistors using device simulation. The dependences of Ileak on the location of light irradiation and drain voltage are reproduced by considering a Schottky barrier at the source contact using a two-dimensional device simulation. First, carrier generation is induced by light irradiation, the generated holes accumulate near the source contact, and some of these are captured in the donor traps. Next, the Schottky barrier becomes narrow, and electron injection increases via a tunneling effect. This discussion also suggests that the off-current is exceedingly low because the Schottky barrier prevents electron injection.

Local structural and electronic properties around Fe in multi-component Cd0.99Fe0.01Te0.97S0.03 system were studied by means of X-ray absorption fine structure (XAFS). Composition of non-polar (110) surfaces of Cd0.97Fe0.03Te and Cd0.99Fe0.01Te0.97S0.03 systems and mechanism of their oxidation in ambient conditions were studied by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). It has been found that Fe preferentially substitutes Cd, but due to much smaller covalent radius and preferences for paring with S, it causes local distortion of the host CdTe lattice. The distortion is confined to the Fe-immediate surrounding and the second and third coordination shell atoms are (inside experimental uncertainties) placed at distances expected in CdTe. Although local structure around Fe is well defined in the bulk of both samples, their near-surface region is completely depleted from Fe, and in case of Cd0.99Fe0.01Te0.97S0.03 somewhat enriched in S. Special attention is, therefore, paid to characterization of the near-surface region and evaluation of its composition and structure. To that end we have introduced a general standard-free algorithm for XPS data analysis of the two-layer surface structure (bulk, oxide layer, and the impurity layer). Results of the in-depth composition analysis revealed that despite different bulk composition and impurity layer thickness, underneath the topmost impurity layer lays approximately one monolayer of CdTeO3 which passivates the surface. © 2018 Elsevier B.V.