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Diamond has the highest sound velocity among all materials and has been applied in high frequency surface acoustic wave (SAW) devices in the gigahertz range. To date, numerous researches have reported that the SAW devices built on a diamond wafer can work in the frequency range from 2 GHz to 10 GHz. S. Fujii et al. reported that the one-port resonator with an interdigital transducer (IDT)/AlN/single...
Automated tow placement has become a widely-used fabrication technique, especially for large aerospace structures. Robotic heads lay down strips of pre-impregnated fiber (called tows) along programmed paths. While the intention is to lay adjacent tows abutted to one another, occasionally a tow is placed leaving a non-zero gap between it and the previously-placed tow. In order to preserve the intended...
RF filtering technologies based on piezoelectric MEMS resonators have been successfully developed and commercialized in the past decade thanks to their size and outstanding performance. The challenge to enhance filter's performance in terms of lower insertion losses and wider bandwidth still makes for an active research topic, especially spurring the interest for new classes of materials such as doped-AlN...
Piezoelectric lead zirconate titanate (PZT) thick films (t>10μm) with excellent electromechanical property have been considered for flexible electronics applications where precise actuation, control and sensing are desired. The main drawback of piezoelectric thick films is the fragility in device fabrication and application. To protect the PZT thick film devices from fracture, a five-layer sandwiched...
RF Voltage transformers operating in one of the ISM frequency bands have recently been demanded in emerging low-power applications, such as wake-up radios in wireless networks, remotely triggered switches, stand-by units in home electronics, etc. S0 Lamb wave resonant (LWR) transformers have been first proposed. Later, SAW transformers designed as “degenerated” CRF have been proposed. Here we demonstrate...
Recently we reported on fabrication and characterization of a novel type of hybrid resonator in which BAW transforms into SAW due to a periodic pillar pattern of piezoelectric material. This device looks promising thanks to high achievable electromechanical coupling (over 4%) and possibility for application as sensor in harsh environment when using AlScN as piezoelectric. The main feature of the device...
Nanoparticle manipulation has a variety of potential applications, from two-dimensional material fabrication to biomedical engineering. Pattern and transportation of nanoparticles has been receiving increasing attention in recent years. Ultrasound as a mechanical wave has proven to be the most effective in the manipulation of micro-objects in a non-contact and non-invasive fashion. However, due to...
SH-SAW In-liquid sensors have been explored extensively in recent decades. They propose an ability to work at higher frequencies, than the well-known QCM, with the aim to reduce the size and ease the integration in sensor arrays. So far SH-SAW liquid phase sensors are designed in two-port delay line configurations because of the need to protect the IDT from the conductive and dielectric loads from...
CMUT efficiency depends on a high electric field over a thin vacuum gap and a dielectric isolation layer. Ideally this high electric field should only exist over the vibrating membrane of the CMUT, but electrical connections between the membranes usually pass over thin dielectric isolation layers (Fig. 1). The resulting high fields on the isolation layer cause charging, dielectric breakdown and reduces...
Piezoelectric ceramics are currently of considerable interest for their capabilities of converting compressive/tensile stresses to an electric charge, or vice versa. The applications of piezoelectric devises are far reaching, ranging from acoustic imaging to energy harvesting. However, conventional manufacturing processes such as etching and dicing for piezoelectric ceramics fabrication have limited...
Microultrasound is a real-time imaging modality that can resolve features <200 μm using frequencies of 15 MHz and above. While attenuation limits the penetration depth, incorporating a miniature transducer within a biopsy needle enables in vivo imaging of structures deep within the body. Imaging from the tip of minimally invasive needles has potential in applications in guiding intervention and...
Development of flexible ultrasonic transducers for non-destructive testing (NDT) application has been desired since many infrastructures were consist of complex geometry. Sol-gel spray technique realized flexible ultrasonic transducers, however, it is difficult for manual spray coating to make quality assurance. In addition, manual spray coating is not suitable for mass production. Therefore, automatic...
Leakage of elastic waves through the anchors is commonly reported as the dominant Q-limiting mechanism in micro-resonators. Bulk mode silicon-based disk resonators are amongst the most attractive designs in literature as they could potentially offer high Q if supported from the center. However, such supporting scheme adds to the fabrication complexity and as such, side supported designs have been...
Diamond is known to have the highest sound velocity of all materials, and therefore, has been applied to high frequency surface acoustic wave (SAW) devices in the gigahertz range. Our earlier research has shown much potential for diamond SAW resonators and filters on single crystal substrates at frequencies above 3 GHz. However, single crystal diamond wafers of only up to two-inch in diameter have...
This paper reports on the investigation of 1 μm thick films of 20% Scandium-doped Aluminum Nitride (ScAlN) for the making of piezoelectric MEMS laterally vibrating resonators (LVRs). The ScAlN films, which can be sputter-deposited such as undoped Aluminum Nitride (AlN) films, were used to demonstrate high performance resonators. These devices showed quality factor (Qs) in excess of 1000 in air centered...
We demonstrated the statistical element selection (SES) technique with an array of 1.15 GHz AlN MEMS subfilters fabricated in an 8” Si fabrication facility by A∗STAR, Institute of Microelectronics (IME), Singapore. The chip integration is achieved through a split-fab process where the hermetically thin-film-encapsulated (TFE) MEMS resonators are solder-bump bonded to a CMOS chip fabricated in a Samsung...
In this paper, we report the development of optical fiber laser-generated-focused-ultrasound (LGFU) transducers for intravascular therapies. By combining advantages of fiber optics and photoacoustics, high frequency (>10 MHz), high pressure (> 10 MPa), short pulse (<10 ns) shock waves can be generated from a small aperture (<1 mm in diameter), which is immune to electromagnetic noise....
Piezoelectric ceramic and the corresponding array are widely used in energy harvesting and ultrasonic application for the capabilities of converting compressive/tensile stresses to an electric charge, or vice versa. However, the need for a complex geometry of array is a major technical challenge for further application. To enable the fabrication of piezoelectric ceramics, additive manufacturing (AM)...
Recent literature has focused on improving piezoelectric coupling coefficients by alloying aluminum nitride (AlN) with scandium (Sc). Akiyama et al. showed the highest piezoelectric coefficient increase of nearly four times for a 41% Sc substitution for Al. Thus far, studies mainly focus on material measurements such as x-ray diffraction or piezoelectric constants to assess the material quality. Although...
In this paper we propose a modified fabrication process to finely define the region surrounding the resonator that undergoes Si etching in CMRs. The unpredictable undercut has been shown to lead to Q instability within microns' variation. High aspect ratio SiO2 trenches were used as barrier to confine the release area. Thanks to the high selectivity of SF6 over SiO2, long Si etch steps can be performed...
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