Characterization of PT ferroelectric thin films on porous silica for pyroelectric IR detectors

Ferroelectric PbTiO₃ thin films were deposited on Pt/DS/PS/SiO₂/Si substrates by sol–gel technique. Porous silica (PS) thin film was used as thermal-insulation layer and dense silica (DS) thin film was a buffer layer to reduce surface roughness of PS layer. Root mean square surface roughness can be effectively reduced from 9.7 to 3.5 nm after PS buffer layer was prepared. The average grain size of PT thin films decreased slightly with increasing thickness of porous silica. Dielectric constant of PT increased from 107 to 171 at 1 KHz as thickness of PS layer increased from 0 to 2,000 nm. PT thin film prepared on 2,000 nm porous silica exhibited good dielectric property. The leakage current density was less than 1.6?×?10^-6 A/cm² when the applied electrical field was 200 kV/cm. The composite film is suitable for preparing pyroelectric IR detectors.     

Pyroelectric properties of sol-gel derived PZT thin films with various Zr/Ti ratios

Abstract

Integrated pyroelectric arrays are receiving serious attention for the next generation of room temperature uncooled IR cameras. Such pyroelectric arrays are based on monolithic ferroelectric(FE) thin films. FE films with large values of reported pyroelectric coefficients include PbTiO₃, Ca-doped PbTiO₃, La-doped PbTiO₃, PZT 53/47 and Pb(Sc_0.5Ta_0.5)O₃. The present paper reports a systematic study of the compositional dependence of PZT thin films on their pyroelectric properties. A series of sol-gel derived PZT (lead zirconate titanate) thin films with various Zr/Ti ratios, namely, PbTiO₃, PZT 20/80, PZT 35/65, PZT 53/47, PZT 65/35, PZT 92/8 and PbZrO₃, were prepared on platinized Si substrates. The films were fired to 650 – 700°C to crystallize them into single-phase perovskite. The degree of preferred orientation, grain size and firing temperature affect the pyroelectric responses. Pyroelectric coefficients as large as 2.5 × 10^?8 C/cm²-K were obtained, making such PZT thin films attractive in pyroelectric arrays.     

A single-mode Mn-doped 0.27PIN-0.46PMN-0.27PT single-crystal ultrasonic motor

Mn-modified rhombohedral phase yPb(In_1/2Nb_1/2)O₃-(1-x-y)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PIN-PMN-PT:Mn) single crystal has attracted considerable attention for its outstanding piezoelectric properties and high mechanical quality factor. Here, we report a device innovation using Mn doped 0.27PIN-0.46PMN-0.27PT single crystal in a single-mode piezoelectric ultrasonic motor. Based on the analyses of actuator characteristics with finite element method, the PIN-PMN-PT:Mn crystal actuator predicts lower excitation frequency, lower driving voltage, and less power loss comparing with the PZT ceramic actuator. A prototype motor (size: 12 × 6 × 1.5 mm³) was fabricated and tested. The typical output of this PIN-PMN-PT:Mn motor is a speed up to 42.3 cm/s, a driving torque of 0.42 N cm, and an output power density of 0.45 W/cm³, under the driving voltage of 21 V_0?P. This work presents that PIN-PMN-PT:Mn single crystal is quite advantageous in making miniaturized and high-power piezoelectric ultrasonic motors.     

A 11×6 element pyroelectric detector array utilizing self-polarized pzt thin films grown by sputtering

Abstract

A planar multi target sputtering approach was used to deposit PbTiO₃ (PT) and Pb(Zr, Ti)O₃ (PZT) films on TiO₂/Pt bottom electrodes for the use in thin film pyroelectric IR detector arrays. PZT films with a Zr content of 28 at% (PZ28T) exhibited the best pyroelectric coefficient of typically 2×10^?4 Cm^?2K^?1. The PZ28T films have been used for fabricating a two dimensional 11×6 pixel pyroelectric detector array on Si wafers. The array pixels with a sensitive area of 280 ×280 μm² have a noise lequivalent power NEP of less than 0.7 nW at 1 Hz. It is planned to use the detector array in systems for motion detection.     

