Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation

Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation

Lead titanate zirconate Pb(Zr,Ti)O₃ (PZT) thin films were deposited on platinized silicon substrates by r.f. magnetron sputtering and crystallized with preferred (110) or (111) orientation by conventional annealing treatment. The film structure evolution was observed as a function of the film thickn...

Ausführliche Beschreibung

Gespeichert in:
Bibliographische Detailangaben
Datum:2002
Hauptverfasser: Haccart, T., Cattan, E., Remiens, D.
Format: Artikel
Sprache:English
Veröffentlicht: Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України 2002
Schriftenreihe:Semiconductor Physics Quantum Electronics & Optoelectronics
Online Zugang:http://dspace.nbuv.gov.ua/handle/123456789/121131
Tags: Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
Назва журналу:Digital Library of Periodicals of National Academy of Sciences of Ukraine
Zitieren:Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation / T. Haccart, E. Cattan, D. Remiens // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2002. — Т. 5, № 1. — С. 78-88. — Бібліогр.: 45 назв. — англ.

Institution

Digital Library of Periodicals of National Academy of Sciences of Ukraine
id irk-123456789-121131
record_format dspace
spelling irk-123456789-1211312017-06-14T03:06:14Z Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation Haccart, T. Cattan, E. Remiens, D. Lead titanate zirconate Pb(Zr,Ti)O₃ (PZT) thin films were deposited on platinized silicon substrates by r.f. magnetron sputtering and crystallized with preferred (110) or (111) orientation by conventional annealing treatment. The film structure evolution was observed as a function of the film thickness. Whatever the film thickness in the range 0.07 - 3 mm, the preferred orientation of the film is maintained. The film microstructure and, in particular, grain sizes varied with the film thickness; more precisely, grain sizes increases, both for (111) and (110) films with the film thickness. The electrical properties such as dielectric, ferroelectric and piezoelectric ones were systematically evaluated functions of the film thickness and their orientation. The relative dielectric constant increases with the film thickness; a saturation value of 920 is attained for film thicknesses higher than 0.6 µm independently of the film orientation. The ferroelectric properties seems to be independent of the film orientation; the coercive field decrease with increasing the film thickness to attain a minimum value of 30 kV/cm for films thicker than 1 mm. The remanent polarization increases with the film thickness and reaches the maximum value of 20 mC/cm². An increase in the piezoelectric constant e₃₁ with increasing the film thickness was observed for two types of films. For films thicker than 0.6 mm, the e₃₁ coefficient remains constant: e₃₁eff.rem. = -4.5 C/m² (which corresponds to d₃₁eff.rem. = -38 pm/V). Identical behavior is observed for the d₃₃eff. coefficient but no saturation effect with the film thickness is observed. The ferroelectric domain walls motion and the interfacial effects could explain partly the observed behavior. 2002 Article Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation / T. Haccart, E. Cattan, D. Remiens // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2002. — Т. 5, № 1. — С. 78-88. — Бібліогр.: 45 назв. — англ. 1560-8034 PACS: 78.20.-e http://dspace.nbuv.gov.ua/handle/123456789/121131 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
description Lead titanate zirconate Pb(Zr,Ti)O₃ (PZT) thin films were deposited on platinized silicon substrates by r.f. magnetron sputtering and crystallized with preferred (110) or (111) orientation by conventional annealing treatment. The film structure evolution was observed as a function of the film thickness. Whatever the film thickness in the range 0.07 - 3 mm, the preferred orientation of the film is maintained. The film microstructure and, in particular, grain sizes varied with the film thickness; more precisely, grain sizes increases, both for (111) and (110) films with the film thickness. The electrical properties such as dielectric, ferroelectric and piezoelectric ones were systematically evaluated functions of the film thickness and their orientation. The relative dielectric constant increases with the film thickness; a saturation value of 920 is attained for film thicknesses higher than 0.6 µm independently of the film orientation. The ferroelectric properties seems to be independent of the film orientation; the coercive field decrease with increasing the film thickness to attain a minimum value of 30 kV/cm for films thicker than 1 mm. The remanent polarization increases with the film thickness and reaches the maximum value of 20 mC/cm². An increase in the piezoelectric constant e₃₁ with increasing the film thickness was observed for two types of films. For films thicker than 0.6 mm, the e₃₁ coefficient remains constant: e₃₁eff.rem. = -4.5 C/m² (which corresponds to d₃₁eff.rem. = -38 pm/V). Identical behavior is observed for the d₃₃eff. coefficient but no saturation effect with the film thickness is observed. The ferroelectric domain walls motion and the interfacial effects could explain partly the observed behavior.
format Article
author Haccart, T.
Cattan, E.
Remiens, D.
spellingShingle Haccart, T.
Cattan, E.
Remiens, D.
Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation
Semiconductor Physics Quantum Electronics & Optoelectronics
author_facet Haccart, T.
Cattan, E.
Remiens, D.
author_sort Haccart, T.
title Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation
title_short Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation
title_full Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation
title_fullStr Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation
title_full_unstemmed Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation
title_sort dielectric, ferroelectric and piezoelectric properties of sputtered pzt thin films on si substrates: influence of film thickness and orientation
publisher Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
publishDate 2002
url http://dspace.nbuv.gov.ua/handle/123456789/121131
citation_txt Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation / T. Haccart, E. Cattan, D. Remiens // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2002. — Т. 5, № 1. — С. 78-88. — Бібліогр.: 45 назв. — англ.
