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Synthesis and characterization of nanostructured BSTO thin-films for microwave applications.

机译：用于微波应用的纳米结构BSTO薄膜的合成与表征。

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摘要

Nanophase synthesis of ferroelectric thin-films of Ba0.6Sr 0.4TiO3 (BSTO) was studied systematically for applications in tunable microwave components. Synthesis of nanostructured BSTO was performed using a pulsed-laser deposition system with real-time in-situ process control. The main research goal was to utilize the pulsed laser deposition parameters to control the grain growth for low microwave loss nanostructured BSTO thin-films on crystalline substrates such as LaAlO3. These parameters include the energy density of the laser pulses, wavelength, oxygen partial pressure, distance between the target and the substrate, and the substrate temperature. The nanostructural characterization was performed using XRD, SEM and AFM. Microwave characterization was done using coplanar waveguide lines to characterize the frequency dependent dielectric properties (&egr; r and tandelta). BSTO films were grown at the same measured temperature and energy density but in different oxygen ambient pressures from 19 mTorr through 300 mTorr. Using contact mode AFM, the grain size was found to decrease as the oxygen ambient pressure was reduced from 150 mTorr to 38 mTorr. The growth process changed when the pressure was increased above 150 mTorr. Nanocluster structures rather than nanoparticles were found at 225 mTorr. Average grain sizes less than 100 nm were obtained for oxygen pressures below 75 mTorr. The XRD spectra indicate the highly crystalline nature of the film. Microwave measurements, performed between 9--18 GHz, suggest the nano-structured BSTO thin-films on LaAlO3 (LAO) substrates are highly tunable (up to 25%). Surface potential imaging indicated that the surface potential of polarized areas to be the sum of contributions from the surface charge and from the vertical part of the oriented dipoles in the areas.
机译：系统地研究了Ba0.6Sr 0.4TiO3（BSTO）铁电薄膜的纳米相合成及其在可调微波组件中的应用。使用具有实时原位过程控制的脉冲激光沉积系统进行了纳米结构BSTO的合成。主要研究目标是利用脉冲激光沉积参数来控制在诸如LaAlO3之类的晶体衬底上的低微波损耗纳米结构BSTO薄膜的晶粒生长。这些参数包括激光脉冲的能量密度，波长，氧分压，靶材与基板之间的距离以及基板温度。纳米结构表征使用XRD，SEM和AFM进行。使用共面波导线对微波进行表征，以表征随频率变化的介电特性（例如r和tandelta）。 BSTO膜在相同的测量温度和能量密度下，但在19 mTorr至300 mTorr的不同氧气环境压力下生长。使用接触模式AFM，发现随着氧环境压力从150 mTorr降低到38 mTorr，晶粒尺寸减小。当压力增加到150 mTorr以上时，生长过程发生了变化。在225 mTorr处发现了纳米簇结构而不是纳米颗粒。对于低于75 mTorr的氧气压力，获得的平均晶粒尺寸小于100 nm。 XRD光谱表明膜的高度结晶性质。在9--18 GHz之间进行的微波测量表明，LaAlO3（LAO）基板上的纳米结构BSTO薄膜具有很高的可调谐性（高达25％）。表面电势成像表明，极化区域的表面电势是表面电荷和区域中定向偶极子垂直部分贡献的总和。

著录项

  • 作者

    Riehl, Bonnie D.;

  • 作者单位

    The University of Dayton.;

  • 授予单位 The University of Dayton.;
  • 学科 Engineering Electronics and Electrical.; Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2004
  • 页码 89 p.
  • 总页数 89
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无线电电子学、电信技术;工程材料学;
  • 关键词

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