M.F. De Riccardis

Low temperature growth of r.f. reactively planar magnetron-sputtered AlN films

Abstract Polycrystalline AlN films were deposited on Si(100) and Si(111) substrates by sputtering in an N 2 + Ar gas mixture at a substrate temperature in the range 200–500 °C. The effect of the preparation conditions—substrate temperature, sputtering pressure, r.f. power and gas mixture—on the physical and chemical properties of the films were investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. The polycrystalline oriented AlN films were obtained at deposition rates in the range 0.20–0.56 μm h −1 with an N 2 Ar gas flow ratio of 100%. The film average grain size was estimated to be 60–80 nm. The good agreement between the measured Auger parameter ( α = 1463.0 ± 0.1 eV) and the tabulated value ( α = 1462.9 eV) with a binding energy standard deviation of 0.05 eV indicated the formation of the AlN compound.

Carbon Nanotube Growth on PAN‐ and Pitch‐Based Carbon Fibres by HFCVD

Abstract Carbon nanotubes (CNT) were grown on carbon fibres, both PAN‐ and pitch‐based, by hot filament chemical vapour deposition (HFCVD) using H2 and CH4 as precursors. Nickel clusters were electrodeposited on the fibre surfaces to catalyse the growth, and uniform CNT coatings were obtained on both PAN‐ and pitch‐based carbon fibres. Ni cluster features varied, depending on the deposition parameters, showing on average larger dimensions and denser distribution on pitch fibres. Multi‐walled CNTs with smooth walls and low impurity content were grown. The morphological features, both before and after the growth process, were characterised by SEM. This novel material based on carbon fibres coated with CNT, shows a potential for applications in polymeric matrix composites.

Strain relaxation onset in In0.08Ga0.92AsGaAs multiple-quantum wells investigated by high-resolution X-ray diffraction and atomic force microscopy

Abstract In this work we analyze the strain relaxation onset in In 0.08 Ga 0.92 As GaAs multiple-quantum wells (MQWs) grown by low-pressure metal organic chemical vapour deposition. The strain field determination and the structural characterization of the epitaxial layers and heterointerfaces are performed by high-resolution X-ray diffraction and reciprocal space mapping, while the surface morphology is analyzed by atomic force microscopy (AFM). An accurate determination of the strain status of the MQWs indicates a pseudomorphic growth in the epilayers. Nevertheless, the reciprocal space measurements show a distinct intensity profile of the diffuse scattering around each satellite peak. The diffuse intensity is very much elongated along the in-plane direction and the elongation is found to increase with the well layer thickness. Furthermore, in some cases lateral lobes appear within the elongated peaks which indicate an enhanced lateral ordering of the interfaces. AFM images of the heterostructure surface reveal the presence of monolayer steps. The step front distance is found to be related to the in-plane ordering measured by the X-ray experiments. In addition, we show that AFM and X-ray measurements combined to each other can provide a deeper insight in the strain relaxation phenomenon as well as direct information on the vertical correlation of the heterointerfaces.

TEM investigations on Ni clusters electrodeposited on Carbon substrate

The role of catalysts in the growth of carbon nanostructures by CVD is particularly critical, since the nano-carbon shape can depend on the catalyst composition and structure besides the deposition parameters [1–3]. In the synthesis of metal catalyzed carbon nanofilaments the performances of the catalyst particles can dramatically depend on both physical and chemical interaction with the substrate. In particular, a good adherence of the clusters to the substrate is necessary to avoid coalescence phenomena during the growth process generally carried out at relatively high temperature. The study of catalyst-substrate microstructure is particularly relevant for the optimization of the whole growth process.