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Abstract: Poly(dimethyl siloxane) (PDMS) has been focused on recently due to its variety of applications specifically in microsystems technology. Many companies market two-component PDMS, which is comprised of a base component and a curing agent. Widely known and used for microsystems applications is Sylgard 184 from Dow Corning. Present work deals with two-component Room Temperature Vulcanized (RTV) PDMS from three different companies. They are Sylgard 184 from Dow Corning, RTV 615 from GE Silicones and RTV 141 from Rhodia Chemicals. Temporary increase in wettability of these three different types of PDMS by oxygen plasma by varying the plasma power and exposure time has been studied and compared with results available in literature. The hydrophobic recovery of the modified surfaces was monitored as a function of time and quantified. The surfaces were characterized using contact angle measurements and ATR-FTIR and XPS spectroscopy, their behavior analyzed in term of free surface energy and work of adhesion. [Copyright &y& Elsevier]

The cutting edge radius is a significant parameter of a micromachining tool. When it is not sufficiently sharp, ploughing, which affects the whole machining process and workpiece quality, will occur. It is then essential to be able to estimate the value of the cutting edge radius accurately. In this paper, a three-dimensional strategy that can be used to measure the microturning tool edge radii is presented. The strategy is based on robust cylinder fitting that is applied to a 3D point cloud of the tool. It is implemented in C++ with Open Computer Vision and Point Cloud Library. It was validated using a virtual point cloud, resulting in errors of 0.42% and 1.11% without noise and with noise, respectively. Additionally, uncertainties of 0. 045 μ m and 0. 082 μ m were obtained. It was successfully applied to six microturning inserts: three unused tools and three used tools. The point clouds were obtained with two different 3D surface reconstruction techniques, focus variation with a photon microscope and a multi-view stereo with a scanning electron microscope. The obtained results were more coherent, i.e., they were less dispersed; for example, in non-used tools, the range was [ 3. 11 μ m– 3. 90 μ m] and for the conventional circle fitting the range was [ 2. 62 μ m– 4. 38 μ m]. The traditional method is indirect: the 3D point cloud is sliced into 2D point clouds (profiles) fitted with circles. This 3D-2D process might result in errors. The proposed method is a direct 3D approach with no slicing step. • Importance of tool edge radii in the overall quality of micromachining. • Development of a method for accurate measurement of micro turning tool edge radii from 3D point cloud. • A method based on robust 3D fitting that avoids the 3D-2D process, which is a potential source of errors. • A semi-automatic and practical tool edge radii measurement method. [ABSTRACT FROM AUTHOR]

A sulfur hexafluoride based reactive ion etching process allowing to etch several micron deep holes with diameters of the order of a few microns in lithium niobate is reported. Etching of deep structures with aspect ratios up to 1.5 was made possible through the use of an electroplated nickel mask exhibiting a selectivity as high as 20 with respect to lithium niobate. Several crystallograpic orientations were investigated, although particular interest was paid to Y-axis oriented substrates. Photoresist as well as metal masks were also tested and their selectivity was compared. The influence of process parameters such as applied rf power or operating pressure on the sidewall slope angle of the etched patterns was investigated. The technique has been successfully applied to the fabrication of phononic crystals consisting of periodical arrays of 9 μm diameter, 10 μm deep holes, with a 10 μm period, and presenting sidewall angles as high as 73° etched in Y-axis oriented lithium niobate. [ABSTRACT FROM AUTHOR]

The present study demonstrates that thin layers of amorphous silicon oxide (SiOx) grown by inductively-coupled plasma enhanced chemical vapor deposition (ICPECVD) technology at lower temperatures can be successfully combined with biosensors. In particular, gold-amorphous silica (Au/SiOx) interfaces were investigated for their potential applications as a low-cost Surface Plasmon Resonance (SPR) sensor chip. ICPECVD silicon dioxide films up to 25 nm-thick were deposited at different pressure. Details of the SiOx thin layer properties in terms of refractive index, deposition rate, roughness, chemical bonds, Si2p and O1s bending energies, residual stress and contact angle were studied. The refractive index was found to decrease with increasing pressure for all the films. The depositions rates were lower for films deposited at higher pressures. We report here on the fabrication and characterization of stable and good reliabilities of SiOx deposited at two temperature 80 °C and 130 °C at pressures ranging from 2 Pa to 20 Pa. The results show that the SPR responses were very sensitive to any changes in the deposition parameters. In this study, we have shown that SiOx has good potential for further developments, as a wideband biosensor application with a higher sensitivity in SPR response. [ABSTRACT FROM AUTHOR]

