Surface acoustic waves device

The major piezoelectric applications are sensors (pickups, keyboards, microphones, etc.), electromechanical transducers (actuators, vibrators, etc ), signal devices, and surface acoustic wave devices (resonators, traps, filters, etc ). Typical materials are ZnO, AIN, PbTiOg, LiTaOg, and Pb(Zr.Ti)03 (PZT). 

The materials listed in Table 5.1 are also not complete but the selection represents the most relevant composites which are of commercial interest. In addition to the performance issue, there is a strong tendency in research and development to reduce the costs. For that reason, a lot of research is devoted to the niobates as possible replacement for the tantalates, because niobium is cheaper than tantalum. In addition, compensated materials with very high values of the permittivity are currently under development. Recently, for the compound Ag(Nbi a Taa )03 with 0.35< x <0.65, er values of 450 were achieved for potential use as filters (to replace the surface-acoustic-wave devices) and planar antennas in mobile phones [19],... 

Figure 3.6 Schematic layout of a single-acoustic-aperture surface acoustic wave device...

Zinc oxide has been investigated already in 1912. With the beginning of the semiconductor age after the invention of the transistor [1], systematic investigations of ZnO as a compound semiconductor were performed. In 1960, the good piezoelectric properties of zinc oxide were discovered [2], which led to the first electronic application of zinc oxide as a thin layer for surface acoustic wave devices [3]. 

First sputtering processes for ZnO deposition were developed in the late 1960s for manufacturing surface acoustic wave devices [2]. The piezoelectric properties of ZnO films are crucial for that application and major efforts were made to develop ZnO sputtering processes which enabled c-axis oriented growth, high resistivity and unique termination of the ZnO crystallites [3,4]. 

Philippe Bergonzo and Richard B. Jackman, Diamond-Based Radiation and Photon Detectors Hiroshi Kawarada, Diamond Field Effect Transistors Using H-Terminated Surfaces Shinichi Shikata and Hideald Nakahata, Diamond Surface Acoustic Wave Device... 

Datta, S. Surface Acoustic Wave Devices, Prentice-Hall Englewood Cliffs, NJ (1986). 

Surface acoustic wave devices Porosity and surface area 103... 

Diamondlike Carbon and Hard Carbon-Based Sensors Sensors that are based upon diamond technology include thermistors, pressure and flow sensors, radiation detectors, and surface acoustic wave devices [103]. The relative ease of depositing prepattemed, dielectrically isolated insulating and. semiconducting (boron-doped p type) diamond films has made polycrystalline diamond-based sensors low-cost alternatives to those based on conventional semiconductors. Diamondlike carbon and diamond films synthesized by chemical... 

Surface acoustic wave devices depend on the modification of the propagation velocity of a generated acoustical wave by the deposition of a definite mass of the analyte. 

The adsorption and desorption isotherms of an inert gas (classically N2 at 77 K) on an outgassed sample are determined as a function of the relative pressure (Prei = p/Po/ the ratio between the applied pressure and the saturation pressure. The adsorption isotherm is determined by measuring the quantity of gas adsorbed for each value of p/po by a gravimetric or a volumetric method (less accurate but simpler). A surface acoustic wave device can also be used as a mass sensor or microbalance in order to determine the adsorption isotherms of small thin films samples (only 0.2 cm of sample are required in the cell) [42,43]. 

Campell, C.K. Surface Acoustic Wave Devices for Mobile and Wireless Communications Academic Press San Diego, 1998. 

G. Schmera, L.B. Kish, "Fluctuation Enhanced Chemical Sensing by Surface Acoustic Wave Devices", Fluct. Noise Lett, 2 (2002) LI 17-L123. 

Important discoveries in sensor platforms include the tin oxide electronic nose, quartz crystal microbalance and related Surface Acoustic Wave devices, field effect transistors, and optical fibers. 

Any type of acoustic transducer, such as quartz crystal microbalance (QCM) or surface acoustic wave device (SAW), is fundamentally based on the piezoelectric effect. This was first described in 1880 by Jacques and Pierre Curie as a property of crystalline materials that do not have an inversion centre. When such a material is subjected to physical stress, a measurable voltage occurs on the crystal surfaces. Naturally, the opposite effect can also be observed, i.e. applying an electrical charge on a piezoelectric material leads to mechanical distortion, the so-called inverse piezo effect. These phenomena can be used to transfrom an electrical signal to a mechanical one and back, which actually happens in QCM and SAW. Different materials are ap-pHed for device fabrication, such as quartz, Hthium tantalate, lithium titanate... 

Ballantine, D.S. et al.. Correlation of surface acoustic wave device coating responses with solubility properties and chemical structure using pattern recognition. Anal. 

Organic polymers and optical fibres [17] have been previously used to detect vapours of explosive analytes [18,19]. The transduction methods include absorption, fluorescence, conductivity, etc [16]. Such simple techniques are promising, because they can be incorporated into inexpensive and portable microelectronic devices. For example, a chemically selective silicone polymer layer on a SAW (surface acoustic wave) device has been shown to provide efficient detection for the nitroaromatic compounds [20]. The fluorescence of pentiptycene conjugated polymers [21,22] and... 

Microcantilever sensors offer many orders of magnitude better sensitivity compared to other sensors such as quartz crystal microbalances (QCM), flexural plate wave oscillators (FPW), and surface acoustic wave devices (SAW). There are several distinct advantages of the microcantilever sensors compared to the above mentioned and other MEMS sensors ... 

There are some excellent review articles on different aspects of mesostructured materials, such as synthesis, properties, and applications. " Extensive research effort has been devoted to the exploitation of new phases (lamellar, cubic, hexagonal structures), expansion of the pore sizes (about 2-50 nm are accessible), and variable framework compositions (from pure silica, through mixed metal oxides to purely metal oxide-based frameworks, and inorganic-organic hybrid mesostructures). Another research focus is on the formation of mesostructured materials in other morphologies than powders, e.g. monolithic materials and films, which are required for a variety of applications including, but not limited to, sensors (based on piezoelectric mass balances or surface acoustic wave devices), catalyst supports, (size- and shape-selective) filtration membranes or (opto)electronic devices. The current article is focused... 

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