Surface Contamination Research Articles

Studying the Photoactivity of Ag-Decorated TiO2 Nanotubes with Combined AFM and Raman Spectroscopy

The drive for the development of systems that can simultaneously investigate chemical and morphological information comes from the requisite to fully understand the structure and chemical reactivity relationships of materials. This is particularly relevant in photocatalysis, a field ruled by surface interactions. An in-depth understanding of these complex interactions could lead to significant improvements in materials design, and consequently, in photocatalytic performances. Here, we present a first approach to a combined atomic force microscopy (AFM) and Raman spectroscopy characterization of anodic TiO2 nanotubes arrays decorated with Ag nanoparticle electrodeposition from either the same anodizing organic electrolyte or from an aqueous one. Photocatalytic substrates were used in up to 15 consecutive photocatalysis tests to prove their possible deterioration with reuse. Sample aging can, in principle, produce changes in both the morphology and the chemical compounds that characterize the photocatalyst surface. Adopting multiple characterization techniques, such as a combination of AFM and Raman spectroscopy in an original setup, can profitably enable the observation of surface contamination. A significant drop in photocatalytic activity was observed after 10 cycles on samples where silver was deposited from the organic electrolyte, while the others remained stable. Such a drop was ascribed to photocatalyst deactivation. While in other cases, a simple recovery treatment allowed the initial photoactivity to be restored, this deactivation was not restored even after chemical and thermal cleaning treatments.

Multifunctional Smart Fabrics with Integration of Self-Cleaning, Energy Harvesting, and Thermal Management Properties.

Due to their good wearability, smart fabrics have gradually developed into one of the important components of multifunctional flexible electronics. Nevertheless, function integration is typically accomplished through the intricate stacking of diverse modules, which inevitably compromises comfort and elevates processing complexities. The integration of these discrete functional modules into a unified design for smart fabrics represents a superior solution. Here, we put forward a rational approach to functional integration for the typical challenges of thermal management, energy supply, and surface contamination in smart fabrics. This sandwich-structured multilayer fabric (MLF) is obtained by continuous electrospinning of two layer P(VDF-HFP) fabric and one layer P(VDF-HFP) fabric functionalized with core-shell SiO2/ZnO/ZIF-8 (SZZ) nanoparticles. Specifically, MLFs achieve effective and stable energy harvesting in triboelectric nanogenerators (TENGs) with hydrophobicity and antibacterial properties. Meanwhile, MLFs also have high mid-infrared emissivity and sunlight reflectivity, successfully realizing radiative cooling under different climates, and have been applied in wearing clothing, roof shading, and car covers. This work may contribute to the design and manufacturing of next-generation thermal comfort smart fabrics and wearable electronics, particularly in terms of the rational design of multifunctional devices.

Scanning electron microscopy imaging of multilayer-doped GaN: Effects of surface band bending, surface roughness, and contamination layers on doping contrast

Dopant profiling by a scanning electron microscope possesses great potential in the semiconductor industry due to its rapid, contactless, non-destructive, low cost, high spatial resolution, and high accuracy characteristics. Here, the influence of plasma and wet chemical treatments on doping contrast was investigated for a multilayered p-n GaN specimen, which is one of the most promising third-generation wide bandgap semiconductors. Angle-resolved x-ray photoelectron spectroscopy and atomic force microscope were employed to characterize the degree of surface band bending, surface roughness, gallium oxides, and hydrocarbons on the surface of GaN. N2 and air plasmas were unable to remove the surface contamination layers, although the degree of surface band bending was suppressed. In contrast, wet chemical methods offer superior capability in removing contamination layers; however, the surface roughness was increased to varying degrees. Notably, NH4F solution is capable of improving the doping contrast. The underlying mechanism was elucidated from the perspective of surface band bending, surface roughness, and contamination. The findings reported here will provide a feasible solution for effective characterization of semiconductor materials and devices.

