The reproducible low-cost fabrication of functional metal-polymer nanocomposites with tailored optoelectronic properties for advanced applications remains a major challenge in applied nanotechnology. To obtain full control over the nanostructural evolution at the metal-polymer interface and its impact on optoelectronic properties, we employed combined in situ time-resolved microfocus grazing incidence small angle X-ray scattering (μGISAXS) with in situ UV/vis specular reflectance spectroscopy (SRS) during sputter deposition of gold on thin polystyrene films. On the basis of the temporal evolution of the key scattering features in the real-time μGISAXS experiment, we directly observed four different growth regimes: nucleation, isolated island growth, growth of larger aggregates via partial coalescence, and continuous layer growth. Moreover, their individual thresholds were identified with subnanometer resolution and correlated to the changes in optical properties. During sputter deposition, a change in optical reflectivity of the pristine gray-blue PS film was observed ranging from dark blue color due to the presence of isolated nanoclusters at the interface to bright red color from larger Au aggregates. We used simplified geometrical assumptions to model the evolution of average real space parameters (distance, size, density, contact angle) in excellent agreement with the qualitative observation of key scattering features. A decrease of contact angles was observed during the island-to-percolation transition and confirmed by simulations. Furthermore, a surface diffusion coefficient according to the kinetic freezing model and interfacial energy of Au on PS at room temperature were calculated based on a real-time experiment. The morphological characterization is complemented by X-ray reflectivity, optical, and electron microscopy. Our study permits a better understanding of the growth kinetics of gold clusters and their self-organization into complex nanostructures on polymer substrates. It opens up the opportunity to improve nanofabrication and tailoring of metal-polymer nanostructures for optoelectronic applications, organic photovoltaics, and plasmonic-enhanced technologies.

The reproducible low-cost fabrication of functional polymer-metal interfaces via self-assembly is of crucial importance in organic electronics and organic photovoltaics. In particular, submonolayer and nanogranular systems expose highly interesting electrical, plasmonic, and catalytic properties. The exploitation of their great potential requires tailoring of the structure on the nanometer scale and below. To obtain full control over the complex nanostructural evolution at the polymer-metal interface, we monitor the evolution of the metallic layer morphology with in situ time-resolved grazing-incidence small-angle X-ray scattering during sputter deposition. We identify the impact of different deposition rates on the growth regimes: the deposition rate affects primarily the nucleation process and the adsorption-mediated growth, whereas rather small effects on diffusion-mediated growth processes are observed. Only at higher rates are initial particle densities higher due to an increasing influence of random nucleation, and an earlier onset of thin film percolation occurs. The obtained results are discussed to identify optimized morphological parameters of the gold cluster ensemble relevant for various applications as a function of the effective layer thickness and deposition rate. Our study opens up new opportunities to improve the fabrication of tailored metal-polymer nanostructures for plasmonic-enhanced applications such as organic photovoltaics and sensors.

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Ultra-thin metal layers on polymer thin films attract tremendous research interest for advanced flexible optoelectronic applications, including organic photovoltaics, light emitting diodes and sensors. To realize the large-scale production of...

We report a method of growing a diamond layer via chemical vapour deposition (CVD) utilizing a mixture of microdiamond and nanodiamond seeding to give a low effective thermal boundary resistance (TBReff) for heat-spreading applications in high-frequency, high-power electronic devices. CVD diamond was deposited onto thin layers of both GaN and AlN on Si substrates, comparing conventional nanodiamond seeding with a two-step process involving sequential seeding with microdiamond then nanodiamond. Thermal properties were determined using transient thermoreflectance (TTR), and the samples were also analysed with SEM and X-ray tomography. While diamond growth directly onto GaN proved to be unsuccessful due to poor adhesion, films grown on AlN were adherent and robust. The twostep mixed-seeding method gave TBReff values <6 m 2 K GW -1 that were 30 times smaller than for films grown under identical conditions but using nanodiamond seeding alone. Such remarkably low thermal barriers obtained with the mixed-seeding process offer a promising route for fabrication of high-power GaN HEMTs using diamond as a heat spreader with an AlN interlayer.

The present paper is concerned with the analysis of size effects in short fibre reinforced composites. The microstructure of such composites often represents the first hierarchy level of a bioinspired material. For modelling fibre cracking as well as debonding between fibre and matrix material, a fully three-dimensional cohesive zone model is applied. It is shown that this model indeed captures the size effect associated with material failure of a single fibre. Furthermore, this scaling effect strongly depends on the shape and orientation of the assumed preexisting crack. For this reason, a two-dimensional description can usually only predict the size effect qualitatively. Based on the aforementioned findings, a representative volume element (RVE) containing ceramic fibres embedded within a polymer matrix is considered. Similar to the single fibre, the RVE also shows a pronounced size effect. However, the underlying physical process is significantly more complex. More explicitly, the size effect of the RVE is a superposition of that related to the isolated fibres as well as of that induced by debonding of the fibres from the matrix material. For estimating the different effects, a perfect bond is also modelled.

Using reactive DC sputtering in a gas aggregation cluster source, we show that pulsed discharge gives rise to a huge increase in deposition rate of nanoparticles by more than one order of magnitude compared to continuous operation. We suggest that this effect is caused by an equilibrium between slight target oxidation (during “time-off”) and subsequent sputtering of Ti oxides (sub-oxides) at “time-on” with high power impulse.