Emphasis on effect of oxygen on structural and ferroelectric properties of lead zirconia titanate thin film is reported. The thin film is prepared using RF sputtering and annealed in air atmosphere to introduce oxygen vacancies. The photoelectron spectroscopy data reveal lead rich film, which decreases with annealing temperature, while oxygen content decreases from 59.32–55.82% after annealing. The decrease in oxygen causes pyrochlore formation along with perovskite phase in annealed film. The polarization graph shows reduction in domain wall mobility and film polarization due to oxygen vacancy. The pure perovskite phase is achieved using CFA by inserting O2in annealing chamber. [ABSTRACT FROM AUTHOR]

This paper presents a method to determine the mechanical properties of piezoelectric thin films. The vibrational behavior of microcantilevers and clamped-clamped beams actuated by aluminum nitride (AlN) piezoelectric films were analyzed in order to investigate the suitability of these devices as characterization tools. Different geometries of resonators composed of a free-standing structure made up of a TiPt/AlN/TiPt piezoelectric stack were tested. The out-of-plane motion of the resonators was assessed by laser Doppler vibrometry. An AlN Young's modulus of about 200 GPa was extracted from resonance-frequency measurements by means of Comsol software simulations that allow taking into account AlN underetching. This value of Young's modulus was compared to the one measured by a nanoindentation technique. The quality of crystallinity was also assessed using X-ray diffraction (XRD) measurements. We then estimated the residual stress (about 200 MPa) using an interferometry measurement. [ABSTRACT FROM AUTHOR]

We present an optimization process to improve the rejection ratio in integrated beam combiners by locking the dark fringe and then monitoring its intensity. The method proposed here uses the electro-optic effect of lithium niobate in order to lock the dark fringe and to real-time balance the photometric flux by means of a twostage Mach--Zehnder interferometer waveguide. By applying a control voltage on the output Y-junction, we are able to lock the phase and stay in the dark fringe, while an independent second voltage is applied on the firststage intensity modulator, to finely balance the photometries. We have obtained a rejection ratio of 4600 (36.6 dB) at 3.39 µm in transverse electric polarization, corresponding to 99.98% fringe contrast, and shown that the system can compensate external phase perturbations (a piston variation of 100 nm) up to around 1 kHz. We also show the preliminary results of this process on wide-band modulation, where a contrast of 38% in 3.25- to 3.65-µm spectral range is obtained. These preliminary results on wide-band need to be optimized, in particular, for reducing scattered light of the device at the Y-junction. We expect this active method to be useful in high-contrast interferometry, in particular, for astronomical spatial projects actually under study. [ABSTRACT FROM AUTHOR]

Abstract: The anodic oxidation of concentrated glycine based aqueous electrolyte on smooth platinum electrode leads to a strongly grafted polyglycine-like coating on the surface in an irreversible way. Due to the proton affinity towards amino groups of polyglycine (PG), the electrodeposited thin film was used as receptor for solid potentiometric pH sensor. In order to reach local pH measurement, we developed miniaturized microelectrodes on glass substrate thanks to photolithography process. We used silver chloride on silver as the reference electrode. The couple (silver chloride, PG based platinum electrode) of microelectrodes gives linear potentiometric response vs. pH in the range [2–12], reversibly and with a sensitivity of 52.4mV/pH (for 1mm electrode size). PG based pH electrode is compared to other organic polymer based pH receptor such as linear polyethylenimine (L-PEI), polyaniline (PANI) and glass membrane. [Copyright &y& Elsevier]

