Quartz Surface Acoustic Wave Research Articles

Doubly rotated SAW quartz cuts with low sensitivity to stress and temperature effects exhibiting a power flow angle close to zero

Three doubly rotated quartz cuts for surface acoustic wave (SAW) devices have been theoretically found exhibiting a very low sensitivity to radial in-plane stresses and to statical temperature effects and also presenting a very small power flow angle. Such a conjunction of these phenomena offers new perspectives in the design of very high stability SAW resonators.

Surface-acoustic-wave devices with low sensitivity to mechanical and thermoelastic stresses.

Surface-acoustic-wave (SAW) devices with a low sensitivity to both temperature and stresses effects are presented and experimentally tested. Devices are built on SAW quartz cuts with zero first-order temperature coefficient and zero sensitivity to planar isotropic stresses. In comparison with similar devices built on conventional (ST, X) cuts, two kinds of experiments are reported. First, devices built on circular quartz plates are submitted to in-plane diametrical compressions. The force-frequency effect is measured and results are compared to theoretical predictions either by analytical models or using finite element analysis. In a second experiment, the same devices are submitted to in-plane thermoelastic stresses in a dynamical thermal regime. It is shown that the sensitivity of the new cuts to dynamical thermal effects is one order of magnitude lower than the conventional (ST, X) cut, an attractive potentiality for fast-warm-up high-stability SAW oscillators in severe environmental conditions.

Response selectivity of etched surface acoustic wave sensors

The etching of a quartz surface acoustic wave crystal is discussed in terms of its effects as a chemical sensor for gas-phase organic vapours. Experimental results are presented for a bare quartz surface and one having a covalently bound film of 3-aminopropyltriethoxysilane (APTES). The sensitivity of the prepared devices was examined using steady-state and transient adsorption measurements, and found to be enhanced when the surface was first subjected to mild etching. This has been attributed to an increase in the density of silanol groups on the surface, providing an increased number of sites for both hydrogen bonding and covalent attachment. Improved selectivity was observed for nitrobenzene over other organic vapours between etched and unetched APTES-coated devices.

An acoustic absorption film for SAW devices

Surface acoustic wave (SAW) devices are used in several sensor applications, such as sensors for humidity, gas concentration, voltage and flow. The reflection of the surface acoustic waves at the edges of a SAW substrate causes interference with the main signal and degrades the characteristics of the device. Therefore, the edges of SAW substrates are often provided with wax or another material which absorbs the surface waves. SAW devices are being fabricated by sophisticated photolithographic processes, while the deposition techniques for the absorber material are mainly screen printing or manual painting. The development of new materials in IC technology gives opportunities for new acoustic absorption films. A very useful material is polyimide, a viscous organic material which maintains its absorptive acoustic properties after curing. Polyimide can be spin coated on the wafer and patterned by photolithographic techniques. Not only thin (0.2–1 μm) but also thick (up to 20 μm and more) polyimide layers can be fabricated, a feature which makes the material very attractive for use on SAW devices in the lower frequency range (80–200 MHz). The layers show good adhesion on the substrate and excellent absorbing properties. In this paper, the technology for fabricating polyimide acoustic absorption layers is described. The relationship between absorber configuration (length, thickness), frequency and the acoustic wave absorption is analysed. Experimental results of polyimide absorber films on STX quartz SAW devices with centre frequencies between 40 and 200 MHz are presented.

Experimental study of SAW quartz cuts with low sensitivity to dynamical thermal effects

Surface acoustic wave (SAW) quartz cuts with a low sensitivity to temperature and planar isotropic stresses have been found. SAW oscillators based on stress- and temperature-compensated cuts have been experimentally tested and compared to the classical (ST, X) cut. A significant reduction (by one order of magnitude) of the sensitivity to dynamic thermal effects is demonstrated.

Miniaturized Bulk and Surface Acoustic Wave Quartz Oscillators Used as Sensors

Miniaturized Bulk and Surface Acoustic Wave Quartz Oscillators Used as Sensors

1/f frequency fluctuations in quartz acoustic resonators

The level of 1/f frequency fluctuations has been measured on numerous quartz surface acoustic wave resonators. When these results are combined with existing data for quartz bulk acoustic wave resonators it becomes clear that the 1/f process is essentially the same in both types of devices. Furthermore, the power spectral density of frequency fluctuations shows a clear power law dependence that is very close to 1/Q4u , where Qu is the unloaded Q. However, the observed dependence on loaded Q is weak.

Stroboscopic synchrotron-X-radiation topography and its application to the imaging of travelling surface acoustic waves

Images of travelling Rayleigh waves on surface acoustic wave (SAW) devices have recently been obtained using high frequency stroboscopic X-ray topography. When the excited SAW was phase locked to the pulsed synchrotron X-radiation emitted from the Daresbury SRS operating in single bench mode, well defined, “time frozen” images of the strains associated with the propagating wavefronts were obtained. The instrumentation and experimental requirements for these and similar stroboscopic experiments using multiple bunches are described. Examples of results of work on LiNbO 3 and quartz SAW devices are given and the extension to more general stroboscopic X-ray scattering experiments is discussed.

