It is often reported that DLC thin films have good corrosion properties due to chemical inertness and low electrical conductivity. Nevertheless, the performance of these coating is highly sensitive to the presence of growth defects. An in situ optical microscopy coupled to an electrochemical test was then developed to evaluate corrosion protection performance of DLC coated steel. A square wave voltammetry was applied to increase the sensitivity of electrochemical techniques based on the detection of the dissolution of the bare metal surface triggered by the presence of uncoated spots due to inherent defects. With this in situ electrochemical test, a clear improvement in optical detection "natural" defects is obtained. SEM coupled with FIB milling technique was used to generate artificial defects with controlled dimensions down to 2.5 mu m diameter to define the sensitivity of the proposed counting procedure. Results showed that it was possible to detect cylindrical defects with diameter down to 2.5 mu m. Moreover, the electrochemical approach allowed to characterize the propagation of the damage under the DLC coatings.

The plasma jet of an atmospheric-pressure chemical vapor deposition system, namely, the axial injection torch, was diagnosed by optical emission spectroscopy (OES) in the conditions corresponding to titanium oxide deposition. Titanium tetraisopropoxide (TTIP) was used as the Ti organometallic precursor. The determination of the spatially-resolved excitation temperatures in the discharge allowed the determination of relative concentrations of atomic emitting species. The entrainment of air was estimated by measuring the relative quantity of N and O atoms in the discharge. The decomposition of TTIP was estimated by measuring the relative concentration of atomic Ti. It was shown that the air is rapidly introduced and distributed in the discharge while TTIP is progressively decomposed. Space-resolved OES measurements allowed to highlight titanium-depletion regions in the discharge. In light of previous results, it was suggested that these Ti-depletion regions reflect TiO2 gas phase nucleation processes. They are thus expected to affect the deposition growth mechanisms: Ti-rich regions would contribute to surface deposition (heterogeneous phase reactions) whereas Ti-depletion regions would contribute to the TiO2 particles deposition (homogeneous phase reactions).

This paper reports a rapid and simple method for the co-deposition of TiO2/SiO2 films, using a microwave plasma torch and organometallic precursors. Both structure and microstructure of the films have particularly been investigated. The results show that the characteristics of the deposits mainly depend on the torch to substrate distance (d). When this distance is short (d=10mm), the co-deposits are quite dense and exhibit crystalline TiO2 phases. By contrast, when d=30mm, the co-deposits are amorphous. At d=30mm, it was also shown that silica could act as an encapsulation matrix for titania particles in only one step. Moreover, for d=30mm, the adjunction of silica, about 40mol% allows enhancing the adherence of the films, whereas pure titania deposits are not adherent at all.

In this study, a microwave plasma torch working at atmospheric pressure has been used for TiO2 thin film synthesis. We first optimised the deposition conditions in order to avoid the formation of powder in the plasma phase. Then, the characterisation of the TiO2 films deposited in the optimised conditions revealed that both morphology and phase structure of the film are radial dependent. At the centre, the film is crystallised, exhibiting a well-defined columnar microstructure. Meanwhile, at the periphery, the film is amorphous, with a cauliflower-like structure.

Hydrogenated amorphous carbon thin films containing aluminum (a-C:H:Al) have been produced by a hybrid technique using plasma enhanced chemical vapor deposition and magnetron sputtering of an aluminum target. Various sputtering powers were used in order to explore different Al/(Al+C) ratios. Two deposition configurations for the substrates were tested: a dynamic and a static. The dynamic mode led to a multilayered structure made of alternating Al-rich and Al-poor layers with a total thickness of about 40nm for each period. Regardless of the deposition mode, nanoindentation showed that an increase in Al concentration resulted in a decrease in hardness compared to the pure a-C:H coatings. Moreover, the hardness of the dynamic a-C:H:Al films was less affected and seemed to be weighted between the power-equivalent static Al-doped DLC and the pure a-C:H. The results of tribological characterization in dry conditions indicated that the friction coefficient was significantly reduced by the introduction of Al from 0.2 to less than 0.1 for all of the Al-doped films. However, the wear resistance was also affected by the doping. Nevertheless, Al doping compatible with industrial purpose (i.e. dynamic mode) can be considered at moderate sputtering power in order to obtain a-C:H:Al coatings that exhibit low friction coefficient and moderate wear rate in relation with good hardness and H/E ratio.