series Semiconductor Physics Quantum Electronics & Optoelectronics
work_keys_str_mv AT haccartt dielectricferroelectricandpiezoelectricpropertiesofsputteredpztthinfilmsonsisubstratesinfluenceoffilmthicknessandorientation
AT cattane dielectricferroelectricandpiezoelectricpropertiesofsputteredpztthinfilmsonsisubstratesinfluenceoffilmthicknessandorientation
AT remiensd dielectricferroelectricandpiezoelectricpropertiesofsputteredpztthinfilmsonsisubstratesinfluenceoffilmthicknessandorientation
first_indexed 2025-07-08T19:14:45Z
last_indexed 2025-07-08T19:14:45Z
_version_ 1837107342015987712
fulltext Semiconductor Physics, Quantum Electronics & Optoelectronics. 2002. V. 5, N 1. P. 78-88. © 2002, Institute of Semiconductor Physics, National Academy of Sciences of Ukraine78 PACS: 78.20.-e Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation T. Haccart, E. Cattan, D. Remiens IEMN - DOAE - MIMM. UMR CNRS 8520 Université de Valenciennes ZI petite savate, 59600 Maubeuge, France e-mail: denis.remiens@univ-valenciennes.fr Abstract. Lead titanate zirconate Pb(Zr,Ti)O3 (PZT) thin films were deposited on platinized silicon substrates by r.f. magnetron sputtering and crystallized with preferred (110) or (111) orientation by conventional annealing treatment. The film structure evolution was observed as a function of the film thickness. Whatever the film thickness in the range 0.07 � 3 µm, the preferred orientation of the film is maintained. The film microstructure and, in particular, grain sizes varied with the film thickness; more precisely, grain sizes increases, both for (111) and (110) films with the film thickness. The electrical properties such as dielectric, ferroelectric and piezoelectric ones were systematically evaluated functions of the film thickness and their orientation. The relative dielectric constant increases with the film thickness; a saturation value of 920 is attained for film thicknesses higher than 0.6 µm independently of the film orientation. The ferroelectric properties seems to be independent of the film orientation; the coercive field decrease with increasing the film thickness to attain a minimum value of 30 kV/cm for films thicker than 1 mm. The remanent polarization increases with the film thickness and reaches the maximum value of 20 µC/cm2. An increase in the piezoelectric constant e31 with increasing the film thickness was observed for two types of films. For films thicker than 0.6 µm, the e31 coefficient remains constant: e31eff.rem. = -4.5 C/m2 (which corresponds to d31eff.rem. = -38 pm/V). Identical behavior is ob- served for the d33eff. coefficient but no saturation effect with the film thickness is observed. The ferroelectric domain walls motion and the interfacial effects could explain partly the ob- served behavior. Keywords: ceramic thin film; sputtering; film thickness and orientation; dielectric, ferroelectric and piezoelectric properties. Paper received 14.01.02; revised manuscript received 20.02.02; accepted for publication 05.03.02. 1.Introduction Lead oxide-based ferroelectric films have attracted considerable attention for potential microelectronic and electromechanical applications; in particular, PZT ma- terials are the most popular candidates. PZT thin films with different composition (ratio Zr/Ti), depending on the desired applications have been extensively studied. The main device applications were semiconductor non- volatile memories [1], pyroelectric detectors [2] and pi- ezoelectric sensors [3] and actuators [4]. For these later applications, the PZT films composition is generally cho- sen on the morphotropic phase boundary, i.e. a Zr/Ti ratio the order of 50/50. For device applications, it is imperative to perfectly T. Haccart et al.: Dielectric, ferroelectric and piezoelectric properties... 79SQO, 5(1), 2002 know the influence of the film characteristics such as: - the structure (epitaxial or polycrystalline films with preferred orientation) - the microstructure (grain size) and the interfaces, - the thickness, � on the electrical properties. For example, for Micro Electro Mechanical Systems (MEMS) applications, the film thickness must be in the order of 1 µm or more [5]; on the contrary, for nonvolatile memories, the film must be very thin6 (0.2 � 0.3 µm). It is evident that the thickness must have a strong influence on the film electrical pro- perties. The structure and the microstructure of PZT films were controlled by many parameters: the growth tech- nique, the substrate nature and orientation, the presence of a seed layer or an electrode surface. The electrode surface has the function to decrease the nucleation en- ergy for a given crystallographic orientation of the nu- cleus. It has been clearly established that the formation of the perovskite phase was nucleation controlled. The film orientation and thickness have also an influence on the physical properties, and it is necessary to precisely evaluate this dependence in order to improve the device performance. Many authors have described the influence of PZT films orientation on their electrical properties but the re- sults were in many cases in contradiction. For example, we can find in the literature that (111)-oriented PZT films are higher coercive field than (100) films, but the oppo- site situation has been also published [7,8]. Identical situ- ation for the film thickness effect9,10 was ascertained. Con- cerning the evaluation of the piezoelectric coefficients e31, d31 and d33 dependence with the PZT film thickness there is a limited number of papers [11,12]. So, in this article we have systematically studied PZT films deposited by r.f. magnetron sputtering followed by a post-annealing treatment on Pt metallized silicon substrates: -the influence of the film thickness on their structural and micro structural properties, -the influence of the film thickness and orientation on their electrical properties: dielectric, ferroelectric and piezoelectric. Some tentative behavior explanations are made, and a correlation between the electrical properties and the microstructure by the way of the existence of an interfa- cial layer between the film and the substrate as well as the domain walls motion is given. 