Thin Oxide Research Articles

Dark Current Reduction and Performance Improvements in Graphene/Silicon Heterojunction Photodetectors Obtained Using a Non-Stoichiometric HfOx Thin Oxide Layer.

Graphene/silicon heterojunction photodetectors suffer from a high dark current due to the high surface states and low barrier height at the interface, which limits their application. In this study, we introduce an HfOx interfacial layer via magnetron sputtering to address this issue. With this new structure, the dark current is reduced by six times under a bias voltage of -2 V. Under 460 nm illumination, the responsivity is 0.228A/W, the detectivity is 1.15 × 1011 cmHz1/2W-1, and the noise equivalent power is 8.75 × 10-5 pW/Hz1/2, demonstrating an excellent weak light detection capability. Additionally, the oxygen vacancies in the HfOx interfacial layer provide a conductive channel for charge carriers, resulting in a 2.03-fold increase in photocurrent and an external quantum efficiency of 76.5%. The photodetector maintains good photoresponse ability at a low bias voltage. This work showcases the outstanding performance of HfOx films as interfacial layer materials and provides a new solution for high-performance photodetectors, as well as a new path to improve the photovoltaic conversion efficiency of solar cells.

Real‐Time Polygonal Lighting of Iridescence Effect using Precomputed Monomial‐Gaussians

AbstractThe real world consists of mass phenomena, such as iridescence on thin film and metal oxide layers, that is only explicable by wave optics. Existing research can reproduce such effects with simple point lights or low‐frequency environmental lighting. However, it remains a difficult task to efficiently rendering these effects when near‐field, high‐frequency area lights are involved. This paper presents a high‐fidelity, real‐time rendering algorithm for the iridescence effect under polygonal lights. We introduce a novel set of spherical functions, Monomial‐Gaussians, to accurately fit iridescent materials' reflectance. With a precomputed lookup table, the Monomial‐Gaussians are easily integrated over spherical polygons in linear time. Importance sampling of Monomial‐Gaussians is also supported to efficiently reduce Monte‐Carlo error. Our approach produces accurate renderings of the iridescence effect while still preserving high frame rates.

First-in-human controlled inhalation of thin graphene oxide nanosheets to study acute cardiorespiratory responses

Graphene oxide nanomaterials are being developed for wide-ranging applications but are associated with potential safety concerns for human health. We conducted a double-blind randomized controlled study to determine how the inhalation of graphene oxide nanosheets affects acute pulmonary and cardiovascular function. Small and ultrasmall graphene oxide nanosheets at a concentration of 200 μg m−3 or filtered air were inhaled for 2 h by 14 young healthy volunteers in repeated visits. Overall, graphene oxide nanosheet exposure was well tolerated with no adverse effects. Heart rate, blood pressure, lung function and inflammatory markers were unaffected irrespective of graphene oxide particle size. Highly enriched blood proteomics analysis revealed very few differential plasma proteins and thrombus formation was mildly increased in an ex vivo model of arterial injury. Overall, acute inhalation of highly purified and thin nanometre-sized graphene oxide nanosheets was not associated with overt detrimental effects in healthy humans. These findings demonstrate the feasibility of carefully controlled human exposures at a clinical setting for risk assessment of graphene oxide, and lay the foundations for investigating the effects of other two-dimensional nanomaterials in humans. Clinicaltrials.gov ref: NCT03659864.

Multiscale Fabrication Process Optimization of DFB Cavities for Organic Laser Diodes.

In the context of the quest for the Organic Laser Diode, we present the multiscale fabrication process optimization of mixed-order distributed-feedback micro-cavities integrated in nanosecond-short electrical pulse-ready organic light-emitting diodes (OLEDs). We combine ultra-short pulsed electrical excitation and laser micro-cavities. This requires the integration of a highly resolved DFB micro-cavity with an OLED stack and with microwave electrodes. In a second challenge, we tune the cavity resonance precisely to the electroluminescence peak of the organic laser gain medium. This requires precise micro-cavity fabrication performed using e-beam lithography to pattern gratings with a precision in the nanometer scale. Optimal DFB micro-cavities are obtained with 300 nm thick hydrogen silsesquioxane negative-tone e-beam resist on 50 nm thin indium tin oxide anode exposed with a charge quantity per area (i.e., dose) of 620 µC/cm2, developed over 40 min in tetramethylammonium hydroxide diluted in water. We show that the integration of the DFB micro-cavity does not hinder the pulsed electrical operability of the device, which exhibits a peak current density as high as 14 kA/cm2.