AlN films were prepared with a Microwave Plasma Enhanced Chemical Vapor Deposition reactor at 1Pa and 700°C using different radiofrequency bias in order to obtain polycrystalline <0001> oriented films with minimal residual stresses for piezoelectric applications. The films developed were characterized in term of microstructure, composition and mechanical properties. Crystalline development, exclusive orientation and high tensile residual stresses were observed when the substrate-holder was at the floating potential. A progressive degradation of the crystalline structure was observed with the increase in the negative bias potential, together with the evolution to compressive residual stresses. Simultaneously, significant changes in the microstructure of the surface were observed by atomic force microscopy, as well as in the preferential orientation from <0001> to <1010>. Film properties for piezoelectric applications were optimized with the adequate selection of bias potential.

Hydrogenated amorphous carbon thin films containing fluorine (a-C:H:F) have been produced by radio-frequency plasma enhanced chemical vapor deposition by using different F/H ratios in the gas phase. The introduction of fluorine from 0 to 19at.% resulted in a decrease of hydrogen content and to the formation of CF and CF2 bonds. For all the films, Raman analysis showed a typical diamond-like carbon response with an evolution of the structure to larger sp2 clusters with less hydrogen while fluorine content increased. The drop in hardness generally observed in the literature with fluorine introduction was less abrupt here: for a fluorine content up to 6.5at.%, the measured hardness was 28GPa, and for 19at.% of fluorine, value was 20GPa. These are quite high values for a-C:H:F thin films. Moreover, fluorine improved tribological behavior in dry conditions with friction coefficient slightly reduced at low fluorine content and wear rate significantly reduced: divided by two to four than the fluorine free reference coating.

SiO x H y C z micrometer thick films are deposited from an argon/hexamethyldisiloxane mixture on Si (100) substrate by plasma enhanced chemical vapour deposition process using an axial injection torch at atmospheric pressure. Results highlight a similar effect of low and high substrate temperatures both on the deposition process and on the microstructure of the deposited films. Mesoscopically, scanning electron microscopy analyses reveal that particles are promptly produced in the gas phase and incorporated to the film. Microscopically, a detailed infrared analysis in transmission mode demonstrates a high carbon contamination in the low and high temperature intervals resulting in a lower stoichiometry. This work allows to define an optimum growth window for the substrate temperature, leading to smooth, particle-free and carbon-free films: [60 °C; 90 °C].

SiO x H y C z nanometric layers are deposited from hexamethyldisiloxane by atmospheric pressuremicrowave plasma torch on Si(100) substrates submitted to temperatures varying on therange [0 °C; 120 °C]. Atomic force microscopy (AFM) characterizations of samples grown atintermediate substrate temperatures (~30 °C) demonstrate a layer-by-layergrowth (Frank van der Merwe growth) leading to smooth flat and compact films while filmsdeposited at lower and higher substrates temperatures show an island-like growth(Volmer-Weber growth) generating a high surface roughness. Concomitantly, a detailedinfrared spectroscopy analysis of the growing films evidences structural modifications dueto changes in the bond types, Si-O-Si conformation and stoichiometry correlated withscanning electron microscopy and AFM characterizations. Then, deposition conditions andspecific microstructure are selected with the aim of generating 3-dimensionalSiO x H y C z nanostructure arrays on nanoindented Si (100) templates. The first results arediscussed.

In this work, vertically oriented multiwalled carbon nanotubes (MWCNTs) were synthesized at 600°C by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapor Deposition (ECR-PECVD) on a silicon substrate from Ni catalyst nanoparticles prepared by electrodeposition. Then CNTs were coated with aluminum nitride (AlN) by Metal Organic PECVD (MO-PECVD). The objective of this work is to obtain new nano-composite film based on AlN thin film containing oriented CNTs expected to enhance the thermal transfer compared to a single AlN layer. The final issue is the realization of thermal evacuators for microelectronic devices. Cauliflower-like structures of hexagonal AlN forming a compact thin film well coating vertically aligned CNTs were obtained and structurally characterized.

Aluminum nitride nano-dots were grown on Si(111) substrates using microwave plasma enhanced chemical vapor deposition (MWPECVD). This technique is used for the first time in this kind of application and we showed the possibility to obtain AlN nano-dots and how to control their size and density on the substrate by adjusting the deposition rate, the substrate temperature and the substrate bias voltage. Atomic force microscopy images have been obtained and Fourier transform infrared spectroscopy has been carried out to ensure that the AlN composition is maintained.