Impact of monolayer WS2 surface properties on the gate dielectrics formation by atomic layer deposition

Two-dimensional transition metal dichalcogenides (2D TMDs), such as MoS2 and WS2, have emerged as promising channel materials for future generation transistors. However, carbon-based surface contaminants pose a significant challenge in the formation of high-quality metal–oxide–semiconductor gate stacks for 2D TMDs. Carbon-based surface contaminants are known to be present even on directly grown 2D TMDs that have not been in contact with polymers. These organic contaminants affect precursor adsorption during atomic layer deposition (ALD) of gate dielectrics on 2D TMDs and as such the 2D-dielectric interface. This study examines the effectiveness of predeposition annealing in mitigating carbon-based contaminants while maintaining the integrity of a directly grown WS2 monolayer on a SiO2 substrate. We show that a WS2 monolayer on a SiO2/Si substrate remains stable during vacuum annealing at temperatures up to 400 °C. Water contact angle measurements and x-ray photoelectron spectroscopy confirm that the surface concentration of carbon starts to decrease at 150 °C. Thermal anneal improves the surface coverage of Al2O3 for both conventional chemisorption-based ALD and physisorbed-precursor-assisted ALD processes by facilitating more effective Al2O3 nucleation on the WS2 monolayer. The impact of predeposition anneal on the Al2O3 growth behavior in both processes can be explained by changes in surface contaminant levels. Our results underscore the importance of surface pretreatment in dielectric deposition on 2D TMDs and demonstrate that predeposition anneal is an effective method to enhance ALD-based dielectric deposition on directly grown 2D TMDs.

Integrated geophysical and geospatial techniques for surface and groundwater modeling

An integrated approach using geophysical and geospatial techniques was employed to model the surface and subsurface water-bearing strata and assess aquifer vulnerability in the Sehnsa town, Kotli district, State of Azad Kashmir, Pakistan. The inadequate scientific studies in the hilly terrain with such complex geological conditions has led to the failure of the boreholes for groundwater extraction. For the evaluation of groundwater potential and subsurface lithology, 30 vertical electrical soundings (VES) stations utilizing the Schlumberger electrode configuration were completed, modeled and analyzed spatially. Numerous geoelectrical parameters like true resistivity, thickness of subsurface layers and Dar-Zarrouk parameters were evaluated. The subsurface lithology delineated comprised topsoil, clayey sand, sandstone, and boulder clays which closely resemble to the borehole lithologs available in the study area. The inversion model confirms the presence of patches of high-resistivity sandstone in the southwestern part of the study area with the maximum thickness of the aquifer up to 140 m. Most aquifers were classified as unconfined with Q–type resistivity curves. The protective overburden capacity of the aquifers is rated as poor at VES 1, 3–5, 8, 10–16, 18, 19, 22–25, 27 and 30 whereas the moderate category was found at VES 2, 9 and 20 and excellent at VES 7 and 28, respectively. Therefore, the VES stations with poor and moderate ratings of overburden protective capacity are vulnerable for surface contaminants. The aquifer recharge was associated with rainfall and partly from the Poonch River. The effective integration of geophysical and geospatial techniques in this study provides sufficient information about the regional water resources and gives a preliminary model that can facilitate efficient water resource management in the area. These approaches can be successfully applied to diverse geographical and hydrogeological sites due to their versatility and reliability.

An Assessment of Surface Contamination and Dermal Exposure to 5-Fluorouracil in Healthcare Settings by UPLC-MS/MS Using a New Atmospheric Pressure Ionization Source