Enhanced Ferromagnetism in Atomically Thin Oxides Achieved by Interfacial Reconstruction

AbstractDiscoveries of ferromagnetic materials with ultrathin thickness are of great importance for both fundamental science and technological applications. Transition metal oxides (TMOs) provide promising candidates in the context of next‐generation spintronics, despite the severe decay of ferromagnetism as the thickness reduces to the nanometer regime. Here, an efficient strategy to eliminate the magnetic dead layer in atomically thin oxides is presented, by using the epitaxial interface of 3d and 5d oxide monolayers that reconciles both strong exchange interaction and large uniaxial magnetic anisotropy. Combining multiple experimental methods, a ferromagnetic transition in an ultrathin oxide heterostructure comprised of only one La0.2Sr0.8MnO3 monolayer sandwiched by SrIrO3 monolayer (total thickness of three unit‐cells) is unambiguously demonstrated. Remarkably, a largely enhanced saturation magnetization (2 µB Mn−1) and Curie temperature (80 K) are observed for the single manganite monolayer, as compared to previously reported ferromagnetic monolayer oxides. The results demonstrate a general strategy for creating robust ferromagnetism in ultrathin TMOs, potentially enabling novel oxide spin‐orbitronic devices.

Photon Echo on Excitons and Its Role in the Development of Nanoelectronic Devices Based on Quantum-Sized Structures in Thin Zinc Oxide Films

Photon Echo on Excitons and Its Role in the Development of Nanoelectronic Devices Based on Quantum-Sized Structures in Thin Zinc Oxide Films

Multi-label oxide classification in float-zone silicon crystal growth using transfer learning and asymmetric loss

AbstractFloat-Zone (FZ) crystal growth process allows for producing higher purity silicon crystal with much lower concentrations of impurities, in particular low oxygen content. Nevertheless, the FZ process occasionally faces the problem of small contamination from oxidation. This can come in the form of a thin oxide layer that may form on un-melted polysilicon surface. The appearance of the oxide layer indicates degraded machine performance and the need for machine maintenance. Therefore, oxide investigation is important for improving both the FZ process and FZ machines, and the first step is oxide recognition. In this study, we characterized oxide into mainly three varieties, according to their surface texture characteristics, which are: (i) spot (ii) shadow and (iii) ghost curtain. We leveraged FZ images captured from the vision system integrated on the FZ machine to establish an oxide dataset. Targeted for data imbalance problem in our dataset, a method based on transfer learning and asymmetric loss for multi-label oxide classification is presented in this work. The results showed that the pre-trained model and the asymmetric loss used for training outperformed the baseline models and improved the classification performance. Furthermore, this study deeply investigated the effectiveness of the components of asymmetric loss. Finally, Gradient-weighted Class Activation Mapping (Grad-CAM) was employed to explain decision process of the models in order to adopt them in the industry.

High-Temperature Corrosion of High- and Medium-Entropy Alloys CrMnFeCoNi and CrCoNi Exposed to a Multi-Oxidant Atmosphere H2O–O2–SO2

The high-temperature corrosion behaviors of the equimolar CrCoNi medium-entropy alloy and CrMnFeCoNi high-entropy alloy were studied in a gas atmosphere consisting of a volumetric mixture of 10% H2O, 2% O2, 0.5% SO2, and 87.5% Ar at 800 °C for up to 96 h. Both alloys were initially single-phase fcc with a mean grain size of ~ 50 μm and a homogeneous chemical composition. The oxide layer thickness of CrMnFeCoNi increased linearly with exposure time while it remained constant at ~ 1 μm for CrCoNi. A Cr2O3 layer and minor amounts of (Co,Ni)Cr2O4 developed on the latter while three oxide layers were detected on the former, i.e., a thin and continuous chromium rich oxide layer at the oxide/alloy interface, a dense (Mn,Cr)3O4 layer in the center and a thick and porous layer of Mn3O4 and MnSO4 at the gas/oxide interface. Additionally, a few metal sulfides were observed in the CrMnFeCoNi matrix. These results were found to be in reasonable agreement with thermodynamic calculations.

