The objective of this work is to determine the origin of a decohesion problem that occurs during the fabrication process of certain integrated circuits. This decohesion takes place at the Ti/dielectric interface with the dielectric being either SiO2 or borophosphosilicate glass (BPSG). The frequency of the decohesion increased when the dielectric is BPSG. In order to understand the reason for the difference in decohesion rates for the two dielectrics, a comparative study was performed before and after annealing. X-ray Diffraction was used to determine the microstructure of the different layers and Transmission Electron Microscopy coupled to Electron Energy Loss Spectroscopy and X-ray Energy Dispersive Spectroscopy was mainly used to characterize the interfaces and nanophases that had formed during annealing. A fundamental difference observed was the Ti/dielectric interface reactivity: in the case of BPSG, an amorphous layer rich in P is formed before the Ti5Si3 silicide. Two hypothesis are put forward in order to explain adhesion failures: a decrease in the rate of Ti5Si3 formation kinetics and/or a decrease of the glass transition temperature induced by P enrichment.

GaN films were grown using metal-organic chemical vapor deposition (MOCVD) on intentionally roughened c-sapphire in order to study the effect of the substrate roughness. Controlled substrate damage was achieved by exposing the substrate surfaces to controlled amounts of trimethylgallium followed by exposure to hydrogen at elevated temperature. The bulk film quality was studied by high-resolution X-ray diffraction and the surface topography was examined by atomic force microscopy. It was observed that mild substrate roughness (surface pit depth up to 30 nm) does not have a significant effect on the bulk film quality nor the GaN surface topography, and that recovery of the surface roughness is observed in very early stages of film growth. Cross sectional transmission electron microscopy confirmed that MOCVD GaN grown on inclined sidewalls etched in c-sapphire maintained the $\{0001\}_{\rm sapphire}\parallel\{0001\}_{\rm GaN}$ epitaxial relationship despite the substrate miscut of ca. 15° with respect to the c-axis.

Atomic force microscopy observations of the fine structure of cracks have been carried out for nickel thin films on polyimide substrates under tensile test. For strains of the order of 10%, the cracking of the metallic thin film induces notable damaging of the polymeric substrate. Post-mortem observations of the substrate and finite element simulations of the stress field at the cracks head have been performed to characterize this unexpected damaging: the crack propagation at the film/substrate interface and inside the substrate.

Differential scanning calorimetry (DSC) and X-ray scattering measurements on water confined in silica gel is studied for several levels of hydration at room temperature and down to 77 K. The DSC analysis of water confined in silica gel in function of the level of hydration shows that the solidification of water inside the pore is sensitive to the pore opening but the fusion is closely related to the curve of the pore. The X-ray pair correlation function showed the presence of a distorted tetrahedral-like hydrogen-bonded network of water characterized by the peaks at ~2.8, ~4.1 and ~4.9 Å. This distortion is caused by the competition between confinement effect and silica-water interaction. To eliminate the contribution of the water-silica gel interaction we have determined the structure of confined water by subtraction of the feebly hydrated silica gel from that strongly hydrated sample. The pair correlation function of extracted water show an oxygen-oxygen correlation at 3.8 Å. A similar peak is observed in the case of water confined in polyHEMA, in charcoal and at vicinity of myoglobin.

This article presents a particle-in-cell (PIC)/test-particle Monte Carlo (TPMC) simulation of the dynamics of Ar+ ions in the region (sheath and presheath) surrounding an attracting cylindrical Langmuir probe at medium He buffer gas pressure. The numerical model is based on a combination of PIC simulation for the ion component and fluid description for the electrons using the Boltzmann relation. The electric field is self-consistently computed via the Poisson equation. The neutrals are modeled directly by an analytical method. The elastic collisions between Ar+ ions and He atoms are accounted for using a TPMC method based on the polarization potential theory. The results of the present simulation are compared with measurements, with other probe theories and the results of other authors simulations.

In point-to-plane corona discharges in air, the collisions of charged particles with neutral particles induce a gas movement between the point to the plane called electric wind. A one-dimensional model of the neutral particle velocity along the discharge axis and between the electrodes is first developed. Laser Doppler Anemometry is used to measure the axial velocity profile of the gas between the electrodes. Discrepancies between experimental results and predictions of the on-axis velocity are discussed. Finally, the measured velocity profile compares quite well with a cos5θ distribution. Significant differences between measured and cos5θ profiles are observed near the discharge axis which could be attributed to the presence of seeding particles.  

In the first part of this work the regime of the DC electrical discharge in nitrogen, in absence and in presence of polystyrene thin films in the cold plasma reactor, for a constant gap length d = 1 cm and for variable pressures ($1~{\rm~mbar} < p < 10~{\rm~mbar}$) is characterized, while the gas flow rate is maintained at Q = 1 sccm. V-I curves underline that in any case a “normal glow-like” discharge is established. Experimental results bring out that the presence of the films in the volume of the produced plasma seems to modify the structure and some of the discharge characteristics, like the cathode secondary emission effects. V-I curves ($I <200~\mu$A), discharge repetitive current impulses, discharge repetitive emitted light impulses along the discharge symmetry axis and photos of the discharge, in presence and in absence of the films, are presented. In the second part of this paper results of polystyrene thin films treatment under the above DC “normal glow-like” discharge regime in nitrogen for improving the wettability of the films are presented. The effect of discharge main parameters (pressure p and mean current I through the discharge) on the treatment is studied under certain experimental conditions. The wettability is characterized by contact angle measurements using deionized water drops and the evolution versus the treatment time ttr of the $\Delta \theta/\theta_{\rm i}=(\theta_{\rm i}-\theta_{\rm f})/\theta_{\rm i}$ ratio ($\theta_{\rm i}$: the contact angle before the treatment and $\theta_{\rm f}$: the contact angle after the treatment) is estimated. It is deduced that optimizing main parameters of the DC electrical discharge in nitrogen it is possible to obtain films with very good wettability (suggestively $\Delta\theta/\theta_{\rm i}=0.951$ corresponding to $\theta_{\rm f}=4^{\circ}$, at p = 4 mbar, $I=200~\mu$A, $t_{\rm tr}\cong 600$ s). A rapid change of the films surface nature ($0~{\rm s} < t_{\rm tr} < 60$ s, suggestively) seems to be followed by a slower one and finally by a saturation. The gas pressure and the discharge mean current seem to play a very important role for the treatment. The experimental results allow us to start a discussion about the possible role of some active particles produced in the plasma to the treatment of the films and especially the role of the neutrals and the metastables.

This article deals with the cold plasma treatment of atactic polystyrene (aPS) and isotactic polystyrene (iPS) thin films with oxygen, oxygen-nitrogen mixture or nitrogen. Experimental results showed that the use of a DC pulsed plasma discharge at low pressure can considerably increase surface hydrophilicity. Variations in macroscopic surface properties were studied by water drop contact angle measurements. It was found that treatment of aPS resulted in a greater change in wettability than that for iPS. This initial observation of the effect of tacticity, and thus polymer microstructure, on surface properties is discussed with regards to the crystalline and helical nature of iPS.

This paper presents a novel design of superconducting coils able to generate a micro-gravity environment for protein crystal growth in aqueous solution. The structures have been calculated thanks to a method for “inverse source synthesis problem” developed at the GREEN Choice of the angular offset between the directions of magnetic force field and magnetic field in the working area as well as convection phenomena are also studied.