5-Fluorouracil (5-FU) is a well-known cytostatic drug, which is often used in cancer treatments. Yet, it is also a very dangerous compound for people who are occupationally exposed to it for a long time, such as pharmacy employees, nurses and cleaning staff. We aimed to improve and implement a LC-MS/MS method for 5-FU quantification on surface contamination samples collected with swabs in a pharmacy department and outpatient nursing station of a university hospital. To improve the existing methods to quantify 5-FU, we compared a LC-MS/MS method using the frequently applied electrospray ionization source (ESI) with a UniSpray ionization source (USI). To determine the contamination of 5-FU in a pharmacy department preparing 5-FU infusion bags, which are then given to patients in the outpatient nursing stations, we collected multiple surface swabs of the laminar flow cabinets and frequently touched objects, before the preparation and administration of 5-FU and afterwards. Furthermore, we sampled the protective gloves and the bare hands of employees of the pharmacy department, involved in the preparation of the infusion bags. Using the USI source, we were able to reach the lowest limit of quantification (LOQ). With this technique, we were able to detect 5-FU contamination on the laminar flow cabinets and frequently used objects in the pharmacy department and the outpatient nursing station in the very low ng/cm2 range. This contamination was mostly higher after preparation or administration than before. While we also found 5-FU on the protective gloves, we almost found no 5-FU on the skin of the pharmacy technicians preparing the 5-FU infusion bags. In conclusion, our method was able to detect very low concentrations of 5-FU contamination, but the contamination we found is very unlikely to result in any issues for the personnel working in these areas.

Decontamination of Fused-Silica Surfaces by UVC Irradiation as Potential Application on Touchscreens.

The contamination of surfaces by antibiotic-resistant pathogens presents an escalating challenge, especially on touchscreens in public settings such as hospitals, airports, and means of transport. Traditional chemical cleaning agents are often ineffective and leave behind harmful residues. Thus, the application of optical radiation is gaining relevance as a rapid, effective, and environmentally friendly disinfection method. This study examines the contamination of publicly accessible touchscreens and the efficacy of an irradiation approach for the radiation disinfection of microorganisms on quartz surfaces with UVC LEDs. In this setup, the LED radiation is laterally coupled into a quartz plate that serves as cover glass of a simplified touchscreen model. The process allows for the irradiation of microorganisms on the surface, without the user being exposed to hazardous radiation. To assess the efficacy of the disinfection process, a range of bacteria, mostly ESKAPE surrogates, such as Staphylococcus carnosus, Acinetobacter kookii, Escherichia coli, Enterococcus mundtii, and additionally Micrococcus luteus, were spread over a quartz plate with a homebuilt nebulization system. After operating the side-mounted LEDs for 30 s, a reduction in all bacteria except M. luteus by more than three orders of magnitude was observed. In the case of M. luteus, a significant reduction was achieved after 60 s (p < 0.05). This result demonstrates the potential of side-mounted UVC LEDs for rapid disinfection of touchscreens between two users and thus for reducing the spread of pathogens without irradiating humans.

Mechanism of Wheel-Rail Adhesion Recovery during Large Sliding processes under Water Lubrication condition

The challenge of low adhesion between the wheel and rail constrains the advancement of train braking technologies, resulting in sliding during braking, increased braking distances, and even operational safety incidents. Low adhesion arises from the contamination of the rail surface by a third body, such as water or oil, significantly reducing adhesion. However, experimental studies have found that wheel-rail adhesion coefficient under water lubrication conditions possesses a recovery capability: In scenarios characterized by low adhesion in water lubrication conditions, a secondary rise in adhesion occurs when substantial wheel-rail sliding is present. This paper focuses on numerically modeling the unique phenomenon of adhesion recovery during large-sliding processes under water lubrication conditions. Considering the notable differences in frictional heating during wheel sliding, as opposed to pure rolling conditions, we construct a wheel-rail contact model under mixed lubrication conditions that incorporates the solid-liquid coupled heat transfer effect. This model achieves stable solutions for the wheel-rail contact relationship and the temperature at the wheel-rail interface. The impacts of velocity, axle load, water temperature, and slide ratio on the adhesion recovery phenomenon are discussed, revealing the underlying mechanism of adhesion recovery during large sliding processes. Finally, brake adhesion tests under water lubrication conditions are conducted on a scaled test rig to validate the proposed theoretical model.

