J. Environ. Nanotechnol. Volume 3, No.3 pp. 106-115 ISSN (Print): 2279-0748 ISSN (Online): 2319-5541 doi: 10.13074/jent.2014.09.143101 * Haresh M. Pandya Tel.: +919894336750 E-mail: haresh.pandya@rediffmail.com SAW Devices – A Comprehensive Review Banu Priya. R 1 , Venkatesan. T 2 , Pandiyarajan. G 2 , Haresh M. Pandya 2* 1 Department of Physics, Gobi Arts & Science College, Gobichettipalayam, TN, India. 2* Department of Physics, Chikkanna Government Arts College, Tiruppur, TN, India. Received:03.05.2014 Accepted:05.08.2014 Abstract Surface Acoustic Waves (SAWs) are elastic waves travelling along the surface of solid piezoelectric materials with amplitude that decays exponentially with depth. Using an Interdigital Transducer (IDT), these waves can be demonstrated and reproduced in the laboratory in devices called SAW devices. Such devices find many applications as delay lines, filters, resonators and sensors. The present paper provides a snapshot review and description of the functioning, operation and latest technical advancements seen in these devices over the period from 2003-2012. For improvement in design, development, fabrication and characterization of these devices, computational modeling plays a prominent and pivotal role. Employing unique custom made software algorithms based on well established principles of physics, these devices are accurately modeled and simulated and a short review and description of the strategy adopted for the same is also provided. Keywords: Surface Acoustic wave; Interdigital Transducer. 1. INTRODUCTION The existence of surface acoustic waves (SAW) was highlighted in by( Lord Rayleigh in 1885). Subsequently in the days to come, a major factor in the emergence of SAW technology was the invention of the Interdigital Transducer (IDT) by (White and Voltmer in 1965). An IDT is a device which consists of two interlocking comb-shaped metallic Aluminium coatings which are fixed on to a piezoelectric substrate such as Quartz or Lithium Niobate to effectively convert applied RF electrical pulses to mechanical energy and vice versa. Such a transducer forms the basis for the design of a wide variety of SAW devices like delay lines, band pass filters, resonators and sensors. One of the most striking properties of SAWs is their extremely low velocity-about 10 5 times less than EM waves and over a wide spectrum of operating frequencies ranging from approximately 10 MHz to 12 GHz. Traditional usage of these devices has been primarily in the telecommunications industry and in mobile phones and related base stations. Emerging applications include SAW sensors for a variety of measurements like torque and tyre pressure sensors biosensors for medical applications (Ballantine. D. S et al., 1997;), gas sensors (Levit. N et al., 2002) and industrial and commercial applications such as: vapor, humidity, temperature, and mass sensors (Bowers. W et al., 1991, Vetelino. K. A et al., 1996, Weld. C. E et al., 1999). The present paper reviews the physics underlying a majority of these devices. 2. SAW DELAY LINE The simplest and the earliest of SAW devices is the SAW delay line consisting of two simple IDT structures (Figure 1). One IDT acts as the input or the transmitting IDT which converts electrical signal to acoustic energy that propagates on the surface of the piezoelectric substrate to the output transducer which converts acoustic energy back to an electric signal creating a delay equivalent to the time taken by SAW to travel between the two IDTs. Variation of the SAW travel length between the IDTs can be manipulated to get delays of different magnitude typically in the range of 1-50 ȝsec. To streamline the direction of flow of SAW and confine it to only one direction, absorbers are used at the end of the device to attenuate it.