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Nucleation and early growth of Li metal is critical to the performance of anode-free solid-state batteries. We report the use of amorphous carbon deposited by direct current magnetron sputtering as an intermediate layer between the Cu current collector and the Lipon solid electrolyte. The density, conductivity, and microstructure of the carbon interlayer are varied and their influence on the reversible formation and removal of the Li metal anode is investigated. It is shown that thin films of amorphous carbon act as seed layers, reducing the overpotential for Li plating and increasing the critical current density for Li plating and stripping from 2 up to 8 mA cm

Aluminum oxynitride (Al-O-N) is a material suitable for hard, transparent thin films. Its physical properties and structure can be adjusted through the O-to-N ratio. Reactive Direct Current Magnetron Sputtering (R-DCMS) is a practical, widespread technique for the deposition of coatings. However, it proves to be challenging in the case of Al-O-N. The reason for this is the high reactivity of O2. Poisoning of Al targets by O2 causes formation of insulating oxide islands and consequently leads to target destruction and a failure of the deposition process. Here, we show that with two separate gas inlets for the two reactive gases, a good process stability can be achieved over the entire range of O-to-N ratios.

An in-situ coil implemented in a confocal magnetron sputtering system is used to modify the ion flux impacting the substrate, thereby tuning the ion-to-neutral ratio. Plasma characterization performed at the substrate is used to map the spatial dependence of the ion flux density and the total energy flux density across the substrate holder. In addition, spatially-resolved temperature measurements are performed for different plasma conditions. Aluminum nitride (AlN) thin films were deposited by reactive sputtering in the fully poisoned mode on Si (100) and borosilicate glass substrates using the open field configuration. Texture, growth morphology, and residual stress of the films were determined and correlated with the plasma conditions and substrate temperatures obtained by applying the coil's magnetic field. All AlN films were stoichiometric and showed a hexagonal structure with (001) texture. The film stress was found to change from 0.9 GPa (tensile) to 4 GPa (compressive) with increasing ion flux density. Electron microscopy revealed an evolution from an open grain boundary to a dense film morphology compatible with the observed residual stress dependence of the films on the ion flux. No change in residual stress and film morphology was observed within the 100 °C–500 °C temperature range used here.

Biofilms causing medical conditions or interfering with technical applications can prove undesirably resistant to silver nanoparticle (AgNP)-based antimicrobial treatment, whereas beneficial biofilms may be adversely affected by the released silver nanoparticles. Isolated biofilm matrices can induce reduction of silver ions and stabilization of the formed nanosilver, thus altering the exposure conditions. We thus study the reduction of silver nitrate solution in model experiments under chemically defined conditions as well as in stream biofilms. Formed silver nanoparticles are characterized by state-of-the art methods. We find that isolated biopolymer fractions of biofilm organic matrix are capable of reducing ionic Ag, whereas other isolated fractions are not, meaning that biopolymer fractions contain both reducing agent and nucleation seed sites. In all of the investigated systems, we find that silver nanoparticle–biopolymer interface is dominated by carboxylate functional groups. This suggests that the mechanism of nanoparticle formation is of general nature. Moreover, we find that glucose concentration within the biofilm organic matrix correlates strongly with the nanoparticle formation rate. We propose a simple mechanistic explanation based on earlier literature and the experimental findings. The observed generality of the extracellular polymeric substance/AgNP system could be used to improve the understanding of impact of Ag+ on aqueous ecosystems, and consequently, to develop biofilm-specific medicines and bio-inspired water decontaminants.

Advancements in the design of mechanical blood circulatory devices have greatly improved patient survival rates, but currently employed metals still provoke a thrombosis response upon contact with blood, with potential life-threatening consequences. While coating strategies have been developed to address this limitation, they possess inherent drawbacks such as susceptibility to crack formation and delamination. Herein, an amorphous metal based on palladium (Pd) is scrutinized and reveals substantial thrombogenic resistance compared to a state-of-the-art titanium alloy. In vitro assessment with human whole blood shows that the Pd glass provokes reduced platelet activation (lower expression of CD62P, CD41/CD61) and greatly retarded fibrin formation, but pronounced platelet spreading therewith challenging the dogma that platelet spreading equals activation. Mechanistic analysis of the early biomaterial–blood interactions reveals that conformational changes of adhered fibrinogen, and modified αIIbβ3 integrin expression and distribution across adhered platelets, underlay the superior performance of Pd glass. The study is accompanied by structural and thermophysical bulk investigations and physicochemical surface characterization to link the materials properties with the observed blood response. The results reveal a remarkable potential of Pd-based glass as direct blood-contacting bulk material without the need for coating., Advanced Functional Materials, 32 (4), ISSN:1616-3028, ISSN:1616-301X

