Giant shear mode electromechanical coupling coefficient k&lt;inf&gt;15&lt;/inf&gt; in c-axis tilted ScAlN films

Yanagitani, Takahiko; Arakawa, Kazuki; Kano, Kazuhiko; Teshigahara, Akihiko; Akiyama, Morito

doi:10.1109/ultsym.2010.5935791

Cited by 46 publications

(24 citation statements)

References 10 publications

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“…Next, we will discuss the feasibility of COP platforms using bonded single-crystal thin films. Different from the conventional approach of sputtering multi-layer tilted c-axis thin films, where the constants are partially modified [64]- [66], bonded piezoelectric thin films [67] enable the implementation of the COP platform through the integration of thin films with different orientations. For Z-cut LiNbO 3 , which can be notated as a Euler angle of (0 [68], an additional layer with a Euler angle of (180 • , 180 • , 0 • ) satisfies the COP requirements for material constants via matrix rotation [68].…”

Section: B Complementarily Oriented Piezoelectric Platformmentioning

confidence: 99%

Enabling Higher Order Lamb Wave Acoustic Devices With Complementarily Oriented Piezoelectric Thin Films

Yang

Link

et al. 2020

J. Microelectromech. Syst.

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In this work, we present a new paradigm for enabling gigahertz higher-order Lamb wave acoustic devices using complementarily oriented piezoelectric (COP) thin films. Acoustic characteristics are first theoretically explored with COP lithium niobate (LiNbO 3) thin films, showing their excellent frequency scalability, low loss, and high electromechanical coupling (k 2). Acoustic resonators and delay lines are then designed and implemented, targeting efficient excitation of higher-order Lamb waves with record-breaking low loss. The fabricated resonator shows a 2 nd-order symmetric (S2) resonance at 3.05 GHz with a high quality factor (Q) of 657, and a large k 2 of 21.5% and a 6 th-order symmetric (S6) resonance at 9.05 GHz with a high Q of 636 and a k 2 of 3.71%, both among the highest demonstrated for higher-order Lamb wave devices. The delay lines show an average insertion loss (IL) of 7.5 dB and the lowest reported propagation loss of 0.014 dB/µm at 4.4 GHz for S2. Notable acoustic passbands up to 15.1 GHz are identified. Upon further optimizations, the proposed COP platform can lead to gigahertz low-loss wideband acoustic components.

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Section: B Complementarily Oriented Piezoelectric Platformmentioning

confidence: 99%

Enabling Higher Order Lamb Wave Acoustic Devices With Complementarily Oriented Piezoelectric Thin Films

Yang

Link

et al. 2020

J. Microelectromech. Syst.

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“…3 The large bandwidth of Sc doped AlN resonators has therefore received increasing interest in recent years. [4][5][6] In 2006, Alsaad and Ahmad predicted the enhancement of piezoelectricity through the Sc doping of GaN in a first principle calculation. 7 After that Akiyama et al experimentally determined a large intrinsic d 33 piezoelectric constant in Sc doped AlN films 8 and our group reported ScAlN film BAW resonators for the first time.…”

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confidence: 99%

“…7 After that Akiyama et al experimentally determined a large intrinsic d 33 piezoelectric constant in Sc doped AlN films 8 and our group reported ScAlN film BAW resonators for the first time. 4 More recently, these studies have been extended to the polarization inverted resonators 9 and YbGaN resonators. 10 Recent Sc x Al (1Àx) N resonator studies 5,6 have focused on the low Sc concentration region (x < 0.15), probably either because the acoustic wave attenuation loss (1/Q factor) in high Sc concentration films was expected to be too large for use as practical resonators or because it is difficult to realize a highly oriented film in the high Sc concentration region, despite the fact that electromechanical coupling has been demonstrated to be proportional to the Sc concentration.…”

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confidence: 99%

Electromechanical coupling and gigahertz elastic properties of ScAlN films near phase boundary

Yanagitani

Suzuki

2014

Applied Physics Letters

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120

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The electromechanical coupling, elastic properties, and temperature coefficient of elastic constant c33D of ScxAl(1−x)N films with high Sc concentration (x) of 0–0.70 were experimentally investigated. Near the phase boundary, a Sc0.41Al0.59N film exhibited a maximum thickness extensional mode electromechanical coupling coefficient kt2 of 12% (kt = 0.35), which is almost double the value of 6.4% for typical pure AlN films. In the region of 0 < x < 0.2, the electromechanical coupling was confirmed to increase without any detectable deterioration in the temperature stability of c33D (=−54.5 ppm/ °C). This region is favorable in terms of temperature stability and is suitable for wideband resonator filter applications.

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“…Its piezoelectricity reaches a maximum when the Sc/Al concentration is approximately 43% which is near the phase boundary between wurtzite and cubical crystal. We have first reported the fabrication of the ultrasonic transducer and FBAR using the ScAlN thin film, and demonstrated high piezoelectricity (k 2 t = 15% [14]), in 2010. A high-frequency ultrasonic transducer such as a micromachined ultrasonic transducer using the AlN thin film and focused transducer using ScAlN thin film are recently reported [15], [16].…”

Section: Introductionmentioning

confidence: 99%

ScAlN Thick-Film Ultrasonic Transducer in 40–80 MHz

Sano

Karasawa

Yanagitani

2018

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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A medical ultrasound diagnostic system and an ultrasonic microscope are generally used in the frequency range of 1-20 MHz and 100 MHz-2 GHz, respectively. Ultrasonic transducers in the frequency range of 20-100 MHz are, therefore, not well developed because of less application into ultrasonic imaging or suitable piezoelectric materials with this frequency range. Polyvinylidene difluoride (PVDF) is usually used for ultrasonic transducers in the 10-50-MHz ranges. However, their electromechanical coupling coefficient k 2 t of 4% is not enough for the practical uses. In order to excite the ultrasonic wave in the 20-100 MHz range, a 125-25-µm-thick piezoelectric film is required when the longitudinal velocity of the material is assumed to be 5000 m/s. However, it is difficult to grow such a thick piezoelectric film without a crack being caused by the internal stress during the dry deposition technique. We achieved a stress-free film growth by employing the unique hot target sputtering technique without heating the substrate. High-efficient 81-(k 2 t = 18.5%) and 43-MHz (k 2 t = 15.2%) ultrasonic generation by using the 43-and 90-µm extremely thick ScAlN (Sc: 39%) films were demonstrated, respectively. We discussed the advantage of ScAlN thick-film transducers by comparing them with the conventional PVDF transducer for the water medium.

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Giant shear mode electromechanical coupling coefficient k<inf>15</inf> in c-axis tilted ScAlN films

Cited by 46 publications

References 10 publications

Enabling Higher Order Lamb Wave Acoustic Devices With Complementarily Oriented Piezoelectric Thin Films

Enabling Higher Order Lamb Wave Acoustic Devices With Complementarily Oriented Piezoelectric Thin Films

Electromechanical coupling and gigahertz elastic properties of ScAlN films near phase boundary

ScAlN Thick-Film Ultrasonic Transducer in 40–80 MHz

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