2. Film deposition and characterization The r.f. magnetron sputtering system, described pre- viously [13], was used to prepare PZT thin films; the films composition, i.e. the (Zr/Ti) ratio, was fixed to 54/46 (near the morphotropic phase boundary). It is well know that in the bulk ceramics the best piezoelectric perform- ance is obtained for this composition. The sputtering target was a mixture of PbO, TiO2 and ZrO2 in the stoichiometric composition (without lead ex- cess); the targets were obtained by uniaxially cold press- ing. The PZT films were deposited onto oxidized silicon (SiO2 - 3000 Å)- (100) n-type Si substrates coated with Ti/ Pt electrodes. The thickness of the Ti and Pt layers was 100 and 1500 Å, respectively. More precisely, we have deposited an oxydized titanium, i.e. TiOx, layer as an adhesion film for the Pt layer on SiO2. The main objec- tive is to limit the diffusion of titanium through Pt; it is well known that the diffusion velocity of TiOx is lower than Ti; then this procedure can stabilize the substrate during the PZT crystallization post-annealing treatment. With the same idea (stabilization of the substrate), just before the PZT deposition, we have made an annealing treatment of the Si/SiO2/TiOx/Pt substrates at a tempera- ture higher to the post-annealing PZT treatment. A more complete description of the substrate preparation is given elsewhere [14]. Hence, with this precaution, we can sup- pose that the substrates used in this experiment are simi- lar and stable. But, as we can see later, this is not the case and the PZT films orientation can varied between two depositions run. We think that only the substrate and, in particular, the bilayers TiOx/Pt can be responsible for this modification. More complete studies are necessary to understand the substrate evolution, which appears during the annealing treatment of the PZT films. The PZT sputtering conditions are summarized in Table 1; they are optimized in order to obtain a stoichio- metric film (measured by Energy Dispersion Spectroscopy) and a relatively important growth rate (for an oxide material). It was estimated to 30 Å/min; for higher r.f. power density (which influence strongly the growth rate) some cracks appear on the target, in par- ticular, in the erosion area (magnetron system). The films were grown without substrate heating and so they are amorphous; a post-annealing treatment is necessary to crystallize the PZT in the desired phase, i.e. in the perovskite phase. We have been optimized two processes [15]: - the conventional annealing in a tubular furnace, - the rapid thermal annealing . Target composition Zr/Ti = 54/46 � without lead excess Target diameter (mm) 76 r.f.power density ( W /cm2) 3 Gas pressure (mT) 30 (Ar) Interelectrodes distance (mm) 60 Substrate temperature (°C) 25-140 (ion bombardment) Annealing temperature (°C) 625 Annealing time (min.) 30 Atmosphere Air Table. Typical sputtering parameters for the PZT films growth and post-annealing conditions. 80 SQO, 5(1), 2002 T. Haccart et al.: Dielectric, ferroelectric and piezoelectric properties... 20 30 40 50 60 P Z T [ ]100 P Z T [ ]110 P t [ ]111 P Z T [ ]200 In te ns ity ( a. u .) A n g le 2Θ ( ) 20 30 40 50 60 In te n si ty ( a . u .) Angle 2Θ ( ) PZT [ ]111 Pt [ ]111 Fig. 1a. Typical XRD patterns example of a 0.7µm thick (110)- oriented PZT. Fig. 1b. Typical XRD patterns example of a 0.7µm thick (111)- oriented PZT. In this paper, we present only the results relative to the conventional treatment. The typical annealing conditions, whatever the film thickness, were given in table; no cracks appear and the films composition are stoichiometric (in par- ticular the lead content) after this treatment. The film structure was analyzed by X-Rays Diffrac- tion (XRD) in the q-2q configuration with the CuKa ra- diation. Fig. 1a shows the XRD pattern of a PZT film, the film thickness is of the order of 0.7 µm. The film is perfectly crystallized in the perovskite phase, and no pyrochlore phase was detected. The film is polycrystalline, i.e.randomly oriented, but the (110) in- tensity peak is largely superior to the others (like PZT ceramics), and we consider that this sample has a pre- ferred (110) orientation. Fig. 1b shows also an XRD pat- tern of a PZT film (0.7 µm thick) which has suffered the same elaboration process as the precedent film. As previ- ously, the film is completely crystallized in the perovskite phase, but it is now (111) preferentially oriented. At present, it is difficult to explain why the crystallographic orientation is different between the PZT films. The sput- tering conditions are identical and the difference could be attributed to the substrate. An hypothesis will be that the degree of oxidation (x) of the TiOx layer varied be- tween the wafers; so, since the TiOx diffusion rate is very sensitive to x, we can suppose that the diffusion of TiOx differs between the wafers and the difference of the «pen- etration depth» of TiOx through Pt (the extreme case is the encapsulation of Pt, i.e. presence of TiOx on the substrate surface) could influence the PZT crystalliza- tion [16,17]. With the same idea, the thickness of the TiOx and Pt layers can be also varied in the deposition proc- esses; in particular, the TiOx layer thickness is very fine (100 Å) and a little increase (decrease) of the thickness could favors the TiOx diffusion through the Pt joints grain and so modify the PZT crystallization [17,18]. These hypotheses must be confirmed more precisely, but certi- tude is that we can reproduce PZT films with (111) or (110)-preferred orientation. Another possibility would be the differences in whether the nucleation occurred from the bottom electrode (where (111) orientation would be favored) or from some other places (perhaps the surface), which would favor randomly oriented PZT, i.e. (110) PZT films [18]. We have studied the evolution of the (110) and (111) PZT films orientation as a function of the film thickness, which varied in the range 0.07� 3.2 µm. A typical exam- ple is given in Figs 2a and 2b, which shows respectively the X ray diffraction structure evolution of (110) and (111)-PZT film. For the (111)-oriented films, the degree of orientation a(111) (defined as a (111) = I (111) / S I (hkl)) varied between 98 and 96 % for respectively a film thickness of 0.09 and 2 µm. Identical results were ob- tained for the (110) PZT films. To complete this study, we have followed the structural film evolution with the thickness by varying the X-ray incident angle (αi). The incident angle controls the analyzed film thickness; more precisely, when the incident angle decreased, the analyzed film depth decreased. An example is given by Fig. 3 for a (110) film; the wavelength of the X-rays used in this experiment is 1.789 Å (cobalt cathode), which ex- plains the variations of the perovskite plane diffraction angles in comparison to the X-ray pattern shown in Fig. 1 (Cu cathode). For