Oriented PZT Thin Films Research Articles

Mechanical properties of sol–gel derived lead zirconate titanate thin films by nanoindentation

Lead zirconate titanate (PZT) thin films are deposited on platinized silicon substrate by sol–gel process. The crystal structure and surface morphology of PZT thin films are characterized by X-ray diffraction and atomic force microscopy. Depth-sensing nanoindentation system is used to measure mechanical characteristics of PZT thin films. X-ray diffraction analyses confirm the single-phase perovskite structures of all PZT thin films. Nanoindentation measurements reveal that the indentation modulus and hardness of PZT thin films are related with the grain size and crystalline orientation. The increases of the indentation modulus and hardness with grain size are observed, indicating the reverse Hall–Petch effect. Furthermore, the indentation modulus of (1 1 1)-oriented PZT thin film is higher than those of (1 0 0)- and random-oriented films. The consistency between experimental data and numerical results of the effective indentation moduli for fiber-textured PZT thin films using Voigt–Reuss–Hill model is obtained.

Preparation of (001)-oriented Pb(Zr,Ti)O/sub 3/ thin films and their piezoelectric applications

Preparation of (001)-oriented Pb(Zr,Ti)O(3) (PZT) thin films and their applications to a sensor and actuators were investigated. These thin films, which have a composition close to the morphotropic phase boundary, were epitaxially grown on (100)MgO single-crystal substrates by RF magnetron sputtering. These (001)-oriented PZT thin films could be obtained on various kinds of substrates, such as glass and Si, by introducing (100)-oriented MgO buffer layers. In addition, the (001) oriented PZT thin films could be obtained on Si substrates without buffer layers by optimizing the sputtering conditions. All of these thin films showed excellent piezoelectric properties without the need for poling treatment. The PZT thin films on the MgO substrates had a high piezoelectric coefficient, d(31), of -100 pm/V, and an extremely low relative dielectric constant, epsilon(r), of 240. The PZT thin films on Si substrate had a very high d(31) of -150 pm/V and an epsilon(r) = 700. These PZT thin films were applied to an angular rate sensor with a tuning fork in a car navigation system, to a dual-stage actuator for positioning the magnetic head of a high-density hard disk drive, and to an actuator for an inkjet printer head for industrial on-demand printers.

EFFECT OF PRE-HEATING TEMPERATURE ON THE CHARACTERISTICS OF PZT THIN FILMS GROWN BY USING A TRIOL SOL–GEL ROUTE

Lead zirconate titanate (PZT) films with compositions near the morphotropic phase boundary were fabricated on Pt (111)/ Ti / SiO 2/ Si (100) using the triol sol–gel method. The effect of the pre-heating temperature on the phase transformations, microstructures, electrical properties, and ferroelectric properties of the PZT thin films was investigated. Randomly oriented PZT thin films pre-heated at 400°C for 10 min and annealed at 600°C for 30 min showed well-defined ferroelectric hysteresis loops with a remnant polarization of 26.57 μC/cm2 and a coercive field of 115.42 kV/cm. The dielectric constant and dielectric loss of the PZT films were 621 and 0.0395, respectively. The microstructures of the thin films are dense, crack-free, and homogeneous with fine grains about 15–20 nm in size.

Dry Etching Process for Pb(Zr,Ti)O3 Thin-Film Actuators

We have developed a Pb(Zr,Ti)O3 (PZT) piezoelectric thin-film-actuator manufacturing technique by sputtering and dry etching processes. PZT etching rate and taper angle were investigated, and we obtained a very high etching rate (about 190 nm/min) and a high taper angle (62°). (001)/(100)-oriented PZT thin films on a (111)Pt/Ti/SiO2/Si substrate (6 in.) were prepared by RF magnetron sputtering, and Pt on PZT were prepared by DC magnetron sputtering. Pt/PZT/Pt piezoelectric thin-film actuators were fabricated by dry etching using an inductively super magnetron (ISM) plasma source. The characteristics of the ISM plasma source are high-density plasma and low-pressure operation attributable to the effect of the permanent magnet. The electrical properties of a piezoelectric thin-film-actuator cell fabricated by dry etching were investigated. The remanent polarization (Pr value) of a piezoelectric thin-film actuator with 3-µm-thick PZT film was 41 µC/cm2 at an applied voltage of 30 V, and remanent polarization characteristics without the dependence on element size (30–300 µm diameter) were obtained. Moreover, the displacement of a PZT thin-film-actuator was measured by contact atomic force microscopy (C-AFM), and a displacement of 4 nm was obtained at 3 µm thickness of the PZT film, 30-µm-diameter element size, and an applied electric field of 100 kV/cm. It was clarified that the fabrication of PZT piezoelectric thin-film-actuators by dry etching using an ISM plasma source is effective.