Optically transparent, colorless Al-O-N and Al-Si-O-N coatings with discretely varied O and Si contents were fabricated by reactive direct current magnetron sputtering (R-DCMS) from elemental Al and Si targets and O2 and N2 reactive gases. The Si/Al content was adjusted through the electrical power on the Si and Al targets, while the O/N content was controlled through the O2 flow piped to the substrate in addition to the N2 flow at the targets. The structure and morphology of the coatings were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM), while the elemental composition was obtained from Rutherford backscattering spectrometry (RBS) and heavy ion elastic recoil detection analysis (ERDA). The chemical states of the elements in the coatings were analyzed by X-ray photoelectron spectroscopy (XPS). Based on analytical results, a model describing the microstructural evolution of the Al-O-N and also previously studied Al-Si-N [1, 2, 3, 4] coatings with O and Si content, respectively, is established. The universality of the microstructural evolution of these coatings with the concentration of the added element is attributed to the extra valence electron (e–) that must be incorporated into the AlN wurtzite host lattice. In the case of Al-O-N, this additional valence charge arises from the e – acceptor O replacing N in the AlN wurtzite lattice, while the e – donor Si substituting Al fulfills that role in the Al-Si-N system. In view of future applications of ternary Al-O-N and quaternary Al-Si-O-N transparent protective coatings, their mechanical properties such as residual stress (σ), hardness (HD) and Young’s modulus (E) were obtained from the curvature of films deposited onto thin substrates and by nanoindentation, respectively. Moderate compressive stress levels between −0.2 and −0.5 GPa, which suppress crack formation and film-substrate delamination, could be obtained together with HD values around 25 GPa.

In this work we prepare Langmuir-Blodgett monolayers with a trifunctional amphiphilic anthraphane monomer. Upon spreading at the air/water interface, the monomers self-assemble into 1 nm-thin monolayer islands, which are highly fluorescent and can be visualized by the naked eye upon excitation. In situ fluorescence spectroscopy indicates that in the monolayers, all the anthracene units of the monomers are stacked face-to-face forming excimer pairs, whereas at the edges of the monolayers, free anthracenes are present acting as edge groups. Irradiation of the monolayer triggers [4 + 4]-cycloadditions among the excimer pairs, effectively resulting in a two-dimensional (2D) polymerization. The polymerization reaction also completely quenches the fluorescence, allowing to draw patterns on the monomer monolayers. More interestingly, after transferring the monomer monolayer on a solid substrate, by employing masks or the laser of a confocal scanning microscope, it is possible to arbitrarily select the parts of the monolayer that one wants to polymerize. The unpolymerized regions can then be washed away from the substrate, leaving 2D macromolecular monolayer objects of the desired shape. This photolithographic process employs 2D polymerizations and affords 1 nm-thin coatings.

Local contact damage as well as cohesive and adhesive failure can limit the lifetime and applicability of hydrogenated diamond-like carbon (DLC) films on metallic substrates. DLC on titanium (Ti) is very interesting for industrial applications (e.g. biomedical applications), while also an excellent model system for the general understanding of hard and brittle films on ductile metallic substrates. Interlayers deposited between the DLC film and the Ti substrate have been shown to affect failure of such DLC coated Ti substrates. In this study, the effect of interlayer structure on contact damage and cohesive and adhesive failure is studied with tantalum (Ta) in its α- and β-phase. In all investigated cases the more ductile α-Ta provides improved results over the hard and brittle β-Ta interlayer. Due to plastic deformation effects, the resistance to contact damage is significantly increased with an α-Ta interlayer. Delamination occurs at the interface between the Ti substrate and the Ta interlayer. Compared to DLC on Ti without a Ta interlayer no enhancement in onset strain of fragmentation and delamination was achieved. A finite-element analysis shows that stress concentrations can be distributed over both interfaces if the Young's modulus of the interlayer material is of the order of the Young's modulus of the DLC.

Coupling of Earth-abundant hydrogen evolution catalysts to photoabsorbers is crucial for the production of hydrogen fuel using sunlight. In this work, we demonstrate the use of magnetron sputtering to deposit Mo2C as an efficient hydrogen evolution reaction catalyst onto surface-protected amorphous silicon (a-Si) photoabsorbers. The a-Si/Mo2C photocathode evolves hydrogen under simulated solar illumination in strongly acidic and alkaline electrolytes. Onsets of photocurrents are observed at potentials as positive as 0.85 V vs RHE. Under AM 1.5G (1 sun) illumination, the photocathodes reach current densities of -11.2 mA cm(-2) at the reversible hydrogen potential in 0.1 M H2SO4 and 1.0 M KOH. The high photovoltage and low-cost of the Mo2C/a-Si assembly make it a promising photocathode for solar hydrogen production.

