We have carried out wetting experiments on textured surfaces with high aspect ratio asperities in the Wenzel state. When inclination is imparted to the asperities, we observe a strictly unidirectional spreading opposite to the direction in which the asperities point. The advancing contact angle decreases markedly as inclination increases. A crude numerical analysis successfully accounts for this behaviour, highlighting the interplay between Gibbs pinning at the top of the structures and imbibition along the valleys between them. In Gibbs pinning non-linearities play a major role and we find that simple line averaging - i.e. a rule of mixture - cannot account for this evolution except for weak surface perturbations, i.e. large inclinations.

Fiber-textured polycrystalline silicon thin films have demonstrated their interest as seed layers for the epitaxial growth of high-quality materials on substrates such as glass or plastics. In the present work, we report a comprehensive study of the aluminum-induced crystallization (AIC) of isolated Si domains. Our study not only demonstrates the fabrication by AIC of shape- and size-controlled Si monocrystals at the nanoscale but also allows for the prediction of minimal annealing conditions for complete crystallization of such structures. These ultrathin [111]-oriented monocrystals are promising candidates as selected-area epitaxy substrates with both an easy control on the morphology of these structures and a low-temperature fabrication process.

Silica (SiO2) is one of the most common materials on Earth. The crystalline form α-quartz is the stable silica polymorph at ambient conditions although metastable forms exist. α-quartz is a piezoelectric material, it can be produced artificially and is widely used for example in electronics and the biosciences. Despite the many application areas, the atomic surface structures of silica polymorphs are neither well understood nor well characterized. Here we present measurements of α-quartz (0001). Helium Atom Scattering combined with Atomic Force Microscopy reveals a giant reconstruction consisting of 5.55 ± 0.07 nm wide ribbons, oriented 10.4° ± 0.8° relative to the bulk unit cell. The ribbons, with the aid of atomistic modelling, can be explained as a self-organised pattern of nano Dauphine twins (nano electrical twins).

The chemistry and intermixing at buried interfaces in sputter deposited ZnO/Ti/ZnO thin layers were studied by hard x-ray photoelectron spectroscopy. The long mean free path of the photoelectrons allowed for detailed studies of the oxidation state, band bending effects, and intrinsic doping of the buried interfaces. Oxidation of the Ti layer was observed when ZnO was deposited on top. When Ti is deposited onto ZnO, Zn Auger peaks acquire a metallic character indicating a strong reduction of ZnO at the interface. Annealing of the stack at 200 °C results in further reduction of ZnO and oxidation of Ti. Above 300 °C, oxygen transport from the bulk of the ZnO layer takes place, leading to re-oxidation of ZnO at the interface and further oxidation of Ti layer. Heating above 500 °C leads to an intermixing of the layers and the formation of a ZnxTiOy compound.

In the thin film area, it is well-known that deposition rate impacts the morphology but tools to quantify online fast growth processes are scarce. Here we show that surface differential reflectivity spectroscopy (SDRS) can be used in real time to follow silver nanoparticle growth during sputtering deposition. The main experimental challenge was to avoid noise and saturation due to the plasma emission and to obtain a reasonable signal/noise ratio to monitor fast deposition. A specific setup was designed resulting in an acquisition speed in the range of hundreds of milliseconds and used to investigate the growth of silver on alumina as a test example. The evolution of the size, density and aspect ratio of growing silver islands were determined by modelling their plasmonic response and compared with previous results obtained at a much lower growth rate using physical vapour deposition (Lazzari and Jupille 2012 Nanotechnology 23 135707). During room-temperature sputter deposition, coalescence leads to significantly larger and flatter aggregates compared to evaporation at the same coverage. However, both deposition techniques lead to similar nucleation and growth behaviours. Higher substrate temperature (575 K) did not change the trend and a sticking coefficient close to one was found. The observed evolution of the particle aspect ratio is discussed in terms of supersaturation and flux driven hindrance of the coalescence.

The structures and properties of zinc oxide thin films deposited by radio-frequency magnetron sputtering were investigated for different substrate biases applied during deposition. The electrical bias determined the crystalline polarity of a nominally undoped film on an amorphous substrate: films with a (0001) surface and a (0001¯) surface were produced under positive and negative biases, respectively. Moreover, the polarity of the films was determined at an early stage of the deposition and could not be reversed by switching the substrate bias.