<001>配向PZT薄膜の作製とマイクロ圧電素子への応用

Preparation of <001>oriented Pb(ZrTi)O3(PZT) thin films and their applications to the micro-piezoelectric devices were investigated. The <001>oriented PZT thin films, which have a composition near the morphotropic phase boundary, were deposited on Pt/MgO and Pt/Ti/Si substrates by rf-magnetron sputtering. Both of these thin films show the excellent piezoelectric properties without a poling treatment. The piezoelectric properties of the PZT thin films were examined on the micro fabricated cantilever structure. The PZT thin films on Pt/MgO have high piezoelectric coefficient d31=100×10-12m/V, extremely low εr=240, and remarkably high electromechanical coupling coefficient k31. The PZT thin films on Pt/Ti/Si have very high d31of 150×10-12m/V and εr=700. The PZT thin films on Pt/Ti/Si were applied to the angular rate sensors with a tuning fork type and the actuators of the ink-jet printer heads with 400 pressure chambers. These PZT thin films are suitable for the use in micro piezoelectric sensors and actuators.

FABRICATION OF PZT THIN FILMS WITH TiOx BUFFER LAYERS BY RF MAGNETRON SPUTTERING

ABSTRACT Lead zirconate titanate thin films were successfully prepared on 5-inch TiOx/Pt/ Ti/SiO2/Si substrates by RF-Magnetron Sputtering method using a 0.8Pb(Zr0.3 Ti0.7)O3 + 0.2PbO ceramic target. The experimental results show that the orientation of PZT thin films can be change from (111) to (100) by precisely controlling the substrate temperature. The (111)-oriented films with the thickness of 500 nm thick, have the remanent polarization of 20 μC/cm2, dielectric constant of 370, dielectric loss of 1.5%, and coercive field of 130 KV/cm. By using dynamic measurement, the pyroelectric coefficient of the order of 10−8C/cm2 K was determined. Thermal-electric conversion studies indicate significant potential for uncooled infrared focal plane detector arrays.

LOW-TEMPERATURE PREPARATION OF Pb(ZrxTi1−x)O3 THIN FILM

ABSTRACT An innovative high oxygen-pressure processing (HOPP) was developed. By HOPP for 10 hours, the spin-eoated PZT 50/50 thin film was successfully crystallized and highly (100) oriented PZT thin film was obtained at temperature as low as 400°C. This noval HOPP is compatible to the ferroelectric PZT film integration with readout integrated chip. The PZT 50/50 thin film by HOPP showed a well-saturated hysteresis loop at an applied electric field of 367 kV/cm with P r and E c of 45 C/cm2 and 121 kV/cm, respectively. The large values of P r and E c result from large leakage.

Characterization of (100)-oriented BiScO3–PbTiO3 thin films synthesized by a modified sol-gel method

The ferroelectric and piezoelectric properties of (100)-oriented BiScO3–PbTiO3 (BSPT) thin films were investigated. (100)-oriented 0.34BiScO3–0.66PbTiO3 thin films were synthesized on Pt(111)∕Ti∕SiO2∕Si(111) substrates using a modified sol-gel method. Saturated polarization hysteresis loops were observed, showing a remanent polarization of 33μC∕cm2. The dielectric constant and loss for the thin films were 1200 and 5%, respectively. The Curie temperature appeared at 435°C, over 80°C higher than that of the Pb(Zr,Ti)O3 (PZT) thin films. The local effective piezoelectric coefficient d33* was approximately 70pm∕V, which was comparable to that of the highly (100)-oriented PZT thin films.

