J. Jabbour

Piezoelectric zinc oxide by electrostatic spray pyrolysis

Zinc oxide (ZnO) possesses many interesting properties, such as a wide energy band gap, large photoconductivity, and high excitonic binding energy. Piezoelectric (ZnO) film has a high electro-mechanical coupling coefficient, which makes it a promising material for high frequency and low surface acoustic wave (SAW), bulk acoustic wave, and microelectromechanical system devices. In this work, we present the first results obtained for piezoelectric ZnO thin films prepared on corning 7059 glass substrate by electrostatic spray pyrolysis (ESP), a simple, cheap and efficient technique not widely used for ZnO deposition, using zinc nitrate in a mixture of deionised water and isopropyl alcohol. The structural morphologic and optical properties of the films have been studied and the effect of the preparation conditions, such as substrate temperature and substrate-nozzle distance, discussed. Highly c-axis preferred orientation, which is critical for piezoelectric applications (ultrasonic oscillators and transducers devices), ZnO thin films are obtained at 350^oC growth temperature and at 4.5cm substrate-nozzle distance.

Measurement of the effect of plasmon gas oscillation on the dielectric properties of p- and n-doped AlxGa1−xN films using infrared spectroscopy

We report on the application of infrared (IR) spectroscopy as an approach to nondestructive optical method for quantitative measurement of relevant optoelectronic properties in complex multilayer systems. We developed a numerical technique to analyze quantitatively the dielectric properties and plasmon gas characteristics from infrared reflectivity measurements. The developed technique is based on the combination of Kramers-Kronig theorem with the classical theory of electromagnetic wave propagation in a system of thin films. We applied the approach to deduce the dielectric properties and plasmon gas characteristics in p- and n-doped AlGaN alloys of various compositions, deposited on AlN(100 nm)/GaN(30 nm)/Al2O3. The results agreed with the electrical measurements, and the back calculation reproduced satisfactory the reflectivity measurements, demonstrating the accuracy of the developed technique.

Synthesis and characterization of a photosensitive organic–inorganic, hybrid positive resin type material: application to the manufacture of microfluidic devices by laser writing

A positive working and chemical amplified photosensitive organic–inorganic hybrid material based on PAA polymer with a lower molecular weight, 1,3,5-tris[(2-vinyloxy)ethoxy]benzene (TVEB) as a crosslinking dissolution inhibitor, a VEPTES pre-hydrolysed as an organic–inorganic material and a PAG photoacid generator was developed. The TVEB was prepared by coupling 1,3,5-trihydroxybenzene and 2-chloroethyl vinyl ether. The hybrid photosensitive material showed sensitivity when exposed to UV light at 375 nm followed by development with a 2.38 wt% aqueous solution of TMAH at room temperature. The synthesis of the material was followed by FTIR spectroscopy to follow the crosslinking of the vinyl ether group from TVEB and VEPTES with the carboxylic group of the PAA polymer.

Design and controlled synthesis by dual polymerization of new organic–inorganic hybrid material for photonic devices

Organic–inorganic hybrid material was synthesized by double polymerization processes i.e. a sol–gel process and organic polymerization respectively. For this study, hybrid monomer, 4-vinyl ether-phenyltriethoxysilane (VEPTES) was used as starting building block. First, the silica matrix with tunable ratio of siloxane and silanol units was synthesized by a sol–gel process under acidic conditions and the organic network was formed by cationic photopolymerization of vinyl ether groups. Mineral and organic polymerization kinetics were respectively monitored by liquid 29Si-NMR and IR spectroscopy. The effect of the silicate backbone on the organic photopolymerization process was studied and elucidated. The optical performance of this new hybrid material has been studied using the near-infrared spectroscopy.

Chemical sensors based on optical sensitivity of metal oxide materials deposited on multimode interference couplers

An optical sensor based on MMI structures has been studied. We have used the optical parameters of a new hybrid material deposited by sol-gel method leading to waveguide structures after UV-photoinscription, and of ZnO, sensitive material characterised in previous studies. The variation of optical properties such as the refractive index of the covering sensitive material leads to a modification of waveguiding conditions in the MMI. A gas sensor can be developed by measuring the variation of light intensity at the output of the MMI structure under gas exposure. Simulations have been performed in order to optimise the output light intensity variations to increase sensitivity. We have shown that these structures are more sensitive than Mach-Zehnder interferometers, and that the relation between dimensions and sensitivity of the MMI is not trivial. Computations have to be performed to optimise the structure for given parameters.

New organic–inorganic hybrid material based on a poly(amic acid) oligomer: a promising opportunity to obtain microfluidic devices by a photolithographic process

Miniaturized total analysis systems are becoming a powerful tool for analytical and bioanalytical applications. Biological and chemical sensors for health and environmental applications often require adaptable technologies. A flexible and low-cost process using a material with efficient mechanical and thermal properties is necessary. Organic–inorganic hybrid materials offer the advantages of the organic content and the inorganic matrix. In this study, a microfluidic sensor is fabricated on a new hybrid photosensitive material using an accurate and flexible process based on pulsed UV laser lithography. The material is based on poly(amic acid) (PAA) oligomer with lower molecular weight and lower cost, 1,3,5-tris[(2-vinyloxy)ethoxy]benzene (TVEB) as a crosslinking dissolution inhibitor, pre-hydrolysed 4-vinylether-phenyltriethoxysilane (VEPTES) as an organic–inorganic material, and a photoacid generator (PAG). A fine positive pattern is fabricated in a 3 μm thick film with laser writing using 125 μW energy. The synthesized hybrid material is characterized by nano indentation to analyze the force required to indent the coating and to predict the coating hardness and elastic modulus. Furthermore, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are used to evaluate its thermal stability. Scanning electron microscopy (SEM) is performed to verify the homogeneity of the material. These newly prepared photosensitive hybrid materials can open the way for potential applications in the fabrication of microfluidic devices.