Optimization of Quartz SAW Resonator Structure with Groove Gratings

Abstruct-A new surface acoustic wave (SAW) resonator optimum design method is proposed to reduce resonator sue. The fundamental design feature is optimization of the interdigital transducer (IDT) electrode period to reflector electrode period ratio, in order to adjust the frequency for the maximum IDT admittance to the maximum reflector reflection point. As a result of the optimized electrode period ratio, both reflector and IDT frequency responses are utilized to advantage, and good resonant Characteristics are obtained with a reduced number of reflector electrode fingers. This design method can be effectively applied for SAW resonators with groove gratings, both on reflectors and transducer, that are formed by a reactive sputter etching process. 145 MHz SAW resonators with groove gratings fabricated on a small 6 mm X 3 mm ST-cut quartz chip have provided good electrical performances, such as high Q values above 2 X lo4 and low resonance resistance in the 20-30 range.

SAW Bandpass Filter Design for 1.6-GHz PCM Timing Tank Applications

A 1.6-GHz surface acoustic wave (SAW) timing tank for a self-timed regenerative repeater for an ultrahigh-speed PCM optical fiber transmission system is described. A SAW narrow bandpass filter with 0.74-mu m linewidth interdigital transducers with double electrode geometry and 20-nm aluminum metallization on AT-quartz substrate is realized by conventional optical photolithography. Typical performance obtained is as follows: center frequency f/sub 0/ is 1.5993 GHz; insertion loss is 22 dB; stopband attenuation is above 23 dB with respect to the passbaand; stability is |2Q/sub L//spl dot/Delta f /f/sub 0/| < 0.1, where Q/sub L/ is loaded Q value and Delta f is mistuning due to temperature effects. It is demonstrated that SAW quartz transversal filters can be made into new practical filters which have both high Q value and high stability fn the GHz range and are satisfactory from the standpoints of precise design, fabrication technique, and performance.

Surface Acoustic Wave UHF Interferometer (Letters)

A 330-MHz surface acoustic wave (SAW) interferometer is described. The delay for the interferometer is provided by a 6.67-/spl mu/s ST quartz SAW delay line. The interferometer is capable of 50-dB nulls of 150-kHz periodicity over a 10-MHZ instantaneous bandwidth.

Application of ultrasonic standing waves to optical-beam scanning: Journal of the acoustical society of America, 36, No. 10, 1706 (1964)

In this paper, we examine the significance of the various higher-order effects regarding calculating temperature behavior from a set of material constants and their temperature coefficients. Temperature-induced velocity shifts have been calculated for quartz surface acoustic wave (SAW) resonators and the contributions of different groups of nonlinear material constants (third-order elastic constants (TOE), third-order piezoelectric constants (TOP), third-order dielectric constants (TOD) and electrostrictive constants (EL)) to the temperature-induced velocity shifts have been analyzed. The analytical methodology has been verified through the comparison of experimental and analytical results for quartz resonators. In general, the third-order elastic constants were found to contribute most significantly to the temperature-induced shifts in the SAW velocity. The contributions from the third-order dielectric constants and electrostrictive constants were found to be negligible. For some specific cases, the third-order piezoelectric constants were found to make a significant contribution to the temperature-induced shifts. The significance of each third-order elastic constant as a contributor to the temperature-velocity effect was analyzed by applying a 10% variation to each of the third-order elastic constants separately. Additionally, we have considered the issues arising from the commonly used thermoelastic expansions that provide a good but not exact description of the temperature effects on frequency in piezoelectric resonators as these commonly used expansions do not include the effects of higher-order material constants.

Ultrasonic atomization-some recent developments: Fuel efficiency, 12, No. 12, 16 (1964)

In this paper, we examine the significance of the various higher-order effects regarding calculating temperature behavior from a set of material constants and their temperature coefficients. Temperature-induced velocity shifts have been calculated for quartz surface acoustic wave (SAW) resonators and the contributions of different groups of nonlinear material constants (third-order elastic constants (TOE), third-order piezoelectric constants (TOP), third-order dielectric constants (TOD) and electrostrictive constants (EL)) to the temperature-induced velocity shifts have been analyzed. The analytical methodology has been verified through the comparison of experimental and analytical results for quartz resonators. In general, the third-order elastic constants were found to contribute most significantly to the temperature-induced shifts in the SAW velocity. The contributions from the third-order dielectric constants and electrostrictive constants were found to be negligible. For some specific cases, the third-order piezoelectric constants were found to make a significant contribution to the temperature-induced shifts. The significance of each third-order elastic constant as a contributor to the temperature-velocity effect was analyzed by applying a 10% variation to each of the third-order elastic constants separately. Additionally, we have considered the issues arising from the commonly used thermoelastic expansions that provide a good but not exact description of the temperature effects on frequency in piezoelectric resonators as these commonly used expansions do not include the effects of higher-order material constants.