Pt/Ti/SiO2/Si基板のプレアニーリングによる(111)面配向のPZT薄膜の作製

Pt/Ti/SiO2/Si基板のプレアニーリングによる(111)面配向のPZT薄膜の作製

Texture control of Pb(Zr, Ti)O 3 thin films with different post-annealing processes

The non-crystalline Pb(Zr, Ti)O 3 thin films sputtered on Pt(1 1 1)/Ti/SiO 2/Si(1 0 0) substrates at room temperature were crystallized by conventional furnace annealing (CFA) and rapid thermal annealing (RTA), respectively. It was found that the RTA process favored the (1 1 1)-preferred orientation in lead zirconate titanate (PZT) thin films while the CFA process favored the (1 0 0)-preferred orientation. The origin of the different orientation selection might be due to the different epitaxial nucleation mechanism. The long heating duration would lead to the aggregation of Pb and the formation of PbO(1 0 0) on film surface; therefore, the nucleation at the PbO(1 0 0)/PZT interface on film surface might lead to the (1 0 0)-preferred orientation. However, the nucleation at the PZT/Pt(1 1 1) electrode interface by RTA process would result in the formation of (1 1 1)-preferred orientation. The RTA-derived (1 1 1)-preferentially oriented PZT thin films exhibited a high remnant polarization of 35 μC/cm 2.

Sol-gel法によるLNO/SiO2/Si基板上への(100)面配向のPZT薄膜の作製

Sol-gel法によるLNO/SiO2/Si基板上への(100)面配向のPZT薄膜の作製

PLT buffer층의 삽입에 따른 강유전 PZT박막의 특성 향상

The Pb(Zr,Ti)O<TEX>$_3$</TEX> thin films were fabricated with Pb(La,Ti)O<TEX>$_3$</TEX> buffers in-situ onto Pt/Ti/SiO<TEX>$_2$</TEX>/Si substrates by pulsed laser deposition method. We have observed the increase of the remanent polarization using PLT buffers. The remanent polarization value of 33.4 <TEX>$\mu$</TEX>C/<TEX>$\textrm{cm}^2$</TEX> and the coercive field value of 66.4 kV/cm were obtained when the PLT tufter was deposited for 15 seconds. Enhancement of the polarization is resulted from the enhanced orientation of PZT thin film because of the PLT buffet layer.

Fatigue properties of oriented PZT ferroelectric thin films

Oriented PZT thin films with Zr/Ti ratio of 60/40 were prepared using a multi-target R.F. sputtering system. The films were (1 0 0) or (1 1 1) oriented when grown on Pt/TiO 2/SiO 2/Si and exhibited c-axis epitaxial microstructure when deposited on Pt/MgO. Electrical measurements were performed in order to investigate the fatigue properties of the films. Fatigue characteristics of the Pt/PZT/Pt capacitors were found to be strongly dependent on their crystalline orientation: (1 1 1) and (0 0 1) oriented films exhibited poor fatigue endurance unlike (1 0 0) oriented films that did not fatigue. Lastly, almost full recovery of polarisation was obtained for c-axis epitaxial films while (1 1 1) oriented films showed only partial restoration.

PZNT epitaxy growth on STO substrates with and without PZT seed layer

PZNT91/9 thick films have been obtained by liquid-phase epitaxy (LPE) on (0 0 1) SrTiO 3 (STO) substrates with and without PZT seed films. These [0 0 1]-oriented PZT thin films are deposited on the (0 0 1) plane of the STO single crystal. The surface morphologies of LPE films are observed by optical microscopy (OM). The compositions of as-grown films are determined by EDS. The XRD analysis is conducted to show an epitaxial orientation relationship between the LPE films and the STO substrates: [1 0 0] (0 0 1) PZNT// [1 0 0] (0 0 1) STO. The effects of PZT seed layer on the crystallinity of PZNT LPE growth have been discussed.

Optical and electrical properties of highly (100)-oriented PbZr1−xTixO3 thin films on the LaNiO3 buffer layer

In this paper, using wet chemical solution deposition processes, the (100)-highly oriented LaNiO3 buffer layers were grown on both silicon and platinized silicon wafers and, sequentially, the highly (100)-oriented PbZr1−xTixO3 thin films with various compositions were obtained on them. The misfit elastic strains were found to be critical factors to determine the orientation of PZT thin films, even though the used LaNiO3 buffer layer reduces the lattice mismatch between PZT films and silicon wafers. For the PZT thin films with x=0.5 and 0.6 on the LaNiO3/platinized silicon substrate, the infrared optical constant, ferroelectric, and dielectric properties were characterized and analyzed with relation to the film orientation and the film grain size. It was found that the finite grain size effect here played a key role in determining these optical and electrical properties. With nanoferroelectric thin films, it is the most useful way of controlling both grain size and crystallographic orientation to tune performance of commercial film devices.