Ferroelectric Properties and Memory Characteristics of Pb(Zr0.52 Ti0.48)O3 Thin Films Crystallized by Hot Isostatic Pressing

Pb(Zr_0.52Ti_0.48)O₃ films with highly uniform c-axis orientation were fabricated on PbTiO₃ (PT)/ Pt(111)/SiO₂/Si(100) substrates by hot isostatic pressing (HIP) from the amorphous state. All the PZT samples HIP-treated 500°C for 1 h under gas pressures of 1.0–2.0 MPa showed the preferred (001) orientation with c-axis orientation, α > 0.80. The relative permittivity tended to decrease gently with increasing HIP pressure, whereas the dielectric loss increased almost linearly in the 1.5–100 MPa. The PZT sample treated at 1.5 MPa had a symmetric and slim hysteresis loop shape with a remanent polarization, P _r = 15 μ C/cm² and coercive field, E _c = 60 kV/cm. Both samples treated at 10 and 100 MPa exhibited almost the fatigue-free behavior that resisted degradation even after 3 × 10¹⁰ cycles.     

Advances in processing and properties of perovskite thin-films for FRAMs,DRAMs, and decoupling capacitors

Abstract

Highly oriented, dense, and crack-free ferroelectric and paraelectric thin-films on three inch diameter Pt/Ti/Si₃N₄/Si (100) substrates were obtained by polymeric sol-gel processing. Ferroelectric PZT thin-films were fabricated at temperatures as low as 550°C within 15 minutes by rapid thermal annealing. The films heat treated at 700°C for 5 minutes were single grain thick and exhibited P_r, P_sp, and E_c in the ranges of 29–32 μC/cm², 44–53 μC/cm², and 50–60 kV/cm, respectively, and high speed switching times below 5 ns on 30×30 μm² electrodes. A switching time of 2.7 ns was observed on 19×19 μm² area electrodes at a field of 200 kV/cm. Results of low and high field characterization on paraelectric PLT thin-films which were conventionally heat treated indicated that it has an excellent potential for use in ULSI DRAMs and as decoupling capacitors. These films showed a high charge storage density (15 μC/cm²) and a low leakage current (0.5 μA/cm²) at a field of 200 kV/cm. Also, the charging time for a capacitor area of 1 μm² at 200 kV/cm was estimated to be 0.10 ns.     

Sol-gel PZT and Mn-doped PZT thin films for pyroelectric applications

Abstract

Thin films of ferroelectric lead zirconate titanate (PbZr_0.3Ti_0.7O₃ PZT30/70) and manganese doped lead zirconate titanate ((Pb(Zr_0.3Ti_0.7)_1?xMn_x)O_{3 ? x} = 0.01, PM01ZT30/70 and x = 0.03, PM03ZT30/70) have been prepared using sol-gei processing techniques. These materials can be used as the pyroelectric thin films in uncooled infrared (IR) detectors. Films deposited on Pt/Ti/SiO₂/Si substrates and annealed on a hot plate at 530°C for 5 min were seen to fully crystallize into the required perovskite phase and showed excellent ferroelectric behavior, demonstrated by reproducible hysteresis loops (P_r = 33 to 37 μC/cm², Ec(+) = 70 to 100 kV/cm, E_c(-) = -170 to -140 kV/cm). The pyroelectric coefficients (p) were measured using the Byer-Roundy method. At 20°C, p was 2.11×10^?4 Cm^?2K^?1 for PZT30/70, 3.00×10^?4 Cm^?2K^?1 for PM01ZT30/70 and 2.40×10^?4 Cm^?2K^?1 for PM03ZT30/70 thin films. The detectivity figures-of-merit (F_D) were 1.07×10^?5 Pa^?0.5 for PZT30/70, 3.07×10^?5 Pa^?0.5 for PM01ZT30/70 and 1.07×10^?5 Pa^?0.5 for PM03ZT30/70. These figures compare well with values reported previously.     

Single-grained PZT thin films for high level FRAM integration—fabrication and characterization

Abstract

A new method for formation of large single grains as large as 40 μm in length of the sputter-deposited PZT(65/35) thin films has been developed in this research group. Crystallized PZT dots were used as a seed and the grains were laterally grown to form a square pattern on the Pt substrate. It turned out that the electrical characteristics of the single grained PZT thin films were much superior to those of the poly-grained PZT thin films. The leakage current was measured to be less than 8x10^?8 A/cm², the breakdown field more than 1,240 kV/cm, the value of saturation polarization and remanent polarization as high as 42 μC/cm², 30 μC/cm², respectively. No degradation of the polarization properties was observed even after the 2×10¹¹ cycles at 1 MHz using a ± 10 V wave form in Pt/PZT/Pt structure. The accelerated retention test revealed that it takes more than 6×10⁷ years for the remanent polarization to be reduced down to 80% of the original value.     