Tungsten oxide WO 3 thin films were prepared by dc reactive magnetron sputtering. The GLancing Angle Deposition (GLAD) technique was implemented to transform the typical dense microstructure into an inclined columnar and porous architecture. The incident angle α of the sputtered particles was 0° and 70° leading to a column tilt angle β of 0° and 40°, respectively. Conventional and inclined WO 3 films were sputter deposited on a commercial hotplate system. Ozone gas was periodically injected from 0 to 220 ppb and the variation of electrical conductance of the system was measured vs. time at 250 °C. The conventional WO 3 films exhibited a significant change of electrical conductance as a function of the ozone injection. GLAD WO 3 films with a columnar angle β =40° were even more sensitive to the ozone pulses and the speed of response or recovery was significantly enhanced. This ozone detection improvement was mainly attributed to the more porous structure of WO 3 films produced by the GLAD method. [ABSTRACT FROM AUTHOR]

• Titanium oxynitride films are sputter-deposited pulsing O 2 and N 2 independently. • Duty cycle of each reactive gas allows a precise control of the sputtering process. • Reactive sputtering alternates between elemental, oxidized and nitrided modes. • A smooth absorbent-to-transparent transition is obtained tuning both duty cycles. Titanium oxynitride thin films are deposited by DC reactive magnetron sputtering. A pure titanium target is sputtered in a reactive atmosphere composed of argon, oxygen and nitrogen gases. The oxygen mass flow rate as well as that of the nitrogen gas are both pulsed during the deposition time using an independent and rectangular signal for each reactive gas. A constant pulsing period T = 45 s is applied for both reactive gases and a delay time δ of 34 s between N 2 and O 2 injection times is set for all depositions. Oxygen and nitrogen duty cycles are systematically and independently changed from 0 to 100 % of their pulsing period. From real time measurements of the Ti target potential and total sputtering pressure, it is shown that the reactive process alternates between oxidized, nitrided and elemental sputtering modes as a function of the oxygen and nitrogen injection times. The full poisoning of the Ti target surface by oxygen and/or nitrogen can be avoided for some given ranges of O 2 and N 2 duty cycles. Deposition rates of titanium oxynitride films are substantially enhanced and can be adjusted between that of pure Ti and TiN films with a gradual transition of their electrical conductivity and optical transmittance in the visible range. These results support that titanium oxynitride compounds exhibiting absorbent to transparent behaviors can be precisely sputter-deposited by means of a two reactive gases pulsing process. [ABSTRACT FROM AUTHOR]

Abstract: We report on two approaches to achieve ultra-smooth structures on lithium niobate (LiNbO3) substrates. The first method relies on ICP-RIE (inductively coupled-reactive ionic etching) or on RIE, and is exploited here for the fabrication of rods with smooth etched surfaces. A series of tests have been performed with fluorine gases. Nanometric rods with 200, 400 or 600nm diameters, with a periodicity of 400, 800 and 1200nm respectively and etched angles close to 68° for the RIE process and 75° for the ICP-RIE process have been fabricated. The second process is based on “optical grade dicing” and is dedicated to the fabrication of deep-etched ridge waveguides. First optical characterization results are reported. They show optical propagation losses value close to 0.1dB/cm. [Copyright &y& Elsevier]

