Electromechanical coupling coefficient for surface acoustic waves in proton-exchanged 128°-rotated Y-cut lithium niobate

Shur

et al. 2002

phys. stat. sol. (b)

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The electromechanical coupling coefficient for surface acoustic waves propagating in GaN-on-sapphire structure has been evaluated using in situ measurements of the SAW attenuation during the evaporation of a metal film on the GaN surface. The extracted values for samples with GaN layer thicknesses of 2.2-2.4 mm were in the range of 0.06-0.09% at SAW frequencies of 200-300 MHz.Introduction Surface acoustic waves (SAWs) have found important applications in material research, signal processing, and telecommunications areas. There is a considerable interest in SAW investigations in thin-film structures based on GaN family of semiconductors. The key parameter for SAW devices is the electromechanical coupling coefficient, K 2 . The efficiency of the SAW interdigital transducer (IDT) is characterized by its radiation conductance G a ðf 0 Þ ¼ 8K 2 f 0 C T N at center frequency f 0 , where C T is the IDT static capacitance and N is the number of the IDT electrode pairs. The electromechanical coupling coefficient for SAWs can be expressed as K 2 ¼ 2DV=V, where DV is the magnitude of the SAW velocity change that occurs when the free surface of the piezoelectric is shorted by a thin highly conducting metal film, and V is the unperturbed SAW velocity. The K 2 values for SAWs in GaN-on-sapphire structures have been evaluated from transducer performance analysis and extracted from the velocity measurements by several authors [1][2][3][4]. However, there is a considerable disagreement in the results, and further investigations are necessary. For this purpose, we have chosen the technique, different from those mentioned above. We report on the evaluation of the electromechanical coupling coefficient for GaNon-sapphire structures using in situ measurements of the SAW attenuation during the evaporation of a metal film on the surface of the piezoelectric [5,6].

mentioning

confidence: 99%

Electromechanical Coupling Coefficient for Surface Acoustic Waves in GaN-on-Sapphire

Shur

et al. 2002

phys. stat. sol. (b)

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“…The value of K 2 for X-propagating SAW in 128 rotated Y-cut LiNbO 3 is 5:3 Â 10 À2 [19]. Our measurements of C T by a Q-meter at low frequencies yielded a value of 20 pF.…”

Section: Experiments and Discussionmentioning

confidence: 69%

Diffraction of Guided Optical Waves by Surface Acoustic Waves in Proton-Exchanged 128� Rotated Y-Cut LiNbO3

Balakauskas

2001

phys. stat. sol. (a)

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The acousto-optic diffraction of guided optical modes by surface acoustic waves in the RamanNath regime in the single-mode optical waveguide formed by the proton exchange technique in 128 o rotated Y-cut lithium niobate has been studied. The experiments have been performed at the optical wavelength 0.6328 mm in a single-TM mode waveguide formed by treatment in pure benzoic acid for 20 min at 230 C and at the SAW frequency of 78 MHz. The measured dependences of the light intensity diffracted into the zeroth, first and second orders on the driving voltage are in good agreement with the theoretical calculations. The values for the acousto-optic figure of merit M 2 ¼ 9:5 Â 10 À15 s 3 /kg and the effective photoelastic cefficient p eff = 0.14 have been evaluated showing the efficiency of the acousto-optic interaction in proton-exchanged lithium niobate being comparable to that in the pure crystal.

“…[3][4][5][6]) was used in our experiments. A pair of identical interdigital transducers (IDTs) was fabricated on the surface of the 36 o rotated Y-cut X-propagation singlecrystal lithium tantalate substrate.…”

Section: Experimental Sample Preparation and Characterizationmentioning

confidence: 99%

Thin film conductivity sensor based on acoustoelectric interaction in 36° YX lithium tantalate

2013 Transducers &Amp; Eurosensors XXVII: The 17th International Conference on Solid-State Sensors, Actuators and Microsystems

Sereika

2013

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The acoustoelectric interaction of leaky surface acoustic wave (LSAW) on 36 o rotated Y-cut Xpropagation lithium tantalate was studied and the thin film conductivity sensor was implemented on this base. The technique of slow evaporation of thin copper film on the wave propagation surface with simultaneous measurements of the wave amplitude and phase was used. The observed strong response of the LSAW to the film conductivity is explained by the acoustoelectric attenuation and velocity change. The sheet conductivity extracted from the changes in wave amplitude and phase was compared with the results of DC resistance measurements. The potential of LSAWs in LiTaO 3 for contactless monitoring of changes in thin film conductivity has been demonstrated. KEYWORDSLeaky surface acoustic waves, lithium tantalate, acoustoelectric interaction, thin metal film, conductivity sensor.