Traditional Quartz Crystal Microbalance (QCM) sensors used for biological detection are limited in mass sensitivity due to their large thickness. This study presents a biosensor utilizing a Shear Horizontal Acoustic Plate Mode (SHAPM) resonator constructed from a suspended Y+36 degrees cut LiNbO3 (LNO) plate. LNO is chosen over quartz or AlN for its higher permittivity, which reduces capacitive coupling when in contact with water. Finite Element Method (FEM) simulations reveal that mass sensitivity (S-m) increases with decreasing LNO plate thickness, yet structural integrity limits the minimum thickness to 2 mu m, resulting in S-m = 70 Hz center dot cm(2)/ng. The device is integrated into a microfluidic system and a printed circuit board for real-time detection. The sensor exhibits a limit of detection (LOD) of 15 ng/cm(2) for non-specific binding of Bovine Serum Albumin (BSA). This is comparable to that of previously reported Love wave devices.

The stability and accuracy of atomic devices can be degraded by the evolution of their cell inner atmosphere. Hence, the undesired entrance or leakage of background or buffer gas, respectively, that can permeate through the cell walls, should be slowed down. In this work, we investigate helium permeation in microfabricated alkali vapor cells filled with He and whose windows are made of borosilicate glass (BSG) or aluminosilicate glass (ASG). The permeation is then derived from routine measurements of the pressure-shifted hyperfine transition frequency of an atomic clock. We first confirm that ASG reduces the He permeation rate by more than two orders of magnitude, in comparison to BSG. In addition, we demonstrate that Al2O3 thin-film coatings, known to avoid alkali consumption in vapor cells, can also significantly reduce He permeation. The permeation through BSG is thereby reduced by a factor up to 130, whereas the one through ASG is decreased by a factor up to 5.0 compared to uncoated substrates. These results may contribute to the development of miniaturized atomic clocks and sensors with improved long-term stability or sensitivity.

Background: High-frequency ultrasonic transducer arrays are essential for high resolution imaging in clinical analysis and Non-Destructive Evaluation (NDE). However, the structure design and fabrication of the kerfed ultrasonic array is quite challenging when very high frequency (>= 100 MHz) is required.Objective and method: Here we investigate the effect of kerf depth on the performances of array transducers. A finite element tool, COMSOL, is employed to simulate the properties of acoustic field and to calculate the electrical properties of the arrays, including crosstalk effect and electrical impedance. Furthermore, Inductively Coupled Plasma (ICP) deep etching process is used to etch 36 degrees/Y-cut lithium niobate (LiNbO3) crystals and the limitation of etching aspect ratio is studied. Several arrays with different profiles are realized under optimized processes. At last, arrays with a pitch of 25 mu m and 40 mu m are fabricated and characterized by a network analyzer.Results: Kerf depth plays an important role in the performance of the transducer array. The crosstalk is proportional to kerf depth. When kerf depth is more than 13 mu m, the array with crosstalk less than -20 dB, which is acceptable for the real application, could provide a desired resolution. Compared to beam focusing, kerf depth exhibits more effect on the beam steering/focusing. The lateral pressure distribution is quantitatively summarized for four types of arrays with different kerf depth. The results of halfcut array are similar to those of the full-cut one in both cases of focusing and steering/focusing. The Full-Width-at-Half-Maximum (FWHM) is 55 mu m for the half-cut array, and is 42 mu m for the full-cut one. The 5-mu m-cut array, suffering from severe undesired lobes, demonstrates similar behaviors with the no-cut one. ICP process is used to etch the 36 degrees/Y-cut LiNbO3 film. The aspect ratio of etching profile increases with the kerf width decreasing till it stops by forming a V-shaped groove, and the positive tapered profile angle ranges between 62 degrees and 80 degrees. If the mask selectivity does not limit the process in terms of achievable depth, the aspect ratio is limited to values around 1.3. The measurement shows the electrical impedance and crosstalk are consistent with the numerical calculation.Conclusion: The numerical results indicate that half-cut array is a promising alternative for the fabrication of high-frequency ultrasonic linear arrays. In fact, the minimum pitch that could be obtained is around 25 mu m, equivalent to a pitch of 1.6 lambda, with a kerf depth of 16 mu m under the optimized ICP parameters. Crown Copyright (C) 2011 Published by Elsevier B. V. All rights reserved.