Estimation of energy density of PMN-PT ceramics utilizing mechanical stress

Abstract

Present study introduces an indirect measurement of energy density of (1-x)Pb(Mg_1/3Nb_2/3)O₃-(x)PbTiO₃ (PMN-PT) ceramics under compressive stress and electric field. The method works analogous to Olsen cycle which is a demonstration of a novel cycle converting mechanical energy into electrical energy. A large amount of electro-mechanical energy conversion can be achieved via this method. The ceramics were investigated under 0–75?MPa and 1–15?kV/cm of applied mechanical stress and electric field, respectively. A maximum energy density of 68?kJ/m³/cycle was achieved in 0.7PMN-0.3PT ceramic. The obtained result is significantly greater than that of linear piezoelectric phenomena.     

Preparation and characterization of PZT ferroelectric thin films by plasma enhanced metalorganic chemical vapor deposition

Abstract

PZT thin films with a uniform distribution of components were prepared by plasma enhanced chemical vapor deposition (PECVD) using Pb(C₂H₅)₄, Z (O-i-C₄H₉)₄, Ti(O-i-C₃H₇)₄, and oxygen. The crystallization of films was occure after annealing in the temperature range between 450 and 550°C under O₂ ambient for 1 hr. The significant change of Pb concentration in PECVD PZT thin films was not observed in the relation to annealing temperature and time. The dielectric constant PECVD PZT thin films increased with the Ti content, showed the maximum value in the vicinity of morphotropic phase boundary (MPB) composition of PZT material, and decreased with the Ti content. The leakage current density of PZT (65/35) thin film of 180 nm in thickness was 3·37 × 10^?7 A/cm² at the applied voltage of 3 V. Remanent polarization increased with increasing of Zr content in the film and coercive field was nearly independent of the composition. The typical values of electrical properties were ε_r = 570, E_c = 90 kV/cm, and P_r = 19 μC/cm² in the PECVD PZT (54/46) thin film of 220 nm in thickness.     

Depth-dependence of electromechanical properties in a thick 0.7Pb(Mg1/3(Nb0.9Ta0.1)2/3)O3–0.3pbtio3 ceramic disk

A thick ceramic disk of 0.7Pb(Mg_1/3(Nb_0.9Ta_0.1)_2/3)O₃–0.3PbTiO₃ (PMNT–PT) was prepared by columbite precursor method with PbO powder buffer surrounding the disk during the sintering process. The Electromechanical properties and the microstructure of PMNT–PT samples cut from the different depths of the disk are studied. Although the phase purity is homogenous in the whole disk, the middle sample has higher electric field induced strain. Electric field of 14 kV/cm induced strain 0.14% was found. It is believed that the prepared processes, especially the Pb volatilization is responsible for these results.     

Dielectric and electrostrictive properties of 0.9PMN-0.1PT multilayer ceramics with ZnO additive

Abstract

Multilayer cermaics based on the 0.9PMN-0.1PT were fabricated by tape casting and their dielectric and electrostrictive properties were investigated as a function of the number of active layers. The 0.9PMN-0.1PT ceramics modified with various amounts of ZnO were prepared by molten salt synthesis. An increase in the number of active layers led to linear increases in levels of capacitance and displacement. These properties increased with up to the 2mol% ZnO addition and then decreased with further addition regardless of number of active layers. In the case of 2 mol% ZnO addition, the specimens consisting of four active layers showed a maximum dielectric constant of 25,200 and electrostrictive strain of 5.8 × 10^?4 at 10kV/cm. These results can be explained by microstructure analysis.     

Effect of excess-PB and prenucleation layer on properties of Pb(ZryTi1-y)O3 thin films prepared by mod process

Abstract

A modified metal-organic decomposition process, MOD has been successfully utilized to improve the ferroelectric properties of Pb(Zr_0.52Ti_0.48)O₃, PZT, thin films. Multilayer PZT/Pt(Si) films, which contain 0.12 μm layer of spin coated PbO-excess (10 mol%) precursors on top of 0.12 μm layer of stoichiometric PZT precursors, exhibit superior ferroelectric properties (P_r=14.2 μC/cm²; E_c=62 kV/cm) to the single layer PZT/Pt(Si) films of the same thickness (0.24 μm), which are either stoichiometric or 10 mol% Pb-enriched. The ferroelectric properties are further improved when the PZT films were synthesized using a thin pulsed laser deposited (PLD) prenucleation layer (0.06 μm). The subsequently MOD-prepared PZT films posses high remanent polarization (P_r=23.2–26.6 μC/cm²) and low coercive field (E_c=62.9–69.0 kV/cm).     

