Near-surface Region Research Articles

The Rectifying Contact of Hydrated Different Size YSZ Nanoparticles for Advanced Electronics.

The paper considers the new effects of the nanoscale state of matter, which open up prospects for the development of electronic devices using new physical principles. The contacts of chemically homogeneous nanoparticles of yttrium-stabilized zirconium oxide (ZrO2-x mol% Y2O3, x = 0, 3, 4, 8; YSZ) with different sizes of 7.5 nm and 9 nm; 7.5 nm and 11 nm; and 7.5 nm and 14 nm, respectively, was studied on direct current using nanostructured objects in the form of compacts obtained by high-hydrostatic pressure (HP-compacts of 300MPa). A unique size effect of the nonlinear (rectifying-type contact) dependence of the electrical properties (in the region U < 2.5 V, I ≤ 2.7 mA) of the contact of different-sized YSZ nanoparticles of the same chemical composition is revealed, which indicates the possibility of creating semiconductor structures of a new type (homogeneous electronics). The electronic structure of the near-surface regions of nanoparticles of studied oxide materials and the possibility of obtaining specifically rectifying properties of the contacts were studied theoretically. Models of surface states of the Tamm-type are constructed considering the Coulomb long-range action. The discovered energy variance and its dependence on the curvature of the surface of nanoparticles made it possible to study the conditions for the formation of a contact potential difference in cases of nanoparticles of the same radius (synergistic effect), different radii (doped and undoped variants), as well as to discover the possibility of describing a group of powder particles within the Anderson model. The determined effect makes it possible to solve the problem of diffusion instability of semiconductor heterojunctions and opens up prospects for creating electronic devices with a fundamentally new level of properties for use in various fields of the economy and breakthrough critical technologies.

On shape forming by contractile filaments in the surface of growing tissues.

Growing tissues are highly dynamic, and flow on sufficiently long timescales due to cell proliferation, migration, and tissue remodeling. As a consequence, growing tissues can often be approximated as viscous fluids. This means that the shape of microtissues growing in vitro is governed by their surface stress state, as in fluid droplets. Recent work showed that cells in the near-surface region of fibroblastic or osteoblastic microtissues contract with highly oriented actin filaments, thus making the surface properties highly anisotropic, in contrast to what is expected for an isotropic fluid. Here, we develop a model that includes mechanical anisotropy of the surface generated by contractile fibers and we show that mechanical equilibrium requires contractile filaments to follow geodesic lines on the surface. Constant pressure in the fluid forces these contractile filaments to be along geodesics with a constant normal curvature. We then take this into account to determine equilibrium shapes of rotationally symmetric bodies subjected to anisotropic surface stress states and derive a family of surfaces of revolution. A comparison with recently published shapes of microtissues shows that this theory accurately predicts both the surface shape and the direction of the actin filaments on the surface.

Effects of interdiffusion in nickel coated AISI 441 steel

Ferritic steel AISI 441, electroplated with nickel, is explored for the use as interconnects in solid oxide cell stacks. High-temperature oxidation tests are performed in air, and samples are investigated using scanning electron microscopy, energy-dispersive x-ray spectroscopy, and electron backscatter diffraction. Results revealed in-depth diffusion of nickel that promotes austenite formation during typical solid oxide cell operating temperatures accompanied by chromium depletion, grain refinement, and an enhanced depletion of Laves phase in the surface-near region of the steel. Effects of a formed interdiffusion zone on the protective oxide scale are discussed, considering the role of diffusion along grain boundaries and across the scale/alloy interface. The interdiffusion zone alters the morphology and continuity of Si-rich oxide that forms in this steel, and an underlying mechanism is suggested. Associated implications on the expected performance of nickel coated AISI 441 as interconnects for solid oxide cell stacks are postulated: Although no corrosion or scale spallation is observed and a good contact to the simulated oxygen electrode is maintained, there are signs of limited oxidation resistance and scale adhesion, which potentially affect lifetime and robustness of solid oxide cell stacks during (cyclic) oxidation of longer exposure than tested here.