We demonstrate that small tilts away from the substrate normal, of short (30–40nm high) nanopillars, may be detected and modeled by spectroscopic UV–Visible Mueller Matrix Ellipsometry (MME). The pillars were produced by sputtering a GaSb substrate with a low energy unfocused ion beam. It has previously been found that the pillars will point in the direction of the ion flux. For both samples reported here, the ion-incidence was unintentionally tilted away from the substrate normal by 2.8 and 4.8°. The MME measurements were performed using both multiple angles of incidence, and 360° rotation of the incidence plane. Graded uniaxial effective medium models were fitted to the experimental data, and through Euler angle rotations of the dielectric tensor, the tilt angle and the orientation of the pillar direction, were obtained. The UV part of the spectrum enhanced the tilt angle sensitivity down to 0.02–0.05°. A data presentation that enhances the understanding of the symmetry in the crystallographic information obtained from spectroscopic MME is proposed. The off block diagonal Mueller matrix elements are more sensitive to the in-plane anisotropy, whereas for small tilt angles m14 scales approximately with θsin(ϕ).

Enhanced control of diffraction through transparent substrates is achieved via disordered gratings in a silica sol-gel film. Tailoring the degree of disorder allows tuning of the diffractive behavior from discrete orders into broad distributions over large angular range. Gratings of optical quality are formed by silica sol-gel nanoimprint lithography and an optical setup for the measurement of continuous diffraction patterns is presented. Sound agreement is found between measurements and simulation, validating both the approach for redirection of light and the fabrication process. The disordered gratings are presented in the context of improved interior daylighting and may furthermore be suited to a wide variety of applications where controlled angular redirection of light is desired.

Broadened plasmon resonances of Cu nanoparticles in nanopatterned mixed oxide sol-gel nanopillars are shown to be readily detected by spectroscopic Mueller matrix ellipsometry. The plasmonic nanomaterials are obtained by low energy ion sputtering of a CuO sol-gel film. Both s- and p-polarized plasmon resonances are observed in the off-block-diagonal and the block-diagonal Mueller matrix elements as well as in the generalized ellipsometric parameters. The resonant features in all elements correlate with both maximum depolarization and a minimum in the reflected intensity. The spectral position and the polarization character of the plasmon resonances are discussed phenomenologically through effective medium theory.

Producing surfaces textured with a homogeneous pattern of nanoscale structures is increasingly important for fabrication of semiconductor devices. Although techniques exist for imaging surface nanostructures on a local scale, these techniques are often impractical for use over large areas for finding average structural information. The nanostructured surface in this study consists of densely packed cones produced by sputtering a mono-crystalline GaSb substrate with a low-energy unfocused ion beam, yielding self-organized cones that are slightly tilted away from the sample normal. Here, we devise an all-optical non-destructive characterization scheme using Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) and Spectroscopic Mueller Matrix Ellipsometry (MME) for obtaining all main dimensions including average height, lateral spacing and packing motifs, and the cone top and bottom diameters. It is further shown that both MME and GISAXS are sensitive to small tilts of the nanocone axis from the surface normal.

We demonstrate the vertical self-catalyzed molecular beam epitaxy (MBE) growth of GaAs nanowires on an amorphous SiO2 substrate by using a smooth [111] fiber-textured silicon thin film with very large grains, fabricated by aluminum-induced crystallization. This generic platform paves the way to the use of inexpensive substrates for the fabrication of dense ensembles of vertically standing nanowires (NWs) with promising perspectives for the integration of NWs in devices.

Ultrafast synchrotron microtomography has been used to study in-situ and in real time the initial stages of silicate glass melt formation from crystalline granular raw materials. Significant and unexpected rearrangements of grains occur below the nominal eutectic temperature, and several drastically different solid-state reactions are observed to take place at different types of intergranular contacts. These reactions have a profound influence on the formation and the composition of the liquids produced, and control the formation of defects.

The formation of GaSb nanopillars by low energy ion sputtering is studied in real-time by spectroscopic Mueller matrix ellipsometry, from the initial formation in the smooth substrate until nanopillars with a height of 200-300 nm are formed. As the nanopillar height increased above 100 nm, coupling between orthogonal polarization modes was observed. Ex situ angle resolved Mueller polarimetry measurements revealed a 180° azimuth rotation symmetry in the off-diagonal Mueller elements, which can be explained by a biaxial material with different dielectric functions εx and εy in a plane parallel to the substrate. This polarization coupling can be caused by a tendency for local direction dependent alignment of the pillars, and such a tendency is confirmed by scanning electron microscopy. Such observations have not been made for GaSb nanopillars shorter than 100 nm, which have optical properties that can be modeled as a uniaxial effective medium.