comprising αi between [0.3°-2°], the film is al- ways (110)-oriented and confirms that the film orienta- tion is maintained constant across the thickness. Identi- cal results were obtained for the (111)- oriented films. We can also remark that, in contradiction to J.C. Kim works [19], the pyrochlore phase doesn�t appear at the film surface, i.e. for very low αi value (αi = 0.3°). We have also evaluated the evolution of the film micro- structure as a function of the film thickness. Firstly, we have compared the microstructure of a (111) and (110)- oriented PZT film. The morphology of these two types of films is very different; the grain size of the (110)-oriented films is large and the grain joints surface is large, too. In comparison, the grain size of the (111)-oriented film is very fine, and their distribution is more homogeneous. It is very difficult to compare our results with those pub- lished in literature, since the films thickness are different and the films is often obtained by sol-gel. Some results are in contradiction; for example, Brooks et al. [20] and Liam et al. [9] have observed that the film microstructure is very fine and homogeneous for (111)-oriented PZT films in comparison to (100) films. Aoki et al. [10] has observed exactly opposite results. Kurchania et al. [11] have ob- served identical results as those presented here, i.e. the T. Haccart et al.: Dielectric, ferroelectric and piezoelectric properties... 81SQO, 5(1), 2002 same difference between (111) and (110) PZT films micro- structure, but grain sizes are smaller in their works. Some authors have studied the evolution of grain sizes as a function of the film thickness. The obtained results are also in contradiction in some cases. Lian et al. [9] and Taylor et al. [21] have observed some modification of the film microstructure; the films are deposited by sol- gel and the thickness varied between 0.37 to 1.8 µm. For PZT films obtained also by sol-gel, Kim et al. [19] and Kurchania et al. [11] have observed a grain growth with the film thickness in the range 0.3 to 2 µm; their results are in perfect agreement with the observations of Chen et al. [22] and Fujisawa et al.[23]. Some explanations are given concerning the variation of grain sizes with the film thickness; the decrease of the residual stresses when the thickness increased could be a response. Our results show an important grain size evolution with the film thickness; an illustration is given by Fig. 4. Fig. 4a is relative to (110)-oriented PZT films; the film thickness varied between 0.3 to 2 µm. The grain size in- creased with the film thickness and their distribution is not homogeneous. Identical distribution has been ob- served for PZT films elaborated by sol-gel [22]. The grain growth with the film thickness for (111)-oriented PZT films is shown in Fig. 4b; as we have mentioned previ- ously, the grain size is smaller in comparison to PZT (110). For example, a 0.3 µm thick PZT films have an 20 30 40 50 60 Angle 2Θ ( ) In te n si ty ( a . u .) e= m2.1 µ PZT [ ]111 PZT [ ]110 PZT [20 ]0 PZT [211]PZT [ ]100 Pt [ ]111 20 30 40 50 60 Angle 2Θ ( ) In te n si ty ( a . u .) e= m0.03 µ PZT [ ]110 Pt [ ]111 Fig. 2a. Evolution of the XRD patterns of a (110)-oriented PZT film function of the thickness. 20 30 40 50 60 Angle 2Θ ( ) In te n si ty ( a . u .) e= m1.9 µ PZT [ ]111 PZT [ ]110 PZT [211]PZT [ ]100 Pt [ ]111 20 30 40 50 60 Angle 2Θ ( ) In te n si ty ( a . u .) e= m0.08 µ PZT [ ]111 Pt [ ]111 Fig. 2b. Evolution of the XRD patterns of a (111)-oriented PZT film function of the thickness. average grain sizes of 0.1 and 0.2 µm for respectively a (111) and (110) orientation. It attains 0.6 and 1 µm for re- spectively a (111) and (110)-oriented films of 2 µm thick. To explain this increase of the grain size with the film thickness some authors have taken into account the exist- ence of the stresses in the films and the possible grain disorientation with the film thickness increase [9, 24, 25]. Since in our case, the crystalline orientation is maintained constant with the thickness (in the thickness range stud- ied), we can suppose that the observed evolution is mainly related the decrease of stresses when the film thickness increases. Fig. 3. (110)-oriented PZT film structural evolution with thick- ness by varying the X-ray incident angle(Cobalt cathode). 82 SQO, 5(1), 2002 T. Haccart et al.: Dielectric, ferroelectric and piezoelectric properties... Fig. 4a. Evolution of grain sizes with the film thickness for a (110)-oriented PZT films. Fig. 4b. Evolution of grain sizes with the film thickness for a (111)-oriented PZT films. T. Haccart et al.: Dielectric, ferroelectric and piezoelectric properties... 83SQO, 5(1), 2002 The microstructure variation with the film thickness must have some issues on the electrical properties of the films. We have evaluated this contribution and also the influence of the film orientation and thickness. 3. Electrical characterization The PZT films were systematically characterized as a function of the film orientation and thickness in terms of dielectric constant, ferroelectric and piezoelectric prop- erties. The embedded beam method and a double beam Michelson interferometric system are used to measure the e31 and d33 piezoelectric coefficients, respectively [26, 27]. For electrical properties evaluation, platinum top electrodes of 0.2 µm thickness were formed by photoli- thography and sputtering (lift-off process). The electrode surface is large for the piezoelectric measurements; it is of 1 mm2; for the dielectric and the ferroelectric evalua- tions we used 150 µm diameter circular electrodes. A- Dielectric constant The relative dielectric constant, er, were measured at 1 kHz with an LCR meter at room temperature. In order to not modify the polarization state of the film, we have applied a very weak ac voltage (100 mV). The results are presented in Fig. 5 both for (110) and (111)-oriented films. The er evolution with the film thickness is similar for two types of films; the curve can be decomposed into two parts: for the film thickness thinner than 0.6 µm, εr increases linearly. For thicker films (> 0.6 µm), εr attains a saturation value of 920 independently of the film orientation. Many papers have been published on this subject and our results are conformed to the observed tendency [28,29,30]: An increase of εr with thickness takes place until it attains a saturation value for a threshold thickness (εth). The eth values are different in literature; typi- cally eth is of the order of 0.3 � 0.5 µm; in our case εth