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1、精品论文Effects of Zr ions substitution on microstructures and electrical properties of Bi3.15Nd0.85Ti3O12 filmsLiao Hui a,b, Zhong Xiangli a,b, Liao Min a,b, Wang Jinbin a,b, ZhouYichun a,ba Key Laboratory of Low Dimensional Materials & Application Technology of Ministry ofEducation, Xiangtan Universit
2、y, Hunan (411105)b Faculty of Materials, Optoelectronics and Physics , Xiangtan University, Hunan (411105)E-mail: AbstractThin films of Bi3.15Nd0.85Ti3O12 (BNT) and Bi3.15Nd0.85Ti3-xZrxO12 (BNTZx， x=0.1 and 0.2) werefabricated on Pt/TiO2/SiO2/Si(100) substrates by a chemical solution deposition (CSD
3、) technique. Structures and electrical properties of the films were studied as a function of Zr ions composition. Experimental results indicate that a small amount of Zr ions substitution in BNT can improve electrical properties and surface morphology of the film. The double remanent polarization (2
4、Pr) androot-mean-square (rms) roughness of BNTZ0.1 film are 52.7 C/cm2 and 9.461 nm, respectively.Keywords: ferroelectric thin films; electrical properties; chemical solution deposition1. IntroductionWith growing interest in ferroelectric material for non-volatile ferroelectric random access memorie
5、s (NvFeRAMs) applications, many efforts have been done to research and develop these ferroelectric films 1. Bismuth layer-structured ferroelectrics (BLSFs) have been recognized as the promising film materials for lead-free ferroelectric oxides for NvFeRAMs application. As one of few BLSFs, Bi4Ti3O12
6、 (BIT) is currently regarded as one of the most promising candidatematerials 2 for NvFeRAMs due to its large spontaneous polarization (Ps) along the a axis (50C/cm2), low processing temperature, high Curie temperature, and lead-free chemical composition properties 3. However, polycrystalline BIT fil
7、m has a reduced remanent polarization (Pr) of approximate 10 C/cm2 and it suffers from severe polarization suppression after 106 read/write switching cycles 4. Many researchers have tried to achieve enhanced ferroelectric property of theBIT film using various techniques. For example, property-design
8、 concept by the substitution of each crystal site in the pseudoperovskite of the BIT thin film, i.e., site-engineering concept, was proposed by Funakubo 5. And the fatigue-free films with excellent ferroelectric properties obtained by the substitution of the A-site ions in BIT film by rare earth ion
9、s have been received great attention 6-9. Noted that Chon et al. reported Nd3+ substituted BIT Bi3.15Nd0.85Ti3O12 (BNT)has a larger 2Pr than that of other A-site substituted BIT 6-9. According to the reported results,however, for the A-site substituted BIT film, the coercive field (2Ec) usually beco
10、mes larger than that of pure BIT film. Recent studies revealed that B-site substitution in BIT film by some ions such as Zr4+, Mo6+, and W6+ could effectively decrease 2Ec10, 11. These imply the fabrication of both A- and B-site cosubstituted BIT for the balance of 2Pr and 2Ec. In former work our te
11、am has found that Zr4+ substitution in BNT film can improve ferroelectric properties and decrease the leakage current effectively 12. In order to further optimize the process, thin films of BNT and Bi3.15Nd0.85Ti3-xZrxO12 (BNTZx, x=0.1 and 0.2) were prepared and the effect of the Zr ions content abo
12、ut their structural, morphological and electrical properties were investigated in this paper.2. ExperimentThe BNT and BNTZx ferroelectric thin films were fabricated on Pt/TiO2/SiO2/Si(100) substrates by a chemical solution deposition (CSD) technique. Bismuth nitrate, neodymium acetate, zirconium pro
13、poxide, and titanium butoxide were used as precursor materials. Glacial- 1 -acetic acid and 2-methoxyethanol were used as solvent. 10% excess of bismuth nitrate was added to compensate for possible bismuth loss during the high temperature process. The precursor solutions were spin coated at a rate o
14、f 4000 rpm for 40 s, followed by a drying process at 180 C for 5 minutes and a pyrolysis process at 400 C for 5 min. These processes were repeated six times. The resultant films were annealed for 10 min in air by a rapid thermal annealing process at 700 C. The structures of the films were characteri
15、zed by x-ray diffraction (XRD) using a D8 advance x-ray diffractometer with Cu K radiation. The surface morphology and the root-mean-square (rms) roughness of the films were evaluated using atomic force microscope (AFM). In order to measure the electrical properties, Pt dot electrodes with diameter of 200 m were deposited on the top surface of the films by dc sputtering through a shadow mask. The ferroelectric properties and leakage current behaviors of the films were measured using a Radiant Technologies Precision Workstation ferroelectric test system.3. Results and discussionsFigure 1 show