Effect of Three-in-One Surface Modification of Spherical, Co-Free Li-Rich Cathode Material for Li-Ion Batteries (Li1.2Mn0.6Ni0.2O2) with Citric Acid

The electrochemical activation of Li2MnO3 domains in Li- and Mn-rich layered oxides (LRLO) is highly important, and can be tuned by surface modification of the active materials to improve their cycling performance. In this study, citric acid was employed as a combined organic acid, reducing agent, and carbon precursor in order to remove surface residues from the calcination process, implement an oxygen deficient layer on the surface of the primary LRLO particles, and cover their surface with a carbon-containing coating after a final annealing step. A broad selection of bulk and surface sensitive characterization methods was used to characterize the post-treated spherical particles, providing the evidence for successful creation of an oxygen deficient near-surface region, covered by carbon-containing deposits. Post-treated materials show enhanced electrochemical discharge capacities after progressive Li2MnO3 activation, reaching maximum capacities of 247 mAh g−1. Gassing measurements reveal the suppression of oxygen release during the first cycle, concomitant with an increased CO2 formation for the carbon-coated materials. The voltage profile analysis in combination with post-mortem characterization after 300 cycles provide insights into the aging of the treated materials, which underlines the importance of the relationship between structural changes during scalable post-treatment and the electrochemical performance of the powders.

Long term behavior of dexamethasone-loaded cochlear implants: In vitro & in vivo

The aim of this study was to better understand the long term behavior of silicone-based cochlear implants loaded with dexamethasone: in vitro as well as in vivo (gerbils). This type of local controlled drug delivery systems offers an interesting potential for the treatment of hearing loss. Because very long release periods are targeted (several years/decades), product optimization is highly challenging. Up to now, only little is known on the long term behavior of these systems, including their drug release patterns as well as potential swelling or shrinking upon exposure to aqueous media or living tissue. Different types of cylindrical, cochlear implants were prepared by injection molding, varying their dimensions (being suitable for use in humans or gerbils) and initial drug loading (0, 1 or 10%). Dexamethasone release was monitored in vitro upon exposure to artificial perilymph at 37 °C for >3 years. Optical microscopy, X-ray diffraction and Raman imaging were used to characterize the implants before and after exposure to the release medium in vitro, as well as after 2 years implantation in gerbils. Importantly, in all cases dexamethasone release was reliably controlled during the observation periods. Diffusional mass transport and limited drug solubility effects within the silicone matrices seem to play a major role. Initially, the dexamethasone is homogeneously distributed throughout the polymeric matrices in the form of tiny crystals. Upon exposure to aqueous media or living tissue, limited amounts of water penetrate into the implant, dissolve the drug, which subsequently diffuses out. Surface-near regions are depleted first, resulting in an increase in the apparent drug diffusivity with time. No evidence for noteworthy implant swelling or shrinkage was observed in vitro, nor in vivo. A simplified mathematical model can be used to facilitate drug product optimization, allowing the prediction of the resulting drug release rates during decades as a function of the implant's design.

Tribological characteristics, phase composition and microhardness of subsurface regions of WC – (Fe – Mn – C) composites after high-speed sliding on steel

