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1.
Xinhua Zhu Tao Zhu Aidong Li Tao Yu Zhguo Liu Naiben Ming 《Integrated ferroelectrics》2013,141(1-4):195-203
Abstract In this work, the microstructural defects in SrBi2Ta2O9 (SBT) ferroelectric thin films were investigated at the atomic-scale by high-resolution transmission electron microscopy (HRTEM). A stacking fault with an extra inserted Bi-O plane normal to the c-axis was observed in SBT film with 10mol% excess bismuth prepared by metalorganic deposition. Edge dislocations with an average space about 3nm were observed at the small misorientation angle (8.2°) tilt grain boundary of SBT film with (001)-orientation prepared by pulsed laser deposition. The Burgers vector b for the edge dislocation was determined to be 1/2[110]α0, where α0 is the parameter of SBT unit cell. Chemical compositions of grains and grain boundaries in SBT films annealed in forming gas at 450°C and 500°C for 60 minutes were analyzed by using energy dispersive spectra at the nano-scale. Effects of the microstructural defects and microchemistry of the grain boundaries on the leakage current of SBT films are briefly discussed. 相似文献
2.
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. 相似文献
3.
Koji Watanabe Masahiro Tanaka Nicolas Nagel Kenji Katori Masataka Sugiyama Hisayoshi Yamoto 《Integrated ferroelectrics》2013,141(1-4):451-460
Abstract Using the Rapid Thermal Annealing (RTA) process, a technique has been established to obtain SrBi2Ta2O9 (SBT) films which showed well-shaped hysteresis curves without a postannealing process after top electrode deposition, maintaining high remanent polarization (Pr) values. RTA conditions were optimized for nucleation of SBT. The effect of a seed layer on the film properties became obvious. This process allowed top electrode materials other than Pt. High remanent polarization (Pr) values could be also obtained with Pd top electrodes. 相似文献
4.
Abstract The effects of sputtering conditions on the SrBi2Ta2O9 films deposited via a single-target RF-sputtering process were investigated in this study. It was found that the composition of targets significantly affected the phases and the composition of the deposited films. When the target contained high bismuth content, SrBi2Ta2O9 and a secondary Bi2O3 phase were formed. When the bismuth content in the targets was insufficient, a pyrochlore phase was produced. SEM images revealed that the composition of the targets also affected the surface morphology of the obtained films. When the target-to-substrate distance was increased, bismuth oxide was formed, which resulted in an increase in the leakage current. By optimizing the deposition conditions, the ferroelectric properties of SrBi2Ta2O9 films were improved. 相似文献
5.
Koukou Suu Takeshi Masuda Yutaka Nishioka Noriakitani 《Integrated ferroelectrics》2013,141(1-4):407-418
Abstract SrBi2Ta2O9 (SBT) thin films were deposited on 6-inch Pt/Ti/SiO2/Si substrates by rf magnetron sputtering using a 12-inch ceramic SBT single target. It is found that several sputtering parameters such as argon (Ar) pressure and rf power were very effective to control the Bi content of SBT thin films which is essential for obtaining good ferroelectric properties. 相似文献
6.
Ho Nyung Lee Dmitri Zakharov Stephan Senz Alain Pignolet Dietrich Hesse 《Integrated ferroelectrics》2013,141(1-4):73-80
Abstract We have successfully grown non-c-axis-oriented epitaxial ferroelectric SrBi2Ta2O9 (SBT) films with (116) and (103) orientations on Si(100) substrates using epitaxial (110)- and (111)-oriented SrRuO3 (SRO) bottom electrodes, respectively. The SRO orientations have been induced by coating the Si(100) substrates with epitaxial YSZ(100) and MgO(111)/ YSZ(100) buffer layers, respectively. All films were sequentially grown by pulsed laser deposition. Specific in-plane orientations of the epitaxial SBT films were found, which are in turn determined by specific in-plane orientations of the epitaxial SRO bottom electrodes. These include a diagonal rectangle-on-cube epitaxy of SRO(110) on YSZ(100) and a triangle-on-triangle epitaxy of SRO(111) on MgO(111). 相似文献
7.