РАДІАЦІЙНИЙ СТАН ЗОНИ ВІДЧУЖЕННЯ В 2023 РОЦІ ЗА РЕЗУЛЬТАТАМИ РАДІАЦІЙНО-ЕКОЛОГІЧНОГО МОНІТОРИНГУ

The article presents results of radiation and environmental monitoring in the Exclusion Zone for the year 2023, after de-occupation of the territory, which was carried out in accordance with the current regulation of work, with the exception of objects on which it is temporarily impossible to carry out work due to the lack of safe access. In 2022, due to the full-scale invasion of russian federation, radiation monitoring of the environment was interrupted, monitoring of radiation-hazardous objects and environmental components of the Exclusion Zone was not carried out. Implementation of priority measures to restore the radiation and environmental monitoring system in the Exclusion Zone, after occupation by russian troops, made it possible to resume the work of the automated radiation monitoring system points, to create an additional network of measurement of gamma radiation indicators in the Exclusion Zone, to restore work of the central analytical laboratory and to restore the work of aspiration units. Thus, the enterprise resumed obtaining the necessary data on the dose rate of gamma radiation, information on the radiation state of the surface layer of the atmosphere, radiation state of surface and underground waters, radiation state of landscapes and places of residence of self-settlers. According to the results of radiation and environmental monitoring in the Exclusion Zone in 2023, important analytical data were obtained: - Maximum power values of the ambient dose equivalent of gamma radiation are characteristic of the territories in the northern and western 'traces' of radioactive fallout; - Radiation state of the Exclusion Zone air environment and its dynamics during 2023 were determined by the nature of surface contamination of the territory, man-made and biological factors, as well as meteorological conditions. Control levels exceeding by 2.5 times of 137Cs volumetric activity in the air was recorded in Chornobyl; - Surface waters remain an important route of radionuclide removal beyond the Exclusion Zone. Removal of 90Sr from Pripyat River in the area of Chornobyl in 2023 was at a level that was 2.4 times higher than the average value for the last 5 years; - As a result of observations of the radiation state of underground waters, it was determined that the average value of radionuclide contamination of eocene and cenomanian-lower cretaceous water-bearing complexes does not exceed 1 Bq/m3 for 137Cs and 5.7 Bq/m3 for 90Sr; - Monitoring results at landscape landfills indicate that the most contaminated component of the environment is the top layer of soil cover; - Radiation survey results of unauthorized residence places of the population in the Exclusion Zone showed that over the years there is an increase in the intake of 90Sr in the food products of 'self-settlers'.

Eliminate all surface contamination

Eliminate all surface contamination

Selective Plasma Treatment Endowing Low-Friction and Wear-Resistant Surface of Polycrystalline Diamond against Copper.

Despite its unrivaled hardness, polycrystalline diamond can be severely worn under the interaction with softer copper during the ultrafine copper wire drawing process. The influence of the polycrystalline diamond surface state on its friction behavior is investigated in this work, and argon, oxygen, and hydrogen plasma treatments are adopted to regulate the surface state of diamond. When sliding against copper, the original diamond plate exhibits a coefficient of friction (COF) exceeding 0.4, copper wears by transferring to the diamond, and diamond wears owing to the carbon cluster removal, as confirmed by the TOF-SIMS analyses of the obvious wear tracks. After hydrogen plasma treatment, the tribological performance of diamond sliding against copper is most significantly improved, in which the COF is more stable and reaches 0.18 with minimal wear debris. Hydrogen plasma treatment generates more hydrogen termination on the diamond surface as well as a hydrogen-containing amorphous carbon layer, which provides an isolated lubrication effect and strongly reduces adhesive wear. Argon plasma treatment also decreases the level of COF to a certain extent, which is attributed to its polishing and cleaning action that removes surface contamination and reduces roughness. In contrast, oxygen plasma treatment induces a pronounced etching effect, resulting in groove-like protrusions on the diamond surface that exacerbates abrasive wear. Our research provides a more sustainable and residue-free solution for minimizing friction and wear of polycrystalline diamond wire drawing dies.