The authors investigated tribological characteristics, phase composition of friction surfaces and microhardness of near-surface regions of WC – (Fe – Mn – C) composites with a two-phase (γ + α′) matrix containing 4 % wt. Mn (WC – 80G4), and a single-phase matrix of γ-iron containing 20 % wt. Mn (WC – 80G20) after friction on a disk of high-speed steel at a contact pressure of 5 MPa and sliding speeds in the range from 10 to 37 m/s. The wear intensity of WC – 80G4 and WC – 80G20 increased with increasing sliding speed, while the wear rate of WC – 80G20 at fixed sliding speeds was approximately three times higher than that of WC – 80G4. The values of the friction coefficient decrease with increasing sliding speed in such a way that at fixed sliding speeds the values of the friction coefficient of WC – 80G4 were lower than those of WC – 80G20. The amount of complex oxide FeWO4 formed during tribo-oxidation of the composites’ worn surface increased with the sliding speed and was directly proportional to the wear intensity and inversely proportional to the friction coefficient values. At fixed sliding speeds, tribooxidation of WC – 80G4 leads to the formation of a larger amount of FeWO4 on the friction surface, compared to the WC – 80G20 composite. Indentation of worn surfaces with a Vickers pyramid showed that the nature of indentation resistance of tribolayers formed at high sliding speeds (30 m/s and 37 m/s) differs from that for tribolayers obtained at relatively low sliding speeds (10 and 20 m/s), namely, the friction surfaces after high sliding speeds were characterized by a more tough behavior. Measurement of microhardness values of the WC – 80G4 and WC – 80G20 composites obtained after indentation from the friction surface into the depth of the material recorded the fact of hardening of the near-surface regions of the WC – 80G4 composites and, on the contrary, softening in the case of WC – 80G20. Thus, under conditions of strong heating and severe plastic deformation of the surface, structural-phase state of the substrate of WC – (Fe – Mn – C) composites, on which this viscous protective tribolayer is formed, turns out to be a very important factor. It is the two-phase (γ + α′) steel matrix that, under conditions of strong frictional heating, provides the conditions for effective formation of a heterophase composite layer that reduces the friction coefficient and has a high resistance to fracture upon indentation.

Surface-controlled sodium-ion storage mechanism of Li4Ti5O12 anode

Sodium-ion batteries (SIBs) are the promising candidate in grid systems owing to the wide distribution and abundance of sodium resources. However, the charge storage mechanism and size-effect of the active materials for SIBs remain largely unexplored. Herein, we synchronously investigate the electrochemical properties and structural evolutions of Li4Ti5O12 (LTO) anode for Li+ and Na+ storage, along with the nano-size effect on their charge storage behaviors. Through detailed kinetic analysis, it is found the Li+ storage in LTO is diffusion-controlled in bulk and shows increased surface-controlled contributions when the size is reduced to 18 nm. In comparison, for the Na+ storage, the domination step is surface-controlled in all the sizes of LTO from 260 to 18 nm, with over 55% contribution even at the low sweep rate of 0.1 mV s−1. The limited near-surface reaction region and low diffusion kinetics determine the surface-controlled Na+ storage behaviors and the specific capacities. The suitable size of LTO-18 nm anode displays a high capacity of ∼140 mAh g−1 (at 0.05 A g−1, ∼0.29C), high-rate capability (42 mAh g−1 at ∼57C), and long-term cycling stability (over 1200 cycles). Our finding provides insights into a precise design of nanomaterials for high-power sodium-ion storage devices.

Influence of Heat Treatments on the Near-Surface Tritium Concentration Profiles

Austenitic stainless steel, type 316, absorbs significant quantities of tritium into the near surface ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ &lt; 1 ~\mu \text{m}$ </tex-math></inline-formula> ) on exposure to tritium containing gases at room temperature. The tritium concentrations that develop in the near-surface region ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ &lt; 1 ~\mu \text{m}$ </tex-math></inline-formula> ) are shown to persist for several years without changing. The current work shows the effect of heat treatments on the near-surface tritium-concentration profiles in stainless steel. Identical stainless-steel samples were exposed to tritium at room temperature and then were heated to different temperatures between 100 °C and 300 °C for 2 h under a stagnant argon atmosphere. After this initial preheating, the concentration profiles in the first <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10 ~\mu \text{m}$ </tex-math></inline-formula> were measured by using a combination of a ZnCl2 wash and an etching procedure. Tritium was thermally released by heating the samples to 550 °C to measure the residual tritium present in the bulk of the sample. The data show two dominant features. First, preheating causes tritium to migrate both out of the sample and deeper than > <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 ~\mu \text{m}$ </tex-math></inline-formula> into the bulk. This effect increases with increasing temperature. Second, the depletion of tritium from the near surface does not occur until a temperature of 200 °C.

