BULK ACOUSTIC WAVE HIGH OVERTONE RESONATOR

(1)

HAL Id: jpa-00230437

https://hal.archives-ouvertes.fr/jpa-00230437

Submitted on 1 Jan 1990

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

BULK ACOUSTIC WAVE HIGH OVERTONE RESONATOR

S. Ivanov, I. Kotelyansky, G. Mansfeld, V. Veretin

To cite this version:

S. Ivanov, I. Kotelyansky, G. Mansfeld, V. Veretin. BULK ACOUSTIC WAVE HIGH OVERTONE RESONATOR. Journal de Physique Colloques, 1990, 51 (C2), pp.C2-599-C2-601.

�10.1051/jphyscol:19902141�. �jpa-00230437�

(2)

COLLOQUE DE PHYSIQUE

Colloque C2, supplément au n°2, Tome 51, Février 1990 C2-599 1er Congrès Français d'Acoustique 1990

BULK ACOUSTIC WAVE HIGH OVERTONE RESONATOR

S. IVANOV, I. KOTELYANSKY, G. MANSFELD and V. VERETIN

Institute of Radloenglneerlng and Electronics Academy of Sciences of the USSR, Marx Avenue 18, 103907, Moscow, V.S.S.R.

Résumé - Les pertes de propagation d 'ondes acoustice dans les solutions solide de Rare Terre de Ittrium Aluminium Grenat. La matrice de Y^ R AlcO-p donne les pertes en quelque fois moin que la matrice de YAG. On étude l'onde harmonique des résonateur acoustique de Yo_ Lu Alt-01?. On trouve expérimentalement que le factor Q est

1.5 - 2.0 • 105 at 3.5 - 4.0 GHz.

Abstract - the acoustic waves propagation losses in solid solutions of Rare Earth in Ittrium Aluminium Garnets. Matrix were Y^^^AlcO..«

found few times lower than that of YAG matrix. The high overtone bulk acoustic wave resonators made of Y-, Lu Alr01o were studies. The Q -

c .5—X X 2 I £.

factor 1.5 - 2.0*10 at 3.5 - 4.0 GHz was experimentally found.

1 - INTRODUCTION

The practical interest to the investigation of the new materials with low acoustic wave losses is due to the possibility of the use of such a materials in acoustoelectron devices particularly in resonators h - 3}• Few years ago it was found that the acoustic wave attenuation in YAG crystals can be drastically decreased if to substitute Yttrium atoms in a crystalline lattice (matrix) [4,5] by the rare earth elements. The purposes of this work were to study the possibility of the use of such a materials in high overtone bulk acoustic wave resonator and obtaining the high values of Q - factor.

2 - EXPERIMENTAL METHODS

The experimental measurements of the coefficient of lattice absorption at , were made with the samples of Y-, R Alc019 using conventional echo

pulse method L6J at microwave frequencies. The resonator structures were made of Y-, Lu Al,-0.,2. Thin plates (200 - 300yii ) with optically polished flat parallel (2") faces of this material were oriented normally to the

[100] crystalline axis. To provide electrical coupling of the resonator to the external circuit the resonator at one of it surfaces thin ZnO films (transducer) supplied with ohmic contacts were deposited. The aperture dia- meter of the transducer was 140/i . To connect the samples with the reflec- tometer microstrip lines of reentrant microwave cavity impedance transformer were used.

3 - RESULTS AND DISCUSSION

Typical dependence of the absorption coefficient for longitudinal acoustic waves as a function of x measured at room temperature on 2.5 GHz is shown on Fig.1a. This figure illustrates the fact that there is a minimum in losses when x =* 0,65 - 0,75. It was experimentally found that the Gruneizen constant ~y2 for longitudinal waves is dependent on the composition of the solid solution. (To derive that dependence the absorption was measured in Landau mechanism temperature range, where T - life time of phonons is not included in the acoustic wave absorption formula.) Solid line on Fig.1a represented results of the theory. It is interesting to compare the possi- bilities of such material with other low loss materials which can be used in acoustic resonators on the well known diagramm til shown on Fig.1b.

This diagramm shows frequency dependencies of the absorption at the same

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19902141

(3)

C2-600 COLLOQUE DE PHYSIQUE

wavelengh for various crystals and the values of the quality factor Q which can be expected, if to use them in high overtone resonators. Lower curve corresponds to the material studies in this work. It is seen that the highest quality factops can be acheived. In our experiments with the resonators the reflection coefficient of the structure has been measured as a function of frequency. To measure this quantity the samples were placed in the reentrant coaxial cavity that served as an impedance transformer. Two typical dependencies of the moduls of the impedance as a function of frequency are shown on Fig.2 and 3. The first one (Fig.2) corresponds to the high efficiency transducer. In this case the set of resonant peaks of high overtone are seen. These peaks are wide enough

-

their mean quality factors are of an order 2.10~. On the Pigs.3a and 3b typical dependencies for the sample with high losses transducer are shown (for poor and high frequency resolution respectively). Solid curves correspond to the numerical calculations of the equivalent curquit of the coaxial resonator loaded on the overtone-mode acoustic resonator. The shapes of the curves are strongly dependent on the equivalent parameters of the acoustic resonator. The best fit of the experimental points and the results of calculations allows to evaluate the effective inductance and the resistivity of the acoustic resonator and hence ducers Q

-

factor is appeared to be of the order of

-

^{the Q}

-

factor. For the samples with hig losses trans- 1.5 10

! .

Using this va- lue of Q and neglecting the energy conversion losses in transducers it is possible to evaluate the coefficient of lattice attenuation (,, L = 5 ~ / 2 ~ s Q

( (2

-

frequency of BAN, vs

-

velocity of sound). This calculation gives d L @ l , 2 dB/cm instead 0,9 dB/cm obtained by conventional echo-pulse method.

4

-

COWCLUSION

In order to realise the good acoustic characteristics of the material used in resonator it is necessary to minimize convertion energy losses in transducers. Heavily doped YAG Y3-xLuxA15012 is a material that can provide a high Q

-

^factor.

Fig.la. Variation of k longi tudional Avi in YLuAlG; solid lines are results of calculation, the point

-

experiment.

T = 300 K.

W

Fig.1 b. Losses per wave length and the. resonator s quality Q as a function of frequency for various materials.

(4)

Fig.2. The dependence of the reflection coefficient on the frequency (transducer with high efficiency).

Fig. 3a Fig.3b 3708 I!Hz

The dependencies of the reflection of the coefficient on the frequency for the sample with high losses transducer (3a

-

^poor,

3b

-

high frequency resolution).

REFEREDCES

1 .R.A.Moore, J.T.Haynes ,B.R.I\,cAvoy ,IEEE U1 trasonics Symp.Proc. 1981,414.

2.Y.~iyasaka,S.HoshinoyS.Takahashi,IEE Ultrasonics Symp.froc.1985,346.

3.A.V.Dobrynin,G.D.Naida,V.X.Novoselov,Phys.~tat.Sol.(a),lO4,K47,l987.

4.S.N.Ivanov,V.V.B~edved.FTT(Sov.)1983,v.25,N010,p.2907.

5 .S .N.Ivanov ,V. V.Kedved ,I .i"vl.Kotelyansky ,..Khazanov.FTT, v ) ,1986,

~.28,N~lO,p.2941.