ELSEVIER Thin S&d Filins 343-34-l i 1999) 90-93 Reactive pulsed laser deposition of piezoelectric and ferroelectric thin films F. Craciun*. P. Verardia. A4. Dinescub. G. Guidarelli” Abstract Piezoelectric (ZnO) and ferroelectric IPZT) thin films were deposited on different substrates (Au coated Si. AlJO;. Coming glass etc.) by reactive pulsed laser deposition. by using a pulsed Nd-YAG laser. ZnO films were deposited starting from high purity Zn plates whIii the-- PZT flms were obtained from sintered targets. in different deposition conditions. The influence of the process parameters on rhe physical and chemical properties of the deposited films was analyzed by SIMS. XPS, XRD, SEM and TEM. XRJI analysis showed rhnt the ZnO films were c-axis orlented. while SEM on cross-sections showed evidence of a columnar bcrucmre. On PZT thin filmsXRD showed evidence of a crystalline pseudo-perovskite structure with ( 1 I I ) orientation. while surface andcross-section SF24 studies showed evidence of a compact round grain structure. Electrical measurements on both ZnO and PZT films found good piezoelecrric coefficients. The ferroeleotric properries of the PZT films have been characterized by a Sawyer-Tower circuit. Samples of ZnO and PZT were selected and employed in rhe construction of acceleration sensor and bulk acoustic wave tBAWj devices. Results on frequency response and hekrivity of constructed devices as well aselectroacustical characteristics are presented anddiscussed. c 1999 Elsevier Science S.A. All rightsreserved. KF~~~~J~: PZT: ZnO: Ferroelectric thin film: PLD; Piezoelrcrric propcmes 1. Introduction In the last few years pulsedlaser deposition (PLD) tech- niqueshave beenapplied to the synthesis and the deposition of many compound films [I]. Pb(Zri,.c.~Ti,,,:)O, (PZT) thin films have been deposited by this technique on different substrates at relatively high temperatures (-600°C) [ l-41. In order to take advantageof existing planar semiconductor technology for fabricating useful piezoelectric microde- vices. deposition of PZT on semiconducting substrates such as Si at lower temperatures must be solved. We have recently reported the successful deposition of oriented piezoelectric PZT films by PLD at low substratetempera- tures (375’0 on silicon substrates [5]. In the present paper we report further achievementsin the deposition and in the characterisation of PZT films aswell as in the construction of test devices. We investigated the obtained thin film samplesby different experimental techniques like XRD. XPS. SIMS and SE.34 in order to obtain information about their structural. compositional and morphologic properties. Their piezoelectric and ferroelectric properties are also reported. In order to characterisethe behaviour of materials * Corresponding aurhor. Tel.: + 39-64993JOX fax: - 39-6-30660061. E+trnil ctddt~rss: rloriana~ldac.mm.cnr.it IF. Craciun) in transducers we constructeda testing transducerconsisting in a cantilever Si beam. Au/Cr bottom electrode. PZT layer and a Au/Cr top electrode. Voltage sensitivity measure- ments as well as dielectric. ferroelectric and piezoelectric characterisation of the film will be discussed in the fo7fow-. ing sections. Results on ZnO thin films depositionand characterisation are also presented. The possibility of combining in PLD the synthesis and deposition of the compound has been applied in this case. A solid target of pure Zn was ablated in a reactive osygen atmosphere. The resulting ZnO was collected on the substrateplaced in the front of the target at a given distance. The films were characterized by XRD, XPS. SEM and TEM techniques. BAW transducers built on thesefilms are described. 2. Experimental Sic1I 1) substrates 0.5 mm thick were thoroughly cleaned and introduced into an evaporation chamber, where Cr was flash-deposited to favour the adhesionof a gold electrode. Au layers with thicknesses of 100nm were evaporatedafter- wards and the subhtrates were mechanically attached to a 0040-6090/99/S - tee front marier G 1999 Elscvier Science S.X. All right> merved. PII: s0010-6090(98,015S’-x