Background: High-frequency ultrasonic transducer arrays are essential for high resolution imaging in clinical analysis and Non-Destructive Evaluation (NDE). However, the fabrication of conventional backing-layer structure, which requires a pitch (distance between the centers of two adjacent elements) of half wavelength in medium, is really a great challenge.Objective and method: Here we present an alternative buffer-layer structure with a silicon lens for volumetric imaging. The requirement for the size of the pitch is less critical for this structure, making it possible to fabricate high-frequency (100 MHz) ultrasonic linear array transducers. Using silicon substrate also makes it possible to integrate the arrays with IC (Integrated Circuit). To compare with the conventional backing-layer structure, a finite element tool, COMSOL, is employed to investigate the performances of acoustic beam focusing, the influence of pitch size for the buffer-layer configuration, and to calculate the electrical properties of the arrays, including crosstalk effect and electrical impedance.Results: For a 100 MHz 10-element array of buffer-layer structure, the ultrasound beam in azimuth plane in water could be electronically focused to obtain a spatial resolution (a half-amplitude width) of 86 mu m at the focal depth. When decreasing from half wavelength in silicon (42 mu m) to half wavelength in water (7.5 mu m), the pitch sizes weakly affect the focal resolution. The lateral spatial resolution is increased by 4.65% when the pitch size decreases from 42 mu m to 7.5 mu m. The crosstalk between adjacent elements at the central frequency is, respectively, -95 dB, -39.4 dB, and -60.5 dB for the 10-element buffer, 49-element buffer and 49-element backing arrays. Additionally, the electrical impedance magnitudes for each structure are, respectively, 4 k Omega, 26.4 k Omega, and 24.2 k Omega, which is consistent with calculation results using Krimholtz, Leedom, and Matthaei (KLM) model.Conclusion: These results show that the buffer-layer configuration is a promising alternative for the fabrication of high-frequency ultrasonic linear arrays dedicated to volumetric imaging. (C) 2011 Elsevier B.V. All rights reserved.

High-frequency ultrasonic transducer arrays are essential for high resolution imaging in clinical analysis and Non-Destructive Evaluation (NDE). However, the structure design and fabrication of the kerfed ultrasonic array is quite challenging when very high frequency (≥ 100 MHz) is required. Inductively Coupled Plasma (ICP) deep etching process is used to etch 36°/Y-cut lithium niobate (LiNbO3) crystals. Furthermore, a finite element tool, COMSOL, is employed to calculate the electrical properties of the arrays, including crosstalk effect and electrical impedance. At last, arrays with a pitch of 40 μm are fabricated and characterized by a network analyzer. The measured results agree well with the theoretical predictions.

The effect of kerf depth is investigated on the performances of array transducers. A finite element tool, COMSOL, is employed to simulate the properties of acoustic field and to calculate the electrical properties of the arrays, including crosstalk effect and electrical impedance. Furthermore, Inductively Coupled Plasma (ICP) deep etching process is used to etch 36°/Y-cut lithium niobate (LiNbO 3 ) crystals and the limitation of etching aspect ratio is studied. Several arrays with different profiles are realized under optimized processes. At last, arrays with different pitches are fabricated and characterized by a network analyzer.

36°/Y-cut lithium niobate (LiNbO 3 ) single crystals have been patterned by means of Inductively Coupled Plasma (ICP) deep etching to create ultrasonic arrays resonating in the frequency range of 100-200 MHz. The limitation of etching aspect ratio and the minimum pitch are explored under the optimized ICP parameters. The experimental results demonstrate that the minimum pitch could be obtained at about 25 μm, equivalent to a pitch of 1.6 λ, with a kerf depth of 16 μm. Focusing Ion Beam (FIB) technique is also studied to etch LiNbO 3 crystals. The aspect ratio is up to as high as 6. A pitch of 0.5 λ can be obtained for a 100 MHz half-kerfed LiNbO 3 array.

There is need for less expensive and rapid tooling for prototyping microfluidic components and systems in thermoplastics using microreplication technique such as microinjection moulding. This paper presents the adaptation of a conventional injection moulding process using a silicon mould insert. A dry-etched silicon mould insert with aspect ratio of 4 was produced by a two-step dry etching process. Cycloolefin copolymer (COC 5013 and 8007) fluidic chips of 560 mu m thickness comprising channels of 100 pm depth and width down to 25 pm were manufactured. The injection processing temperature and mould temperature were varied from 265 degrees C to 305 degrees C and 40 degrees C to 190 degrees C respectively to study their effect on the COC replicas.