Surface characteristics and high cycle fatigue behaviors of Ti47Al2Cr2Nb alloy subjected to different surface processes and thermal exposure

The Ti47Al2Cr2Nb alloy fatigue specimens were prepared by investment casting, and three kinds of surface processes were applied to fatigue specimens. These three processes were sand-blasting (SB), sand-blasting and shot-peening (SBSP) and sand-blasting and mechanical grinding (SBMG). The surface characteristics before and after thermal exposure at 700 °C for 24 h were investigated. The high cycle fatigue behaviors of specimens after thermal exposure were evaluated. The results showed that the surface roughness (Ra) values after SB, SBSP and SBMG processes were 1.71, 0.99 and 0.06 μm, respectively. After thermal exposure, they increased slightly for all three processes. The SB process caused work hardening in the near-surface region and the work hardening reached saturation after the SB process. Due to the mechanical grinding process removing an uncertain thick hardening layer, the maximum hardness after SBMG process was noticeably lower than those after SB and SBSP processes. After thermal exposure, the maximum hardness after all three processes significantly recovered. Deformed layers were formed beneath SB and SBSP surfaces. After thermal exposure, a depth-dependent gradient microstructure was formed in the surface layer. The SBMG specimens had the highest fatigue limit of 350 MPa. This was attributed to the SBMG specimens having very smooth surfaces and keeping some work hardening in the surface layers. The fatigue fractures were typical brittle cleavage fractures. The fracture modes included interlamellar and trans-lamellar fractures. The dislocation slip and mechanical twins were the main deformation mechanisms.

Simulation of Liquid Lithium Divertor Geometry Using SOLPS-ITER

Plasma-facing component (PFC) geometries are evaluated for a Fusion Nuclear Science Facility (FNSF) design to find solutions that are compatible with flowing liquid lithium components while satisfying requirements from the perspective of plasma and neutral particle transport. Flowing liquid metal (LM) divertor systems offer important advantages due to continual regeneration of the surface material, but may require modifications from standard optimized tokamak divertor designs. Scrape Off Layer Plasma Simulator for the International Thermonuclear Experimental Reactor (SOLPS-ITER) simulations are used to compare standard vertical target, open, and balanced baffled geometries. It is found that the open geometry offers little control of neutral particles and has narrow operating windows where the divertor fluxes can be lowered to acceptable levels, while maintaining the required upstream density. The addition of neutral baffles allows greater control over the divertor conditions with less impact on the upstream density. The divertor neutral pressure in the baffled geometry is slightly higher than the open divertor, but not as large with a vertical target. A first-pass coupling of the SOLPS solution with sheath and implantation/erosion models to compute the lithium emission shows that the lithium is largely confined to the near-surface region due to the small ionization mean free path and large main ion flow toward the surface. The lithium source was varied by three orders of magnitude. At the highest rate, when the sourced lithium approaches the level of the main ion recycling flux, a high core lithium concentration (~10%) is observed with only moderate power dissipation to affect the divertor plasma.

Tribological Characteristics, Phase Composition and Microhardness of Subsurface Regions of WC–(Fe–Mn–C) Composites after High-Speed Sliding on Steel

The authors investigated tribological characteristics, phase composition of worn surfaces and microhardness of subsurface regions of WC–(Fe–Mn–C) composites with a two-phase (γ + α′) matrix containing 4 wt % Mn (WC–80G4), and a single-phase matrix of γ-iron containing 20 wt % Mn (WC–80G20) after sliding against a disk of high-speed steel at a contact pressure of 5 MPa and sliding speeds in the range from 10 to 37 m/s. The wear intensity of WC–80G4 and WC–80G20 increased with increasing sliding speed, while the wear rate of WC–80G20 at fixed sliding speeds was approximately three times higher than that of WC–80G4. The values of the friction coefficient decrease with increasing sliding speed in such a way that at fixed sliding speeds the values of the friction coefficient of WC–80G4 were lower than those of WC–80G20. The amount of mixed oxide FeWO4 formed during tribo-oxidation of the composites’ worn surface increased with the sliding speed and was directly proportional to the wear intensity and inversely proportional to the friction coefficient values. At fixed sliding speeds tribooxidation of WC–80G4 leads to the formation of a larger amount of FeWO4 on the friction surface compared to the WC–80G20 composite. Indentation of worn surfaces with a Vickers pyramid showed that the nature of indentation resistance of tribolayers formed at high sliding speeds (30 m/s and 37 m/s) differs from that for tribolayers obtained at relatively low sliding speeds (10 and 20 m/s), namely, the friction surfaces after high sliding speeds were characterized by a more tough behavior. Measurement of microhardness values of the WC–80G4 and WC–80G20 composites obtained after indentation below tha worn surfaces recorded the fact of hardening of the near-surface regions of the WC–80G4 composites and, on the contrary, softening in the case of WC–80G20. Thus, under conditions of intensive heating and severe plastic deformation of the surface, structural-phase state of the substrate of WC–(Fe–Mn–C) composites, on which this viscous protective tribolayer is formed, turns out to be a very important factor. It is the two-phase (γ + α′) steel matrix that, under conditions of intensive frictional heating, provides the conditions for effective formation of a heterophase composite layer that reduces the friction coefficient and has a high resistance to fracture upon indentation.