S. Migita K. Sakamaki H. Ota S.-B. Xiong Y. Tarui S. Sakai 《Integrated ferroelectrics》2013,141(1-5):135-143
Abstract Epitaxial thin film growth of SrBi2Ta2O9/SrTiO3/Ce0.12Zr0.88O2 on Si was studied, and this epitaxial layer structure was applied to fabrication of ferroelectric-gate field effect transistors (FETs). The films were prepared by a pulsed laser deposition technique and epitaxial growth was identified by x-ray diffraction. The devices exhibited excellent electrical performances: Capacitance-voltage characteristic of a metal-ferroelectric-insulator-semiconductor (MFIS) diode showed a retention longer than 10 days and Id-Vg characteristic of an MFIS-FET showed 1 day retention. It is proved that the crystalline quality of ferroelectric thin films is of great importance to develop integrated devices with high performance. 相似文献
8.
Growth of SrBi2Ta2O9 (SBT) thin films has been carried out in the presence of O2-plasma created by applying a potential at an auxiliary ring electrode placed near the substrate. Effect of plasma excitation potential and polarity, especially negative polarity, on the formation of a proper SBT phase at 700°C and in modifying crystallite orientation and microstructure of SBT films over (1 1 1) oriented Pt film coated over TiO2/SiO2/Si(1 0 0) substrates has been demonstrated. Preferred c-axis orientation of SBT films changes to (a–b) orientation with decrease in plasma excitation potential from –700 to –350 V and eliminates secondary Bi2Pt phase formation even at 600°C Microstructural study show a 2-dimensional large flat c-oriented crystallites formed at –700 V change to small crystallites in conformity with the changed aspect ratio for crystallites in (a–b) plane parallel to film plane. Spectroscopic ellipsometric results are in agreement with the microstructural data. These affects are attributed to O2-ion bombardment during film growth which reduces nucleation barrier for growth of crystallites in (a–b) plane. O2-plasma sustains the cationic species formed by laser ablation, which along with O
2
+
ions, provide necessary activation energy and enhance the oxidation rates required for SBT phase formation even at 700°C. SBT films grown in O2-plasma show enhancement in remnant polarization value from 1.2 to 6.6 C/cm2 and display ferroelectric properties superior to those formed without plasma. Further O2-plasma eliminates post deposition annealing step for observance of enhanced polarization values. This study shows O2-plasma excitation potential could be exploited as a new process parameter in laser ablation growth of ferroelectric oxide thin films. 相似文献
9.
Abstract Bi–layered ferroelectric SrBi2Ta2O9 (SBT) films were successfully prepared on Pt/Ti/SiO2/Si substrates at 650°C by a modified rf magnetron sputtering technique. The SBT films annealed for 1 h in O2 (760 torr) and again for 30 min in O2 (5 torr) at 650°C show a average grain size of about 49 nm. The SBT films annealed at 65 0°C have a remanent polarization (Pr) of 6.0 μC/cm2 and coercive field (Ec) of 36 kV/cm at an excitation voltage of 5 V. The films showed fatigue–free characteristics up to 4.0 × 1010 switching cycles under 5 V bipolar pulse. The retention characteristics of SBT films looked very promosing up to 1.0 × 105 s. 相似文献
10.
Abstract Bismuth-layer-structured ferroelectric thin films, SrBi2Ta2O9 and Bi4Ti3O12, have been prepared by laser ablation method on both Pt sheets and Si wafers at low temperatures of 400 ~ 500°C. These thin films have been characterized by XRD, XPS, AFM, C-V, D-E hysteresis and J-V measurement. SrBi2Ta2O9 thin films have a good (105) preferential orientation, and Bi4Ti3O12 thin films have (117) and c-axis orientation on these substrates. Ferroelectric film-SiO2-Si structures show good C-V hysteresis curve owing to Si surface potential controlled by the D-E hysteresis. D-E hysteresis is obtained in Bi4Ti3O12 thin film prepared on Pt sheet, and the remnant polarization and the coercive force are 7.5 μC/cm2 and 72 kV/cm, respectively. 相似文献
11.
Tao Yu Dong-Sheng Wang Di Wu Ai-Dong Li Xin-Hua Zhu An Hu 《Integrated ferroelectrics》2013,141(1-4):333-339
Abstract Ferroelectric SrBi2Ta2O9(SBT) thin films prepared by metalorganic decomposition (MOD) method were annealed in forming gas (5% hydrogen + 95% nitrogen) at different temperatures for 60 min. SEM analysis results showed that an amount of columnar structures appeared on SBT surface when the annealing temperature was up to 450°C. When the annealing temperature raised up to 500°C, these columnar structures grew along one dimension and changed into wire structures. The EDX micro-area mapping analysis result showed that Bi was concentrated in the columnar or wire structures on SBT surface. The ferroelectric property analysis results showed that the hysteresis loops still existed after 5 min forming gas processing (350°C or 400°C), but when the annealing time was longer than 10 min, the resistance of the SBT samples became too low to measure the hysteresis loops. 相似文献
12.
