China
Africa
Explore chapters and articles related to this topic
Nanoelectronics and Nanophotonics
Published in M S Shur, R A Suris, Compound Semiconductors 1996, 2020
We investigate the low-temperature photoluminescence of a single undoped 10nm wide InGaAs/GaAs QW under the influence of intense surface sound waves in the GHz regime. On both ends of the sample several lithographically defined interdigital transducers (IDT) operating at different frequencies are fabricated by successively evaporating NiCr and Al directly on the surface. The interdigital electrode spacing establishes the fundamental acoustic wavelength λ0 and frequency f0 by f0 = υ/λ0, where υ is the sound velocity. The SAW is launched by the application of a HF signal at the fundamental or harmonic frequency to one of these IDT. A tunable Titanium-Sapphire laser is used for the optical excitation and the PL signal is detected using a triple grating spectrometer.
Sensor Structures with Sensitive Polymers
Published in Gábor Harsányi, Polymer Films in Sensor Applications, 2017
Waves can be generated quite easily in piezoelectric substrates using an IDT electrode, which can be fabricated microlithographically from thin-film metallization. The time-varying voltage will result in a synchronously varying deformation of the piezoelectric substrate and the subsequent generation of a propagating Rayleigh surface wave. The counterpart of the phenomenon can also occur: SAWs can generate alternating voltage in another IDT called a receiver. Delay line is a configuration consisting of two (or more) IDTs and a propagation path between them (see Figure 2.14). The first interdigital transducer excites an SAW whose frequency is mainly determined by the elastic constants of the piezoelectric material and the geometrical sizes of the generator IDT. An SAW will be received by the receiver IDT after travelling along the surface of the substrate. The propagation path is the sensitive area. All changes in the boundary conditions for SAW propagation lead to a variation of the SAW received by the second IDT. This well-known fact can be used for sensor applications.
Acoustic Sensors
Published in J. David, N. Cheeke, Fundamentals and Applications of Ultrasonic Waves, 2017
SAW can be generated in a piezoelectric substrate in a number of different ways, but the interdigital transducer is the method of choice for acoustic microsensors. The main reason is that the planar electrodes can be fabricated by standard microelectronic techniques, which allows great flexibility in design and high volume production. IDT techniques have also become the basis for generating and detecting other guided modes to be discussed in this chapter. The basics of IDT theory and technology have been described in the previous chapter, and this will be sufficient for present purposes. A typical dual-channel SAW sensor is shown in Figure 16.5. A difference measurement between sensing and reference channels eliminates the temperature dependence to first order.
Propagation characteristic of Love-type wave in different types of functionally graded piezoelectric layered structure
Published in Waves in Random and Complex Media, 2022
Interdigital transducers (IDT) were invented for transmitting and receiving surface acoustic waves (SAW) signals [1], therefore, SAW devices are adopted successfully in the engineering applications based on the propagation characteristics of surface waves such as Rayleigh waves and Love waves. SAW sensors [2,3] are highly sensitive devices owing to the concentration of acoustic energy within a few wavelengths of the surface. Also, there exists initial stress in the sensors during the manufacturing process, especially for the composite multilayered structures which consist of two different kinds of materials, bonded together alternately. Initial stress exists due to the thermal mismatch of materials properties. Therefore, it is worthy of attention to investigate the effects of the initial stress on the propagation behavior of waves in multilayered piezoelectric structures. To manufacture SAW devices, functionally graded piezoelectric materials (FGPMs) can be used to improve the efficiency and durability of such devices. Henceforth the propagation of waves in FGPM layered structures has become a research interest.
Ferroelectric, Piezoelectric Mechanism and Applications
Published in Journal of Asian Ceramic Societies, 2022
Arun Singh, Shagun Monga, Neeraj Sharma, K Sreenivas, Ram S. Katiyar
The acoustic wave can be generated in piezoelectric materials by applying an external ac electrical signal. The utmost significant application of ferroelectrics is based on their high coefficients of piezoelectricity. Surface acoustic wave devices use the piezoelectric property of the ferroelectric films. A delay line is a device, which causes the output to lag behind the input by a finite delay time. A simple delay line is shown in Figure 13. An Inter Digital Transducer Electrode (IDT) transforms the incident electromagnetic wave into a Rayleigh surface acoustic wave, which propagates on the piezoelectric crystal/film surface. After the required delay, another transducer at the output reconverts the acoustic wave back into an electromagnetic signal [40,41]. In layered structures, there exists more than one way of locating the IDTs on the piezoelectric surface as shown in Figure 14. For an AO device, a thin film layer that can be utilized as a waveguide medium is required. This waveguide layer itself can be piezoelectric in nature so as to generate surface acoustic wave, or another piezoelectric layer is required to generate SAW. The configuration of such an AO device is illustrated in Figure 15.
An asymptotic approximation of Love wave frequency in a piezo-composite structure: WKB approach
Published in Waves in Random and Complex Media, 2021
Propagation of surface waves in a composite structure has many applications in geoscience, engineering, ocean acoustics, non-destructive evaluation, as well as in designing of surface acoustic wave (SAW) devices. An inter-digital transducer (IDT) is a device which is made up of two interlocking comb-shaped arrays of metallic electrodes (in the fashion of a zipper). These metallic electrodes are embedded on the surface of a piezoelectric material substrate (such as quartz niobate or lithium niobate), to form a periodic structure. White and Voltmer [1] designed the inter-digital transducers (IDT) to study the piezoelectric coupling in the surface elastic waves. IDT’s primary function is to transform electric signals to SAW by generating periodically allotted mechanical forces via piezoelectric effect (an input transducer). The same principle is postulated to the change of SAW back to electric signals (an output transducer). These techniques of generation and reception of SAW can be used in different types signal processing devices, like bandpass filters, delay lines, resonators, sensors, etc. SAW devices work on the principle of mechanical surface wave existing in an elastic structural body of free surfaces where the distribution is spread around the surface area. Various investigations have been undertaken to examine the characteristics of surface waves in PE layered structure [2–8].