The aim of this work is to study in a pulsed magnetron discharge of acetylene at 10−1 Torr, the influence of tOFF parameter on roughness and morphology of films deposited on silicon substrates. By using a low power discharge (long tOFF and short tON for a given power), a coating with unique morphology is deposited. This film is formed of nanoparticles and particular agglomerates called ‘flowers’ of micrometric size. To the best of our knowledge, it's the first time that such ‘flowers’ structures have been observed for a pulsed plasma polymerization of acetylene. According to the obtained results in mass spectrometry of plasma, nanoparticles and ‘flowers’ are probably formed in gas phase. A growth mechanism in several steps is proposed.

Thin films deposited on silicon substrate by three different methods of plasma polymerization of acetylene were analyzed by direct laser desorption/ionization Fourier transform mass spectrometry. High-resolution mass spectra showed the presence of carbon clusters and hydrocarbon oligomers in different relative abundances. During unipolar and continuous discharge polymerization of acetylene-hydrogen gas mixtures, quadrupole mass spectra of the plasma constituents showed the presence of molecular species with m/z lower than 100 -mainly peaks of C 4 H 2 and C 6 H 2 . Films produced had smooth surfaces and the corresponding LDI-FTMS spectra displayed only carbon cluster signals in the positive ion mode and both hydrocarbon and carbon cluster signals (with much higher relative abundance of carbon cluster signals) in the negative ion mode. Alternatively, during bipolar discharge with either higher acetylene gas flux (Ͼ40 cm 3 /min) or longer deposition times (Ͼ10 min), quadrupole mass spectra of the plasma constituents showed signals corresponding to polycyclic aromatic hydrocarbons (PAH) with m/z higher than 100. SEM pictures of the bipolar thin films demonstrated the presence of "flower" structures and nanoparticles developed on the surface. LDI-FTMS spectra of such thin films showed either total absence or lower relative abundance of carbon cluster signals, compared with hydrocarbon signals. (J Am Soc Mass Spectrom 2010, 21, 411-420)

The growth of hydrogenated amorphous carbons (a-C:H) produced by continuous or pulsed discharges of acetylene (C(2)H(2)) in an unbalanced magnetron setup was investigated. At 5 × 10(-3) Torr, only smooth films are obtained, whereas at 5 × 10(-1) Torr using a pulsed discharge some microtextured films are formed if the duty cycle is low. The morphology of these microtextured films consists of nanoparticles, filamentary particles, and particular agglomerates ("microflowers"). This paper presents a study of acetylene gas phase polymerization by mass spectrometry, and a detailed analysis of bulk structure of films by combining three techniques which include IR spectroscopy, Raman spectroscopy, and laser desorption/ionization Fourier transform mass spectrometry (LDI-FTMS). Finally, based on the study of gas phase and film structure, we propose a model for the growth of both smooth and microtextured films.

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Laboratoire d'Analyses par Re'actions Nucl/aires, Facult'is Universitaires Notre-Dame de la Paix, B-5000 Namur, Belgium In the living world, we find many beautiful examples of natural iridescent colours in the Coleoptera (beetles), i.e. vivid colours of physical origin (optical interferences) which result from specular reflection of the light by thin films [1][2]. Detailed studies involving morphological characterization through scanning/transmission electron microscopy, optical reflectance measurements and numerical modelling not only reveal photonic structures responsible for iridescence but also provide optical engineers with ideas for fabrication of devices such as mirrors or filters [3][4]. In many instances, a single biological material (chitin -a polysaccharide based on glucose and similar to cellulose), in combination with air gaps, is used to produce a multilayer structure, which is located within the exocuticle. Periodic air/chitin multilayers give rise to a relatively narrow reflection band which, in the case of Hoplia coerulea, lies in the blue part of the visible spectrum and moves only slightly with the angle of incidence [1] and, in the case of Chrysochroa vittata, shifts from red to green as the incidence is changed from normal to grazing [2]. Chirped multilayers, composed of chitin and another constituent, give rise to a broad-band reflection producing gold and silver mirror aspects in Chrysina resplendens and Chrysina optima, respectively. We derived an analytical formula based on a semi-infinite one-dimensional photonic crystal model, which has turned out to be useful for the design of colour-selecting devices based on multilayer films [3][4]. Applications include biomimetics and optical engineering. In the former, one aims to reproduce the visual aspect of a biological sample by transposing the original multilayer structure into an artificial one using a combination of two materials such as SiO2 and TiO2 [3]. Transposition is not as straightforward as one might think, as it is revealed by careful analysis of the influences of layer thickness ratio and refractive index contrast on the spectral richness of the reflector [3]. In the latter, one exploits design ideas from various biological multilayer structures in order to design versatile mirrors or filters [4]. At the conference, we will report on reflectance of SiO2/TiO2 multilayer films deposited on glass substrate by dc magnetron sputtering (Figure 1-a). We will show how radically different visual aspects (quantified by chromaticity coordinates, Figure 1-b) can be obtained using the same materials but different bio-inspired multilayer designs. 60 4-0 A 400i 45Q 5% 5% 00 6 Q {% 7 00 OSO I-III 40~~~~~~~~~~~~~0 2.0 30 400 450 5X0 50 600 65 70 750 0 85 wVe1eh (nmI Figure 1. Theoretical reflectance (a) of SiO2(n=1.5)/TiO2(n=2.7) multilayer films and corresponding chromaticitycoordinates (b) as the angle of incidence is increased from 00 to 700. Hoplia-type design: 14-periods, ds102=8 nm, dT.02=80 nm (a: top, b: circles); Chrysochroa-type design: ...