Thin Oxide Research Articles

Effect of microstructure and micromechanics on wear/wear-corrosion mechanism of laser-repaired Ni-WC coating

Repairing drilling tools with laser cladding technology becomes a meaningful way to reduce costs and increase efficiency. The relationship between the wear/wear corrosion mechanism and micromechanics of laser-repaired Ni-WC coating was investigated. It is found that the received Ni-WC coating is mainly composed of γ-Ni, WC, W2C, and a small amount of CrC and MoC. In dry environment, the surface fatigue crack gradually propagates and develops along the surface as the load increases, forming a peeling phenomenon on the surface. Conversely, the water film was formed as lubrication to reducing the formation of peeling in wet environment. It is found that the wear and damage of the laser-repaired Ni-WC coating in wet environment is lower than that in dry environment. The effect of water film and water cooling on wear of the laser-repaired Ni-WC coating is higher than that of corrosion. In addition, a thin oxide interfacial layer is found under dry sliding at the boundary of WC particle with the maximum width of about 3 μm, leading to low microhardness (H) / elastic modulus (E) of the oxide interfacial layer, which weakens the wear resistance of WC particles in laser-repaired Ni-WC coating.

Dynamics of early-stage oxide formation on a Ni-Cr-Mo alloy

Corrosion results in large costs and environmental impact but can be controlled by thin oxide films that passivate the metal surfaces and hinder further oxidation or dissolution in an aqueous environment. The structure, chemistry, and thickness of these oxide films play a significant role in determining their anti-corrosion properties and the early-stage oxidation dynamics affect the properties of the developed oxide. Here, we use in situ X-ray Photoelectron Spectroscopy (XPS) to study the early-stage oxidation of a Ni-Cr-Mo alloy at room temperature and up to 400 °C. Cr and Mo begin to oxidize immediately after exposure to O2, and Cr3+, Mo4+, and Mo6+ oxides are formed. In contrast, Ni does not contribute significantly to the oxide film. A self-limiting oxide thickness, which did not depend on temperature below 400 °C, is observed. This is attributed to the consumption of available Cr and Mo near the surface, which results in an enrichment of metallic Ni under the oxide. The self-limited oxide thickness is 6–8 Å, which corresponds to 3–4 atomic layers of cations in the oxide. At 400 °C, sublimation of Mo6+ oxide is observed, resulting in the formation of an almost pure layer of Cr2O3 on the alloy surface. Lastly, a mechanism is presented that explains the formation of the bi-layer oxide structure observed for Ni-Cr-Mo alloys, which involves the enhanced migration of hexavalent Mo ions in the electric field, which drives mass transport during oxidation according to both the Cabrera Mott model and the Point Defect Model.

Impact of Gate Oxide Thickness on Flicker Noise (1/f) in PDSOI n-channel FETs

This work reports the impact of gate oxide thickness on flicker noise (1/f) in 45-nm RFSOI NFET devices. In addition, the effect of finger width scaling on 1/f noise parameters is studied in linear region. The dominant source of 1/f noise is also analyzed. It is observed that thin oxide devices show carrier number fluctuation; however, for thick oxide devices, correlated number-mobility govern the noise. Extracted trap densities using 1/f noise show higher volume trap densities in thin oxide devices. Moreover, trap distribution behavior is analyzed using frequency exponent. Further, GLOBALFOUNDRIES PDK is utilized to model 1/f noise behavior of the devices.

Surface Structuring of the CP Titanium by Ultrafast Laser Pulses

Surface structuring by ultrafast lasers is a promising technique to modify surface-related properties of materials to tailor them for specific applications. In the present study, we experimentally investigated the laser structuring of commercially pure titanium (CP Ti) using ultrafast pulses to understand the role of the laser input parameters on the development of surface morphology, optical properties, surface chemistry, and wettability behaviour. The processed surfaces were characterized by a scanning electron microscope, energy-dispersive X-ray spectroscopy (EDX), Raman microscope, optical microscope, and sessile drop method. Laser-induced periodic surface structures decorated with nanodroplets were noted to be formed on the surface of the laser-structured CP Ti. The surface roughness measurements showed that the laser-structured surfaces had nanoscale roughness values. The EDX and the Raman analyses show that laser-structured surfaces of CP Ti have a thin oxide film. Different colours on different surfaces processed by different laser parameters were observed. The wettability assessment shows that CP Ti can transition from hydrophilic–hydrophobic and vice versa depending on the environmental conditions. This study shows that laser structuring can be utilized to modify CP Ti surfaces to obtain desirable surface properties that can find potential applications in different fields.