The role of secondary phase precipitates in zircaloy corrosion: From point defects to local percolation

A thin oxide film on NZ alloy (Zr-1Sn-0.3Nb-0.3Fe-0.1Cr) was formed to investigate the correlation of microstructure and corrosion behavior at the initial stage by directly identifying defect-enriched sites. The sites of high conductivity are revealed and labelled by silver deposition, and in the further investigation of microstructure secondary phase precipitates (SPPs) interconnected with micro cracks are found below. Enrichment of oxygen-18 and deuterium in SPPs after isotopic tracing by secondary corrosion highlights their influence on carrier diffusion. Thus, the percolation for corrosion media transportation is reached locally by SPPs interconnected with micro cracks.

Dependence of the Metal-Insulator-Semiconductor Schottky Barrier Height on Insulator Composition.

The effects of different high-κ tunnel oxides on the metal-insulator-semiconductor Schottky barrier height (ΦB) were systematically investigated. While these high-κ interlayers have been previously observed to affect ΦB, there has never been a clear consensus as to why this ΦB modulation occurs. Changes in ΦB were measured when adding 0.5 nm of seven different high-κ oxides to n-Si/Ni contacts with a thin native silicon oxide also present. Depending on the high-κ oxide composition and ΦB measurement technique, increases in ΦB up to 0.4 eV and decreases up to 0.2 eV with a high-κ introduction were measured. The results were compared to several different hypotheses regarding the effects of tunnel oxides on ΦB. The experimental data correlated most closely with the model of a dipole formed at the SiOx/high-κ interface due to the difference in the oxygen areal density between the two oxides. Knowledge of this relationship will aid in the design of Schottky and ohmic contacts by providing criteria to predict the effects of different oxide stacks on ΦB.

Studies on Surface Characteristics and Biocorrosion Behavior of Ultrafast Laser‐Structured Titanium Alloy (Ti6Al4V)

Herein, the detailed corrosion behavior of ultrafast laser‐surface structured Ti6Al4V (using a Ti: Sapphire laser processed under optimum parameters) is carried out in simulated body fluid using electrochemical impedance spectroscopy and correlated with surface characteristics. Laser structuring leads to a topographically modified surface consisting of periodic surface patterns (nanoripples, nanodots) in the presence of a thin oxide layer. Surface processing introduces strain on the surface up to a depth of 150 μm, with the grains aligned along the and planes. The detailed electrochemical impedance spectroscopic studies show the formation of stable passive layers in surface‐structured Ti6Al4V as compared to as‐received Ti6Al4V.

Exploring the microwave assisted sol-gel synthesized multivalent doped thin films of iron oxide for detailed impedance and magnetodielectric response

Extensive research is carried out now a days to explore multifunctional materials for electronic, optoelectronic and spintronic devices. Multifunctionality that depends on the coupling between magnetic and electronic polarization, is a big challenge particularly for electronic and spintronic applications. This research focuses on the development of material and methodology to produce strong coupling between two polarizations/orders. Thin iron oxide films are prepared by the combined effect of microwaves and sol-gel after irradiating the solution at 720W. Multivalent doped sols are synthesized with variation in aluminum (Al) and cobalt (Co) concentrations in the range of 2 to 10 wt%. Crystal phase change from maghemite to magnetite, at Al–Co content of 8 to 10 wt%, is observed by XRD results. Phase transformation from maghemite to magnetite shows that probability of occupancy of Al3+and Co2+ ions of vacancies on B and A sites is affected by the microwave irradiation. Structural phase transition is also accompanied by the increased saturation magnetization. Undoped thin films, i.e. maghemite, exhibit dielectric constant ∼100 (log f = 4.5). Various relaxation phenomena are observed in impedance analyses. Room temperature magnetic and dielectric coupling is observed under multivalent doping conditions.

