On the effectiveness of lateral excitation of shear modes in AlN layered resonators

Clément, M.; Iborra, E.; Olivares, J.; DeMiguel-Ramos, M.; Mirea, Teona; Sangrador, J.

doi:10.1016/j.ultras.2014.04.014

Cited by 17 publications

(9 citation statements)

References 24 publications

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“…A piezoelectric film with a c -axis inclined from its surface normal is the most effective method to excite the shear resonance, and this can be achieved by using seed layers with controlled roughness combined with an off-axis deposition 12, 13 . Yanagitani et al .…”

Section: Introductionmentioning

confidence: 99%

Gravimetric sensors operating at 1.1 GHz based on inclined c-axis ZnO grown on textured Al electrodes

Rughoobur

DeMiguel-Ramos

Escolano

et al. 2017

Sci Rep

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Shear mode solidly mounted resonators (SMRs) are fabricated using an inclined c-axis ZnO grown on a rough Al electrode. The roughness of the Al surface is controlled by changing the substrate temperature during the deposition process to promote the growth of inclined ZnO microcrystals. The optimum substrate temperature to obtain homogeneously inclined c-axis grains in ZnO films is achieved by depositing Al at 100 °C with a surface roughness ~9.2 nm, which caused an inclination angle of ~25° of the ZnO c-axis with respect to the surface normal. Shear mode devices with quality-factors at resonance, Q r and effective electromechanical coupling factors, , as high as 180 and 3.4% are respectively measured. Mass sensitivities, S m of (4.9 ± 0.1) kHz · cm2/ng and temperature coefficient of frequency (TCF) of ~−67 ppm/K are obtained using this shear mode. The performance of the devices as viscosity sensors and biosensors is demonstrated by determining the frequency shifts of water-ethanol mixtures and detection of Rabbit immunoglobin G (IgG) whole molecule (H&L) respectively.

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Section: Introductionmentioning

confidence: 99%

Gravimetric sensors operating at 1.1 GHz based on inclined c-axis ZnO grown on textured Al electrodes

Rughoobur

DeMiguel-Ramos

Escolano

et al. 2017

Sci Rep

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“…This geometric arrangement would provide, according to previously reported works [2,3], a straightforward excitation of the shear mode. The second configuration is based on the conventional excitation of AIN films using two electrodes placed on each side of the piezoelectric layer, but in this case, the AIN is made of microcrystals uniformly tilted with respect to the normal of the film, and this to the electric field [4], This solution has proven to be far more effective than the lateral excitation [5], It has been reported that tilt angles ranging from 20° to 45° provide the greatest values of the electromechanical coupling factor for the shear mode (fe 2 ) [6], Among the different techniques developed to achieve AIN films with tilted grains [7][8][9], off-axis sputter deposition over rough under-layers turns out to be the most effective [8], In these kind of substrates, when the flux of atoms impinging on the different inclines is uniform, AIN grains tend to grow normally to the slopes in equal number in all directions, giving rise to a randomlyoriented AIN layer with averaged null piezoelectric response. However, if an impinging direction is encouraged (e.g.…”

Section: Introductionmentioning

confidence: 99%

Substrate texturing for homogeneous deposition of tilted c-axis AlN films for shear mode operation

Sierra-Zapata

Clément

Mirea

et al. 2017

2017 Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFC)

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We propose two methods to improve the growth process of AIN films displaying the c-axis uniformly tilted, intended for the excitation of shear modes in acoustic resonators. The two methods aim at modifying the surface topography of the substrates in order to produce a family of parallel planes offering a suitable orientation for the subsequent growth of uniformly tilted AIN microcrystals. The first method is based on an ion milling process over rough substrates. Rough substrates, obtained by depositing a W layer on sputtered porous silicon oxide layers, are bombarded with a wide beam of Ar ions impinging on the sample surface at an angle of 65°. All treated surfaces lead to increased mean tilt angles of the subsequently grown AIN films, which in turn improves the coupling factor of the shear mode resonators. The second method consists in transferring the topography of a blazed diffraction grating to a photoresist layer spun over metal substrates. The photoresist pattern is then transferred to the substrates by a non-selective directional reactive ion etching process with SFÓ.

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“…1 The quartz crystal microbalance (QCM) is a well-established technology where a shear mode is generated across the thickness of a quartz substrate. 2 However the quartz substrates are thick (330 -55 μm), consequently QCMs resonate at low frequencies (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). 2 This limits the maximum mass sensitivity of QCMs, which according to Sauerbrey, is proportional to the square of the operating frequency.…”

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confidence: 99%

“…In practice, the electric fields between the coplanar electrodes are weak, and excited shear modes have low electromechanical coupling coefficients (<0.01%) in SMRs. 12 Stronger shear resonances can be achieved by thickness excitation of films with the c-axis inclined with respect to the surface normal, through the component of the electric field perpendicular to the c-axis and the d15 coefficient. 12 In order to effectively excite the shear mode, the polarization axis of the film should have an inclination angle between 20° and 50° from the surface normal.…”

mentioning

confidence: 99%

“…12 Stronger shear resonances can be achieved by thickness excitation of films with the c-axis inclined with respect to the surface normal, through the component of the electric field perpendicular to the c-axis and the d15 coefficient. 12 In order to effectively excite the shear mode, the polarization axis of the film should have an inclination angle between 20° and 50° from the surface normal. 13 Piezoelectric ZnO films with grains inclined away from the surface normal can be sputtered on substrates with controlled roughness so that the local surface on which the ZnO grains are nucleating is not parallel to the macroscopic plane of the substrates.…”

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confidence: 99%

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Room temperature sputtering of inclined c-axis ZnO for shear mode solidly mounted resonators

Rughoobur

DeMiguel-Ramos

Mirea

et al. 2016

Applied Physics Letters

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ZnO films with a c-axis significantly inclined away from the surface normal were grown by a remote plasma sputtering technique at room temperature. The films were used to make solidly mounted resonators (SMRs) operating in shear mode at a resonant frequency of 1.35 GHz. Control of the ZnO microstructure was achieved using a polycrystalline AlN seed layer which can be added on top of a sputtered acoustic mirror to give a complete SMR device. The ZnO was reactively sputtered in an atmosphere of argon and oxygen from a zinc target. The c-axis of the ZnO was estimated to be at an angle of ~ 45° to the surface normal. SMRs were measured to have quality factors (Q) of up to 140 and effective electromechanical coupling coefficients of up to 2.2% in air. Although an inclined c-axis can be achieved with direct growth onto the acoustic mirror, it is shown that the AlN seed layer provides higher coupling coefficients and narrower inclination angular distribution. The responses of the devices in liquids of different viscosities (acetone, water and AZ5214E photoresist) were measured. The shear mode Q decreased by 45% in acetone, 72% in water and 92% in AZ5214E.

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On the effectiveness of lateral excitation of shear modes in AlN layered resonators

Cited by 17 publications

References 24 publications

Gravimetric sensors operating at 1.1 GHz based on inclined c-axis ZnO grown on textured Al electrodes

Gravimetric sensors operating at 1.1 GHz based on inclined c-axis ZnO grown on textured Al electrodes

Substrate texturing for homogeneous deposition of tilted c-axis AlN films for shear mode operation

Room temperature sputtering of inclined c-axis ZnO for shear mode solidly mounted resonators

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