Nanostructured composite electrode materials play a major role in the field of catalysis and electrochemistry. Self‐assembly of metallic nanoparticles on oxide supports via metal exsolution relies on the transport of reducible dopants towards the perovskite surface to provide accessible catalytic centers at the solid/gas interface. However, it is unclear if exsolution can be driven from the oxide bulk or if the process is limited to surfaces and interfaces, where strong electrostatic gradients and space charges typically control the properties of oxides. Here we reveal that the nature of the surface‐dopant interaction is the main determining factor for the exsolution kinetics of nickel in SrTi0.9Nb0.05Ni0.05O3‐ẟ and that the exsolution depth is strongly limited to the near‐surface region of the perovskite oxide. Electrostatic interaction of dopants with surface space charge regions forming upon thermal annealing result in strong surface passivation i.e. a retarded exsolution response. We furthermore demonstrate the controllability of the exsolution response via engineering of the perovskite surface chemistry. Our findings indicate that tailoring the electrostatic gradients at the perovskite surface is an essential step to improve exsolution type materials in catalytic converters.

Polysilicon (poly-Si) passivating contacts have enabled some of the highest lab-scale crystalline silicon (c-Si) solar cell conversion efficiencies, largely due to their excellent surface passivation quality, which can be aided by means of hydrogenation treatments. One frequently applied method is to use hydrogen-rich capping layers, such as Al2O3 or SiNx, which can provide hydrogen to the poly-Si/SiOx/Si interface upon annealing. In this work, the effect of the deposition conditions of the Al2O3 layers, fabricated by various types of atomic layer deposition (ALD), on the hydrogenation of p(+) poly-Si is investigated, and it is compared to the direct passivation of c-Si by the same Al2O3 layers. It is found that excellent hydrogenation of the p(+) poly-Si by Al2O3 could be reached by a wide range of ALD conditions, but higher annealing temperatures were required as compared to passivation of c-Si. The different ALD conditions result in Al2O3 layers with varying refractive indices, O/Al ratios, and hydrogen content, although these material properties become highly similar upon annealing. Furthermore, the p(+) poly-Si layer appears to act as a reservoir for hydrogen, which alters the hydrogen effusion profiles of the Al2O3 layers. The results show that a wide range of Al2O3 layers are highly suitable for hydrogenation of p(+) poly-Si and provide more insight into the hydrogenation process of poly-Si passivating contacts.

Double layers of deuterated and hydrogenated amorphous silicon (a‐Si:H) on glass are heated in the ambient by scanning with a green (532 nm) continuous wave laser. The hydrogen diffusion length in the laser spot is obtained from the deuterium (D)–hydrogen (H) interdiffusion measured by secondary ion mass spectrometry (SIMS), the temperature in the laser spot is obtained by calculation. Under certain conditions, detachment of the deuterated layer from the hydrogenated layer is observed in the SIMS depth profiles, visible by rising oxygen and carbon signals at the D/H interface attributed to in‐diffusion of atmospheric gas species like water vapor, oxygen, and carbon oxide. Stacks involving both undoped and boron‐doped a‐Si:H films show disintegration. The results suggest that the parameters leading to the disintegration effects are the presence of a plane of reduced material cohesion at the D/H interface, a sizeable H diffusion length and a rather high heating rate. Herein, it is likely considered that the observed layer disintegration process is involved in the peeling of a‐Si:H films upon fast heating. Furthermore, the results show that rapid laser heating can be used to detect planes of reduced material cohesion which may compromise the electronic properties of a‐Si:H‐based stacks.

The development of topography plays an important role when low-energy projectiles are used to modify the surface or analyze the properties of various materials. It can be a feature that allows one to create complex structures on the sputtered surface. It can also be a factor that limits depth resolution in ion-based depth profiling methods. In this work, we have studied the evolution of microdendrites on poly(methyl methacrylate) sputtered with a Cs 1 keV ion beam. Detailed analysis of the topography of the sputtered surface shows a sea of pillars with islands of densely packed pillars, which eventually evolve to fully formed dendrites. The development of the dendrites depends on the Cs fluence and temperature. Analysis of the sputtered surface by physicochemical methods shows that the mechanism responsible for the formation of the observed microstructures is reactive ion sputtering. It originates from the chemical reaction between the target material and primary projectile and is combined with mass transport induced by ion sputtering. The importance of chemical reaction for the formation of the described structures is shown directly by comparing the change in the surface morphology under the same dose of a nonreactive 1 keV xenon ion beam.