Although titanium dental implants are biocompatible, exhibit excellent corrosion resistance and high mechanical resistance, the material fails in providing resistance to infection because it exhibits poor antimicrobial activity. To address these issues, we deposited silver onto titanium abutments (Grade 5 titanium discs) using direct current (DC) sputtering and assessed the antimicrobial activity and biocompatibility of the modified implant material. Atomic absorption spectrometry and X-ray photoelectron spectroscopy were employed to investigate the concentration and elemental composition of the deposited silver. As expected, silver deposited using DC plasma was uniform and good control over the deposition could be achieved by varying the sputtering time. Moderate biocompatible responses (up to 69% viability) were observed in primary human gingival fibroblast cells incubated in the presence of Ti sputtered with Ag for 5 min. Silver deposited titanium (Ti-Ag) showed excellent antibacterial effects on Pseudomonas aeruginosa and Streptococcus mutans at a very low concentration (Ag content 1.2 and 2.1 μg/mm 2 ). However, higher concentration of silver (6 μg/mm 2 ) was required to achieve a reduction in cell viability of Staphylococcus aureus and Candida albicans . The silver sputtered Ti abutments could maintain a long-term antibacterial activity as evidenced by the release of silver up to 22 days in simulated body fluid. Our study illustrates that silver deposited titanium is indeed a promising candidate for soft tissue integration on dental abutments and prevents initial microbial adhesion. [ABSTRACT FROM AUTHOR]

A metal-containing polymer has been prepared by electropolymerization of an homoleptic Ru(II)-terpyridine complex bearing pyrrole heterocycles. The polymer is obtained as a thin film at the surface of electrodes, and has been characterized by electrochemical measurements, XPS and microscopy. It has been shown that this polymer acts as an active gas sensitive layer since it enables the detection of an ammonia gas flow through layer’s resistivity measurements. [ABSTRACT FROM AUTHOR]

Vanadium and vanadium oxide thin films are deposited by DC magnetron sputtering. A first series of pure vanadium films are prepared by glancing angle deposition (GLAD). The incident angle α of the particle flux is systematically changed from 0 to 85°. For the second series, the angle α is kept at 85° and oxygen gas is injected during the growth by means of the reactive gas pulsing process (RGPP). A constant pulsing period P = 16 s is used whereas the oxygen injection time t ON is varied from 0 to 6 s. After depositing, films are annealed in air following 11 incremental cycles from room temperature up to 550 °C. For both series, the DC electrical resistivity is systematically measured during the annealing treatment. Vanadium films sputter deposited by GLAD become sensitive to the temperature for incident angles α higher than 60°. The most significant annealing effect is observed for films prepared with α = 85° with a strong increase of resistivity from 2.6 × 10 − 5 to 4.9 × 10 − 3 Ωm. It is mainly assigned to the oxidation of GLAD vanadium films, which is favoured by the high porous morphology produced for the highest incident angles. The resistivity vs. temperature evolution is also measured and related to the occurrence of the VO 2 phase. By combining GLAD and RGPP processes, the reversible variation of resistivity associated to the VO 2 phase is even more pronounced. Oxygen pulsing during deposition and the voided structure produced for the highest incident angles enhance the oxidation of vanadium through the films thickness. The porous architecture by GLAD and the oxygen injection by RGPP have to be carefully controlled and optimized for the growth of vanadium oxide compounds, especially to favour the formation of the VO 2 phase. [ABSTRACT FROM AUTHOR]

The article presents the design, fabrication and characterization of platinum thin-film Resistance Temperature Detectors (RTDs) for heat flux sensing applications. The microfabrication process is described and the thin films are analysed by several methods including SEM, XRD and profilometry. Estimation of experimental uncertainties is performed. The influence of annealing, self-heating, 2-wire and 4-wire connections are studied. The analysis and experimental results show that the RTDs have a good repeatability when an annealing process is performed and a maximal injected current are used. A measurement uncertainty of 0.14 °C is achieved. The observed Temperature Coefficient Ratio is sufficient to ensure variation of the resistance in the temperature range. The heat flux measurements made with the sensor are validated in a dedicated test bench and present a good repeatability. [ABSTRACT FROM AUTHOR]

Abstract: A gas sensor consisting in polypyrrole films electrochemically deposited on microelectrodes arrays was fabricated using silicon microtechnologies. Polypyrrole was electrodeposited on platinum microelectrodes using four different electrodeposition potentials, five counter-ions and three salt concentrations to assess the effects of these parameters on the sensing properties of polypyrrole films. The change in conductance of thin polymer layers, due to adsorption of ammonia gas, was used as a sensor signal. The behaviors of the polymer-based gas sensors, including response time, response amplitude, reproducibility and reversibility, to various ammonia gas concentrations ranging from 1 to 100ppm were investigated. The experimental results showed that these ammonia gas sensors were efficient since they were sensitive to ammonia, and since their response was fast and reproducible at room temperature. The most efficient ammonia gas sensor was obtained with a 248nm-thick polypyrrole film electrosynthesized from 0.1M pyrrole and 0.1M LiClO4 under an electrodeposition potential of +2.0V/SCE. [Copyright &y& Elsevier]