Manfred Mört Nicolas Nagel Günther Schindler Thomas Mikolajick Walter Hartner Marcus J. Kastner 《Integrated ferroelectrics》2013,141(1-4):125-134
Abstract The dependence of morphology of SrBi2Ta2O9 (SBT) deposited by Metal Organic Decomposition (MOD) on film thickness and annealing temperature during the crystallization anneal was investigated. From Atomic Force Microscope (AFM) images of these films it can be seen that nucleation and grain growth strongly depends on SBT thickness which also affects the electrical characteristics of the correspondent Pt/SBT/Pt-capacitors. In this work results of a morphological study of SBT films with thicknesses between 40 and 110nm and annealing temperatures between 650°C and 725°C will be presented. 相似文献
13.
Degradation mechanisms of SrBi2Ta2O9 ferroelectric thin film capacitors during forming gas annealing
Walter Hartner Peter Bosk Günther Schindler Herbert Schroeder Rainer Waser Christine Dehm 《Integrated ferroelectrics》2013,141(1-4):341-350
Abstract The effects of annealing in forming gas (5% hydrogen, 95% nitrogen; FGA) are studied on spin coated SrBi2Ta2O9 (SBT) thin films. SBT films on platinum bottom electrode are characterized with and without platinum top electrode by Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES), High Temperature X-Ray Diffraction (HT-XRD) and Secondary Ion Mass Spectrometry (SIMS). High Temperature X-Ray Diffraction (HT-XRD) of blanket Ti/Pt/SBT films in forming gas revealed that the bismuth layered perovskite structure of the SBT is stable up to approx. 500°C. SIMS analysis of Pt/SBT/Pt samples annealed in deuterated forming gas (5% D2, 95% N2) showed that the hydrogen accumulates in the SBT layer and at the platinum interfaces next to the SBT. After FGA of blanket SBT films, tall platinum-bismuth whiskers are seen on the SBT surface. Performing the FGA of the whole Pt/SBT/Pt/Ti stack, two different results are found. For the samples with a high temperature annealing (HTA) step in oxygen after top electrode patterning, top electrode peeling is observed after FGA. For the samples without a HTA step after top electrode patterning, no peeling is observed after FGA. 相似文献
14.
In this study, radio frequency (RF) sputtering was used as the method and the layer-structured bismuth compound of SrBi4Ti4O15 + 4 wt% Bi2O3 ferroelectric ceramic was used as the target to deposit the SrBi4Ti4O15 (SBT) thin films. The addition of excess Bi2O3 content in the target ceramic was used to compensate the vaporization of Bi2O3 during the sintering and deposition processes. SBT ferroelectric thin films were deposited on Pt/Ti/SiO2/Si under optimal RF magnetron sputtering parameters with different substrate temperatures for 2 h. After that the SBT thin films were post-heated using rapid temperature annealing (RTA) method. The dielectric and electrical characteristics of the SBT thin films were measured using metal-ferroelectric-metal (MFM) structure. From the physical and electrical measurements of X-ray diffraction pattern, scanning electronic microscope (SEM), I-V curve, and C-V curve, we had found that the substrate temperature and RTA-treated temperature had large influences on the morphology, the crystalline structure, the leakage current density, and the dielectric constant of the SBT thin films. 相似文献
15.
ABSTRACT In this work, metal-ferroelectric-insulator-silicon (MFIS) devices were fabricated using HfSiON as buffer layers and their electrical properties were studied. Ultra-thin HfSiON films were fabricated by electron-beam evaporation at room temperature and post-annealed using different parameters such as temperature, time in O2. By annealing a 2 nm-thick HfSiON film at 800°C for 60s in O2, a negligible hysteresis loop and small equivalent oxide thickness of 2.3 nm were obtained with a corresponding leakage current density of 6.8 × 10? 5 A/cm2 at a voltage shifted from the flat band voltage by 1 V. In the fabrication of MFIS diodes, Sr0.8Bi2.2Ta2O9 (SBT) films with 400 nm thickness were formed by chemical solution deposition. For Pt/SBT (400 nm)/HfSiON(2 nm)/Si diodes, a memory window of 0.8 V in width was observed during double capacitance-voltage sweep between +5 and –5 V. At the same time, excellent data retention properties were observed. The high and low capacitances in the hysteresis loop were well distinguishable even after 24 h had elapsed. 相似文献
16.