Friction and wear minimizing coatings are crucial for applications in combustion engines and medical implants. Their performance is typically limited by mechanical failure especially due to local overload. In this work, the contact damage creation, evolution, and final morphology of hydrogenated diamond-like carbon (DLC)-coated titanium (Ti) substrates are investigated. The influence of the DLC film thickness and the elastic–plastic deformation of the Ti on the contact damage are studied by microindentation and static finite-element analysis. Film thickness, indenter radius, and applied load as well as the elastic–plastic deformation of the Ti are shown to significantly affect contact damage. A failure plot is presented with the location of first failure in the DLC and compared to the experimental observation. In addition, a case study with variable fracture toughness of the DLC and its influence on the failure plot is shown. The stress distribution in the DLC follows a transition from a membrane-like to a plate-like deformation behavior upon increasing the DLC film thickness. Thin DLC films reveal increased cracking in the inner zone of the indent, while thicker DLC films reveal pronounced edge cracking. These edge cracks were correlated to pop-ins in force–displacement curves upon microindentation. Finally, a film thickness optimization process is presented for hard and brittle films on soft and ductile metallic substrates.

Using the model system hydrogenated diamond-like carbon (a-C:H) on titanium (Ti) substrates the effect of a changing film thickness on the cohesive and adhesive failure of hard and brittle films on ductile metallic substrates is analyzed by uniaxial loading. A film thickness size effect has been observed for the fracture strength and the onset strain of delamination. For a a-C:H film thickness 1 μm, whereas for film thicknesses of 200 and 500 nm the effect of the strain is only secondary. Upon uniaxial loading the Ti substrate exhibits an anisotropic deformation which affects the cohesive and adhesive failure of thin a-C:H films. The energy release rates for cohesive and adhesive failure and the fracture toughness of a-C:H are all independent of film thickness. The corresponding values have been determined to be 63.5 ± 2.6 J m −2 , 579 ± 20 J m −2 and 3.2 ± 0.1 MPa m 1/2 , respectively. Finally, a schematic is presented to determine qualitatively the adhesion of ductile and moderately brittle films on any kind of substrate.

This overview article on diamond-like carbon (DLC) coatings in medical applications covers the interaction of cells and tissue with DLC and alloyed DLC to generate desired cell reactions as well as the release of toxic elements. The promising in vitro results of DLC to prevent thrombus formation in vascular applications are summarized and the problems of transferring these results to in vivo applications are described. Since DLC shows extremely low wear in technical applications, a desired implementation is also to build wear particle free, articulating joint replacements by coating the bearing surfaces. Several in vivo studies using DLC coatings on articulating joints resulted in a failure due to partial coating delamination some years after implantation. It will be shown that this delayed delamination was caused by crevice corrosion (CC) of the adhesion-promoting interlayer and the reason why different corrosion processes may prevent an easy transfer of a successful technical application of DLC onto an implant will be discussed. The main issue for successful, long-term, in vivo applications of DLC coatings on implants is to predict the in vivo survival time and especially the long-term adhesion stability of the coating. The formation at the interface of a few atomic layers of reaction products, usually a metal-carbide, will be addressed. Furthermore, any contamination from residual gas or any cross contamination will result in a different reactively formed interface material with different properties. Delamination can then occur by a slowly advancing crack in this thin carbidic layer governed by the laws of stress corrosion cracking (SCC). It will be shown that if a stable coating adhesion is obtained, DLC coated articulating implants show basically no wear of the coating up to 101 million articulations on a simulator corresponding to about 101 years of in vivo articulation.

Diamond-like carbon (DLC) coatings are known to have extremely low wear in many technical applications. The application of DLC as a coating has aimed at lowering wear and to preventing wear particle-induced osteolysis in artificial hip joints. In a medical study femoral heads coated with diamond-like amorphous carbon, a subgroup of DLC, articulating against polyethylene cups were implanted between 1993 and 1995. Within 8.5 years about half of the hip joints had to be revised due to aseptic loosening. The explanted femoral heads showed many spots of local coating delamination. Several of these explanted coated TiAlV femoral heads have been analyzed to investigate the reason for this failure. Raman analysis and X-ray photoelectron spectroscopy (XPS) depth profiling showed that the coating consists of diamond-like amorphous carbon, several Si-doped layers and an adhesion-promoting Si interlayer. Focused ion beam (FIB) transverse cuts revealed that the delamination of the coatings is caused by in vivo corrosion of the Si interlayer. Using a delamination test set-up dissolution of the silicon adhesion-promoting interlayer at a speed of more than 100 μm year−1 was measured in vitro in solutions containing proteins. Although proteins are not directly involved in the corrosion reactions, they can block existing small cracks and crevices under the coating, hindering the exchange of liquid. This results in a build-up of crevice corrosion conditions in the crack, causing a slow dissolution of the Si interlayer.