Scalable Generation of Hybrid Graphene Nanoscrolls for High-Performance Solid Lubricants

Graphene and other 2D materials have been extensively studied as solid lubricants in recent years. Low friction can sometimes be observed in those 2D lubricants, and one possible mechanism is that scroll-shaped nanostructures are formed during friction, which decreases the contact area and energy barrier, thus substantially reducing friction. The integration of graphene with metal or metal oxide nanostructures can further enhance its lubrication properties by increasing film formation ability and easy shearing of the nanosheets. However, it is not possible to reliably promote the formation of such nanoscroll-shaped low friction wear products, which limits the reproducibility and application of such nanostructures as solid lubricants. In this study, we address this issue by creating a scalable method for the synthesis of hybrid graphene-titanium oxide (G–TiO2) nanoscrolls and demonstrating their potential as solid lubricants with macroscopic coefficient of friction as low as 0.02 in ambient conditions. Our approach to generate the nanoscrolls is based on the in situ sol–gel synthesis of TiO2 on graphene followed by spray-freeze-drying–induced shape transformation. The solid lubrication performance of such G–TiO2 nanoscrolls can be further enhanced by applying a thin graphene oxide primer layer, which provides high affinity to both the substrate and the active materials. These hybrid nanoscrolls hold promising potential for applications in aerospace, automotive, and precision manufacturing fields as effective solid lubricants.Graphical

Review of: "Then the transistor with upper gate also which were suitable for use in integrated circuits , with the addition of an upper gate by The thin oxide layer is separated from the nanotube channel"

Review of: "Then the transistor with upper gate also which were suitable for use in integrated circuits , with the addition of an upper gate by The thin oxide layer is separated from the nanotube channel"

Controlling Nucleation Sites for Metal Oxide Film Growth on Glassy Carbon via Electrochemical Preoxidation.

Coating electrode materials with metal oxide thin films can improve the performance of electrocatalysts and charge storage materials. Atomic layer deposition (ALD) enables the deposition of conformal, uniform films on a wide range of electrodes; however, an even film depends on the availability of nucleation sites directly on the electrode surface. Here, we show that the electrochemical oxidation of glassy carbon electrodes prior to the deposition of alumina thin films by ALD leads to more uniform electrochemically passivating films. Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) demonstrate that film uniformity increases with the increasing potential of preoxidation until 2.50 V versus Ag/AgCl, at which point the films are fully passivating and appear continuous by SEM. Further increasing the potential of preoxidation leads to uniform but less consistently passivating alumina films. These findings show that electrochemical preoxidation is a rapid and readily tunable strategy for controlling oxygenic nucleation sites and therefore the growth of thin metal oxide films on glassy carbon electrodes.

Large second-order susceptibility from a quantized indium tin oxide monolayer.

Due to their high optical transparency and electrical conductivity, indium tin oxide thin films are a promising material for photonic circuit design and applications. However, their weak optical nonlinearity has been a substantial barrier to nonlinear signal processing applications. In this study, we show that an atomically thin (~1.5 nm) indium tin oxide film in the form of an air/indium tin oxide/SiO2 quantum well exhibits a second-order susceptibility χ2 of ~1,800 pm V-1. First-principles calculations and quantum electrostatic modelling point to an electronic interband transition resonance in the asymmetric potential energy of the quantum well as the reason for this large χ2 value. As the χ2 value is more than 20 times higher than that of the traditional nonlinear LiNbO3 crystal, our indium tin oxide quantum well design can be an important step towards nonlinear photonic circuit applications.

Solution-processed Sb2Se3 photocathodes under Se-rich conditions and their photoelectrochemical properties.

In this study, selenium (Se)-rich antimony selenide (Sb2Se3) films were fabricated by applying a solution process with the solvents ethylenediamine and 2-mercaptoethanol to optimize the photoelectrochemical (PEC) performance of the Sb2Se3 photocathode. Various antimony (Sb)-Se precursor solutions with different molar ratios of Sb and Se (Sb : Se = 1 : 1.5, 1 : 3, 1 : 4.5, 1 : 7.5, and 1 : 9) were prepared to attain Se-rich fabrication conditions. As a result, the Se-rich Sb2Se3 films fabricated using the Sb-Se precursor solution with a molar ratio of Sb : Se = 1 : 7.5 exhibited an improved PEC performance, compared to the stoichiometric Sb2Se3 film. The charge transport was improved by the abundant Se element and thin selenium oxide (Se2O3) layer in the Se-rich Sb2Se3 film, resulting in a decrease in Se vacancies and substitutional defects. Moreover, the light utilization in the long wavelength region above 800 nm was enhanced by the light-trapping effect because of the nanowire structure in the Se-rich Sb2Se3 film. Hence, the optimal Se-rich Sb2Se3 photocathodes showed an improved photocurrent density of -0.24 mA cm-2 at the hydrogen evolution reaction potential that was three times higher than that of the stoichiometric Sb2Se3 photocathodes (-0.08 mA cm-2).