As layer transfer techniques have been notably improved these passed years, lithium niobate (LiNbO3) appears as a candidate for the next generation of ultra wide band RadioFrequency (RF) filters. Depending on the crystalline orientation, LiNbO3 can achieve electromechanical coupling factors Kt(2) more than 6 times larger than those of sputtered aluminium nitride films. In this paper, a process based on direct bonding, grinding, polishing and Deep Reactive Ion Etching (DRIE) is proposed to fabricate a single crystal LiNbO3 Film Bulk Acoustic Resonator (FBAR). From the fabricated test vehicles K-t(2) of 45% is measured confirming the values predicted by theoretical computations.

Two 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).

In this paper, we present new results on the development of piezoelectric transducers based on periodically poled ferroelectric domains in a lithium niobate plate bonded between two silicon wafers. The fabrication of the periodically poled transducers operating in the range 50 - 500 MHz has been achieved on a 3 inches 500 pm thick wafer. These devices then have been bonded on silicon wafers to fabricate a waveguide. Guided elliptic as well as partially guided longitudinal modes are excited. The experimental responses of the tested devices are compared to predicted harmonic admittances, showing a good agreement between both results and allowing for a reliable analysis of the nature of the excited modes. We also show interesting studies of material combinations used to guide ultrasonic waves. Dispersion properties have also been studied for a structure Si/PPT/Si.

As 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 Kt(2) 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, Kt(2) of 43% is measured confirming the values predicted by theoretical computations.

New guiding principles and concepts are currently investigated for developing high frequency devices capable to answer the RF manufacturer demand for telecommunication an remote transmission modern components. Beside the use of physically or chemically deposited piezoelectric overlays, the use of composite wafers composed by single crystal layers and wafers obtained by wafer bonding and lapping/polishing techniques offers attractive opportunities for overpassing the known limitations of acoustics-based radio-frequency devices. In this paper, we present different approaches for manufacturing such composite wafers and we describe different applications taking advantage of their unique characteristics. Lithium niobate is particularly considered for the piezoelectric layers because of its exceptional piezoelectric properties and its very high acoustic quality, and various substrate such as silicon, sapphire and lithium niobate again are used to guide and trap the excited waves. State-of-the-art Surface Acoustic Wave (SAW) devices, Harmonic Bulk Acoustic Resonators (HBARS) and Periodically Poled Transducers developed on such wafers are presented to illustrate the potential of this technological approach.

Reactive ion etching (RIE) has been used to etch micron-sized holes which are several microns in depth in lithium niobate, mostly on Y- and Y-rotated cut substrates, the underlying idea being the realization of phononic crystal devices. The etching process is based on the use of sulfur hexafluoride as the etching gas. Photoresist and sputtered or electroplated metals masks were used and compared to ensure high process selectivity and good sidewall verticality. Maximum mask selectivity was found to be of the order of 20. Etched depths larger than 10 mum and aspect ratios above 1.5 have been achieved. Sidewall verticality higher than 73deg is also reported. The technique has been applied to the fabrication of phononic SAW devices designed to operate at a frequency around 200 MHz. The phononic structure consists of periodical arrays of 9 mum diameter, with a 10 mum period etched in Y-cut lithium niobate.

Complex permeability spectra of CoNbZr thin films have been measured up to 4GHz by a single coil pertubation technique. In addition to the well-known ferromagnetic resonance, multiple resonant modes have been evidenced in the increasing branches of the spectra. The number of “secondary peaks” observed depends on the sample thickness. Their resonance frequencies follow a nonlinear dispersion law versus the ratio of the mode number over the sample thickness with a power factor close to 1.5.

This paper demonstrates that the monitoring of the microwave permeability of thin films is an efficient way to obtain a real-time information on the in-plane uniaxial anisotropy, both in magnitude and in direction. Theoretical guidelines required to extract relevant information on the in-plane uniaxial anisotropy are presented. This technique has evidenced a fast decrease in the anisotropy followed by a slower rotation process of the uniaxial anisotropy in a Co91Nb6Zr3 film during thermo-magnetic annealing.

Dynamic permeability measurements of soft magnetic films are performed and their corresponding domain configurations are observed with a Kerr effect microscope. Measurable discrepancies can be observed between the effective permeabilities of layers of different macroscopic sizes and in layered structures. These effects can be associated with the presence of a domain configuration at the edges of the sample. A phenomenological method is proposed to describe these discrepancies. It is supposed that a region at the edge of the sample exhibits a perturbed microwave permeability with lower frequency signals. These outcomes have consequences on the conception of devices using high permeability layers.