Analysis of silver metal with a Thermo Scientific K-Alpha XPS instrument at 50 and 200 eV pass energies

Silver metal was analyzed by x-ray photoelectron spectroscopy using a Thermo Scientific K-Alpha instrument with an Al Kα x-ray source (1486.6 eV). The silver survey spectrum and high-resolution Ag 3d, Ag M4N45N45, Ag M5N45N45, Ag 3p, O 1s, C 1s, Ar 2p, Ag 4p, and Ag 4s narrow scans were obtained. The sample analyzed is the standard instrument calibration silver foil mounted inside the analysis chamber of the K-Alpha. Sputtering with monoatomic Ar+ was performed prior to analysis to remove surface contamination. Narrow and survey scans were collected at 50 and 200 eV pass energy, respectively.

How long do bacteria, fungi, protozoa, and viruses retain their replication capacity on inanimate surfaces? A systematic review examining environmental resilience versus healthcare-associated infection risk by "fomite-borne risk assessment".

SUMMARYIn healthcare settings, contaminated surfaces play an important role in the transmission of nosocomial pathogens potentially resulting in healthcare-associated infections (HAI). Pathogens can be transmitted directly from frequent hand-touch surfaces close to patients or indirectly by staff and visitors. HAI risk depends on exposure, extent of contamination, infectious dose (ID), virulence, hygiene practices, and patient vulnerability. This review attempts to close a gap in previous reviews on persistence/tenacity by only including articles (n = 171) providing quantitative data on re-cultivable pathogens from fomites for a better translation into clinical settings. We have therefore introduced the new term "replication capacity" (RC). The RC is affected by the degree of contamination, surface material, temperature, relative humidity, protein load, organic soil, UV-light (sunlight) exposure, and pH value. In general, investigations into surface RC are mainly performed in vitro using reference strains with high inocula. In vitro data from studies on 14 Gram-positive, 26 Gram-negative bacteria, 18 fungi, 4 protozoa, and 37 viruses. It should be regarded as a worst-case scenario indicating the upper bounds of risks when using such data for clinical decision-making. Information on RC after surface contamination could be seen as an opportunity to choose the most appropriate infection prevention and control (IPC) strategies. To help with decision-making, pathogens characterized by an increased nosocomial risk for transmission from inanimate surfaces ("fomite-borne") are presented and discussed in this systematic review. Thus, the review offers a theoretical basis to support local risk assessments and IPC recommendations.

Analysis of the radiation accidents prevalence in nuclear medicine in the Russian Federation

Radiation events (accidents) appearance is an integral part of the use of ionizing radiation sources in medicine in general and nuclear medicine in particular. To minimize the negative impact on patients, workers, and public due to such events, it is necessary to have reliable information about real prevalence of the radiation events (accidents). The current work presents the analysis of the radiation accidents with medical ionizing radiation sources registered in the “Data bank of radiation accidents and incidents” of the Rospotrebnadzor Information and Analytical Centre for Radiation Safety and the results of workers questionnaires conducted in 25 nuclear medicine departments (about 30% of all nuclear medicine departments in the Russian Federation). The results of the analysis showed that the most common registered radiation accidents in the “Data bank of radiation accidents and incidents” are identification of passengers with high external dose rate as well as identification of waste contaminated by medical radionuclides. The results of the questionnaire showed that the most common radiation accidents (events) in nuclear medicine are contamination of work clothes or work surfaces with radionuclides, or patient fluids containing radionuclides; conducting examination without proper referral; extravasation of radiopharmaceutical. Existing systems of identification and registration of radiation accidents do not allow to identify radiation events (accidents) specific to nuclear medicine. The further research aimed at developing a classification of radiation events (accidents) in medicine and methods for responding to such events are feasible.