Hiroshi Funaakubo Masatoshi Mitsuya Norimasa Nukaga Katsuyuki Ishikawa 《Integrated ferroelectrics》2013,141(1-4):225-234
Abstract SrBi2(Ta0.7Nb0.3)2O9 (SBTN) films were first prepared on (111)Pt/Ti/SiO2/Si substrates by MOCVD from only two organometallic source bottles. Bi(CH3)3 and the mixture of Sr[Ta(O°C2H5)6]2 and Sr[Nb(O°C2H5)6]2 were used as source materials. High compositional reproducibility was obtained; the Nb/(Ta+Nb) ratio was the same as the mixing ratio of the source. Sr/(Ta+Nb) and Bi/(Ta+Nb) ratios can be controlled by the reactor pressure and the input gas flow rate ratio of the source gases. Almost single phase of SBTN was obtained for the film deposited at 500°C and the following heat-treated at 800°C in O2 atmosphere. Pr and Ec values of 330 nm-thick SBTN film were 8.5 μC/cm2 and 91 kV/cm, respectively and were larger than those of SrBi2Ta2O9 film. There was no degradation after 5x1010 cycles polarization switching. 相似文献
17.
Si-added SrBi2Ta2O9 (SBT) ferroelectric films were prepared by RF magnetron sputtering on a Pt/Ti/SiO2/Si (100) structure. The films were deposited at temperatures below 100°C for surpressing Bi evaporation, and crystallized at 800°C in air. A typical composition was Sr0.79Bi2.37Ta2.00Si0.2Ox. The remanent polarization value (2Pr) of the Si-added SBT film was 16 μC/cm2. The Si atom addition was found to be effective in improvement of the fatigue and leakage current of SBT ferroelectric films. The leakage current density was further improved by annealing in the high-pressure oxygen ambient at 7 atms. 相似文献
18.
Woong Chul Shin Kyu Jeong Choi Nak Jin Seong Soon Gil Yoon 《Integrated ferroelectrics》2013,141(1-4):295-304
Abstract Ferroelectric SrBi2Ta2O9 thin films were deposited on the Bi2O3 buffered Pt/Ti/SiO2/Si substrates using liquid-delivery metalorganic chemical vapor deposition. SBT films with 5nm thick-Bi2O3 buffer layer on Pt bottom electrode showed stronger (115) orientation than those without Bi2O3 buffer layer after annealing at 750°C. The value of the remanent polarization of SBT films with Bi2O3 buffer layer were improved significantly in comparison with those for the films without Bi2O3 buffer layer. The remanent polarization(2Pr) and coercive field(Ec) of SBT films without and with Bi2O3buffer layer annealed at 750°C were 11.9, 20.8 μ C/cm2 and 57, 37.8kV/cm at an applied voltage of 5 V, respectively. 相似文献
19.
Abstract We demonstrate the ferroelectric behavior of Sr0.8Bi2.2Ta2O9 (SBT) films grown on Si(100) substrates by using lanthanum aluminate (LaAlO3) buffer layers. LaAlO3 films were prepared by vacuum evaporation method. Then, they were subjected to ex situ dry N2 annealing in a rapid thermal annealing (RTA) furnace. From the capacitance-voltage (C-V) measurement, the dielectric constant of LaAlO3 was estimated to be 20~25. On these substrates, SBT films (210nm) were deposited by sol-gel method and they were characterized by XRD analysis after annealing under various conditions. It was found from C-V characteristics that the memory window of an SBT film annealed at 750°C for 30min in O2 atmosphere was about 3.0V for the voltage sweep of ±10V. It was also found from the retention measurement that the capacitance values of the SBT film annealed at 750°C did not change over 12hours. It is concluded from these results that the SBT/LaAlO3/Si(100) structure is one of the most promising structures for realizing MFISFETs (metal-ferroelectric-insulator-semiconductor field-effect-transistors). 相似文献
20.
《Integrated ferroelectrics》2013,141(1):915-922
Ba(Mg1/3Ta2/3)O3 (BMT) microwave dielectric thin films were successfully synthesized by a modified pulsed laser deposition (PLD) process, which includes low temperature (200°C) deposition and high temperature (>500°C) annealing. Crystalline structured BMT thin films were obtained when the PLD-deposited films were post-annealed at a temperature higher than 500°C in oxygen atmosphere. The characteristics of BMT thin film, including crystallinity, grain size, film roughness, and dielectric properties were improved with annealing temperature, achieving dielectric constant K = 23.5 and dissipation factor tan δ = 0.015 (at 1 MHz) for the 800°C-annealed films. 相似文献