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LaAlO3/BaTiO3超晶格薄膜的生长及结构分析 总被引:1,自引:0,他引:1
采用激光脉冲分子束外延技术,在(100)取向的SrTiO3 单晶基片上成功外延生长了LaAlO3/Ba TiO3 超晶格薄膜。在超晶格薄膜生长过程中,采用高能电子衍射技术(RHEED)对LaAlO3/BaTiO3 超晶格薄膜的生长过程以及平面晶格变化进行了分析。通过对超晶格薄膜中各层RHEED衍射条纹的分析计算发现超晶格薄膜存在一个临界厚度,其值约为 17nm,当超晶格薄膜的厚度小于该临界厚度时,晶格畸变在逐渐增加,当厚度超过该临界厚度时,晶格畸变因弛豫现象的产生而逐渐减小。超晶格薄膜中不同层的RHEED衍射条纹的差别说明了由于不同应力的作用使超晶格薄膜中LAO层和BTO层表面粗糙度不同。 相似文献
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通过研究发现,利用激光分子束外延技术生长的LaAlO3/BaTiO3超晶格薄膜具有良好的电学性能,其剩余极化可达到25μc/cm2.性能决定于结构,因此本文分析研究了LaAlO3/BaTiO3超晶格薄膜的界面结构.首先通过高能电子衍射技术在薄膜生长过程中对各层的生长及界面状况进行观测,再通过小角X射线衍射曲线及其计算机拟合曲线进一步确定超晶格薄膜的界面及结构参数,如界面的粗糙度、单层厚度等.通过研究发现,由于晶格之间的差异,LaAlO3/BaTiO3超晶格薄膜中LaAlO3和BaTiO3层的生长过程及微结构存在着一定的差异. 相似文献
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用激光分子束外延(LMBE)设备,在SrTiO3(001)基片上外延生长BaTiO3/CoFe2O4/BaTiO3多层复合磁电薄膜结构。通过反射式高能电子衍射(RHEED)对薄膜生长过程进行原位监测,结果显示,随着CoFe2O4厚度的增加薄膜内应力逐渐被释放,并且应力释放的过程导致了薄膜生长模式的变化。高分辨X射线衍射(XRD)发现,随着CoFe2O4厚度的增加,CoFe2O4对BaTiO3薄膜的张应力逐渐增大,BaTiO3晶胞的c轴晶格常数逐渐变小。理论计算给出了BaTiO3面外晶格常数c随CoFe2O4沉积时间的变化规律。原子力显微镜(AFM)对表面形貌进行表征,进一步证明了复合薄膜生长模式的变化。 相似文献
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采用脉冲激光分子束外延(PLMBE)方法,通过优化的工艺参数,在SrTiO3(100)单晶基片上外延结构为(8/8)的BaTiO3/SrTiO3超晶格薄膜.综合利用反射式高能电子衍射系统(RHEED)、高分辨率X射线衍射(HRXRD)以及高分辨率透射电镜选区电子衍射(SAED)技术,研究超晶格薄膜的晶格应变现象和规律.研究结果表明,在制备的BaTiO3/SrTiO3超晶格薄膜中,BaTiO3晶胞面外晶格增大,面内晶格减小;而SrTiO3晶胞面内及面外方向晶格都被拉伸,但面外晶格拉伸程度较大,SrTiO3晶胞产生了与BaTiO3晶胞方向一致的四方相转变. 相似文献
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本实验研究利用激光分子束外延法(L-MBE)研究在SrTiO3(STO)(001)基片上生长的BaTiO3(BTO)/SrTiO3(STO)超晶格的微结构,利用小角X射线衍射光谱(SAXRD)的计算机模拟来获得BaTiO3/Sr-TiO3超晶格的微结构参数,如:总的膜厚度,超晶格周期,表面和界面的均方根粗糙度等。实验结果表明超晶格的表面和界面非常平整,均方根粗糙度大约为0.2nm,原子力显微镜(AFM)的实验研究已经证明了超晶格结构的平滑程度,超晶格的<001>方向存在着微弱的关联现象。 相似文献
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用激光分子束外延技术在SrTiO3(001)衬底上外延生长SrTiO3/BaTiO3多层膜,通过反射式高能电子衍射(RHEED)原位实时监测并结合原子力显微镜(AFM),研究了不同基片温度下所生长薄膜的表面平整度,利用X射线衍射(XRD)对外延薄膜进行了结构分析,结果表明薄膜具有二维生长模式,在基片温度为380~470℃之间生长的薄膜具有原子级光滑,并且具有完全C轴取向.同时运用X射线光电子能谱(XPS)研究了薄膜界面的互扩散,结果表明降低制备薄膜时的基片温度有利于减少互扩散. 相似文献
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在LaAlO3(001)、MgO(001)、SrTiO3(001)衬底以及SrTiO3(001)/PZT(001)种膜上用液相外延方法生长了PZNT薄膜。生长结果表明:在LaAlO3(001)基片PZNT晶粒以三维岛状自发生长。薄膜中有大量的焦绿石异相;在MgO(001)和SrlriO3(001)衬底上,为三维岛状异质外延生长。薄膜中焦绿石异相几乎消失;引入[001]取向的PZT种膜后,岛状三维生长变为二维生长,显著改善了外延膜的质量,获得了完整的PZNT膜。分析了衬底取向对紧邻层纳米尺寸范围的晶粒形成、薄膜晶粒的发育、克服薄膜中异相形成等的影响,总结了获得完整PZNT薄膜的生长条件。 相似文献
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采用脉冲激光沉积技术,在(100)LaAlO3单晶基片上生长SrTiO3/Y1Ba2Cu3O7-x(STO/YBCO)多层薄膜。XRD分析表明:YBCO薄膜和STO薄膜均为C轴取向,STO(002)/YBCO(006)衍射峰摇摆曲线半高宽为0.73°。AFM分析表明,STO/YBCO多层薄膜表面平整、均匀,在77K,100kHz的测试条件下,STO薄膜介电损耗tgδ<10-2,在53.6kV/cm电场作用下,介电常数的相对变化为38%。 相似文献
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We have synthesized stoichiometric Ba(Cd1/3Ta2/3)O3 [BCT] (100) dielectric thin films on MgO (100) substrates using Pulsed Laser Deposition. Over 99% of the BCT film was found to be epitaxial [BCT (100) || MgO (100) and BCT (010) || MgO (010)] when grown with an elevated substrate temperature of 635 °C, an enhanced oxygen pressure of 53 Pa and a Cd-enriched BCT target with a 1 mol BCT: 1.5 mol CdO composition. A dielectric constant of 32 was inferred from low-frequency capacitance measurements of a planar interdigital metal pattern. Analysis of ultra violet optical absorption results indicates that BCT has a bandgap of 4.9 eV; while the interference pattern in the visible range is consistent with a refractive index of 2.1. Temperature-dependent electrical measurements indicate that the BCT films have a room temperature conductivity of 3 × 10− 12 Ω− 1 cm− 1 with a thermal activation energy of 0.7 eV. A mean particle size of ~ 100 nm and a root mean square surface roughness of 5 to 6 nm were measured using Atomic Force Microscopy. 相似文献