Micropillar Compression of Additively Manufactured 316L Stainless Steels after 2 MeV Proton Irradiation: A Comparison Study between Planar and Cross-Sectional Micropillars

A micropillar compression study with two different techniques was performed on proton-irradiated additively manufactured (AM) 316L stainless steels. The sample was irradiated at 360 °C using 2 MeV protons to 1.8 average displacement per atom (dpa) in the near-surface region. A comparison study with mechanical test and microstructure characterization was made between planar and cross-sectional pillars prepared from the irradiated surface. While a 2 MeV proton irradiation creates a relatively flat damage zone up to 12 µm, the dpa gradient by a factor of 2 leads to significant dpa uncertainty along the pillar height direction for the conventional planar technique. Cross-sectional pillars can significantly reduce such dpa uncertainty. From one single sample, three cross-sectional pillars were able to show dpa-dependent hardening. Furthermore, post-compression transmission electron microscopy allows the determination of the deformation mechanism of individual micropillars. Cross-sectional micropillar compression can be used to study radiation-induced mechanical property changes with better resolution and less data fluctuation.

Elucidation for coordination features of N-(benzothiazol-2-yl)-3-oxo-3-(2-(3-phenylallylidene)hydrazineyl)propanamide on Co2+, Ni2+and Cu2+: Structural description, DFT geometry optimization, cyclic voltammetry and biological inspection

A series of transition metal complexes were prepared through a reaction of novel N-(benzothiazol-2-yl)-3-oxo-3-(2-(3-phenylallylidene)hydrazineyl)propanamide (H2BTOPP) ligand with divalent Co2+, Cu2+, and Ni2+ metal cations. The structures of the complexes were interpreted via several spectroscopic techniques including (FT-IR, UV–Visible, 1H/13C NMR, XRD, MS, EDX, and ESR), besides elemental analysis and magnetic measurements. SEM was subjected to the Schiff base ligand and its complexes to provide a microscopic approach to the surface or near-surface region of a specimen, in addition to clarifying the extent of the change in the ligand surface morphology as a result of the formation of metal complexes. Also, the thermal stability of the synthesized complexes was discussed through (TGA/DTA) techniques. Moreover, computational simulation through (DFT/GGA/RPBE) was applied to the molecular skeleton of all compounds associated with the evaluation of some characters (EHOMO, ELUMO, binding energy, dipole moment, MEP). Furthermore, electrochemical studies included in cyclic voltammetry were measured for Cu2+ in (absence-presence) of the ligand to realize the effect of complexation in solution, kinetic parameter (stability constant), and thermodynamic parameter (Gibbs free energy). Finally, all samples were screened for anti-bacterial against (Bacillus subtilis and Escherichia coli), anti-fungal against (Candida albicans), antioxidant, MTT cytotoxicity, and DNA binding studies to predict the biological activity of the synthesized compounds.