Passivation of semiconductor surfaces is crucial to reduce carrier recombination losses and thereby enhance the device performance of solar cells and other semiconductor devices. Thin-film stacks of phosphorus oxide (POx) and aluminum oxide (Al2O3) have recently been shown to provide excellent passivation of semiconductor surfaces, including crystalline silicon and indium phosphide, and can also be highly interesting for passivation of other semiconductor materials such as Ge and III-V semiconductors. On silicon, the excellent passivation is attributed to the combination of a high positive fixed charge and a very low interface defect density. On InP nanowires, application of the POx/Al2O3 stacks improves charge carrier lifetime threefold as compared to unpassivated nanowires. In this work, we review and summarize recent results obtained on POx/Al2O3 stacks for semiconductor surface passivation. Several topics are discussed, including the passivation performance on various semiconductor surfaces, the processing of the POx and Al2O3 layers, the role of the capping layer, and aspects related to device integration. The POx/Al2O3 stacks feature some unique properties, including an unusually high positive fixed charge density, a low interface defect density, and can be prepared over a wide deposition temperature range. These unique properties arise in part from the mixing process that occurs between the POx and Al2O3 layers, which upon post-deposition annealing leads to the formation of AlPO4. The surface passivation provided by POx/Al2O3 stacks is highly stable and the stack can be used to conformally coat high-aspect-ratio structures such as nanowires, showing their promise for use in semiconductor devices.

Due to the increasing number of applications for ceramic components in reactive etching processes, the interest in the specific erosion behavior of highly etch-resistant materials like yttrium oxide (Y2O3) has increased in the past years. Despite the large number of investigations already existing in this field, a more general understanding of the erosion mechanisms still lacks due to the limited comparability of these investigations. The huge difference in the kind of etching setups, processing parameters (bias voltage and plasma gas composition), and sample microstructures prevented consistent conclusions so far. To achieve a more general understanding, this study investigates the erosion behavior Y2O3 under a broad spectrum of plasma etching parameters. Therefore, the bias voltage is increased from 50 to 300 V and the plasma gas composition is gradually changed from Ar-rich to CF4-rich compositions. This systematic approach allows to directly correlate the morphology changes caused by plasma erosion with the related plasma etching parameters and enables to better understand their influence on the depth of physical and chemical interactions, surface damage, and etching rate. We discovered three distinct erosion regimes, which exhibit specific erosion characteristics. Using these observations, a schematic processing map for Y2O3 was developed, which could help to estimate the severity of the erosion attack dependent on the processing parameters.

Doping of Ni-rich cathode active materials with boron is a promising way to improve their cycling stability and mitigate their degradation, but it is still not understood how this effect is achieved and where the boron is located. To receive deeper insights into the impact of doping on atomic and microscale properties, B-doped Li[Ni0.8Co0.1Mn0.1]O-2 (NCM811) cathode materials were synthesized by a hydroxide coprecipitation as a model compound to verify the presence and location of boron in B-doped, Ni-rich NCM, as well as its impact on the microstructure and electrochemical properties, by a combined experimental and theoretical approach. Besides X-ray diffraction and Rietveld refinement, DFT calculation was used to find the preferred site of boron absorption and its effect on the NCM lattice parameters. It is found that boron shows a trigonal planar and tetrahedral coordination to oxygen in the Ni layers, leading to a slight increase in lattice parameter c through an electrostatic interaction with Li ions. Therefore, B-doping of NCM811 affects the crystal structure and cation disorder and leads to a change in primary particle size and shape. To experimentally prove that the observations are caused by boron incorporated into the NCM lattice, we detected, quantified, and localized boron in 2 mol % Bdoped NCM811 by ion beam analysis and TOF-SIMS. It was possible to quantify boron by NRA with a depth resolution of 2 mu m. We found a boron enrichment on the agglomerate surface but also, more importantly, a significant high and constant boron concentration in the interior of the primary particles near the surface, which experimentally verifies that boron is incorporated into the NCM811 lattice.

