We present a study of the surface effects and optical properties of the self-assembled nanostructures comprised of vertically aligned 5 nm-diameter Al nanowires embedded in an amorphous Si matrix (a-Si:Al). The controlled (partial) removal of Al nanowires in a selective etching process yielded nanoporous a-Si media with a variable effective surface area. Different spectroscopy techniques, such as X-ray photoelectron spectroscopy (XPS), UV-Vis spectrophotometry and photoluminescence (PL), have been combined to investigate the impact of such nanostructuring on optical absorption and emission properties. We also examine long-term exposure to air ambient and show that increasing level of surface oxidation determines the oxide defect-related nature of the dominant PL emission from the nanoporous structures. The role of bulk, nanosize and surface effects in optical properties has been separated and quantified, providing a better understanding of the potential of such nanoporous a-Si:Al structures for future device developments.

This paper describes the high-rate (~1.5 μm/min) growth of Si films on Si supporting substrates with (100) crystallographic orientation at 600 °C, 800 °C, and 1000 °C in a vacuum environment of ~1 × 10⁻⁵ mbar using electron beam (e-beam) evaporation. The microstructure, crystallinity, and conductivity of such films were investigated. It was established that fully crystalline (Raman spectroscopy, EBSD) and stress-free epi-Si layers with a thickness of approximately 50 µm can be fabricated at 1000 °C, while at 600 °C and 800 °C, some poly-Si inclusions were observed using Raman spectroscopy. Hall effect measurements showed that epi-Si layers deposited at 1000 °C had resistivity, carrier concentration, and mobility comparable to those obtained for c-Si wafers fabricated through ingot growth and wafering using the same solar grade Si feedstock used for the e-beam depositions. The dislocation densities were determined to be ∼2 × 10⁷ cm⁻² and ∼5 × 10⁶ cm⁻² at 800 and 1000 °C, respectively, using Secco etch. The results highlight the potential of e-beam evaporation as a promising and cost-effective alternative to conventional CVD for the growth of epi-Si layers and, potentially, epi-Si wafers. Some of the remaining technical challenges of this deposition technology are briefly indicated and discussed.

We report on the effect of butane and butylene on hydrogen permeation through thin state-of-the-art Pd–Ag alloy membranes. A wide range of operating conditions, such as temperature (200–450 °C) and H₂/butylene (or butane) ratio (0.5–3), on the flux-reducing tendency were investigated. In addition, the behavior of membrane performance during prolonged exposure to butylene was evaluated. In the presence of butane, the flux-reducing tendency was found to be limited up to the maximum temperature investigated, 450 °C. Compared to butane, the flux-reducing tendency in the presence of butylene was severe. At 400 °C and 20% butylene, the flux decreases by ~85% after 3 h of exposure but depends on temperature and the H₂/butylene ratio. In terms of operating temperature, an optimal performance was found at 250–300 °C with respect to obtaining the highest absolute hydrogen flux in the presence of butylene. At lower temperatures, the competitive adsorption of butylene over hydrogen accounts for a large initial flux penalty.

Thin-film piezoelectrics are widely investigated for actuators and energy harvesters, but there are few alternatives to toxic lead zirconate titanate. Biocompatible Ca- and Zr-modified BaTiO₃ (BCZT) is one of the most promising lead-free alternatives due to its high piezoelectric response. However, the dielectric/piezoelectric properties and structural integrity of BCZT films, which are crucial for their applications, are strongly influenced by the substrate upon which the film is grown and the related processing methods. Here, the in-plane stress, microstructure, dielectric, and piezoelectric properties of 100–500 nm thick high-temperature RF-sputtered BCZT films on industrially relevant Si-based substrates were investigated. Obtaining polycrystalline piezoelectric films required deposition temperatures ≥ 700 °C, but this induced tensile stresses of over 1500 MPa, which caused cracking in all films thicker than 200 nm. This degraded the dielectric, piezoelectric, and ferroelectric properties of films with larger electrode areas for applications. Films on SrTiO₃, on the other hand, had a compressive residual stress, with fewer defects and no cracks. The grain size and surface roughness increased with increasing deposition temperature. These findings highlight the challenges in processing BCZT films and their crucial role in advancing lead-free piezoelectric technologies for actual device applications.

This paper reports the findings of a FP7/FCH JU project (ReforCELL) that developed materials (catalysts and membranes) and an advance autothermal membrane reformer for a micro Combined Heat and Power (CHP) system of 5 kWel based on a polymer electrolyte membrane fuel cell (PEMFC). In this project, an active, stable and selective catalyst was developed for the reactions of interest and its production was scaled up to kg scale (TRL5 (TRL: Technology Readiness Level)). Simultaneously, new membranes for gas separation were developed. In particular, dense supported thin palladium-based membranes were developed for hydrogen separation from reactive mixtures. These membranes were successfully scaled up to TRL4 and used in lab-scale reactors for fluidized bed steam methane reforming (SMR) and autothermal reforming (ATR) and in a prototype reactor for ATR. Suitable sealing techniques able to integrate the different membranes in lab-scale and prototype reactors were also developed. The project also addressed the design and optimization of the subcomponents (BoP) for the integration of the membrane reformer to the fuel cell system.