We report on soft nanoimprint lithography using masters obtained by high order symmetry interference lithography. The use of high order symmetry leads to the formation of three-dimensional structures with features smaller than 40 nm. Masters were realized in silicon in a two-step process without transfer layer. Pure silicon masters allow mechanical stability and potential surface functionalization. We further demonstrate the ability of these masters as mold for nanoimprint lithography. High fidelity replication in hybrid sol-gel and pure silica with conservation of both minute features and long distance organization is observed over large areas.

The application of alumina-doped ZnO (AZO) films as luminescent material for large area lighting sources has been evaluated. Thin films were grown on quartz using magnetron sputtering and subsequently annealed under argon atmosphere in a rapid thermal annealing experiment. Below 550°C, red-shift of the optical band gap and increase of the visible emission are observed in agreement with Al diffusion and formation of interstitial oxygen atoms. At temperatures higher than 800°C, diffusion is activated and Ostwald ripening leads to the formation of larger grains and an increase of the crystalline phase. The photoluminescence (PL) intensity is enhanced, specifically in the UV range. As a result the emission spectrum of AZO thin films can be adjusted by the annealing conditions, with equal contributions from the UV and orange parts of the PL spectrum resulting in an efficient white emission as quantified using the color space map of the Commission Internationale de l'Éclairage.

We present a simple and cheap method for fabrication of silica nanofluidic devices for single-molecule studies. By imprinting sol-gel materials with a multi-level stamp comprising micro- and nanofeatures, channels of different depth are produced in a single process step. Calcination of the imprinted hybrid sol-gel material produces purely inorganic silica, which has very low autofluorescence and can be fusion bonded to a glass lid. Compared to top-down processing of fused silica or silicon substrates, imprint of sol-gel silica enables fabrication of high-quality nanofluidic devices without expensive high-vacuum lithography and etching techniques. The applicability of the fabricated device for single-molecule studies is demonstrated by measuring the extension of DNA molecules of different lengths confined in the nanochannels.

The formation of GaSb nanopillars have been studied in real-time by spectroscopic Mueller matrix ellipsometry. Low energy ion sputtering of GaSb leads to the formation of densely packed nanopillars on the surface. A graded anisotropic effective medium model was developed to characterize the structures from ellipsometry measurements; based on ex situ ellipsometry, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. This model was applied to derive the height of the nanopillars from real-time ellipsometry measurements during sputtering. The real-time observations revealed an interesting and surprising evolution of the GaSb nanostructures. The formation could be divided into three regimes; first an initial stage with removal of oxide and some delay, followed by a second regime with a rapid and steady increase of the pillar height, and finally the formation changes to a third regime with a slow and linear increase of the pillar height. The dependence of the formation on experimental conditions, such as the temperature and the flux and energy of the ion beam, was studied. It was found that the ion flux determines the timescale of the formation, while the pillar height scale and late stage formation rate was controlled by the energy and the temperature. The real-time observations of GaSb during sputtering provide new insight into why the GaSb nanopillars are formed. Traditionally the formation of patterns on GaSb during sputtering was explained by the Bradley–Harper model, where the structures are formed by a competition between curvature dependent sputtering yield and diffusion. However, this model can not explain the observation of the three different formation regimes. Instead, the real-time observations of the nanopillar formation supports the self sustained etch masking mechanism [S. Le Roy et al. Journal of Applied Physics 106 094308 (2009)]. In this explanation, the pillars are formed due to segregation of Ga and the difference in sputtering yield between Ga and Sb. GaSb nanopillars with a height of less than 100 nm were found to have uniaxial optical properties, with the optical axis parallel to the pillar axis. For larger structures, the uniaxial effective medium model was not able to represent the optical properties of the pillars. For sputtering with an ion energy of 500 eV, nanopillars with a height up to 300 nm can be formed. By real-time Mueller matrix measurements of the formation of such pillars, it was observed that the pillars had biaxially optical properties as the height surpassed 100 nm. Fourier analysis of a scanning electron microscope image of the final nanopillars showed that the lateral anisotropy can be attributed to a direction dependent nearest neighbor distance. Each individual pillar has uniaxial symmetry; the biaxial symmetry comes from the anisotropic organization of the pillars. A commercial Mueller matrix ellipsometer was applied for the real-time measurements, based on ferroelectric liquid crystals as polarization modulating elements. Improvements of such a system were proposed by optimizing the design with a genetic algorithm. The new design promise to reduce the measurement noise significantly compared to previous designs, in addition to extending the spectral range into the infrared