Defect-engineered or substoichiometric TiOx is of interest for use in photo- and electrocatalytic processes both as active material and catalyst support. Electrochemical doping of TiO2 via cathodic polarization is an appealing preparation method and frequently employed. Here, we explored the electrochemical preparation of TiOx in an undivided cell using iridium-based (iridium mixed-metal-oxide) and boron doped diamond (BDD) counter electrodes. Cyclic voltammetry and impedance spectroscopy revealed superior charge transfer properties of crystalline TiOx electrodes prepared with BDD (TiOx-BDD). It is shown that the electrochemical properties correlate well with intensities of the H-signals determined using Time of Flight - Secondary Ion Mass Spectrometry (ToF-SIMS). Thus, it is concluded that electrochemical preparation using BDD causes favourable H+ intercalation and/or H diffusion into the sub-surface layers of TiOx. Our extensive analysis using a combination of electrochemical and surface characterization (LEIS and XPS) techniques, additionally suggests that cathodic deposition of Ir, originating from the Ir-based counter electrode, present in sub-ppm concentrations only results in less-efficient doping. Instead in the presence of sub-ppm level Ir contamination hydrogen evolution is favoured during cathodic polarization. The results presented within this study highlight the necessity to use inherently stable counter electrodes for electrochemical preparation and reveal the pronounced influence of trace contamination in electrochemistry in general and the doping mechanism of TiOx electrodes in particular.

Exsolution phenomena are highly debated as efficient synthesis routes for nanostructured composite electrode materials for the application in solid oxide cells (SOCs) and the development of next-generation electrochemical devices for energy conversion. Utilizing the instability of perovskite oxides, doped with electrocatalytically active elements, highly dispersed nanoparticles can be prepared at the perovskite surface under the influence of a reducing heat treatment. For the systematic study of the mechanistic processes governing metal exsolution, epitaxial SrTi0.9Nb0.05Ni0.05O3-δ thin films of well-defined stoichiometry are synthesized and employed as model systems to investigate the interplay of defect structures and exsolution behavior. Spontaneous phase separation and the formation of dopant-rich features in the as-synthesized thin film material is revealed by high-resolution transmission electron microscopy (HR-TEM) investigations. The resulting nanostructures are enriched by nickel and serve as preformed nuclei for the subsequent exsolution process under reducing conditions, which reflects a so far unconsidered process drastically affecting the understanding of nanoparticle exsolution phenomena. Using an approach of combined morphological, chemical, and structural analysis of the exsolution response, a limitation of the exsolution dynamics for nonstoichiometric thin films is found to be correlated to a distortion of the perovskite host lattice. Consequently, the incorporation of defect structures results in a reduced particle density at the perovskite surface, presumably by trapping of nanoparticles in the oxide bulk.

The thermal stability of thick (≈4 μm) plasma‐grown hydrogenated amorphous silicon (a‐Si:H) layers on glass upon application of a rather rapid annealing step is investigated. Such films are of interest as precursor layers for laser liquid‐phase crystallized silicon solar cells. However, at least half‐day annealing at T ≈550 °C is considered to be necessary so far to reduce the hydrogen (H) content and thus avoid blistering and peeling during the crystallization process due to H. By varying the deposition conditions of a‐Si:H, layers of rather different thermal stability are fabricated. Changes in the surface morphology of these a‐Si:H layers are investigated using scanning electron microscopy and profilometry measurements. Hydrogen effusion, secondary‐ion mass spectrometry (SIMS) depth profiling, and Raman spectroscopy measurements are also carried out. In summary, amorphous silicon precursor layers are fabricated that can be heated within 30 min to a temperature of 550 °C without peeling and major surface morphological changes. Successful laser liquid‐phase crystallization of such material is demonstrated. The physical nature of a‐Si:H material stability/instability upon application of rapid heating is studied.

