Spectroscopic Characterization of a new organic-inorganic sol-gel material for photonic devices.

1. ν Si-O (Si-O-Si) ν Si-O (Si-OH) ν O-H ν Si-O (Si-OCH3) ν C-H (CH2) ν C-H (CH2) ν C-O-C ν OH δ C-H (CH2) 9. Device Fabrication Process 10. Fabricated devices Photonic circuit (demultiplexer) - optical microscopy Spectroscopic Characterization of a new organic-inorganic sol-gel material for photonic devices. J. Jabboura,b, S. Calas-Etienneb, S. Gattib, M. Smaïhic, R. K. Kribichb, M.Myarab, G. Pilleb, Y. Moreaub and P. Etienneb. a Institut d’Electronique du Sud (IES)-Montpellierb Groupe D’Etude des Semi-Conducteurs (GES)-Montpellierc Institut Européen des Membranes (IEM) -Montpellier 3. Precursor 1. Introduction 2. Main Objectives • The main advantage of cationic polymerization in contrast with radical polymerization is its non inhibition by oxygen • good adhesion of epoxy groups on various substrates [1] • Cycloaliphatic structure very important reactivity and high conversion rate [2]. This poster deals with organic-inorganic hybrid materials prepared by sol-gel process for integrated optics fabrication via UV laser writing. We choose to use a new precursor, working with cationic polymerization : the [2-(3,4 epoxycyclohexylethyltrimethoxysilane)] (EETMOS). -29Si-RMN spectroscopy, is used to follow hydrolysis and polycondensation of the inorganic part. - IR spectroscopy is used to put in evidence the different groups in material, especially SiOH groups, correlated to the propagation losses bin waveguids 3 simple photonic devices with a cross section of 5x5 µm2 were imprinted and tested in the IR range (1.3 µm) • To simplify the protocol of synthesis. • To extend our work at a smaller laser wavelength (262 nm) for better imprint resolution. • To obtain oligomers with multifunctional organic part to succeed at the highest polymerization rate. • To reduce the OH groups which compete with the light propagation by absorption process near 1550 nm. • To put in evidence the differents groups in the material. 6. Si-NMR caracterization • 29Si-NMR is a convenient technique to follow hydrolysis and condensation reactions. • Hydrolysis and condensation of precursor can be monitored, to leave the sol with only a few silanol groups on oligomers species, with the highest reactive multifunctional oligomer 4. Synthesis of organic networks 5. Synthesis of inorganic network • The polymerization is performed by UV laser radiation in the presence of a cationic photoinitiator. • We chose the Iodonium, (4-methylphenyl)[4-(2-methylpropyl)phenyl]-hexafluorophosphate (Irgacure 250) [3]. Its maximum UV absorbance is at approximatively 230 nm. However, there is a tail absorption that extends to the 260 nm region, which corresponds to our laser writing wavelength (=262 nm). • The photoinitiator generates protonic acids upon its photolysis. The attack of the epoxide ring leads to an oxiranium ion. The initiation of cationic polymerization takes place by nucleophilic attack of an epoxide monomer on the oxiranium ion. The reactions propagate in chain and lead to a formation of the organic network [4]. • Mineral network was synthesized via sol-gel process. • Hydrolysis (formation of Si-OH species) • Condensation (formation of Si-O-Si species). • Hydrolysis is usualy enhanced by acid catalysis and condensation reactions produce much faster in basic catalysis. 7. IR Spectroscopy • IR spectroscopy, is a convenient technique to evolve and to put in evidence the differents groups in the material • To optimize the post-bake. • To reduce to the maximum the residuel OH groups. Irgacure 250 8. Results and discussion Figure 2:Near infrared spectra of EETMOS, and the sol. Figure 4 : middle infrared spectra of sol-gel thin films before and after irradiation. • Before irradiation • Large peak centered near 910 cm-1,and concealing the peak of the epoxy (885 cm-1). It’s assigned to characteristic modes of vibration of Si-OH, which can form in the sol hydrogens links which