Hydrogenated amorphous carbon (a-C:H) films were deposited on flat samples and engine components using an industrial scale reactor. Characterization of the coating allowed validating its application on engine parts due to high hardness (32GPa) and high level of adhesion achieved using sublayers. The original approach of this work concerned the use of Raman analysis not only on flat samples after tribometer tests but also directly on coated engine parts with complex shape (like cam/follower system), in order to understand wear mechanisms occurring in motorsport engines. As wear could lead to a coating thickness decrease, a particular attention was paid on the Raman signal of the sublayers. Among the different values extracted from Raman spectrum to characterize structural organization, the value of G peak intensity appeared as a criterion of validity of analyses because it is directly linked to the remaining thickness of the a-C:H layer. For flat samples tested on ball-on-disc tribometer, structure of a-C:H film observed by Raman spectroscopy in the wear track remained stable in depth. Then, a-C:H coated engine components were studied before and after working in real conditions. Two different wear mechanisms were identified. The first one did not show any structural modification of the bulk a-C:H layer. In the second one, the high initial roughness of samples (Rt=1.15µm) lead to coating delaminations after sliding. Massive graphitization which decreases drastically mechanical properties of the coatings was observed by Raman analyses on the contact area. The increase of the temperature on rough edges of the scratches could explain this graphitization.

Coaxial injection microwave excited plasma torch, operating at atmospheric pressure has been tested to treat greased metallic surfaces. The treatment conditions were controlled using optical emission spectroscopy. The plasma treatment was carried out using argon plasma, with argon or oxygen in the periphery. The effect of plasma treatment on the grease was evaluated, using gravimetric analysis by weighing the sample before and after treatment, surface energy and X-ray photoelectron spectroscopic measurements. Initial period of treatment yielded etching of the grease, but, later on, the grease stabilized forming polymeric films, independent of the gas present in the periphery. The etching behavior was explained by different mechanisms involved in the plasma grease surface and sub-surface interactions.

AlN films were prepared with a microwave plasma enhanced chemical vapor deposition reactor working at different process temperatures in order to obtain polycrystalline 〈0001〉 oriented films for piezoelectric applications. The films developed were characterized in terms of microstructure, composition, and mechanical properties. Crystalline development and a single orientation were obtained at high temperatures, where at the same time an increase in mechanical intrinsic stresses was observed. Well crystallized 〈0001〉 films were obtained at temperature as low as 500 °C. Furthermore, the evolution of microstructure with thickness at higher temperatures showed a single 〈0001〉 orientation with progressive increase of the texture as the thickness increased. This fact was related with changes in the observed microstructure along the film z-axis, evaluated by high resolution transmission electronic microscopy and selected area electron diffraction. Although orientation dispersion of these films, evidenced by the rocking curves FWHM, remained relatively high (>9°), they can be regarded as promising for piezoelectric applications. Annealing tests conducted at relatively high temperatures with films deposited at low temperature indicated that thermal effects have only a major effect during the film growth for the temperature values employed.

The chemical, structural, mechanical and optical properties of thin aluminum oxide films deposited at room temperature (RT) and 800 degrees C on (100) Si and Si-SiO2 substrates by pulsed laser deposition and plasma enhanced chemical vapor deposition are investigated and compared. All films are smooth and near stoichiometric aluminum oxide. RT films are amorphous, whereas gamma type nano-crystallized structures are pointed out for films deposited at 800 degrees C. A dielectric constant of similar to 9 is obtained for films deposited at room temperature and 11-13 for films deposited at 800 degrees C. Young modulus and hardness are in the range 116-254 GPa and 6.4-28.8 GPa respectively. In both cases, the results show that the deposited films have very interesting properties opening applications in mechanical, dielectric and optical fields. (C) 2007 Elsevier B.V. All rights reserved.

This paper presents recent results on the development of high power MEMS switched varactors. Design methodology as well as fabrication and measurement results are presented. The MEMS varactors are made of a thick metal gold cantilever, with a reduced contact area, that allows to control high power microwave signals. Operation up to 5 watts CW is demonstrated, with good reliability. First results on applications to phase shifters is presented