Fabrication of high temperature surface acoustic wave devices for sensor applications

Surface acoustic devices have been shown to be suitable not only for signal processing but also for sensor applications. In this paper high temperature surface acoustic wave devices based on gallium orthophosphate have been fabricated, using a lift-off technique and tested for high frequency applications at temperatures up to 600 ºC. The measured S-parameter (S11) has been used to study the mass loading effect of the platinum electrodes and turnover temperature of GaPO4 with a 5? cut. The analysis of these results shows that the mass loading effect can be used to predict the desired resonant frequency of the SAW devices. Also two different adhesion layers for Pt metallisation were studied. Our results show that Zirconium is a more suitable under layer than Titanium

High-temperature 434 MHz surface acoustic wave devices based on GaPO₄

Research into surface acoustic wave (SAW) devices began in the early 1970s and led to the development of high performance, small size and high reproducability devices. Much research has now been done on the application of such devices to consumer electronics, process monitoring and communication systems. The use of novel materials such as gallium phosphate (GaPO4), extends the operating temperature of the elements. SAW devices based on this material operating at 434 MHz up to 800C, can be used for passive wireless sensor applications. Interdigital transducer (IDT) devices with Platinum/ Zirconium metallization and 1.4 micron finger-gap ratio of 1:1 have been fabricated using direct-write e-beam lithography and a lift-off process. The performance and long term stability of these devices has been studied, and the results are reported in this paper

Replacing the rod with the cone transducin α subunit decreases sensitivity and accelerates response decay

Cone vision is less sensitive than rod vision. Much of this difference can be attributed to the photoreceptors themselves, but the reason why the cones are less sensitive is still unknown. Recent recordings indicate that one important factor may be a difference in the rate of activation of cone transduction; that is, the rising phase of the cone response per bleached rhodopsin molecule (Rh*) has a smaller slope than the rising phase of the rod response per Rh*, perhaps because some step between Rh* and activation of the phosphodiesterase 6 (PDE6) effector molecule occurs with less gain. Since rods and cones have different G-protein α subunits, and since this subunit (Tα) plays a key role both in the interaction of G-protein with Rh* and the activation of PDE6, we investigated the mechanism of the amplification difference by expressing cone Tα in rod Tα-knockout rods to produce so-called GNAT2C mice. We show that rods in GNAT2C mice have decreased sensitivity and a rate of activation half that of wild-type (WT) mouse rods. Furthermore, GNAT2C responses recover more rapidly than WT responses with kinetic parameters resembling those of native mouse cones. Our results show for the first time that part of the difference in sensitivity and response kinetics between rods and cones may be the result of a difference in the G-protein α subunit. They also indicate more generally that the molecular nature of G-protein α may play an important role in the kinetics of G-protein cascades for metabotropic receptors throughout the body