Acute, controlled inhalation of thin graphene oxide nanosheets in humans with null cardiorespiratory effects.

Acute, controlled inhalation of thin graphene oxide nanosheets in humans with null cardiorespiratory effects.

Colloidal Atomic Layer Deposition on Nanocrystals Using Ligand-Modified Precursors.

Atomic layer deposition (ALD) is a method to grow thin metal oxide layers on a variety of materials for applications spanning from electronics to catalysis. Extending ALD to colloidally stable nanocrystals promises to combine the benefits of thin metal oxide coatings with the solution processability of the nanocrystals. However, challenges persist in applying this method, which relate to finding precursors that promote the growth of the metal oxide while preserving colloidal stability throughout the process. Herein, we introduce a colloidal ALD method to coat nanocrystals with amorphous metal oxide shells using metal and oxygen precursors that act as colloidal stabilizing ligands. Our scheme involves metal-amide precursors modified with solubilizing groups and oleic acid as the oxygen source. The growth of the oxide is self-limiting and proceeds in a layer-by-layer fashion. Our protocol is generalizable and intrinsically scalable. Potential applications in display, light detection, and catalysis are envisioned.

Interlaced stacked hollow Cu2O dendrite for stable lithium metal anode

The stable operation of lithium metal batteries faces hindrances due to the persistent issue of uncontrolled lithium dendrite growth. In this study, we present a facile approach wherein 3D structured cuprous oxide (Cu2O) dendrites are constructed on flat copper foil through a straightforward process involving electrodeposition and subsequent high-temperature treatment. The thin lithium oxide (Li2O) layer stemming from lithiophilic Cu2O further establishes a conducive channel for the swift diffusion of lithium ions (Li+) at the solid-liquid interface. Notably, the staggered stacking of Cu2O dendrite results in a 3D structure with a significantly enlarged specific surface area, which not only mitigates current density but also promotes a uniform distribution of Li flow. The proposed Cu2O electrode yields superior performance, achieving a Coulombic efficiency of up to 98.2% and a sustained lithium deposition/stripping process lasting an impressive 880 h. In the full cells, employing Li/Cu2O dendrite electrode, an exceptional Coulombic efficiency (CE) of 99.9% is attained after 160 cycles at 1C, coupled with an admirable capacity retention rate of 84%. These findings underscore the promising potential of the Cu2O dendrite electrode for advancing the practical applications of lithium metal batteries.

Nano-scale corrosion mechanism of T91 steel in static lead-bismuth eutectic: A combined APT, EBSD, and STEM investigation

T91 steel is a candidate material for structural components in lead-bismuth-eutectic (LBE) cooled systems, for example fast reactors and solar power plants [1]. However, the corrosion mechanisms of T91 in LBE remain poorly understood. In this study, we have analysed the static corrosion of T91 in liquid LBE using a range of characterisation techniques at increasingly smaller scales. A unique pattern of liquid metal intrusion was observed that does not appear to correlate with the grain boundary network. Upon closer inspection, electron backscatter diffraction (EBSD) reveals a change in the morphology of grains at the LBE-exposed surface, suggesting a local phase transition. Energy dispersive X-ray (EDX) maps show that Cr is depleted in the T91 material near the LBE interface. Furthermore, we observed the dissolution of all Cr-enriched precipitates in this region. Although the corrosion is conducted in an oxygen deficient environment, both scanning transmission electron microscopy (STEM) and atom probe tomography (APT) reveal a thin surface oxide layer (presumably wüstite) at the LBE-steel interface. Using electron energy loss spectroscopy (EELS) in the STEM, as well as APT, the atomic scale elemental redistribution and 3D morphology of the corrosion interface is investigated. By combining results from these different techniques, several types of oxide phases and structures can be identified. Based on this detailed nano-scale information, we propose potential mechanisms of T91 corrosion in LBE.