Sodium is a promising candidate for stationary storage applications, especially when the demand for lithium-ion batteries increases due to electromobility applications. Even though its energy density is lower, Na-ion technology is estimated to lead to a cost reduction of 30% compared to Li-ion technology. To improve safety as well as energy density, Na-based all-solid-state-batteries featuring solid electrolytes such as beta-alumina and sodium superionic conductors and cathode materials such as Na3V2(PO4)3 and NaxCoO2 have been developed over the past years. However, the biggest challenge are mixed cathodes with highly conductive interfaces, especially when co-sintering the materials. For example, a promising sodium superionic conductor type Na3Zr2Si2PO12 electrolyte sinters at 1,250°C, whereas the corresponding Na3V2PO12 cathode decomposes at temperatures higher than 900°C, posing a bottleneck. Thus in this paper, we synthesized Na0.62 [Ni0.10Fe0.10Mn0.80]O2 as cathode material for all-solid-state sodium-ion batteries via a relatively cheap and easy solution-assisted solid state reaction processing route. The thermal investigations of the pure cathode material found no degradation up to 1,260°C, making it a perfect match for Na3.4Zr2Si2.4P0.6O12 electrolyte. In our aim to produce a co-sintered mixed cathode, electron microscopy investigation showed a highly dense microstructure and the elemental mapping performed via energy dispersive X-ray spectroscopy and secondary ion mass spectrometry confirm that Na3.4Zr2Si2.4P0.6O12 and Na0.62 [Ni0.10Fe0.10Mn0.80]O2 do not react during sintering. However, the active cathode material forms a sodium rich and a sodium deficient phase which needs further investigation to understand the origin and its impact on the electrochemical performance.

Herein, the application of laser radiation to locally modify the hydrogen distribution within hydrogenated amorphous silicon films on a short time scale is studied. The impact of laser power and irradiation time on the temperature of the silicon layer during the laser treatment and the hydrogen outdiffusion is analyzed. Moreover, the resulting optoelectronic properties of the amorphous silicon are examined. On a timescale of a few seconds or less, the hydrogen concentration in the near‐surface region of the silicon layer can be successfully decreased without major impact on the optoelectronic properties.

•13CD4 co-deposits from EAST D- and He-plasma tracer injection.•1.4 MeV deuteron ion beam analysis in ≈ 3000 points on about 8500 mm2.•24% (D plasma) and 16% (He plasma) deposition efficiency.•98% of 13C found within 20 mm around the injection hole.•D-NRA yields additional physics via D/C ratios, ExB correlation and fall-off length.

Germanium-tin (GeSn) alloys have emerged as a promising material for future optoelectronics, energy harvesting, and nanoelectronics owing to their direct band gap and compatibility with existing Si-based electronics. Yet, their metastability poses significant challenges calling for in-depth investigations of their thermal behavior. With this perspective, this work addresses the interdiffusion processes throughout thermal annealing of pseudomorphic GeSn binary and SiGeSn ternary alloys. In both systems, the initially pseudomorphic layers are relaxed upon annealing exclusively via thermally induced diffusional mass transfer of Sn. Systematic postgrowth annealing experiments reveal enhanced Sn and Si diffusion regimes that manifest at temperatures below 650 degrees C. The amplified low-temperature diffusion and the observation of only subtle differences between binary and ternary hint at the unique metastability of the Si-Ge-Sn material system as the most important driving force for phase separation.

Y. Wang,1,2 M. Schnedler ,1,* Q. Lan,1,3 F. Zheng,3 L. Freter ,1,2 Y. Lu,3 U. Breuer ,4 H. Eisele,5 J.-F. Carlin,6 R. Butté ,6 N. Grandjean,6 R. E. Dunin-Borkowski ,1,3 and Ph. Ebert 1,† 1Peter Grünberg Institut, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany 2Lehrstuhl für Experimentalphysik IV E, RWTH Aachen University, 52056 Aachen, Germany 3Ernst Ruska Centrum, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany 4Zentralinstitut für Engineering, Elektronik und Analytik (ZEA-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany 5Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany 6Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland

Future development of the modern nanoelectronics and its flagships internet of things, artificial intelligence, and neuromorphic computing is largely associated with memristive elements, offering a spectrum of inevitable functionalities, atomic level scalability, and low-power operation. However, their development is limited by significant variability and still phenomenologically orientated materials' design strategy. Here, we highlight the vital importance of materials' purity, demonstrating that even parts-per-million foreign elements substantially change performance. Appropriate choice of chemistry and amount of doping element selectively enhances the desired functionality. Dopant/impurity-dependent structure and charge/potential distribution in the space-charge layers and cell capacitance determine the device kinetics and functions. The relation between chemical composition/purity and switching/neuromorphic performance is experimentally evidenced, providing directions for a rational design of future memristive devices.