is equal to 0.5 � 0.6 µm whatever the film orientation. The origin of er variation with the film thickness can be attributed to different factors: - The existence of a material with a very low dielectric constant (non-ferroelectric state also called �dead� layer) at 1200 1000 800 600 400 200 0 0 0.5 1 1.5 (111) (110) R el at iv e di el ec tr ic c on st an t, ε F i lm th ickn ess ( m )µ R Fig. 5. Evolution of the relative dielectric constant function of the film thickness for a (110) and a (111)-oriented PZT films. the interface between the film and the Pt bottom elec- trode can explain the low er-values of the structure for very thin PZT films18. For example, we have measured εr = 225 for a film thickness of 0.08 µm. When the film thickness increases this effect becomes minor. - The correlation between the grain size and the relative dielectric constant, i.e. an increase of the grain size, resulting from an increase of the thickness, induces an increase of εr [23,31]. The increase of εr with the film thickness is directly related to the decrease of the stresses with the film thickness increase [28]. Cho et al. [29] and Xu et al.[32] have made a complete study of the PZT film relative dielectric constant and loss factor (tan δ) evolutions with the thickness as functions of the applied electric field amplitude (Eac.) as well as the tem- perature. In their analysis, they introduce the intrinsic and extrinsic contributions into the PZT film dielectric proper- ties. More precisely, the lattice contribution corresponds to the intrinsic part and domain wall motion corresponds to the extrinsic properties. The dielectric measurements at a very low temperatures (close to 0K) «block» the domain walls and only the intrinsic contribution must be taking into account in the dielectric response. An excellent paper pub- lished recently by S. Hiboux et al. described also different contribution deduced by the C(V) measurements [33]. The dielectric evolution with the applied electric field is related to the domain wall motion. Their result shows that the ex- tent of domain wall motion increased with film thickness. The intrinsic effects contribute to all films and show a satu- ration whatever the film thickness, so the difference in the observed dielectric permittivity values is attributed to the extrinsic contribution. This behavior could be explained by the existence of an interfacial layer between the film and the substrate. The composition and the thickness of this interfacial zone are unknown, and it doesn�t present ferroelectricity. The film can be decomposed into two parts: the interfacial layer and the ferroelectric layer. The main consequence is that the number of domains, which contribute to the extrin- sic effect, is limited for films thickness thinner than 0.6 µm, i.e, the �effective� PZT ferroelectric film thickness is much less than 0.6 µm . The presence of this interfacial layer has also a negative effect on the domain wall mobility by the introduction of pinning centers, the domains preferentially localized near this interfacial layer are blocked. When the film thickness increases, the domain density increases, and then the extrinsic effect increases. The thickness of the �ef- fective� ferroelectric film becomes larger than the �dead� zone. The pinning centers localized near the interface have also a minor effect when the thickness increases. The micro- structure evolution with the film thickness, and, in particu- lar, the increase of the grain size induce an enhancement of the domain wall motion since the joints grain density, which act as pinning center, decreases. The er evolutions, in the first part of the curve (Fig. 5), can be explained by these different contributions; in particular, the interfacial layer plays a major role. The fact that er attains a saturation value (for films thicker than eth) can�t be explained com- 84 SQO, 5(1), 2002 T. Haccart et al.: Dielectric, ferroelectric and piezoelectric properties... 0.05 0.04 0.03 0.02 0.01 0 0 0.5 1 1.5 2 2.5 Film thickness ( m)µ L o ss f a c to r ( ta n )δ (110) (111) Fig. 6. Evolution of the loss factor function of the film thickness for a (110) and a 111)-oriented PZT films. 0 5 10 15 20 25 0 0.2 0.4 0.6 0.8 1 Film thickness ( m)µ (µ C /c m ) 2 ( P P P = R e m R e m R e m )/ 2 - - + (110) (111) Fig. 7. Evolution of the average remanent polarization (Pav.rem.) function of the film thickness for a (110) and a (111)-oriented  PZT films. pletely by these arguments and complementary studies are necessary [32]. The evolutions of the loss factor, tan δ, with the film thickness are presented in Fig. 6. There are many contribu- tions to the dielectric losses. The loss factor corresponds to the losses induced by the energy dissipation during the do- main wall motions [29, 32], and there are also contributions from conductivity. The loss factor of the (111)-oriented PZT films is very similar to the (110) PZT films for films thinner than 0.6 µm; it is of the order of 1.8%. For thicker films, tan δ increases linearly for the two types of films, but it seems higher for the (111) orientation. It is well known that in bulk hard and soft PZTs, as the domain mobility increases, the dielectric losses increase. Then, these results are in per- fect agreement with the increases of the permittivity with the film thickness but we have no explanation concerning the difference observed between the (111) or (110) oriented films; may be it is connected with the interfacial layer nature, thickness. No tan δ saturation is detected as on the εr varia- tion with the film thickness. B- Ferroelectric properties The ferroelectric nature of the films was examined by observing the hysteresis loop taken at room temperature by means of a RT 6000 system (Radian Technology). Polari- zation reversal is generally taken as a measure of the degree of ferroelectricity. Fig. 7 shows the evolution of the average remanent po- larization (Pr.aver.