Analysis of SAW propagation in gratings on ZnO/diamond substrates
The space harmonic method is used to analyze surface acoustic wave (SAW) propagation under an infinite periodic metal grating on ZnO/diamond composite layered substrates. Dispersion properties for shorted and open gratings are derived as a function of the thickness of the grating electrodes. From these dispersion relations, the coupling of modes (COM) parameters are derived. Energy profiles inside ZnO/diamond show that the energies contained in each of the ZnO and diamond layers are of the same order when the thickness of the ZnO layer is P//spl pi/r (P=grating period) and that the energy is contained within two wavelengths below the ZnO/diamond interface.
A Novel Saw Device in CMOS: Design, Modeling, and Fabrication
The design, finite element modeling, fabrication, and characterization of a novel surface acoustic wave (SAW) delay line for bio/chemical and telecommunication applications in CMOS technology are introduced. A full modeling was carried out. The devices are designed in a standard semiconductor foundry 1.5-mum two-metal two-poly process. A unique maskless postprocessing sequence is designed and completed. The three postprocessing steps are fully compatible with any standard integrated circuit technology such as CMOS. This allows any signal control/processing circuitry to be easily integrated on the same chip. ZnO is used as the piezoelectric material for SAW generation. A thorough characterization and patterning optimization of the sputtered ZnO was carried out. The major novelties that are introduced in the SAW delay line features are the embedded heater elements for temperature control, compensation, and acoustic absorbers that are designed to eliminate edge reflections and minimize triple transit interference that is amplified by edge reflections. Both of these attributes are designed by using CMOS materials without disturbing SAW performance
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.