A capacitively coupled low frequency PACVD device (ν = 50 kHz, DC bias: |Vdc| = 0 to 400 V) is used to deposit hard amorphous silicon carbide films (a-SiC:H), from the decomposition of precursor tetramethylsilane (TMS) diluted in argon. Such a deposition process induces an ion bombardment of the growing films: energetic ions can sputter atoms from the near surface of the coatings, leading to strong alterations in the microstructure of the deposited material. In order to draw the particular influence of ion bombardment on the coatings, partly compensated by growth phenomena, some deposited films are post-treated in pure argon plasma, then submitted to a crossed analysis by RBS, FTIR and XPS techniques. These results are also compared to previous gas phase considerations [A. Soum-Glaude, L. Thomas, E. Tomasella, J.M. Badie, R. Berjoan, Surf. and Coat. Technol. 200 (1–4), (2005) 855]: Optical Emission Spectroscopy (OES) measurements near films surface, and SRIM© 2003 sputtering simulation. The confrontation of gas phase study, simulation and material analysis highlights general trends. First, silicon can be selectively sputtered in regard to carbon in the DC bias domain [150–250 V], as shown by OES observations on Si+ and H emitting species, Si / C ratio given by RBS, Si–C and Si–H absorption bands on FTIR spectra, and Si sputtering yield calculation with SRIM 2003. More precisely, in this DC bias domain, XPS measurements on the C1s core level peak, SRIM sputtering yields, and the observation of C–H and Si–C absorption bands with FTIR technique, show that sp3 carbon environments (C–C + C–H) can be favored in spite of the Si–C and C–Csp2 ones. Beyond the [150–250 V] domain, this phenomenon is no more noticeable, meaning sputtering is no more selective at higher DC bias. This selectivity can be used to improve hardness of the coatings that can reach 30 GPa.

Selective effect of ion/surface interaction in low frequency PACVD of SIC:H films: Part B. Microstructural study

Influence of RF PACVD process parameters of diamond-like carbon films on optical properties and nano-hardness of the films

Diamond-like carbon (DLC) films on polyethylene terephthalate (PET) are nowadays intensively studied composites due to their excellent gas barrier properties and biocompatibility. Despite their applicative features being highly explored, the interface properties and structural film evolution of DLC coatings on PET during deposition processes are still sparsely investigated. In this study two different types of DLC films were gradually deposited on PET by radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) using acetylene plasma. The surface morphology of the deposited samples has been analyzed by atomic force microscopy (AFM). Their chemical composition was investigated by diffusive reflectance infrared Fourier transform (DRIFT) and Raman spectroscopy analysis and the surface wettability by contact angle measurements. Subplantation processes and interface effects are revealed through the morphological and chemical analysis of both types. During plasma deposition processes the increasing carbon load causes the rise of intrinsic film stress. It is proven that stress release phenomena cause the transition between polymer-like to a more cross-linked DLC network by folding dehydrogenated chains into closed 6-fold rings. These findings significantly lead to an enhanced understanding in DLC film growth mechanism by RF-PECVD processes.

Morphological and Chemical Evolution of Gradually Deposited Diamond-Like Carbon Films on Polyethylene Terephthalate: From Subplantation Processes to Structural Reorganization by Intrinsic Stress Release Phenomena

The detailed structural evolutions in polycarbosilane-derived carbon-rich amorphous SiC were investigated semiquantitatively by combining experimental and analytical methods. It is revealed that the material is comprised of a Si-containing matrix phase and a free-carbon phase. The matrix phase is amorphous, comprised of SiC4 tetrahedra, SiCxOx–4 tetrahedra, and Si–C–C–Si/Si–C–H defects. With increasing pyrolysis temperature, the amorphous matrix becomes more ordered, accompanied by a transition from SiC2O2 to SiCO3. The transition was completed at 1250 °C, where the matrix phase started to crystallize by forming a small amount of β-SiC. The free-carbon phase was comprised of carbon nanoclusters and C-dangling bonds. Increasing pyrolysis temperature led to the transition of the free carbon from amorphous carbon to nanocrystalline graphite. The size of the carbon clusters decreased first and then increased, while the C-dangling bond content decreased continuously. The growth of carbon clusters was attribute...

Structural evolutions in polymer-derived carbon-rich amorphous silicon carbide.

The influence of CH4 addition on composition, structure and optical characteristics of SiCN thin films deposited in a CH4/N2/Ar/hexamethyldisilazane microwave plasma

Structural and mechanical properties of a-C:H thin films grown by RF-PECVD

The structural evolutions of a-C:H thin films prepared by r.f. plasma-enhanced chemical vapor deposition from a CH 4 /Ar or CH 4 /He gas mixture have been investigated. Elastic recoil detection analysis, infrared and Raman spectroscopies have been used to quantify, respectively, hydrogen content, the bonding and sp 2 proportion carbon of thin films. The variations of electron spin resonance parameters, the peak-to-peak linewidth Δ H pp , g -factor and the spin density, as a function of the film preparation are discussed on the basis of the complete physico-chemical characterization. The type of defects do not change drastically when the conditions of the film preparation vary contrary to the spin–spin interaction: a stronger exchange resulting from the greater delocalization of the π-electron occurs when the bias voltage increases. Moreover, the hyperfine interaction of the spins with the hydrogen atoms decreases. We have found that the optical band gap E g of these films decreases with the loss of hydrogen (bonded and unbonded) and the increasing of sp 2 content while E u gap increases. These results have been related to the spin densities.

Characterization by electron spin resonance of defects in a-C:H thin films. Correlation between structural evolutions and optical properties

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Structural and mechanical properties of a-C:H thin films grown by RF-PECVD

Characterization by electron spin resonance of defects in a-C:H thin films. Correlation between structural evolutions and optical properties