Electrochemistry of Molybdenum Single Crystals and Thin Wires in Cyanide and Gold Cyanide Electrolytes

Thin wires of molybdenum coated with gold are used for space applications and the adhesion of the gold layer is decisive for their use. The surface morphology of the wires is determined by the manufacturing process and preferential orientation of single crystal surfaces is expected. In this work three different single crystal surfaces were studied together with a 20 μm molybdenum wire to elucidate the importance of surface morphology on the electrodeposition process for gold. Electrochemical impedance spectroscopy was used to study the molybdenum samples in the absence and presence of gold cyanide complexes. The results show large pseudocapacitance prior to gold deposition, indicating the presence of a thin molybdenum oxide film on the surface. Thus, the electrodeposition takes place on the surface oxide and is afflicted with a nucleation overpotential. The overpotential is only slightly dependent on the single crystal orientation, while it is more negative for the wire. The adhesion of gold on the flat single crystal surfaces is weak but marginally better on the wire. This clearly shows that strong chemical binding to the surface is absent and that other processes, such as physical interlocking of the gold layer is necessary for good adhesion.

Passive and active oxidation of Al in the Al–Al2O3 composite refractory at high temperatures in air

The active and passive oxidation of Al in Al–Al2O3 composites was investigated in air at high temperatures. As fresh air impinged on the surface of the Al–Al2O3 composite sample, a thin Al2O3 layer was preferentially formed via passive oxidation of Al, which consumed most of the oxygen and lowered the local Po2 inside the sample. At low Po2, active oxidation of Al occurred and predominated in the interior transition layer, which further lowered the local Po2 to extremely low values within the non-oxide stability field. The local equilibrium PAlxOy generated by the active oxidation of Al reached a micro-positive pressure state and served as a gas barrier, hindering the inward diffusion of O2. The Po2 inside the composite was lowered by Al in the outer layers via a self-gettering process. Subsequently, Al4O4C and Al2OC-AlN solid solution were formed by both the direct reaction of Al(l) and the indirect reaction of AlxOy(g). After sintering in air, the Al–Al2O3 composite exhibited a functional gradient structure with a thin oxide layer and an interior non-oxide-reinforced corundum. A reaction mechanism model was established.

Suppressed Gold Penetration with the Molybdenum Oxide Interlayer to Increase Power Conversion Efficiency of Perovskite Solar Cells

Perovskite solar cells (PSCs) have undergone an unprecedentedly rapid development in both power conversion efficiency (PCE) and operational durability. However, a number of unknown challenges remain before PSC products are ready to launch. Herein, it is demonstrated that the vacuum deposition of gold (Au) onto the organic hole‐transport layer (HTL) results in Au penetration into the perovskite layer. This Au penetration proves to be a limiting factor in PCE due to detrimental carrier recombination caused by the penetrated Au component inside the perovskite light absorber. To mitigate this issue, a thin molybdenum oxide (MoOx) interlayer between the organic HTL and the Au electrode is introduced, effectively reducing the Au penetration and suppressing the carrier recombination. Consequently, this MoOx introduction increases PCEs from ≈16.9% to ≈19.6% by ≈2.7%. Furthermore, using the MoOx interlayer improves the long‐term durability of PSCs. These findings are crucial in elucidating a basic mechanism that limits PCE and in advancing the fabrication of PSC products with even higher performance.

Analysis of Current-Voltage Properties of Al/p-si Schottky Diode with Aluminium Oxide Layer

In our study, the effects of the metal oxide (aluminum oxide, Al2O3) thin film placed between the metal and the semiconductor on the diode's characteristics were investigated. The Al2O3 thin film was suitable for its growth on a p-type silicon substrate by the atomic layer deposition (ALD) technique. In this study, a diode structure with an oxide interlayer was fabricated. To investigate the electrical parameters of the fabricated Schottky diode, measurements of current-voltage (I-V) were carried out at room temperature and in the 5 V voltage range. Using the I-V measurements, diode parameters such as the barrier height (Φb), the ideality factor (n), and the current density (I0) were evaluated using the theory of thermionic emission (TE) and Cheung's method. Using the TE method and Cheung’s method, the approximate values of Φb, n parameters were calculated as 0.77 eV, 5.43, and 0.77 Ev, 5.97, respectively. According to calculations, the developed Schottky diode is a rectifier diode and has been determined to have photodiode properties. This research offers an understanding of the production and electrical characteristics of Schottky devices based on Al2O3.