Unwanted physiological reactions, caused by particle release in articulating joints, are still a major concern in total hip arthroplasty. Diamond-like carbon coatings (DLC) show very low wear values in many technical applications. Attempts to transfer these outstanding tribological properties to in-vivo load bearing articulating joints turned out to be extremely problematic. A DLC coated metallic metatarsophalangeal (MTP) prosthesis, with both articulating surfaces coated, was explanted after approximately 4 years. The DLC-coating was removed from the entire face of the phalangeal component and from most of the face of the metatarsal component. It appeared that the coating was scratched and then delaminated parallel to the scratches. To retrospectively investigate the reason for the in-vivo failure, the explanted prosthesis was analyzed by X-ray photoelectron spectroscopy (XPS) depth profiling and cross sectional scanning electron microscope (SEM) analysis. The coating consisted of an approximately 180 nm thick DLC film and a circa 120 nm thick silicon based adhesion promoting interlayer on a CoCrMo base material. SEM observation of transversal cuts showed that the delamination of the DLC-coatings was mainly caused by a slow in-vivo corrosion of the whole Si interlayer due to crevice corrosion. Additionally, a weak mechanical bond between the CoCrMo substrate and the Si-based interlayer further facilitated the access of body liquid below the Si interlayer. The instability of Si toward crevice corrosion was also demonstrated by a separate crevice experiment using silicon single crystals.

A 5 nm Mo2C film is deposited on an amorphous Si photocathode by confocal magnetron co-sputtering.

Diamond like carbon (DLC) coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the orthopaedic field, layer performance, stability and adhesion in physiologically relevant setups are crucial and not consistently investigated. In vitro wear testing as well as adequate corrosion tests of interfaces and interlayers are of great importance to verify the long term stability of DLC coated load bearing implants in the human body. DLC coatings were deposited on articulating lumbar spinal disks made of CoCr28Mo6 biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD) process. As an adhesion promoting interlayer, tantalum films were deposited by magnetron sputtering. Wear tests of coated and uncoated implants were performed in physiological solution up to a maximum of 101 million articulation cycles with an amplitude of ±2° and −3/+6° in successive intervals at a preload of 1200 N. The implants were characterized by gravimetry, inductively coupled plasma optical emission spectrometry (ICP-OES) and cross section scanning electron microscopy (SEM) analysis. It is shown that DLC coated surfaces with uncontaminated tantalum interlayers perform very well and no corrosive or mechanical failure could be observed. This also holds true in tests featuring overload and third-body wear by cortical bone chips present in the bearing pairs. Regarding the interlayer tolerance towards interlayer contamination (oxygen), limits for initiation of potential failure modes were established. It was found that mechanical failure is the most critical aspect and this mode is hypothetically linked to the α-β tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD). It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs. ceramic., International Journal of Molecular Sciences, 15 (6), ISSN:1422-0067

The exchange-bias effect provides unidirectional anisotropy to ferromagnetic thin-films in GMR and TMR sensors. It is weak because it relies on an inherently compensated coupling across a ferromagnet/antiferromagnet interface. We replace the antiferromagnet with a TbFe-based perpendicular-anisotropy amorphous ferrimagnet, coupling to an adjacent ferromagnet with 13-5 mJ/m2 for temperatures within 7.9–280 K. A large exchange-bias between 1.1 and 0.7 T in that temperature range ensues. The temperature dependence of the bias is step-like, and thus different from that of antiferromagnet-based exchange-bias systems. It suggests using this material in exchange-biased temperature assisted magnetic writing.

Solution-processed lead sulfide quantum dots (PbS QDs) are very attractive as NIR-active semiconductors for the fabrication of cost-efficient optoelectronic devices. To control the thin film carrier transport, as well as stability, surface passivation is of crucial importance. Here, we present the successful surface passivation of PbS QDs by the formamidinium lead iodide (FAPbI(3)) ligand. An effective procedure for the fabrication of FAPbI(3)-passivated PbS QDs through a binary-phase ligand exchange protocol in hexane and n-methylformamide is demonstrated. It is shown that this solution-processed ligand exchange drastically changes the photoluminescence intensity, exciton recombination dynamics, and carrier lifetime of the nanocrystals. The solution casting of the ligand-exchanged nanocrystals into thin films results in the periodic ordering of QDs in a square superlattice with close contacts. Planar graphene/QD photodetectors fabricated with PbS QDs passivated with FAPbI(3) show substantially increased thermal stability as compared to similar devices using PbS QDs passivated with commonly used methylammonium lead iodide.