P-type nickel oxide (NiOx) films with adjustable properties are essential for advanced optoelectronics and photovoltaics. We show that the power of ALD H2O plasma (50-200 W) serves as a key parameter for controlling structural, optical, electrical, and electronic properties of NiOx films grown from Ni(acac)(2) precursor. Structurally, all obtained films had nano-crystalline cubic NiO phase; a secondary Ni3C phase emerged only for 200 W plasma, producing large crystallites (similar to 10-13 nm) and surface roughness (0.85-2.39 nm). Visible light transmittance varied with plasma power from >80% (50 W) to similar to 60% (200 W) due to increased scattering on incorporated defects. All films had p-type conductivity (similar to 10(-4) S/cm). The 200 W sample featured the highest mobility (10.07 cm(2)/V & centerdot;s) and conductivity (8.91 & times; 10(-4) S/cm). XPS analysis confirmed formation of non-stoichiometric NiOx with plasma-dependent defect configurations. The CNi peak appeared only at high plasma power. Electronic structure analysis confirmed that plasma power can be used for the efficient fine-tuning of band gap (3.35-3.54 eV), work function (5.17-5.70 eV), and the position of valence band maximum (-0.73 to -0.35 eV relative to the Fermi level E-F). The films deposited with 50 W plasma featured a promising parameter balance for hole transport layers: high transparency (>80%), low roughness (0.85 nm), good band alignment (E-F - 0.73 eV) and conductivity (3.45 & times; 10(-4) S/cm). These results establish the H2O plasma power as a versatile parameter for defect engineering and control of band alignment in NiOx, capable of producing good-quality hole transport layers for perovskite solar cells and other transparent optoelectronic devices.

This study reports on electronic properties and cationic defects in the thin films of non-stoichiometric nickel oxide (NiOx) synthesized with plasma-enhanced atomic layer deposition (PEALD). Starting from nickel acetylacetonate [Ni(acac)2] as a metal-organic precursor, we employed water (P-W), ozone (P-Oz), and oxygen plasma (P-Ox) as oxidizing agents for direct plasma-enhanced ALD (DPALD) to evaluate their impact on the electronic structure of NiOx. The primary objective is to identify the most suitable oxidizing agent for producing NiOx films with optimal performance for hole transport layers (HTLs) in optoelectronic devices. Angle-resolved X-ray photoelectron spectroscopy (AR-XPS) confirmed the non-stoichiometric nature of our films. Measurements made at the 45 degrees takeoff angle revealed significant variations in the Ni2+/Ni3+ ratio depending on the oxidizing agent chosen, increasing from 0.80 (P-W) to 0.89 (P-Ox). This trend indicates improved defect formation control, permitting to achieve valence band shift of 0.98 eV for P-Ox sample relative to EV of MAPbI3. Additionally, reflection electron energy loss spectroscopy (REELS) revealed band gap narrowing from 3.53 eV (P-W) to 3.38 eV (P-Ox), suggesting enhancement of electronic properties. Band alignment analysis based on XPS and REELS data demonstrates that NiOx films synthesized with oxygen plasma exhibit favorable band alignment with MAPbI3 perovskite. Moreover, contact angle measurements reveal that subtle changes in defect chemistry affect the wettability of NiOx surfaces with respect to perovskite precursor solutions. Put together, these findings identify oxygen plasma-assisted synthesis as the most promising strategy for fabricating NiOx-based HTLs with superior electronic properties and advantageous interface characteristics, which are promising for the next-generation optoelectronic devices. This work emphasizes the importance of PEALD oxidazing agent choice for achieving a precise tailoring of NiOx electronic structure and enhancing the resulting device performance.

Lead iodide (PbI2) is a 2D layered semiconductor used in several electronic applications, such as solar cells, X-ray, and gamma-ray detectors. Most of its properties have been reported for monocrystals or polycrystalline thick films used in high-energy photon detectors. As for thin films used in other optoelectronic devices, the reported properties are limited to the conditions adopted in manufacturing the devices. Furthermore, very little is known about the properties of films deposited by sputtering. Here, we investigate the optical and structural properties of PbI2 thin films deposited by rf-sputtering a PbI2 target. The deposition temperature significantly influences the film's properties, as determined by X-ray, scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-vis, and Raman spectroscopy. A common characteristic at all temperatures was forming metallic lead (Pb) segregated in the surface of films, with concentration depending on the deposition temperature. These lead clusters were successfully converted into PbI2 using an iodination process, allowing the synthesis of pure PbI2 films without lead segregation. The activation energy for the reaction between Pb clusters and iodine vapor was determined by adopting the Arrhenius equation. It was also observed that converting PbI2 film into perovskite through the two-step process, by immersion of the PbI2 film into methylammonium iodide solution, transforms the segregated lead into perovskite. The sputtering technique allows the deposition of uniform films over large areas compatible with roll-to-roll processes, which are desired to produce large-area detectors and perovskite solar cells.