Real-time, specific, and label-free transistor-based sensing of organophosphates in liquid

Organophosphates (OP), commonly used in agriculture and as chemical warfare agents, pose significant environmental risks, necessitating real-time, low-cost OP detection methods. In particular, liquid-phase OP sensing with minimal sample volumes is crucial. While several methods allow rapid detection of low concentrations of OP vapors, they are effective only in the short term, while vapors are still being produced. Many OP compounds are semi-volatile, leading to the contamination of water, soil, and surfaces, posing a risk of secondary, long-term exposure. Detecting this contamination requires methods that can be directly applied to droplets of the affected medium. Currently, no method provides the desired combination of ultra-sensitivity, quantitative detection, rapid response, and low-cost for detecting OPs in liquid samples. This study aims to demonstrate quantitative, low-cost, real-time, specific, and label-free OP sensing in ultra-small samples using a transistor-based approach. The current work employs the 2-(4-Aminophenyl)-1,1,1,3,3,3-hexafluoro-2-propanol (aminophenyl-HFIP) functionalized meta-nano-channel field-effect chemical sensor (MNChem sensor) to monitor the organophosphate, diethyl cyanophosphonate (DCNP), in liquid samples. The silicon component of the MNChem is fabricated using a complementary metal-oxide semiconductor (CMOS) process, and the amine-based chemical functionalization of the sensing area is performed post-fabrication. The MNChem sensor provides electrostatic control over the source-drain current (IDS), allowing an optimized channel configuration that efficiently transduces localized OP recognition events into significant IDS variations. Sensing is performed using 0.5 μL buffer solution to simulate a miniature field-deployable sensor for on-site liquid analysis. We report the sensing of DCNP with a limit-of-detection of 100 fg/mL, a dynamic range of 9 orders of magnitude, and excellent linearity (≥0.97) and sensitivity. Control measurements confirm the specificity and reliability of the sensor's response, validating its applicability. This study introduces a novel method for OP detection in contaminated droplets using a low-cost disposable transistor technology.

BINGO innovative assembly for background reduction in bolometric [formula omitted] experiments

BINGO is a project aiming to set the grounds for large-scale bolometric neutrinoless double-beta-decay experiments capable of investigating the effective Majorana neutrino mass at a few meV level. It focuses on developing innovative technologies (a detector assembly, cryogenic photodetectors and active veto) to achieve a very low background index, of the order of 10−5 counts/(keV kg yr) in the region of interest. The BINGO demonstrator, called MINI-BINGO, is designed to investigate the promising double-beta-decay isotopes 100Mo and 130Te and it will be composed of Li2MoO4 and TeO2 crystals coupled to bolometric light detectors and surrounded by a Bi4Ge3O12-based veto. This will allow us to reject a significant background in bolometers caused by surface contamination from α-active radionuclides by means of light yield selection and to mitigate other sources of background, such as surface contamination from β-active radionuclides, external γ radioactivity, and pile-up due to random coincidence of background events. This paper describes an R&D program towards the BINGO goals, particularly focusing on the development of an innovative assembly designed to reduce the passive materials within the line of sight of the detectors, which is expected to be a dominant source of background in next-generation bolometric experiments. We present the performance of two prototype modules – housing four cubic (4.5-cm side) Li2MoO4 crystals in total – operated in the Canfranc underground laboratory in Spain within a facility developed for the CROSS double-beta-decay experiment.

Rapid virus inactivation by nanoparticles-embedded photodynamic surfaces

The persistent threat of viral epidemics poses significant risks to human health, highlighting the urgent need for antiviral surfaces to mitigate viral transmission through bioaerosols and surface contamination. However, there is still a scarcity of readily accessible antiviral coatings to address this critical concern. In this study, we demonstrate that photodynamic nanoparticle-embedded surfaces can swiftly inactivate both enveloped and non-enveloped viruses. We prepared core–shell structured methylene blue (MB)-loaded SiO2 nanoparticles with a high reactive oxygen species (ROS) yield (0.47 ± 0.02). The superior ROS production was maintained after modifying these nanoparticles onto air filter fibers, likely due to the prevention of aggregation-caused quenching effects. Three viruses, including both enveloped and non-enveloped types, were rapidly inactivated within just 12 min (>6 log units) under medium light intensity (660 nm, 30 mW/cm2). Mechanistic studies revealed that envelope glycoproteins are the primary targets for this rapid inactivation. Thus, photodynamic nanoparticle-embedded surfaces offer a straightforward and adaptable strategy in the fight against viral epidemics.