=P+ r - P- r / 2) as a function of the film thickness for the two types of films. The remanent polariza- tion increases with the film thickness and attains a satura- tion value for films thicker than 0.6 µm, whatever the film orientation; typically, the remanent polarization is of the order of 20 µC/cm2. The maximum polarization (PM) vari- ations are similar to those of Pr.aver. and PM is equal to 40 µC/cm2, independently of the film orientation, for films thicker than 0.6 µm. The variations of the coercive field with the film thickness are presented in Fig. 8. The coercive field decreases with the film thickness and a saturation value of 30 kV/cm is measured for films thicker than 0.7 µm. The variations are similar for two types of films except for the very thin film (< 0.7 µm) where the (111)-oriented PZT film presents higher coercive field. These results are in perfect agreement with those published in the literature [30,32,34]. For very thin film, the presence of an interfa- cial layer (�dead� layer) between the PZT film and the substrate degrades the ferroelectric performances; when the PZT film thickness increases, these layer have a less effect. So, the domain wall mobility increases, which in- duces an improvement of the domain switching; as a con- sequence, the coercive field decreases. 70 60 50 40 30 20 10 0 0 1 0.5 1.5 E E C C C + ( - = E Film thickness ( m)µ (110) (111) Fig. 8. Evolution of the coercive field (Ec) function of the film thickness for the two type of films. Fig. 9 shows the evolution of the internal electric field (Eint.) as a function of the film thickness. The behavior is similar for Both types of films: a decrease with the film thickness, but in general, the internal elec- tric field is more important for a (110) PZT film rather than for a (111) film. A saturation is observed for films thicker than 1µm. The existence of this internal elec- tric field is often attributed to the space charges, the oxygen defects and the stresses [35]. It is admitted that the space charges and the oxygen vacancies are lo- cated near the bottom electrode and act as pinning centers. Therefore, the maximum of the internal and the coercive fields are obtained for very thin films; the space charges influence is neglected when the film thickness increase, i.e. for film thickness higher than 1 µm in our case and the hysteresis loops asymmetry dis- appears. T. Haccart et al.: Dielectric, ferroelectric and piezoelectric properties... 85SQO, 5(1), 2002 -15 -10 -5 0 0 0.5 1.51 E E C C + + ( = E in t. Film thickness ( m)µ (111) (110) Fig. 9. Evolution of the internal electric field (Eint.)function of the film thickness for the two types of films. -0.3 -0.2 -0.1 0 0 1 20.5 1.5 Film thickness ( m)µ e 3 1 e ff .i n it . (C /m ) 2 Fig. 10. Evolution of the initial effective e 31 coefficient (e 31 eff.init. ) function of the films thickness. C- Piezoelectric properties We have systematically evaluated the e31 and the d33 piezoelectric coefficients. As the films are clamped by the substrate, the measured coefficients are effective (e31eff. and d33eff.), and it is difficult to compare the coefficients values with those obtained on bulk ceramics [36]. The measurements are made for both types of film orientation and the obtained values are very similar. So, we present only the re- sults relative to (110)-oriented PZT films. The details for the experimental set-up as well as for the beam embedded method [37] (e31eff. meas- urement) and for the double beam interferometric method [38] (d33eff. measurement) are described pre- viously. From the e31eff measured values, we can de- duce, by a simple calculation, which used the elec- tromechanical properties of the PZT bulk ceramics and the Si substrate, the d31eff. piezoelectric coeffi- cient. Fig. 10 shows the initial e31eff. (noted e31eff.init.) evolution with the film thickness. The e31eff.init. cor- responds to the piezoelectric response of the film without poling treatment (virgin film). For films thinner than 0.6 µm, the e31eff.init. is constant; it is in the order of - 0.25 C/m2 (d31eff. = - 2.2 pm/V). For films thicker than 0.6 µm, the e31eff.init. decreases continuously; for example, e31eff.init is equal to - 0.05 C/m2(d31eff. = - 0.45 pm/V) for a 1.75 µm thick PZT film. The existence of this piezoelectric signal from PZT films has been observed by some authors [39,40,41]; it is directly related to the preferential orientation of some domains in the film induced by the internal electrical field. An important result is that the e31eff.init. is maximum for films thinner than 0.6 µm which corresponds to film thickness where the internal electric field is maximum (Fig. 9). The deposition of PZT films by sputtering leads to an orientation of the ferroelectric domains, which in- duced this piezoelectricity in the unpoled films. This phenomenon, also observed for PZT films deposited by other techniques, is currently called «self-polarization» effect. The existence of this �self polarization� is related to non-uniformly distributed oxygen vacan- cies [42], the formation of dipoles with oxygen va- cancies and negatively charged acceptors [43], and also to non-uniform compensation of oxygen vacan- cies. This characteristic of ferroelectric thin films is not observed in bulk ceramics that have zero net polarization due to the initial random orientation of ferroelectric domains inside the grains. The pref- erential orientation of domains in virgin films is in- complete since a polishing treatment induces an op- timization of their piezoelectric performances. The polishing treatment has been optimized in terms of applied electric fields and polishing time: the pol- ishing electric field is near the saturation electric field and the polishing time is fixed to 20 min at room temperature [44]. The e31eff. evolution as a function of the film thickness is given in Fig. 11; the e31eff. coefficient presented in this curve corresponds to the remanent coefficient (e31eff.rem.) since the DC poling voltage is removed when we want to acquire the piezoelectric signal. The variations can be de- composed into two parts: an increase of e31 eff. rem. for films thinner than 0.6µm; in the second part of the curve, the piezoelectric coefficient remains con- stant in the order of - 4.5 C/cm2 (the d31eff.rem. asso- ciated is � 38 pm/V). The increase of e31 eff. rem. is directly related to the domain contribution, which increases with the film thickness. The maximum is attained for a PZT film thickness of 0.6µm as for the dielectric permittivity. An illustration of the e31eff. evolution with the film thickness is given in Fig.12, which shows the e31eff. piezoelectric hyster- esis loops for two PZT films of different thickness. The experimental procedure is described elsewhere; an important asymmetry is observed as in the ferroelectric hysteresis loops [35]. The e31 eff. rem. saturation value de- tected for films thicker than 0.6µm was not observed in the d33eff. variation. An example is given in Fig. 13; typically, d33eff.rem. is of the order of 45 pm/V and 86 SQO, 5(1), 2002 T. Haccart et al.: Dielectric, ferroelectric and piezoelectric properties... 