Abstract: Polyethyleneimine films have been deposited on platinum electrode surfaces by electrochemical oxidation of ethylenediamine H2N–CH2–CH2–NH2 (EDA) in acetonitrile solutions. This electrochemical synthesis was realized by cyclic voltammetry and gravimetry techniques. Then, the characterization of the thin solid polyethyleneimine film was performed using X-ray photoelectron spectroscopy and infrared spectroscopy. It was also shown, using atomic force microscopy, that the solid polymeric coating has a granular and homogeneous structure. The influence of EDA concentration on the electropolymerization process was studied leading to the conclusion that the reaction is easier for high EDA concentration. Then, the influence of the nature and concentration of the supporting salt was investigated, showing that its nature is not very important, contrary to its concentration. [Copyright &y& Elsevier]

Abstract: A new type of pH biosensor was developed for biological applications. This biosensor was fabricated using silicon microsystem technology and consists in two platinum microelectrodes. The first microelectrode was coated by an electrosynthesized polymer and acted as the pH sensitive electrode when the second one was coated by a silver layer and was used as the reference electrode. Then, this potentiometric pH miniaturized biosensor based on electrosynthesized polypyrrole or electrosynthesized linear polyethylenimine films was tested. The potentiometric responses appeared reversible and linear to pH changes in the range from pH 4 to 9. More, the responses were fast (less than 1min for all sensors), they were stable in time since PPy/PEI films were stable during more than 30 days, and no interference was observed. The influence of the polymer thickness was also studied. [Copyright &y& Elsevier]

This paper reports on an original architecture of microfabricated alkali vapor cell designed for miniature atomic clocks. The cell combines diffraction gratings with anisotropically etched single-crystalline silicon sidewalls to route a normally-incident beam in a cavity oriented along the substrate plane. Gratings have been specifically designed to diffract circularly polarized light in the first order, the latter having an angle of diffraction matching the (111) sidewalls orientation. Then, the length of the cavity where light interacts with alkali atoms can be extended. We demonstrate that a longer cell allows to reduce the beam diameter, while preserving the clock performances. As the cavity depth and the beam diameter are reduced, collimation can be performed in a tighter space. This solution relaxes the constraints on the device packaging and is suitable for wafer-level assembly. Several cells have been fabricated and characterized in a clock setup using coherent population trapping spectroscopy. The measured signals exhibit null power linewidths down to 2.23 kHz and high transmission contrasts up to 17%. A high contrast-to-linewidth ratio is found at a linewidth of 4.17 kHz and a contrast of 5.2% in a 7-mm-long cell despite a beam diameter reduced to 600 μm. [ABSTRACT FROM AUTHOR]

The constant improvement of industrial needs to face modern telecommunication challenges leads to the development of novel transducer principles as alternatives to SAW and BAW solutions. The main technological limits of SAW (short-circuit between electrodes) and BAW (precise thickness control) solutions can be overcome by a new kind of transducer based on periodically poled ferroelectric substrate. The approach proposed in this paper exploits a ridge structure combined with a periodically poled transducer (PPT), allowing for the excitation of highly coupled modes unlike previously published results on planar PPTs. High-aspect-ratio ridges showing micrometer dimensions are achieved by dicing PPT plates with a diamond-tipped saw. An adapted metallization is achieved to excite acoustic modes exhibiting electromechanical coupling in excess of 15% with phase velocities up to 10 000 m?s?1. Theoretical predictions show that these figures may reach values up to 20% and 18 000 m?s?1, respectively, using an appropriate design. [ABSTRACT FROM AUTHOR]