We use non-resonant Raman scattering to demonstrate a large enhancement of the effective refractive index experienced by Raman photons in a scattering medium comprising spatially-correlated photonic structures of core-shell TiO2@Silica scatterers mixed with silica nanoparticles and suspended in ethanol. We show that the high refractive index extends outside the physical boundary of the medium, which is attributed to the evanescent contributions of electromagnetic modes that are strongly localized within the medium. Notably, the effective enhancement can be observed even at very low intensities of Raman emission. This anomalous non-linear phenomenon could be explained by the successive polarization of valence electrons to virtual states induced by the strong photon correlations in the strongly localized electromagnetic modes. The enhancement of refractive index and its extension in the vicinity of the medium's interface provide new opportunities for controlling the electromagnetic fields in advanced photonic devices.

Interfacial defects at the buried junction between the electron transport layer (ETL) and perovskite absorber critically hinder the performance of perovskite solar cells (PSCs). In this work, we report that a CdS quantum dot (QD) interlayer, deposited onto SnO2 via a scalable successive ionic layer adsorption and reaction (SILAR) method, provides a practical and scalable strategy to improve charge transport across this interface. The CdS QD layer not only suppresses oxygen vacancies but also reacts with hydroxyl groups on the SnO2 surface, thereby improving surface potential uniformity and enhancing the electron extraction rate. Impedance spectroscopy further confirms improved interface homogeneity and charge transport, which correlate with higher fill factor and short-circuit current density. As a result, CdS modification enables a-25 % efficiency enhancement on PSCs, highlighting the potential of QD-based interfacial engineering towards high-performance PSCs.

In perovskite solar cells, understanding how transition metals penetrate the perovskite layer and affect its degradation and optoelectronic properties is crucial for designing more stable devices. Here, we combine experiments and density functional theory to investigate the interaction of Ni, Cu, Ag, and Au with MAPbI3. Our simulations show that Au and Ni spontaneously incorporate into MAPbI3, as revealed by their negative formation energies. Although Au, Cu, and Ag prefer interstitial configurations, Au behaves distinctly, indicating that the atomic radius plays a more decisive role than the valence configuration. Ni, in turn, preferentially substitutes Pb sites without introducing midgap states despite its partially filled 3d shell. Experimentally, X-ray photoelectron spectroscopy, current-voltage measurements, and UV-vis absorption reveal that all metals diffuse into MAPbI3, but only Ag and Cu form semiconductor halide phases that degrade device performance. In contrast, Au and Ni migrate without compromising optical absorption or charge transport, consistent with theoretical predictions. In general, these results highlight Au and Ni as promising contact materials for perovskite solar cells, as their incorporation avoids detrimental electronic or radiative effects compared to other metals.

The reduction processes of graphene oxide (GO) aim to remove functional groups such as H2O, CO, and CO2 to promote the properties of GO towards those of pure graphene. We adopted the thermal reduction process from room temperature to 320 °C. The transmission electron microscopy (TEM) technique was used to probe the effect of reduction mechanisms. It was observed that the plasmon peaks, referring to sp2 carbon bonds in crystalline structures, are more evident in the reduced graphene oxide (rGO) than GO. The fine structure at the K edge of carbon shows differences in shape linked to the density of states above the Fermi level. Electron energy loss spectroscopy (EELS) analyses revealed an increase in the fraction of sp3 bonds in the reduced sample, consistent with the reduction of functional radicals in the GO structure.

Raman spectroscopy is a powerful technique for studying the interaction between light and matter. Here we show a significant enhancement of Raman emission over a broad range of pumping wavelengths from strongly scattering media comprising spatially correlated photonic structures of core-shell TiO 2 @Silica scatterers mixed with silica nanoparticles and suspended in ethanol. Long-range Coulomb interactions between nanoparticles inside these photonic colloidal structures induce a correlation in the scatterers' positions (TiO 2 @Silica), affecting local and global photonic properties. The anomalous enhancement in Raman signal increases as the scattering strength is increased (through either scatterer concentration or pumping wavelength); however, the signal strength continues to behave linearly with excitation power, ruling out classical nonlinear and interferential phenomena. These observations may indicate strong photon correlation in strongly localized electromagnetic modes, inducing successive photon interactions with the atoms or molecules. Aside from the fundamental relevance to understanding measurable properties in this regime of strongly localized electromagnetic modes, our demonstration of strongly enhanced Raman emission over a broad range of pumping wavelengths provides new opportunities for the development of advanced photonic materials and devices. (c) 2024 Optica Publishing Group