Parasitic absorption and limited fill factor (FF) brought in by the use of amorphous silicon layers are efficiency-limiting challenges for the silicon heterojunction (SHJ) solar cells. In this work, postdeposition phosphorus (P) catalytic doping (Cat-doping) on intrinsic amorphous silicon (a-Si:H(i)) at a low substrate temperature was carried out and a P concentration of up to 6 × 1021 cm-3 was reached. The influences of filament temperature, substrate temperature, and processing pressure on the P profiles were systemically studied by secondary-ion mass spectrometry. By replacing the a-Si:H(n+er with P Cat-doping of an a-Si:H(i) layer, the passivation quality was improved, reaching an iVOC of 741 mV, while the parasitic absorption was reduced, leading to an increase in JSC by ∼1 mA/cm2. On the other hand, the open-circuit voltage and the FF of a conventional SHJ solar cell (with the a-Si:H(n) layer) can be improved by adding a Cat-doping process on the a-Si:H(i) layer, resulting in an increase in FF by 4.7%abs and in efficiency by 1.5%abs.

Tungsten-chromium-yttrium (WCrY) smart alloys are foreseen as first wall materials for future fusion devices such as DEMO. While suppressing W oxidation during accidental conditions, they should behave like pure W during plasma operation due to preferential sputtering of the lighter alloying elements Cr and Y causing W enrichment at the surface. This paper reports on the results of the simultaneous exposure of WCrY and pure W reference samples to mixed D.+.1%Ar+5 %He plasma in the linear plasma device PSI-2. Further, a comparison with exposures to pure D and D + 1 %Ar plasma is made. At incident ion energies of 120 eV, exposure to pure D plasma results in a W-enriched alloy surface due to the preferential sputtering of Cr and Y, while the addition of Ar leads to enhanced erosion for W and WCrY and reduces the W enrichment in smart alloys. With the addition of He to the plasma, erosion of WCrY is enhanced compared to that of pure W. To investigate the plasma impact on the oxidation behaviour, plasma-exposed and reference samples were oxidised in controlled dry oxygen-containing atmosphere at 1000 degrees C. The sample geometry has a great impact on the oxidation behaviour. Yet, it can be shown that the good oxidation-suppressing properties of WCrY smart alloys are preserved during plasma exposure.

Herein, the effectiveness of post‐deposition catalytic‐doping (cat‐doping) on various doped silicon alloys, i.e., microcrystalline silicon (μc‐Si:H), nanocrystalline silicon oxide (nc‐SiOx:H), and microcrystalline silicon carbide (μc‐SiC:H), for the use in silicon heterojunction solar cells is investigated. Phosphorous (P) profiles by secondary ion mass spectrometry (SIMS) reveal the P distribution and its difference in these three silicon alloy films. Conductivity and effective charge carrier lifetime of different samples are found to increase to different extents after cat‐doping process. Coexistence of thermal annealing, hydrogenation, and phosphorus doping is confirmed by using different gases during the cat‐doping process.

The interface between electronic components and biological objects plays a crucial role in the success of bioelectronic devices. Since the electronics typically include different elements such as an insulating substrate in combination with conducting electrodes, an important issue of bioelectronics involves tailoring and optimizing the interface for any envisioned applications. In this paper, we present a method for functionalizing insulating substrates (SiO2) and metallic electrodes (Pt) simultaneously with a stable monolayer of organic molecules ((3-aminopropyl)triethoxysilane (APTES)). This monolayer is characterized by high molecule density, long-term stability, and positive surface net charge and most likely represents a self-assembled monolayer (SAM). It facilitates the conversion of biounfriendly Pt surfaces into biocompatible surfaces, which allows cell growth (neurons) on both functionalized components, SiO2 and Pt, which is comparable to that of reference samples coated with poly-L-lysine (PLL). Moreover, the functionalization greatly improves the electronic cell-chip coupling, thereby enabling the recording of action potential signals of several millivolts at APTES-functionalized Pt electrodes.