Low‐Power Crystallization Process in In3SbTe2 Phase Change Memory Devices with Thin Oxide Layer

Phase change memory (PCM) technology is a strong contender for the next‐generation memory in today's data‐centric era. In3SbTe2 (IST) phase change material is recently explored due to its good thermal stability, rapid electrical switching, and significant resistance contrast for multibit storage. However, the main concern in PCM devices is the high‐energy usage during the phase switching process. Herein, a thin oxide (HfO2) layer is inserted between the IST active layer and bottom electrode in PCM device. Such a device exhibits amorphous‐to‐crystalline phase switching (crystallization or SET operation) at a lower voltage of (2.1 ± 0.1) V and 66% reduction in energy consumption compared to the device using only IST active layer. Higher temperature of 688 K is acquired in the device with the oxide layer demonstrating that the Joule heat is effectively confined by the oxide layer assisting the crystallization process in the active layer at a less voltage. Such a device also exhibits a significant resistance contrast of ≈2 orders magnitude, allowing for stable data storage. These results reveal that the switching performance of PCM device using IST phase change material is improved by the oxide layer, which is beneficial for energy‐efficient, nonvolatile data storage applications.

Effect of Electrolyte Thickness of Thin Film Solid Oxide Fuel Cell on Nanostructure and Performance

Effect of Electrolyte Thickness of Thin Film Solid Oxide Fuel Cell on Nanostructure and Performance

Nanopatterning of thin amorphous vanadium oxide films by oxidation scanning probe lithography

Oxidation scanning probe lithography is one of the most promising techniques for nanostructuring. Vanadium oxides constitute a class of functionally rich materials that are promising for various practical applications and have unique physical properties. Currently, the formation of nanocrystals and nanostructures with well-defined dimensions is a challenging task. This study presents a detailed investigation of the processes involved in oxidation scanning probe lithography on the surface of thin amorphous vanadium oxide (VOx) films. It was shown that the oxidizable regions of the film transform into a water-soluble vanadium pentoxide (V2O5) in accordance with classical redox reactions. The oxidation kinetics was shown to be consistent with the Cabrera-Mott model. Dissolving the oxidized regions in water resulted in the formation of nanohole arrays with defined sizes in VOx films. Nanostructures with a depth of less than 0.3 nm and lateral dimensions of less than 50 nm were obtained at relative humidity of about 10 %. It was demonstrated that VOx films about 10 nm thick can be completely oxidized in local areas, enabling the formation of isolated nanostructures. The considered method of nanostructuring VOx is promising for the formation of novel photonic and nanoelectronic devices.

A Hot‐Stamped Medium‐Mn Steel with Superior Strength–Ductility–Bendability Combination and Thin Oxidation Layer

A hot‐stamped medium‐Mn steel containing 3.84 wt% Mn is designed for the manufacture of hot‐stamped automotive components. The effects of intercritical temperatures employed for hot forming on the microstructure, tensile properties, and three‐point bending behaviors are investigated. The result shows that the microstructure can be controlled by intercritical temperatures, leading to different phase fractions of martensite, retained austenite, and ferrite in the steels. Besides, the tensile strength increases with increasing intercritical temperature, while both the total elongation and the bending angle show reverse change trend, which are related to the various phase fractions and the different transformation‐induced plasticity effects during deformation. Importantly, the medium‐Mn steel subjected to heat treatment at 800 °C possesses tensile strength of 1535 MPa, total elongation of 13.8%, and bending angle of ≈56°. Therefore, its total elongation is significantly higher than hot‐stamped 22MnB5 steel under the same tensile strength grade, and the bending angle of the former is close to the latter. Moreover, the thickness of oxidation layer on the medium‐Mn steel is only ≈3.5 μm after heat treatment at 800 °C, much thinner than the ≈57 μm‐thick oxidation layer on the 22MnB5 steel after austenitizing at 930 °C.

Assessing the Natural Source Zone Depletion of a Petroleum-Contaminated Clayey Soil Site in Southern China Combining Concentration Gradient Method and Metagenomics.