Filament-assisted pulsed laser deposition of epitaxial PbZrxTi1−xO3 films: Morphological and electrical characterization

Abstract

A modification of the conventional pulsed laser deposition technique was employed, whereby a low energy electron emitting filament was placed between the target and the substrate (-20 V filament/substrate bias) in order to produce reactive species (O_2- and O_?) during deposition. Using this modification, epitaxial thin films of PbZr_xTi_1?xO3 (PZT, 0 ≤ × ≤ 0.6) were prepared in situ on virgin (100) MgO and (100) Pt/(100) MgO substrates at a substrate temperature of 550°C and in an oxygen ambient (0.3 Torr). The topography of films prepared without a filament on virgin MgO were porous and composed of grains of about 1000 Å in diameter. As the emission current was increased from 0 to 400 μA, the grain size decreased to less than 100 Å with a concomitant decrease in the porosity. The nucleation of crystallites of other orientations was observed at emission currents greater than about 500 μA. Trilayer structures (Pt/PZT/Pt/<100>MgO) were fabricated for electrical measurements. Non-filament-assisted PZT cells usually failed because of a high probability of conductive paths through the PZT layer. Filament-assisted films were much less prone to this problem. Typical remanent polarizations and coercive fields were 15–20 μC/cm² and 30–50 kV/cm, respectively.     

Synthesis and characterizations of the (1 − x)Pb(Sc1/2Nb1/2)O3–xPbTiO3 solid solution ceramics

We report a systematic study of the (1???x)Pb(Sc_1/2Nb_1/2)O₃–xPbTiO₃ (PSN–PT) solid solution in the form of ceramics with compositions at or near the morphotropic phase boundary (MPB) region (0.35?≤?x?≤?0.50). The PSN–PT ceramics have been synthesized by an improved two-step wolframite precursor method. The synthetic process has been optimized in terms of calcining and sintering conditions. Both dielectric permittivity measurements and differential scanning calorimetry (DSC) show a clear peak at T _C, at which the transition from the paraelectric to ferroelectric phase takes place. Interestingly, the solid solution of the MPB compositions displays a T _C?>?200 °C, i.e. higher than the T _C of the Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ and Pb(Zn_1/3Nb_2/3)O₃–PbTiO₃ solid solutions, making the PSN–PT system very promising piezoelectric and ferroelectric materials for high-temperature applications. A dielectric maximum as high as 50,000 is obtained for the 0.65PSN–0.35PT ceramic with losses smaller than 0.05. The values of the remnant polarization and the strain level of the PSN–PT ceramics are comparable to those of the PZT ceramics.     

Ferroelectric PbZr0.2Ti0.8O3 thin films on epitaxial Y-Ba-Cu-O

Abstract

Using a combination of pulsed laser deposition and sol-gel processing, we have fabricated epitaxial PbZr_0.2Ti_0.8O₃/YBa₂Cu₃O₇-x heterostructures on single crystalline [001] LaAlO₃. Rutherford back-scattering studies show the composition to be the same as the nominal starting composition. Transmission electron microscopy shows the existence of a randomly oriented polycrystalline microstructure in the PZT layer with a grain size of about 500–1000Å. Microscopic pores were also observed in the PZT layer. The PZT film exhibits ferroelectric hysteresis with a saturation polarization of 22–25μC/cm² (at 7.5V, 1kHz), a remanence of 5–6μC/cm² and a coercive field of about 40kV/cm.     

Characterization of the CeO2 thin films for insulation layer and Pt/SrBi2Ta2O9/CeO2/Si MFISFET structure

Abstract

CeO₂ and SrBi₂Ta₂O₉ (SBT) thin films for MFISFET (metal-fcrroelectrics-insulator-semiconductor field effect transistor) were deposited by rf sputtering and pulsed laser deposition method, respectively. The effects of oxygen partial pressure during deposition for CeO₂ films were investigated. The oxygen partial pressure significantly affected the preferred orientation, grain size and electrical properties of CeO₂ films. The CeO₂ thin films with a (200) preferred orientation were deposited on Si(100) substrates at 600°C. The films deposited under the oxygen partial pressure of 50 % showed the best C-V characteristics among those under various conditions. The leakage current density of films showed order of the 10^?7～10^?8 A/cm² at 100 kV/cm. The SBT thin films on CeO₂/Si substrate showed dense microstructure of polycrystalline phase. From the C-V characteristics of MFIS structure composed of the SBT film annealed at 800°C, the memory window width was 0.9 V at ±5 V. The leakage current density of Pt/SBT/CeO₂/Si structure annealed at 800°C was 4×10^?7 A/cm² at 5 V.     