We report on water (H2O) and carbon oxides (CO and CO2) effusion from multilayered graphene oxide (GO) films during thermal reduction. The effusion of molecules was monitored through the thermal desorption spectroscopy (TDS) technique in films prepared by evaporating a colloidal solution of GO. This method reduces the presence of adsorbed/trapped H2O molecules between adjacent GO planes. That allows the observation of additional effusion mechanisms. Thermal reduction process, from room temperature to 1000 °C, was performed in a high-vacuum system with a mass spectrometer to monitor the outgassed species. A collective outgassing of H2O, CO2, CO species is observed and centered at approximately 230 °C. Above 400 °C, CO2 and CO are the only observed outgassed species. Multiple origins for water outgassing were inferred from the TDS spectrum asymmetry, revealing an intricate superposition of mechanisms. The thermal treatment also reduces both the GO interlayer separation and the film surface roughness.

Metal contacts are an extremely important part of photovoltaic devices, since they might decrease device stability, or underperform in their function of current extraction. In the case of perovskite solar cells, the metallic component has been less investigated than other cell components, either in the back (rear) contact, or in the form of grid collectors in the front contact. The interaction between the perovskite layer and the metal contact is of utmost importance, since it has been demonstrated for gold and silver (most used metals in perovskite cells) that degradation processes might derive from unwanted contacts between the metal and the perovskite components. Herein, we present a systematic investigation of a series of metals typically used in the electronic or photovoltaic industries (Ag, Al, Au, Cu, Mo, Ni, Pd, Pt, and Ta) in order to assess their stability towards the processing steps of a typical perovskite cell assembly, and also when direct contact between the perovskite and the metal layer takes place. By assessing the morphological and electrical properties of the metal layer after performing a variety of tests, we observed that only four of those metals maintained their integrity. Based on the results, we point out which metal is expected to be most suitable one, from an industrial point of view, and to enable long-term device operation.

In recent years, aluminum-doped zinc oxide (AZO) has attracted much attention due to its high transmittance and low resistivity, which makes it an excellent candidate for various applications in photovoltaic field, photoelectric, and transparent electronic devices. However, producing an AZO film with a desirable electronic property is still a challenge. In this work, we demonstrate that AZO can be successfully deposited by the atomic layer deposition (ALD) technique. The results showed that it is possible to dope ZnO with aluminum through the ALD technique using multiple layers composed of ZnO and Al2O3. Films with transmittance above 80

This study presents an innovative dual-layer coating approach integrating titanium dioxide (TiO2) onto diamond-like carbon (DLC)-coated 316L stainless steel. The combination of PECVD-deposited DLC and ALD-deposited TiO2 aims to preserve the inherent tribological properties of DLC while mitigating UV-induced degradation. By leveraging the ability of TiO2 to absorb, reflect, and scatter UV light, this dual-layer strategy significantly enhances the durability of DLC coatings in radiation-prone environments. The effects of accelerated aging through UV exposure on DLC and DLC/TiO2 films were evaluated using an Accelerated Weathering Tester. Comprehensive analyses were conducted to assess the structural and mechanical properties before and after UV exposure, including Raman spectroscopy, profilometry, SEM, EDS, nanoindentation, and tribometry. The results demonstrate that the TiO2 layer effectively mitigates UV-induced damage, preserving the DLC film’s integrity and tribological performance even after 408 h of UV aging. Specifically, the DLC/TiO2 coatings maintained lower roughness, higher hardness, and better adhesion than DLC-only coatings under identical conditions. This research significantly advances protective coating technology by enhancing the durability and performance of DLC films, particularly in aerospace and other demanding industries where exposure to UV radiation is a critical concern.

Brazil has great potential for this type of energy generation due to its geographic location, allowing the development of viable photovoltaic (PV) projects in several regions. its use in places close to the sea has increased, with its use on boats and even resorts and hotels. This proximity to the sea requires attention to the local salinity, more precisely to the saline mist. This article will describe the methodology used to carry out the salinity resistance test of PV modules, choosing a specific classification of corrosive atmosphere according to the brazilian environment on the coast where the module will be placed in real conditions.