Optimal control analysis on the spread of COVID-19: Impact of contact transmission and environmental contamination

The study investigates the intricate dynamics of SARS-CoV-2 transmission, with a particular focus on both close-contact interactions and environmental factors. Using advanced mathematical modeling and epidemiological analysis, explored the effects of these transmission pathways on the spread of COVID-19. The equilibrium points for both the disease-free and endemic states calculated and evaluated their global stability. Additionally, the basic reproduction number (R0) is derived to quantify the transmission potential of the virus.To ensure model accuracy, numerical simulations are performed using MATLAB, utilizing daily COVID-19 case data from India. Parameter values are sourced from existing literature, with certain parameters estimated through fitting the model to observed data. Crucially, the model incorporates environmental transmission factors, such as surface contamination and airborne spread. The inclusion of these factors provides a more comprehensive understanding of the virus’s spread, demonstrating the importance of interventions like use of face masks, environmental sanitization, vaccine efficacy, availability of treatment resources underappreciated when focusing solely on direct human contact. A sensitivity analysis is conducted to assess the impact of different parameters on R0, with results visualized through heat maps to identify the most influential factors.Furthermore, Pontryagin’s maximum principle is employed to develop an optimal control model, enabling the formulation of effective intervention strategies. By analysing both interpersonal and environmental transmission mechanisms, this study offers a more holistic framework for understanding SARS-CoV-2 transmission. The insights gained are critical for informing public health strategies, emphasizing the necessity of addressing both direct contact and environmental sources of infection to more effectively manage current and future outbreaks.

Schottky Diode Leakage Current Fluctuations: Electrostatically Induced Flexoelectricity in Silicon.

Nearly four decades have passed since IBM scientists pioneered atomic force microscopy (AFM) by merging the principles of a scanning tunneling microscope with the features of a stylus profilometer. Today, electrical AFM modes are an indispensable asset within the semiconductor and nanotechnology industries, enabling the characterization and manipulation of electrical properties at the nanoscale. However, electrical AFM measurements suffer from reproducibility issues caused, for example, by surface contaminations, Joule heating, and hard-to-minimize tip drift and tilt. Using as experimental system nanoscale Schottky diodes assembled on oxide-free silicon crystals of precisely defined surface chemistry, it is revealed that voltage-dependent adhesion forces lead to significant rotation of the AFM platinum tip. The electrostatics-driven tip rotation causes a strain gradient on the silicon surface, which induces a flexoelectric reverse bias term. This directional flexoelectric internal-bias term adds to the external (instrumental) bias, causing both an increased diode leakage as well as a shift of the diode knee voltage to larger forward biases. These findings will aid the design and characterization of silicon-based devices, especially those that are deliberately operated under large strain or shear, such as in emerging energy harvesting technologies including Schottky-based triboelectric nanogenerators (TENGs).

Wet-Chemical Synthesis of a Protective Coating on NCM111 Cathode: The Quantified Effects of Washing, Sintering and Coating

LiNixCoyMn1-x-yO2 (NCM) cathodes, especially with high Ni content, are widely expected to keep advancing the energy density of Li-ion batteries. However, ensuring a good cycle life remains a key challenge. Applying inert protective coatings on the surface of NCMs is a common route for mitigating surface-based degradation. In this study a sustainable ethanol-based wet-chemical coating method for covering the material with Al2O3 is developed and demonstrated on NCM111. The effect of the synthesis procedure is carefully evaluated to distinguish the benefits of the protective coating from the contributions of re-sintering and removal of surface contaminants, all taking place during the synthesis of the coated material. We show that while the cycling stability is significantly improved by the material regeneration alone (65% vs 79% state-of-health after 500 charge-discharge cycles at voltage range 2.7–4.3 V vs Li/Li+), the Al2O3-coated material displays further cycle life gains, maintaining 88% of initial capacity after 500 charge-discharge cycles. This work thus demonstrates both a sustainable wet-chemical coating method and the importance of establishing a proper baseline for characterization of inert protective coatings in general. The importance of both gains further prominence with the transition to inherently less stable higher Ni content NCMs.