Page 336 - Microsensors, MEMS and Smart Devices - Gardner Varadhan and Awadelkarim

316 INTRODUCTION TO SAW DEVICES

Table 9.2 Structures of Love, Rayleigh SAW, SH-SAW, SH-APM and FPW devices and compar-
ison of their operation

Device Love Rayleigh SH-SAW SH-APM FPW
type SAW SAW
Substrate ST-quartz ST-quartz LiTaO 3 ST-quartz Si xN y/ZnO
Typical 95-130 80-1000 90-150 160 1-6
frequency
(MHz)

Ua
Transverse Transverse Transverse Transverse Transverse
parallel parallel
b
U t Parallel Normal Parallel Parallel Normal
Media Ice to liquid Strain Gas liquid Gas liquid Gas liquid
chemosensors chemosensors
a
U is the particle displacement relative to wave propagation
b
U t is the transverse component relative to sensing surface
components. For this reason, either a Love SAW or an SH wave-based APM device
could be used. However, because the ratio of the volume of the guiding layer to the total
energy density is the largest for a Love wave device, it is natural to choose a Love wave
device for the higher sensitivity toward any perturbation at the liquid interface.
Finally, Table 9.2 summarises the different types of SAW devices described in this
chapter. This reference table also gives the typical operating frequencies of the devices,
along with the wave mode and application area.

REFERENCES

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Bechmann, R., Ballato, A. D. and Lukaszek, T. J. (1962). "Higher order temperature coefficients
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