【作者】 何世明；

【导师】 李言荣；

【作者基本信息】 电子科技大学 ， 材料物理与化学， 2006， 博士

【摘要】 SrTiO₃（STO）薄膜在液氮温区具有良好的非线性介电性质，且可与高温超导薄膜，如YBa₂Cu₃O_7-x（YBCO）薄膜，组成异质外延多层薄膜，是研制各种高品质压控微波器件的重要材料。 本论文首先开展了STO薄膜的脉冲激光沉积技术（PLD）生长研究，系统研究了各种工艺参数（沉积温度、氧分压、激光能量密度、脉冲频率、原位退火时间等）以及基片（基片种类、基片台阶结构等）对STO薄膜微观结构影响的规律，优化了STO薄膜的生长工艺，制备出了高质量的STO薄膜；并在此基础上，提出了采用基片斜切处理和间隙式沉积相结合的方法，实现了STO薄膜的二维层状异质外延生长，获得了结晶良好、表面平整的STO外延薄膜，当薄膜厚度为300nm时，薄膜均方根表面粗糙度RMS=0.25nm，达到了原子级平整。为STO／YBCO集成薄膜的生长奠定了基础。 在工艺参数优化的基础上，本论文还系统研究了STO薄膜介电性质与微观结构的关系，重点讨论了晶粒尺寸、薄膜应力等对STO薄膜非线性介电性质的影响。研究结果表明：晶粒尺寸较大的STO薄膜，体现出较强的非线性介电性质；当STO薄膜存在压应力时，薄膜在应力方向的非线性介电性减弱，当STO薄膜存在张应力时，薄膜在应力方向的非线性介电性增强。这些研究结果为优化STO薄膜非线性介电性质提供了必要的理论依据。 作为氧化物薄膜，氧空位必然对STO薄膜的非线性介电性质产生影响，为此本论文还系统研究了氧空位浓度对STO薄膜介电性质的影响。实验发现：含有较高浓度氧空位的STO薄膜，其非线性介电性较高，但是耐压能力下降，而含有较低浓度氧空位的STO薄膜，其非线性介电性较低，但是耐压能力较强，为此，本论文提出了通过在STO薄膜生长过程中连续改变沉积氧分压的办法，制备出了氧空位浓度梯度变化的STO薄膜，该薄膜体现出良好的非线性介电性和抗电强度，具有较大的实用价值，目前尚未见报导。 为了定量研究STO薄膜的介电性质，本论文在总结介质薄膜覆盖的叉指电容计算方法的基础上，利用有限元建模，分析了高介电常数铁电薄膜叉指电容器的特性，优化了叉指电容拓扑结构，从而提高电容可调率。研究发现：当薄膜介电常数为基片介电常数3倍以上时，叉指电容量与薄膜介电常数近似成线性关系；更多还原

【Abstract】 Because of the excellent non-linear dielectric properties at low temperature （nitrogen boiling temperature）, and the good compatibility with high temperature superconductors （HTSC）, such as Y₁Ba₂Cu₃O_7-x （YBCO）, SrTiO₃ （STO） thin films was regarded as a good candidate for high quality microwave tunable components.The STO thin films were prepared by pulsed laser deposition （PLD） method, the effect of growth parameters and substrate treatment, such as, the substrate temperature, the oxygen pressure, the laser energy density, the repetition rate, the in-situ annealing time, the mismatch between substrate and thin films and the step-terrace of substrate surface, on the microstructure of STO thin films were systematically studied in the dissertation. The interval deposition process was proposed. Two dimensional layer-by-layer mode was realized for heteroepitaxial growth of STO thin films on step-terraced substrate by the interval deposition process. STO thin films with atomic flat surface and excellent crystalline quality were prepared on step-terraced LaAlO₃（100） substrate by interval deposition process under optimum growth parameters. The root-mean-square （RMS） roughness of STO thin films with thickness of 300 nm was only 0.25 nm.The relationship between the microstructure and the non-linear dielectric properties of STO thin films was studied in the dissertation. The investigation was focused on the grain size and internal stress. The STO thin films with large grain size have large dielectric tunability. The tensile stress increase the tunability of STO thin films, while the compressive stress decrease the tunability of STO thin films. The experimental results are benefit for the optimization of the non-linear dielectric properties of STO thin films. The effect of oxygen vacancy on the dielectric properties of STO thin films was investigated. Although STO thin films with low oxygen vacancy concentration demonstrated low dielectric tunability, high dielectric dissipation, the STO thin films however, could withstand a large electric field; while the STO thin films with high concentration of oxygen vacancy exhibited reduced dielectric loss, and更多还原