Recent Developments on MOCVD of Ferroelectric Thin Films

Ferroelectric Pb(Zr, Ti)O3 thin films were fabricated by liquid delivery MOCVD using Pb(DPM)2, Ti(OiPr)2(DPM)2 and Zr(DIBM)4. The deposition rate of 12.3 nm/min was attained on 6-inch Pt/Ti/SiO2/Si wafers at 550∘C. The average and the deviation of twofold remanent polarization were 45.5 μ C/cm2 and ± 6.4%, respectively, over the 6-inch wafer. Step coverage was improved from 44% to 90% by decreasing deposition temperature from 550 to 400∘C although the deposition rate decreased by 60%. TiO2 nanoparticles diffused to the surface of platinum bottom electrodes were effective as a seed to obtain 111 preferential oriented PZT thin films at the deposition temperature of 550∘C. Iridium oxide bottom electrodes were reduced to metal ones by CO and/or H2 gases generated by decomposition of precursors. Oxide materials seem to be not the best as bottom electrodes in liquid delivery MOCVD. A cocktail source consisted of Pb(METHD)2, Ti(MPD)(METHD)2 and Zr(METHD)4 was also examined. PbPt x alloy phase existed in PZT films deposited at 500∘C was disappeared by post-annealing at 600∘C and the annealed film showed hysteresis properties with the 2P r of 56 μ C/cm2 and the 2E c of 181 kV/cm.

Electrical Properties of c-axis oriented PZT Thin Films by Electric-Field-Assisted Annealing

Electrical Properties of c-axis oriented PZT Thin Films by Electric-Field-Assisted Annealing

The grain size effect of the Pb(Zr 0.45Ti 0.55)O 3 thin films deposited on LaNiO 3-coated silicon by modified sol–gel process

Highly (1 0 0) oriented PZT thin films with different grain sizes have been deposited on an LaNiO 3-coated silicon substrate by a modified sol–gel process. The growth mechanism of films with high (1 0 0) orientation and the effects of grain size on the dielectric and ferroelectric properties of the films are qualitatively discussed. Measurements of dielectric and ferroelectric properties reveal that films of large grain sizes present large relative dielectric permittivity and large remnant polarization.

Growth and electrical properties of Pb(Zr,Ti)O 3 thin films by a chemical solution deposition method using zirconyl heptanoate as zirconium source

Pb(Zr,Ti)O 3 (PZT) thin films were prepared on (1 1 1) Pt-coated Si substrates by a chemical solution deposition method using zirconyl heptanoate as zirconium source instead of commonly used zirconium alkoxides. The effects of processing conditions on the microstructure and electrical properties of the PZT thin films were investigated. The texture of the PZT thin films could be changed by selecting different heat-treatment methods. Orientation-dependent electrical properties, including dielectric constant, polarization, and coercive field, were examined. The randomly oriented PZT thin films annealed at 600°C for 0.5 h showed a well-defined ferroelectric hysteresis loop with a remanent polarization of 18 μC/cm 2 and a coercive field of 74 kV/cm.

Ferroelectric properties of Pb(Zr,Ti)O 3 thin films prepared by low-temperature MOCVD using PbTiO 3 seeds

Low-temperature metalorganic chemical vapor deposition (MOCVD) of Pb(Zr,Ti)O 3 (PZT) thin films, as low as 370 °C, was successfully achieved. Influence of the crystalline nature of PbTiO 3 seeds on crystalline and ferroelectric properties of PZT thin films were investigated. The orientation of PZT thin films and its degree were strongly influenced by those of PbTiO 3 seeds. PbTiO 3 seeds were very useful to decrease growth temperature of PZT films. The PZT film was successfully obtained at 370 °C only when PbTiO 3 seeds were used, exhibiting remanent polarization (2P r) of 4.2 μC/cm 2 and coercive field (2E c) of 63 kV/cm.