PZT capacitors using IrO2 electrode by RF magnetron sputtering

Abstract

RF magnetron sputtered Pb(Zr_x, Ti_1-x)O₃ [PZT] films were prepared on IrO₂/SiO₂/Si and Pt/IrO₂/SiO₂/Si substrates using the ceramic PZT target with Pb_1.1(Zr_0.52Ti_0.48)O₃ composition. In order to obtain single perovskite phase, PZT film was sputtered at room temperature under Ar plasma and followed by high temperature annealing under oxygen atmosphere. In case of Pt/PZT/IrO₂ capacitor, Δ P (=P*-P∧) was decreased with oxygen annealing temperature. However, it was increased in Pt/PZT/Pt/IrO₂ capacitor. Leakage current density of Pt/PZT/Pt/IrO₂ capacitor, which was used for improving leakage characteristics, was about 10^-2A/cm^?2 order lower than that of Pt/PZT/IrO₂ capacitor. Leakage current density of Pt/PZT/Pt/IrO₂ capacitor annealed at 700°C was 6.6x10^-6A/cm². From the fatigue test, Pt/PZT/IrO₂ capacitor annealed at 650°C and Pt/PZT/Pt/IrO₂ capacitor annealed at 700°C showed 3% and 12% degradation of Δ P after 5×10¹⁰ fatigue cycles, respectively.     

Effects of transition metal (Ni, Mn, Cu) doping on ferroelectric properties of Bi0.9Nd0.1FeO3 thin films prepared by chemical solution deposition method

Transition metal (Ni, Mn, Cu) doped Bi_0.9Nd_0.1FeO₃ thin films were prepared on Pt(111)/Ti/SiO₂/Si(100) substrates by using a chemical solution deposition method. Compared to pure BiFeO₃ (BFO) thin film, improved ferroelectric and leakage current properties were observed in the transition metal doped thin films. The values of remnant polarization (2P _r ) and coercive electric field (2E _c ) of the transition metal doped thin films were 59 μC/cm² and 690 kV/cm at 700 kV/cm for the Ni-doped Bi_0.9Nd_0.1FeO₃ thin film, 57 μC/cm² and 523 kV/cm at 670 kV/cm for the Mn-doped thin film, and 85 μC/cm² and 729 kV/cm at 700 kV/cm for the Cu-doped thin film, respectively. The 2P _r values observed in the transition metal doped thin films were much larger than that of the BFO thin film, 21 μC/cm² at 660 kV/cm. Also the 2E _c values of in the transition metal doped thin films were lower than that of the BFO thin film, 749 kV/cm at 660 kV/cm. The reduced leakage current density was observed in the transition metal doped thin films, which is approximately two orders of magnitude lower than the BFO thin film, 2.6?×?10^?3 A/cm² at 100 kV/cm.     

Low temperature sintering of screen-printed Pb(ZrTi)O3 thick films

Abstract

There has been increasing interest in ferroelectric lead zirconate titanate (PZT) films for the applications in piezoelectric and pyroelectric devices. Many potential applications require a film thickness of above 10 μm for higher force, better sensitivity and stability. But it is very difficult to fabricate the PZT thick film on the silicon substrate because of the volatility of PbO and the interdiffusion of the Pb and Si through the bottom electrode during the sintering at normal temperatures (such as above 1200°C). We speculated densification and reaction mechanism of the PZT thick films fabricated at relatively low temperature (under 1000°C) without sintering aids. The PZT thick films were screen-printed on Pt / Al₂O₃ substrate using a paste of PbO, ZrO₂ and TiO₂ powder mixture. Highly densified PZT thick films could be fabricated on Pt / Al₂O₃ substrate at 1000°C, and we achieved the density, remanent polarization, coercive field, dielectric permittivity, dissipation factor and breakdown field of 98%, 10 μC/cm² and 20 kV/cm, 540, 0.009 and 15 MV/m, respectively. The results show the possibility of densification of the PZT thick film at relatively low temperature without sintering aids, and the results are promising for the use of PZT thick films in various applications.