80 pm/V for PZT films of 1and 1.7 µm thickness respectively. A limited number of papers have been published concerning the dependence of the e31 and d33 piezoelectric coefficients with the film thickness and no explanation has been given. Lee et al.[45] have shown that the d31 coefficient increases with the film thickness but saturates for PZT films thicker than 1µm. Liam et al.[9] and Taylor et al.[21] have presented some d33 measurements on PZT films with different thickness, d33 increases monotically with the film thickness increase. -6 -5 -4 -3 -2 -1 0 0 1 20.5 1.5 2.5 Film thickness ( m)µ ef f. re m . (C /m ) 2 e 3 1 Fig. 11. Evolution of the remanent effective e 31 coefficient (e 31eff.rem. ) function of the film thickness. 0 0 -4 -2 2 4 -300 -200 -100 100 200 300 e ff .r e m . (C /m ) 2 e 3 1 e= m1.02 µ e= m0.41 µ Fig. 12. Typical example of piezoelectric e 31 hysteresis loops for PZT films of different thickness. d re m . (p m /V ) 3 3 e = m0.973 µ e = m1.711 µ 120 80 40 0 -40 -80 -120 -120 -100 -50 50 100 1500 Electrical field (kV/cm) Fig. 13. Typical example of piezoelectric d 33 hysteresis loops for PZT films of different thickness. Conclusion A study on the film orientation and thickness effects on the PZT structure, microstructure and electrical prop- erties is given in this paper. The PZT films are fabricated by r.f. magnetron sputtering followed by a conventional annealing treatment on Si/SiO2/TiOx/Pt substrates. The fabrication processes are similar for all the films pre- sented in this paper: bottom electrode deposition, pre- sputtering, sputtering, and annealing conditions. But even with this rigourous procedure two preferred PZT films orientation: (110) and (111) are obtained. This struc- tural difference is probably due to an evolution of the TiOx/Pt bilayers (diffusion of the TiOx through the Pt joints grain) during the PZT crystallization treatment. Transmission Electron Microscopy is now in progress to iden- tify the interfacial layer and may be enable understand the observed structural modification. No change in the structural evolution was observed with the film thickness (in the thickness range studied): the preferred orientation (111) or (110) is maintened whatever the film thick- ness. In terms of micro-structure, the grain size was larger for (110) PZT films in comparison to (111) oriented films; an in- crease with the film thickness is systematically observed. Variations of the main electrical properties variation can be summarized as follows: - The relative dielectric constant increase with the film thickness whatever the film orientation and a satura- tion value (920) is attained for film thickness higher than 0.6µm. The loss factor increases also with film thickness, but no saturation effect is observed. - The ferroelectric properties seem to be independ- ent of the film orientation, and a marked dependence with the film thickness is observed. In particular, the coercive field decrease when the film thickness attains the satura- tion value of 30kV/cm for film thickness higher than 1µm. The internal electric field decrease with the film thick- ness. The remanent and the maximum polarization in- crease with the film thickness. - The virgin films (without polishing treatment) present piezoelectric activity. This piezoelectric response is maximum for film thinner than 0.6µm, where the inter- nal electric field is also maximum. The e31 and d33 piezo- electric coefficients increase with the film thickness and a saturation effect is observed only for the e31 coefficient. The electrical properties dependence with the PZT film thickness can be explained by the existence of an interfacilal layer also called a �dead� layer (which re- duce the �effective� thickness of the ferroelectric mate- rial), the contribution of the domain structure (increase of the domain density and the domain wall mobility), the pinning centers and the microstructure (grain size, joint grain,). A better undestanding of the PZT film properties evolution with the film thickness necessitates to study the dynamic behavior of the domains. To this fact, studies are now in progress in our laboratory concerning the evo- lution of the domain motion by using atomic force microscopy in the contact and no contact mode. T. Haccart et al.: Dielectric, ferroelectric and piezoelectric properties... 87SQO, 5(1), 2002 References 1. J.F. Scott, � Status report on ferroelectric memory materi- als �, // Integrated Ferroelectrics, 20, 15-23 (1998). 2. S.L.Bravina, N.V. Morozovsky, � Pyroelectricity in some ferroelectric semi conductors and its applications �, // Ferroelectrics, 118, 217-224, (1991). 3. P.Muralt, � Ferroelectric thin films for microsensors and actuators ; a review �, // J.Microeng., 10, 136-146, (2000). 4. D. Eichner, M.Giousouf, W. Von Munch, � Measurements on micromachined silicon accelerometers with piezoelec- tric sensor action �, // Sensors & Actuators, 76, 247-252, (1999). 5. A. Schroth, C. Lee, S.Matsumoto, R. Maeda, � Application of sol-gel deposited thin PZT film for actuation of 1D and 3D scanners �, // Sensors & Actuators, 73, 144-152, (1999). 6. S-K. Hong, C.S. Hwang, O.S. Kwon, N.S. Kang, � Polarity dependent rejunevation of ferroelectric properties of inte- grated SrBi2Ta2O9 capacitors by electrical stressing �, // Appl.Phys.Lett., 76(3), 324-326, (2000). 7. J.F.M. Cillessen, M.W. Prins, R.M. Wolf, � Thickness de- pendence of the switching voltage in all-oxide ferroelectric thin film capacitors prepared by pulsed laser deposition �, // J.Appl.Phys., 81(6), 2777-2783, (1997). 8. S- Yan Chen, I-Wei Chen, � Comparative role of metal-or- ganic decomposition-derived [100] and [111] in electrical properties of Pb(Zr,Ti)O3 �, // Jpn.J.Appl.Phys., 36(7A), 4451- 4458, (1997). 9. L. Lian, N.R. Sottos, �Effect of thickness on the piezoelectric and dielectric properties of lead zirconate titanate thin films �, // J.Appl.Phys., 87(8), 3941-3949, (2000). 10. K. Aoki, Y. Fukuda, K. Numata, A. Nishima, A. Nishimura, � Dielectric properties of (111) and (100) lead zirconate titanate thin films prepared by sol-gel technique �, // Jpn.J.appl.Phys.part.1, 33(9B), 5155-5158, (1994). 11. R. Kurchania, S.J. Milne, �  Characterization of sol-gel Pb(Zr0.53Ti0.47)O3 films in thickness range 0.25-10µm �, // J.Mater.Res., 14(5), 1852-1859, (1999). 12. H-J. Nam, H-H.Kim, W-J.Lee, � The effects of the prepara- tion conditions and the heat treatment conditions of Pt/Ti/ SiO2/Si substrates on the nucleation and growth of Pb(Zr,Ti)O3 thin films �, // Jpn.J.appl.Phys., 37(6A), 3462-3470, (1998). 