Atomic layer deposition modified PIM-1 membranes for improved CO2 separation: A comparative study on the microstructure-performance relationships

The use of atomic layer deposition (ALD) technology has recently been extended to membrane-based gas separation, whereas how the ALD of metal oxides can tailor the membrane microporosity, and the contribution of the interactions between ALD-grown metal oxide clusters and gas molecules to the resultant gas separation performance, remain largely unclear. Here, a comparative study was performed by individually confining three different metal oxides, including Al2O3, ZnO, and TiO2, to the near-surface region of polymers of intrinsic microporosity (PIM-1) membranes in an attempt to clarify the relationships between microstructural properties and CO2 separation performance. Based on experimental characterizations and density functional theory (DFT) calculations, it is suggested that ALD of metal oxides on PIM-1 membranes can not only effectively narrow the micropore sizes, but also enable enhancement of the solubility of CO2 molecules. Meanwhile, gas permeation results revealed that the CO2 permeation behavior through either Al2O3- or ZnO-modified membranes is diffusion-dominated, while that of the TiO2-modified membranes is sorption-dominated, primarily due to the distinct differences in the loading amount of metal oxides and their interaction strength with the CO2 molecules. As a result, the TiO2-modified membranes achieved a significant increase in the CO2 permeability as the ALD cycle numbers increased together with no sacrifice of CO2/N2 and CO2/CH4 selectivities. This study is expected to lend important insight to the development of ALD-modified membranes for efficient CO2 separation.

Anomalous Wear Behavior of UHMWPE During Sliding Against CoCrMo Under Varying Cross-Shear and Contact Pressure

Wear of ultra-high-molecular weight polyethylene (UHMWPE) in joint implant applications has been shown to increase with cross-shear (CS, i.e., multidirectional sliding) but decrease with higher contact pressure (CP). Moreover, structural changes, resulting in protrusions, are known to occur to the surface of the pin following multidirectional sliding. However, these phenomena are not yet fully understood. In this study, we simultaneously varied CP and CS to derive an empirical formula for the wear factor as a function of these parameters. The wear factor increased when going from unidirectional sliding to multidirectional sliding but decreased with increasing CP, as has been previously observed. Following these tests, the protrusions on the pin surface were chemically and mechanically characterized to gain insights into both their origin and influence on wear behavior. Micro-FT-IR confirmed that the structures consist of polyethylene, rather than adsorbed, denatured proteins. It also allowed the crystallinity of both the protrusions and unaffected UHMWPE to be estimated, showing a strong positive correlation with the hardness of these different areas on the surface. Time-of-flight secondary-ion mass spectrometry was used to probe the chemistry of the surface and near-surface region and indicated the presence of contamination from the test fluid within the structure. This suggests that the protrusions are formed by the folding of UHMWPE following plastic deformation. It is also suggested that the higher hardness of the protrusions affords some protection of the surface, leading to the observed anomalous behavior, whereby wear increases with decreasing CP.Graphical

Evaluation of fatigue damage of a railhead using an indentation test, acoustic methods and microstructural observations

The paper presents an investigation of the railhead steel R260. Brinell hardness was measured, spherical microindentation tests were performed and the microstructure was analysed using optical microscopy and SEM images. Fatigue damage in various near-surface regions of the railhead was estimated on the basis of local deterioration of elastic modulus and the development of plastic work in cyclic microindentation tests. There is a clear difference in hardness and fatigue damage between the used and the virgin regions of the railhead. The Brinell hardness and ultrasonic measurements show a change in material properties due to rail manufacturing process.

Strong Isotopic Fractionation of Oxygen in TiO2 Obtained by Surface-Enhanced Solid-State Diffusion.

Isotopically pure semiconductors have important applications for cooling electronic devices and quantum computing and sensing. Raw materials of sufficiently high isotopic purity are expensive and difficult to obtain; therefore, a post-synthesis method for removing isotopic impurities would be valuable. Through isotopic self-diffusion measurements of oxygen in rutile TiO2 single crystals immersed in water, we demonstrate fractionation of 18O by a factor of 3 below natural abundance in a near-surface region up to 10 nm wide. The submerged surface injects O interstitials that displace lattice 18O deeper into the solid as a result of the statistics of interstitialcy-mediated diffusion combined with steep chemical gradients of O interstitials. Slightly acidic and slightly basic liquid solutions both enhance the fractionation and affect the details of isotopic profile shapes through several chemical and physical mechanisms.