Natural source zone depletion (NSZD) is the main process of LNAPL (Light Non-Aqueous Phase Liquid) removal under natural conditions. The NSZD rates assessed ranged from 0.55 to 11.55 kg·m-2·a-1 (kilograms per square meter per year) in previous studies. However, most of these data were obtained from sandy sites, with few clayey sites. To gain knowledge of NSZD in clayey soil sites, the study assessed the NSZD of a petroleum hydrocarbon-contaminated clayey soil site in China, combining the concentration gradient method with metagenomic sequencing technology. The results show that the abundance of methane-producing key enzyme mcrA gene in the source zone was more abundant than in background areas, which suggests that there was methanogenesis, the key process of NSZD. The concentration gradients of oxygen and carbon dioxide existed only in shallow soil (<0.7 m), which suggests that there was a thin methane oxidation zone in the shallow zone. The calculated NSZD rates range from 0.23 to 1.15 kg·m-2·a-1, which fall within the moderate range compared to previous NSZD sites. This study expands the knowledge of NSZD in clayey soil and enriches the attenuation rate data for contaminated sites, which is of significant importance in managing petroleum contaminants.

Chemisorption-Induced Robust and Homogeneous Tungsten Disulfide Interlayer Enables Stable PEDOT-Free Organic Solar Cells with Over 19% Efficiency.

Construction of a high-quality charge transport layer (CTL) with intimate contact with the substrate via tailored interface engineering is crucial to increase the overall charge transfer kinetics and stability for a bulk-heterojunction (BHJ) organic solar cell (OSC). Here, we demonstrate a surface chemistry strategy to achieve a homogeneous composite hole transport layer (C-HTL) with robust substrate contact by self-assembling two-dimensional tungsten disulfide (WS2) nanosheets on a thin molybdenum oxide (MoO3) film-evaporated indium tin oxide (ITO) substrate. It is found that over such a well-defined C-HTL, WS2 is homogeneously tethered on the ITO/MoO3 substrate stemming from the strong electronic coupling interaction between the building blocks, which enables a favorable interfacial configuration in terms of uniformity. As a result, the D18:L8-BO-based OSC with C-HTL exhibits a power conversion efficiency (PCE) of 19.23%, an 11% improvement over the WS2-based control device, and the highest efficiency among single-junction PEDOT-free binary BHJ OSCs.

The microstructural evolution and densification process of titanium or tin doped indium zinc oxide ceramic targets

Herein, titanium or thin doped indium zinc oxide (IZO) ceramic targets, composed of TiO2/SnO2, In2O3 and ZnO were prepared. The preparation of composite powders, microstructure evolution, densification and photoelectric properties of these ceramic targets were systematically in detail. The results indicated that doping of SnO2 was more conducive to the density of IZO targets than the doping of TiO2, while they all were beneficial for optimizing electrical performance of IZO ceramic targets due to the solid solution of TiO2/SnO2 in phases, thus the doped IZO ceramic targets had lower resistivity than nondoped IZO targets. In addition, 1wt% SnO2 doped in IZO ceramic targets performed the best (relative density &gt; 99%, resistivity &lt; 1.1 mΩ·cm, average grain size &lt; 2 µm).

Nanocrystalline Silicon Layers for the Application in Silicon Heterojunction Solar Cells

After application in thin-film silicon tandem solar cells and in lab-scale silicon heterojunction (SHJ) devices, doped nanocrystalline silicon (nc) layers now arrived on the industrial stage. Despite their challenging deposition, the benefits they hold with respect to even higher device performance compared to their amorphous counterparts are significant and justify additional effort. In this contribution we report on developments towards industrially applicable processes for n- and p-doped silicon layers, nc-Si(n) and nc-Si(p), and their implementation in SHJ cells. Our investigation focuses on the impact of deposition temperature (Tdep) and the need for a thin oxide layer to promote fast nucleation of thin, sufficiently crystalline, doped nc-Si films in a single deposition chamber powered at 13.56 MHz. We identified main challenges for thin film and contact engineering and reached efficiencies of 23.0% with n- and 23.1% with p-type nc-Si approaching cell performances of our process of record based on amorphous Si (a-Si) layers.