13. B. Jaber, D. Remiens, B. Thierry, � Substrate temperature target composition effects on PbTiO3 produced in-situ by sputtering �, // J.Appl.Phys, 79(4), 1182-1187, (1996). 14. G. Velu, D. Remiens, � Electrical properties of sputtered PZT films on stabilized platinum electrodes �, // J.Europ.Ceram.Soc., 19, 2005-2015, (1999). 15. G.Velu, D. Remiens, B. Thierry, � Ferroelectric properties of PZT film prepared by sputtered with stoichiometric single oxide target : comparison between conventional and RTA annealing �, // J.Europ.Ceram.Soc, 1749-1758, (1997). 16. I. Stolichnov, A. Tagantsev, N. Setter, S.S. Okhonin, P. Fazan, J.S. Croos , M. Tsukada, � Dielectric breakdown in (Pb,La) (Zr,Ti)O3 ferroelectric thin films with Pt and oxide elec- trodes �, // J.Appl.Phys. 87(4), 1925-1931, (2000). 17. K.H . Park, C.Y. Kim, Y.W. Jeong, H.J.K. Won, K.Y. Kim, J.S. Lee, S.T. Kim, � Micro structures and interdiffusion of Ti/Pt electrodes wtih respects to annealing in the oxygen ambiant �, // J.Mater.Res., 10(7), 1791-1794, (1995). 18. H-J.Nam, D-K.Choi, W-J.Lee, � Formation of hillocks on Ti/Pt electrodes and their effects on short phenomena of PZT films deposited by reactive sputtering �, // Thin Solid Films, 371, 264-271, (2000). 19. J.C. Kim, D.S. Yoon, J.S. Lee, C.G. Choi, K. No, � A study on the micro structure of the prefered orientation of lead zirconate titanate (PZT) thin films �, // J.Mater.Res. 12(4), 1043-1047, (1997). 20. K.G. Brooks, I.M. Reaney, R. Klissurka, Y. Huang, L. Bursill, N. Setter, � Orientation of rapid thermally annealed lead zirconate titanate thin films on (111) Pt substrates �, // J.Mater.Res., 9(10), 2540-2553, (1994). 21. D.V. Taylor, D. Damjanovic, � Piezoelectric properties of rhomboedral Pb(Zr,Ti)O3 thin films with (100) and (111) and � random crystallographic orientation �, // Appl.Phys.Lett., 76(12), 1615-1617, (2000). 22. H.D.Chen, K.R.Udayakumar, C.J. Gaskey, L.E. Cross, J.J. Bernstein, L.C. Niles, � Fabrication and electrical proper- ties of leas zirconate titanate thick films �, // J.Am.Ceram.Soc., 79(8), 2189-2192, (1996). 23. H. Fujisawa, S. Nakashima, M. Shimuzu, H. Niu, � Depend- ence of electrical properties of Pb(Zr,Ti)O3 thin films on the grain size and film thickness �, // Proc. Of the 11th Int. Symp. on Applications of Ferroelectrics �ISAF-, 77-80, (1998). 24. H.J. Kim, J.H. Oh, H.M. Jang, �  Thermodynamic theory of stress distribution in epitaxial Pb(Zr,Ti)O3 thin films �, // Appl.Phys.Lett., 75(20), 3195-3197, (1999). 25. D.Fu, T. Ogawa, H. Suzuki, K. Ishikawa, � Thickness de- pendence of stress in lead titanate thin films deposited on Pt- coated Si �, // Appl.Phys.Lett., 77(10), 15321534, (2000). 26. J.L. Deschanvre, P. Rey, G. Delabouglise, M. Labeau, �Char- acterization of piezoelectric properties of zinc oxide thin films deposited on silicon for sensors applications �, // Sen- sors & Actuators, A33, 43-45, (1992). 27. A.L. Kholkin, C. Wutchrich, D.V. Taylor, N. Setter, �Inter- ferometric measurements of electric field-induced displace- ment in piezoelectric thin films �, // Rev.Sci.Instrum., 65(5), 1935-1941, (1996). 28. H. Okino, T. Nishikawa, M. Shimuzu, T. Horiuchi, K. Matsushige, �Electrical properties of highly strained epitaxial Pb(Zr,Ti)O3 thin films on MgO (100) �, // Jpn.J.Appl.Phys., 38(9B), 5388-5391, (1999). 29. C.R. Cho, W.J. Lee, B.G. Yu, B.W. Kim, �Dielectric and ferroelectric response as a function of annealing tempera- ture and the film thickness of sol-gel deposited Pb(Zr0.52,Ti0.48)O3 thin films �, // J.Appl.Phys., 86(5), 2700- 2711, (1999). 30. S-I. Hirano, T. Yogo, K. Kikuta, Y. Araki, M. Saitoh, S. Ogasahara, �Synthesis of highly oriented lead zirconate-lead titanate films using metallo-organic�, // J.Am.Ceram.Soc., 75(10), 2785-2789, (1992). 31. F. Fujisawa, S. Nakashima, K. Kaibara, M. Shimuzu, H. Niu, �Size effects of epitaxial and polycristalline Pb(Zr,Ti)O3 thin films grown by metalorganic chemical vapor deposi- tion �, // Jpn.J.appl.Phys., 38(9B), 53925396, (1999). 32. F. Xu, S. Trolier-Mckinstry, W. Ren, B. Xu, Z-L. Xie, K.J. Hemker, �Domain wall motion and its contribution to the dielectric and piezoelectric properties of PZT films �, // J.Appl.Phys., 89(2), 1336-1349, (2000). 33. S. Hiboux, P. Muralt, �Piezoelectric and dielectric proper- ties of sputter deposited (111), (100) and random oriented Pb(Zrx,Ti1-x)O3 (PZT) thin films �, // Ferroelectrics 224(1-4), 315-322, (1999). 34. S.Y. Chen, I.W. Chen, � Comârative role of metalorganic decomposition �derived [100] and [111] in electrical proper- ties of Pb(Zr,Ti)O3 thin films �, // J.Am.Ceram.Soc., 36(7A), 4451-4458, (1997). 35. A.L. Kholkin, K.G. Brooks, D.V. Taylor, S. Hiboux, N. Setter, � Self-polarization effects in Pb(Zr,Ti)O3 thin films �, // Int.Ferroelectrics, 22(1-4), 525-533, (1998). 36. K.Lefki, G.J.M. Dormans, �Measurement of piezoelcetric coefficients of ferroelectric thin films �, // J.Appl.Phys., 76(3), 1764-1767, (1994). 37. E. Cattan, T. Haccart, D. Remiens, � e31 piezoelectric con- stant measurement of lead zirconate titanate thin films �, // J.Appl.Phys., 86(12), 7017-7023, (1999). 88 SQO, 5(1), 2002 T. Haccart et al.: Dielectric, ferroelectric and piezoelectric properties... 38. A.L. Kholkin, A.K. Tagantsev, E.L. Colla, D.V. Taylor, N. Setter, �Piezoelectric and dielectric aging in pb(Zr,Ti)O3 thin films and bulk ceramics �, // Int.Ferroelectrics, 15, 317- 324, (1997). 39. K. Carl, K.H. Hardtl, �Electrical after effects in Pb(Zr,Ti)O3 ceramics �, // Ferroelectrics 17, 473-486, (1978). 40. S. Sun, Y. Wang, P.A. Fuierer, B.A. Tuttle, �Annealing effects on the internal bias field in ferroelectric PZT thin films with self-polarization �, // Int.Ferroelectrics, 23, 25-43, (1999). 41. U. Robels, L. Schneider-Stormann, G. Arlt, �Domain wall trapping as a result of internal bias fields�, // Ferroelectrics 133,(1-4), 223-228, (1992). 42. W.L. Warren, B.A. Tuttle, D. Dimos, G.E. Pike, H.N. Al- Shareef, R. Ramesh, J.J.T. Evans, �Imprint in ferroelectric capacitors �, // Jpn.J.appl.Phys., 35(Part.1-2B), 1521-1524, (1996). 43. M.V. Raymond, D.M. Smyth, � Defects and charge trans- port in perovskite ferroelectrics �, // J.Phys.Chem.Solids, 57(10), 1507-1511, (1996). 44. B. Jaber, E. Cattan, P. Tronc, D. Remiens, B. Thierry, �Pi- ezoelectric properties of sputtered PbTiO3 films : growth tem- perature and poling treatment effect �, // J.Vac.Sci.Tech., A16(1), 144-152, (1998). 45. C. Lee, T. Itoh, T. Suga, � Characterization of micro me- chanical piezoelectric PZT force sensors for dynamic scan- ning force microscopy �, // Rev.Sci.Instrum. 68(5), 2091-2100, (1997).

Ähnliche Einträge