Thin-film-based optical fiber interferometric sensor on the fiber tip for endovascular surgical procedures.

Endovascular surgery requires accurate measurement of parameters such as pressure, temperature, and biomarkers within vessels for real-time tissue response monitoring and ensuring targeted therapeutic interventions. However, the availability of small tip-based sensors capable of precise application, for example, navigating an aneurysm's lumen, is limited. With their capabilities for real-time analysis, flexibility, and biocompatibility, optical fiber sensors (OFS) hold promise in addressing this need. This proof-of-concept study investigates the feasibility of OFS in endovascular surgery scenarios. The sensor is based on a single-mode silica fiber with an interferometric forward-facing thin-film tip. The thin-film materials may be tailored for detecting various physical parameters and, when functionalized, also specific analytes. Materials applied in this sensor are thin metal oxides deposited using magnetron sputtering. A full-scale 3D-printed vascular model was employed to simulate endovascular setup. The experiments showed the high mechanical robustness of the approach, i.e., the sensor maintained functionality while being maneuvered through the endovascular model. The forward-facing tip remained intact and worked adequately, ensuring consistent and stable readouts. Moreover, the fiber showed sufficient flexibility, with no significant bending loss observed during simulations. Finally, the performance of the OFS in bovine serum samples was assessed. The sensor performed well in serum, and the results suggest that low-concentration serum may be used to reduce nonspecific surface interactions. Overall, this OFS system offers a promising solution for endovascular surgery and other biomedical applications, allowing for precise and on-the-spot analysis. Our study pioneers the feasibility of thin-film interferometric label-free OFS with a forward-facing sensitive area for sensing during endovascular procedures.

Laser color marking of stainless steel – Investigation of the fluence-dependent and thermal mechanisms in generating laser induced surface modifications

Laser color marking is an attractive process to generate functional, aesthetic and durable colorations on various suitable metals such as stainless steel or titanium. The color generation is mainly based on interference effects on thin oxide layers, usually induced by nanosecond pulsed laser irradiation. Due to the large number of mutually influencing processing parameters and different thermal, chemical, structural and topological influences on the coloring results, the process is still not fully understood. Moreover, the reproducibility of the markings and the processing times often do not meet the requirements of industrial manufacturing processes. To improve the understanding of the underlying phenomena comparable colors are generated using different parameter sets. Spectroscopic, microscopic and SEM/EDS analyzes are carried out to investigate the effects of the surface topology, oxide layer properties, chemical composition and heat accumulation on the marking results.

Role of oxide barrier in a NbOx layer with noninert electrodes for high-yield threshold switching characteristics

This study shows how the threshold switching (TS) characteristics of a NbOx layer with noninert W electrodes can be improved by introducing an oxide barrier. The ∼10-nm-thick NbOx layer exhibits TS, which is known to originate from NbO2, after electroforming. However, an unwanted formation of a Nb2O5 layer at the top electrode (TE) interface has been observed, which deteriorates the TS, given the switching capability of Nb2O5. Therefore, a thin oxide layer was introduced to overcome the issue and enhance the TS behavior. Furthermore, the role of the oxide barrier is investigated systematically considering its location and unique properties. This study reveals that depositing a barrier at the bottom electrode interface makes the formation of NbO2 difficult, resulting in poor TS behavior, while placing the barrier at the TE interface could mitigate the Nb2O5 creation, promoting TS. Finally, the effect of incorporating various oxide types has been investigated, showing different switching behavior. Through examining the temperature dependence of the TS obtained from the W/NbOx/W and W/ZrO2/NbOx/W stacks, it was found that the suppression of Nb2O5 at the top interface is indirectly shown as a strengthened Schottky barrier from an electrical measurement perspective. As a result, excellent cell-to-cell uniformity of the TS is achieved in the ZrO2/NbOx stack, which not only prevents the formation of Nb2O5 but also stabilizes NbO2 in the NbOx layer.