Strong enhancement of the Raman signal is observed in ethanol suspension of TiO 2 @Silica, being stronger as the TiO 2 @Silica filling fraction is increased above threshold, and when silica nanoparticles are added.

Polyurethane (PU) substrates are biocompatible materials widely used to manufacture endotracheal tubes. However, in common with other biomedical materials, they are liable to the formation of microbial films. The occurrence of pneumonia in intubated patients treated at intensive care units often takes the form of ventilator-associated pneumonia (VAP). The issue relates to the translocation of pathogenic microorganisms that colonize the oropharyngeal mucosa, dental plaque, stomach, and sinuses. New protective materials can provide a more effective therapeutic approach to mitigating bacterial films. This work concerns microcrystalline carbon film containing dispersed silver nanoparticles (μC-Ag) deposited on PU substrates using a physical vapor deposition sputtering process. For the first time, carbon paper was used to produce a carbon target with holes exposing a silver disk positioned under the carbon paper, forming a single target for use in the sputtering system. The silver nanoparticles were well distributed in the carbon film. The adherence characteristics of the μC-Ag film were evaluated using a tape test technique, and electron dispersive x-ray mapping was performed to analyze the residual particles after the tape test. The microbicidal effect of the thin film was also investigated using speciesS. aureus, a pathogenic microorganism responsible for most infections of the lower respiratory tract involving VAP and ventilator-associated tracheobronchitis (VAT). The results demonstrated that μC-Ag films on PU substrates are promising materials for mitigating pathogenic microorganisms on endotracheal tubes.

Graphene oxide (GO) reduced by thermal or chemical processes has been used in conductive transparent layers, solar cells, chemical sensors among dozens of other applications. Although some researchers have focused on identifying the reduction mechanisms, there is a lack of detailed investigation of species effusion processes. Here we report a systematic investigation on the effusion of chemical species from thermally reduced multilayered GO using the thermal desorption mass spectroscopy technique. The identification of chemical species with the use of the mass spectrometer associated with the formation energy was used to identify the reactions that occur in GO during the thermal reduction. This allows to give support or rule out numerous proposals for effusion processes in GO presented in the literature. It was observed that the main desorption regime centered at similar to 230 degrees C encompassed a collective desorption of H2O, CO2, CO, and H with formation energies ranging from 1.20 to 1.40 eV. For temperatures higher than 400 degrees C, uncoupled CO2 and CO desorptions were the only species detected, with formation energies of 1.87 and 3.09 eV, respectively. An insulating-conductive transition occurred in the annealing temperature range (ambient to 1000 degrees C) with a variation of 7 orders of magnitude in conductivity. The results support new routes for reducing GO in order to obtain films closer to pristine graphene multilayers.

Bismuth triiodide (BiI3) is a possible candidate to replace lead in perovskite-like materials for photovoltaic applications. Besides this applicability as an active layer in solar cells, BiI3 can also be converted, using methylammonium iodide, to the perovskite-like material MA3Bi2I9, that is also suitable for photovoltaic applications. Here we investigate the thermal stability of thermally evaporated BiI3 thin films annealead up to 150 °C in ambient atmosphere (in a closed oven in the absence of illumination). BiI3 films show similar X-ray diffratrograms with indexed peaks related to an R-3 rhombohedral crystal structure. The bandgaps of BiI3 thin films were determined by Tauc plots of transmittance data in UV-vis range and indicate a bandgap of 1.72 eV regardless of annealing temperature and suitable for photovoltaic applications. We verified that its morphological properties, observed through SEM images, are also not changed with respect to its annealing at temperatures up to 150 °C. Thereby, the structural, morphological and optical properties of annealing on thermally evaporated BiI3 are not considerably altered, the films retaining their properties when heated up to 150 °C, temperature higher than the operation temperature of solar cells and below the melting point of BiI3.

Titanium dioxide (TiO2) thin films have been widely used in transparent optoelectronic devices owing to their excellent optical properties also is used in photocatalysis, cosmetics, and many other biomedical applications. However, a lack of studies was published on microstructure and adherence comparison of the TiO2 deposited on both AISI substrates. In this work, TiO2 thin films were deposited onto AISI 304 and AISI 316L stainless steel (SS) substrates via atomic layer deposition. Its heterostructure, morphology, and adhesion were compared in both substrates looking for synergistic and multifunctional properties. Raman spectroscopy mapping and X-ray diffraction using the Rietveld refinement method showed that the films are composed of anatase and rutile phases in different percentages. Scratching tests were used to analyze the film adher-ence and friction between a diamond tip and TiO2 film, showing well adhered in both substrates.