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Kinbara H Harigai T Kakemoto H Wada S Tsurumi T 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(12):2541-2547
Perovskite-type BaTiO(3)/SrTiO(3) (BTO/STO) artificial superlattices were fabricated by the molecular beam epitaxy method. The X-Ray diffraction (XRD) profiles and reflection, high-energy, electron diffraction (RHEED) oscillations during the growth of superlattices indicated that crystalline orientation toward [001] direction and two-dimensional layer-by-layer growth were achieved. The capacitance, dielectric loss tangent, and complex admittance were measured up to 145 degrees C and up to the frequency of 100 MHz with the microplaner interdigital electrodes. Dielectric permittivity of superlattices was evaluated from the complex admittance with an electromagnetic field analysis as a function of temperature. The [BTO(10)/STO(10)](4) superlattice showed the enormous relative permittivity of 19,000 at room temperature and the dielectric relaxation was observed. The linear relations in the charge versus voltage curves were observed in these superlattices, and the shape of Q-V curves were not changed as a function of temperature. Temperature dependence of dielectric properties of the BTO/STO superlattices was evaluated. It was found that the BTO/STO superlattices did not show a peak in the dielectric permittivity versus temperature curve, which was different from the behavior of BTO-STO bulk ceramics and normal thin films. These results strongly supported that the high permittivity of the superlattices was caused by temperature-stable anisotropic strains induced in the superlattices. 相似文献
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Epitaxial SrTiO3(STO)/BaTiO3(BTO) artificial superlattices have been grown on TiN buffered Si (001) substrates by pulsed laser deposition method and the effects of stacking periodicity and processing oxygen partial pressure on their crystallinity and dielectric properties were studied. The crystal orientation, epitaxy nature, and microstructure of STO/BTO superlattices were investigated using X-ray diffraction and transmission electron microscopy. The TiN buffer layer and superlattice thin films were grown with cube-on-cube epitaxial orientation relationship of [110](001)films∣∣[110](001)TiN∣∣[110](001)Si. The c-axis lattice parameter of the STO/BTO superlattice decreased from 0.412 nm to 0.406 nm with increasing oxygen partial pressure and the dielectric constants, measured at the frequency of 100 kHz at room temperature, of the superlattices with 2 nm/2 nm periodicity increased from 312 at 1 × 10− 5 Torr to 596 at 1 × 10− 3 Torr. The dielectric constants of superlattices grown at oxygen partial pressure of 1 × 10− 3 Torr increased from 264 to 678 with decreasing periodicity of the superlattices from 10 nm/10 nm to 1 nm/1 nm. 相似文献
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以共沉淀法、喷雾干燥法制备了三元正极材料LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2,应用基于密度泛函理论的第一性原理计算方法,与实验制备的LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2进行对比,对3种不同的预想结构模型(堆叠结构、随机排列结构、超晶格结构)进行研究。实验结果表明,两种方法制备的三元材料都具有良好的层状结构,其中共沉淀法制备的层状结构更加明显,而喷雾干燥法制备的材料中过渡金属元素比更接近LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的化学计量比。计算结果表明,随机排列的结构模型能量最低、最稳定,与实验制备的三元正极材料结构最为相似。 相似文献