International audienceTwo dry subtractive techniques for the fabrication of microchannels in borosilicate glass were investigated, plasma etching and laser ablation. Inductively coupled plasma reactive ion etching was carried out in a fluorine plasma (C4F8/O2) using an electroplated Ni mask. Depth up to 100 μm with a profile angle of 83°-88° and a smooth bottom of the etched structure (Ra below 3 nm) were achieved at an etch rate of 0.9 μm/min. An ultrashort pulse Ti:sapphire laser operating at the wavelength of 800 nm and 5 kHz repetition rate was used for micromachining. Channels of 100 μm width and 140 μm height with a profile angle of 80-85° were obtained in 3 min using an average power of 160 mW and a pulse duration of 120 fs. A novel process for glass-glass anodic bonding using a conductive interlayer of Si/Al/Si has been developed to seal microfluidic components with good optical transparency using a relatively low temperature (350°C)

Amorphous silica exhibits a complex mechanical response. The elastic regime is highly non linear while plastic flow does not conserve volume, resulting in densification. As a result the quantification of a reliable constitutive equation is a difficult task. We have assessed the potential of micro-pillar compression testing for the investigation of the micromechanical properties of amorphous silica. We have calculated the response of amorphous silica micropillars as predicted by Finite Element Analysis. The results were compared to preliminary micro-compression tests. In the calculations an advanced constitutive law including plastic response, densification and strain hardening was * Email: remi.lacroix@saint-gobain.com. 1This is the pre-peer reviewed version of the following article: International Journal of Applied Glass Science 3 [1] 3643 (2012), which has been published in final form at http: //onlinelibrary.wiley.com/doi/10.1111/j.2041-1294.2011.00075.x/abstract used. Special attention was paid to the evaluation of the impact of substrate compliance, pillar misalignment and friction conditions. We find that amorphous silica is much more amenable than some metals to microcompression experiments due to a comparatively high ratio between yield stress and elastic modulus. The simulations are found to be very consistent with the experimental results. However full agreement cannot be obtained without allowance for the non linear response of amorphous silica in the elastic regime.

International audienceAs layer transfer techniques have been notably improved in the past years, lithium niobate (LiNbO3) appears as a candidate for the next generation of ultrawide band radio frequency (rf) filters. Depending on the crystalline orientation, LiNbO3 can achieve electromechanical coupling factors Kt2 more than six times larger than those of sputtered aluminum nitride films. In this letter, a process based on direct bonding, grinding, polishing, and deep reactive ion etching is proposed to fabricate a single crystal LiNbO3 film bulk acoustic resonator. From the fabricated test vehicles, Kt2 of 43% is measured confirming the values predicted by theoretical computation

International audienceWe 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 600 nm diameters, with a periodicity of 400, 800 and 1200 nm 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 0.1 dB/cm

The dynamic properties of a 30-nm-thick permalloy film have been investigated through permeability measurements in the 100-MHz to 3-GHz range, in the presence of an external field applied along the easy axis. The permeability depends not only on the applied field, but also on the orientation of the field compared to the remnant magnetization of the sample. The application of an external field antiparallel to the magnetization may decrease the resonance frequency compared to the zero-field permeability. Ferromagnetic resonance equations provide a good description of the dynamic bistability at low fields, but do not account for the observed behavior in the whole bistability range. This is attributed to the occurrence of a nonuniform resonance.

Microfluidics on foil is gaining momentum due to a number of advantages of employing thin films combined with the capability of cost-effective high-volume manufacturing of devices. In this work, ultra-thin, flexible Y-microreactors with microchannels of 100 lm width and 30 lm depth were fabricated in thermoplastic polymer foils. The fluidic pattern was hot roll embossed in 125 lm thick poly-methyl-methacrylate (PMMA) and 130 lm thick cyclic-olefin-copolymer (COC) films using a dryetched microstructured silicon wafer as a flat embossing tool in a laminator. The sealing of the channels was performed with two different techniques, one based on lamination of SU8 dry film resist (DFR) and the other one based on spin-coated poly-dimethylsiloxane (PDMS). Testing of the interconnected microreactor was carried out using two dye colorant solutions to demonstrate mixing.

Magnetization reversal and magnetoresistance behavior of perpendicularly magnetized [Co/Pd]4/Au/[Co/Pd]2 nanowires J. Appl. Phys. 112, 073902 (2012) Electric-field control of CoFeB/IrMn exchange bias system J. Appl. Phys. 112, 064120 (2012) Critical effect of spin-dependent transport in a tunnel barrier on enhanced Hanle-type signals observed in threeterminal geometry Appl. Phys. Lett. 101, 132411 (2012) Giant tunneling magnetoresistance in epitaxial Co2MnSi/MgO/Co2MnSi magnetic tunnel junctions by halfmetallicity of Co2MnSi and coherent tunneling Appl. Phys. Lett. 101, 132418 (2012) Interface mediated ferromagnetism in bulk CuO/Cu2O composites Appl.Thin permalloy films without and with an 8 nm IrMn exchange layer have been grown by sputter deposition. Permalloy thickness ranges from 15 nm to 50 nm. The microwave permeability of these layers has been investigated in the 50 MHz to 3 GHz range using a permeameter based on a microstrip cell. A satisfactory measurement precision is observed on permalloy films as thin as 15 nm. The gyromagnetic resonance frequency increases from 670 MHz for the unbiased sample, to 2.7 GHz for the thinner biased sample. This increase in frequency is slightly larger than expected from the exchange-bias field measured by Kerr effect using a simple model for the gyromagnetic behavior. The properties of a two-period superlattice are also reported.

30 nm permalloy thin films have been grown by sputter deposition with and without an 8 nm IrMn exchange bias layer. The microwave permeability of these layers has been investigated in the 100 MHz–3 GHz range with a permeameter based on a microstrip cell, applying an external field along the easy axis. A comparison between the bias field deduced from magneto-optical Kerr effect measurements and a fit of the dynamic permeability spectra is made. Significant hysteresis effect on the microwave permeability of the biased sample is observed and modeled.