explains a large band of absorption at 3390 cm-1. • The peak at 1090cm-1 comes from the stretching of Si-O in the pure precursor. Enlarge designating a characteristic region of the presence of siloxanes links (SiOSi) • After Irradiation • Remarkable enhancement of the intensity at 3390 cm-1more OH groups are formed after irradiation, results from the air humidity. • This humidity, inhibit the reaction of the cationic polymerization while reacting on the active site to form some diols [8]. Pure EETMOS 3 principal bands : 1210, 1410, 1700 nm attributed to C-H groups [7]. hydrolysis sol • Progressive reduction in the transmission is observed between 1210 and 1700 nm. • The absorption between 1300 and 1480 nm and between 1480 nm and 1700 nm correspond to free OH species and linked OH species respectively[7]. Figure 1 : 29Si-NMR spectra of A (R=3) , B (R=10) and C (R=10+HF) sols*. • Kinetics of hydrolysis depends mainly on steric hindrance of aliphatic chain, for a given type of ORMOSIL. hydrolysis is encouraged by short aliphatic chain [5]. As the chain of the EETMOS bonded to silicon is cycloaliphatic type, it presents some sufficient steric hindrance to slow down the hydrolysis (spectrum A). • Increasing the water quantity (HCl 0.1 N) enhance hydrolysis kinetic (spectrum B).Only totally hydrolysis monomer species (T30) remained. Condensations reactions are more advanced to form oligomers with one or two siloxane bonds. • For a total disappear of T0 species, we decided to use a derivative version of the double step process by replacing the base by HF [6] (spectrum C). • Solution in spectrum (C) is the best choise to have lowest OH groups and as consequences, highly reactive oligomers for the inorganic polymerizaation. • A heat treatment is necessary first to decrease the OH content and second to improve mechanical propreties of Films. Figure 5 : spectra before and after the post-bake at 110°C, during 1h, 2h, 3h, 4h. Figure 3 : middle infrared spectrum of pure EETMOS. • Important decrease on the level of the absorption band at 3390 cm-1 for an irradiated layer, after the post bake at 110°C during 1 hour. • Diminuation of the absorbance band at 3390 cm-1 is negligible for a post-bake below and over 110°C, it can be explain that for a post-bake below 110°C, the thermal treatment is insufficient to evacuate the OH groups. Also over 110°C, the inorganic part becomes sufficiently rigid, forming a real trap for the OH group, preventing their evacuation easily • 885 cm-1, stretching vibration of C-O-C, (Epoxy ring). • 1090 cm-1, stetching vibration of Si-O links (related at the Si-OCH3 groups). * Notation Tij i : number of Si-OH j : Numbre of Si-O-Si 11. Conclusions References [1] M. J. M. Abadie, N. K. Chia, F. Boey, Journal of Applied Polymer Science, Vol 86, 1587-1591 (2002). [2] J.V. Crivello and U. Varlemann, Journal of polymer science: Part A: Polymer chemistry Vol 33, 2473-2486 (1995). [3] S.R. Akhtar, J.V. Crivello,and J.L. Lee, J.Org.Chem.1990, 55, 4222-4225. [4] S.K Rajaraman, W.A. Mowers, J.V. Crivello. Journal of polymer science: Part A: Polymer chemistry Vol 37, 4007-4018, (1999). [5]  F. Babonneau, J. Maquet, Poly Hedron, 19, 3, 2000, 315 [6] T.N.M. Bernards and M.J. Van Bommel, J.A.J. Jansen, journal of sol-gel science and technology13, 749-752 (1998). [7] Oubaha, M.; Smaihi, M.; Etienne, P.; Coudray, P.; Moreau, Y. J. Non-Cryst. Solids 2003,318, 305. [8] Thesis Mathieu FEUILLADE university HAUTE-Alsace,France; (2005) • Formation of a sol with highest reactive species. • Reducing OH groups in solution. • Evolution of chimical groups via IR spectroscopy • Reducing residuel OH in waveguide by post-bake at 110°C,1h • Imprinting simples photonic devices whose cross-section is in the order of 5× 5µm2 adapted to the kind of circuits developed in the laboratory. 12. Future Work • Reducing the intrinsic losses in waveguide. • Imprinting WDMA circuits. Rhodes, Greece XI international conference on the physics of Non Crystalline solids