Atomic Layer Grown Zinc–Tin Oxide as an Alternative Buffer Layer for Cu2ZnSnS4-Based Thin Film Solar Cells: Influence of Absorber Surface Treatment on Buffer Layer Growth

Zn1-x Sn x O y (ZTO) deposited by atomic layer deposition has shown promising results as a buffer layer material for kesterite Cu2ZnSnS4 (CZTS) thin film solar cells. Increased performance was observed when a ZTO buffer layer was used as compared to the traditional CdS buffer, and the performance was further increased after an air annealing treatment of the absorber. In this work, we study how CZTS absorber surface treatments may influence the chemical and electronic properties at the ZTO/CZTS interface and the reactions that may occur at the absorber surface prior to atomic layer deposition of the buffer layer. For this, we have used a combination of microscopy and synchrotron-based spectroscopies with variable information depths (X-ray photoelectron spectroscopy, high-energy X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy), allowing for an in-depth analysis of the CZTS near-surface regions and bulk material properties. No significant ZTO buffer thickness variation is observed for the differently treated CZTS absorbers, and no differences are observed when comparing the bulk properties of the samples. However, the formation of SnO x and compositional changes observed toward the CZTS surface upon an air annealing treatment may be linked to the modified buffer layer growth. Further, the results indicate that the initial N2 annealing step integrated in the buffer layer growth by atomic layer deposition, which removes Na-CO x species from the CZTS surface, may be useful for the ZTO/CZTS device performance.

Nanostructures evolution assessment and spectroscopic properties modification induced by electronic energy loss in KTaO3 crystal

Modifications of micro/nanostructure and photoelectric properties under swift ion irradiation (645 MeV Xe35+) of KTaO3 crystal with varying electronic energy losses (7.2–31.4 keV/nm) and ion velocities (0.18–5.00 MeV/u) have been studied by combining experimental and calculated approaches. The i-TS calculations combined with molecular dynamics simulations are compared with the experimental observations, revealing the inner track fine structures from individual spherical defects to continuous ion tracks with core–shell morphologies, and a quantitative relationship, including the melting (0.42 eV/atom), damage (0.75 eV/atom), and amorphous (1.71 eV/atom) thresholds, is established to successfully predict the inner disorder/amorphous proportions and track damage morphologies. The surface nanostructures of nanohillocks (isolated or partial overlaps) and nanopits (serious overlaps) directly depend on the combined action of the deposited potential and kinetic energies of incident ions, which induce local melting and sublimation in the near-surface region. Owing to the decreased recombination and the increased separation efficiency between electrons and holes, the higher photogenerated charge carrier mobility enhanced the photocurrent effect, further optimizing the photoconductivity performance in Xe35+-irradiated KTaO3. Therefore, controlled defect engineering using the ion irradiation technique, as an effective strategy, could design tailored nanostructure systems and regulate photoelectric properties, further promoting the development of novel technological applications.

The Technology of Upward Capillary Formation of Waste for Creating a Deposit before Land Reclamation

Mineral resources in the subsoil are classified as exhaustible. One of the ways to potentially replenish the sources of mineral resources is presented in the materials of these studies. In this article, we studied the natural formation in the bowels of the array of zones of high concentrations of compounds of useful components. We aimed to develop the technological methods of mass transfer and directed deposition of useful components. The technological transition of mineral resource extraction from the “gathering” paradigm to the “growing” paradigm is commonly performed by fluid filtration mass transfer in the near-surface region through the capillary system in the subsoil. In this article, we proposed a new technique for the upward capillary movement and extraction of useful components based on the framework of the new paradigm of “deposit growing”. This new approach focused on lifting useful components to the surface of the massif. The experiments and the associated results concerning the mass transfer of water-soluble compounds are presented here. Experiments were conducted on the kinetics and concentrations of fluids and sediments at physical and geochemical barriers. Natural materials of non-ferrous metal enrichment waste and artificial water-soluble compounds of non-ferrous metals were used. The results suggested the viability of the new methods proposed for the ascending filtration capillary rise of useful components present in the fluids. The technological methods presented in this article might help to expand the mineral resource base and increase the efficiency of the process. New processes for the development of new ore bodies on the surface of objects on the evaporation and geochemical barriers were experimentally validated in this article. Additionally, new technological solutions were proposed in the framework of the formation of new ore bodies before surface reclamation.