导电氧化物SrRuO3薄膜的生长及铁电集成性研究
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II
ABSTRACT
Finally, SRO thin films were deposited on Pt/Ti/SiO2/Si substrates. The effect of growth temperature and pulse laser energy on crystal structure and surface morphology of SRO thin films were studied. It was found that amorphous films were obtained when the pulse laser energy intensity was lower than 130mj/pulse while crystalline films were obtained when the pulse laser energy intensity was higher than 130mj/pulse. BST films fabricated on SRO/Pt composite electrode by sputtering were polycrystalline, exhibiting a dielectric constant and loss tangent measured at 100KHz and 300K of 1030 and 3%, respectively.
第二章 实验方法和装置 ............................................................................................ 13 2.1 脉冲激光沉积(PLD) ..................................................................................... 13 2.1.1 脉冲激光沉积的过程 ........................................................................ 13 2.1.2 PLD 镀膜的工艺参数........................................................................ 14 2.1.3 脉冲激光沉积(PLD)的特点 .............................................................. 16 2.2 薄膜的微观结构分析方法 ........................................................................... 16 2.2.1 XRD 原理........................................................................................... 16 2.2.2 AFM 原理 .......................................................................................... 17 2.3 电性能测试方法 ........................................................................................... 19 2.3.1 四探针法测量原理 ............................................................................ 19 2.3.2 介电性能测试方法 ............................................................................ 20
最后，用 PLD 法在 Pt/Ti/SiO2/Si 基片上制备 SRO 薄膜，研究了激光能量密度 和沉积温度对 SRO 薄膜表面形貌和微结构的影响。结果表明，激光能量密度过低 时（小于 130mj/Pulse），得到的是非晶薄膜，增大激光能量密度，得到（200）择 优取向的多晶薄膜。用溅射法在 SRO/Pt 复合电极上制备的 BST 薄膜为多晶结构。 在测试频率为 100KHz，无外加偏压时，在 700℃制备的 SRO 薄膜电极上的 BST 薄膜的介电常数为 1030,损耗小于 3%。
摘要
摘要Байду номын сангаас
铁电薄膜由于具有一系列重要的特性而应用广泛，目前铁电薄膜在其各种功 能器件的应用中电极材料主要是 Pt 等贵金属。由于金属电极与铁电材料在结构上 不匹配，难以在电极上生长外延铁电薄膜，而且金属电极存在易氧化，附着能力 差，与薄膜之间互扩散严重等缺点，因此人们开始研究与铁电薄膜具有相近结构， 且化学和热稳定性较好的导电金属氧化物。具有金属导电性的钙钛矿结构氧化物 SrRuO3(简称 SRO)由于其优良的电学和磁学性能而备受关注。SRO 的室温电阻率 为 280µΩ.cm,具有高电导率、高化学稳定性和热稳定性，与目前广泛研究的铁电 薄膜(BST、PZT)具有类似的晶格结构和良好的晶格匹配性，是铁电薄膜器件理想 的电极材料之一。因此我们开展了 SRO 薄膜的制备及其与铁电薄膜集成的研究。
关键词：SRO，BST，脉冲激光沉积（PLD），薄膜
I
ABSTRACT
ABSTRACT
Ferroelectric thin films have been used in a lot of devices due to their important characteristics. The electrode of ferroelectric thin film devices mostly use precious metals such as Pt. Epitaxial ferroelectric thin film can not be obtained on metal electrode because of lattice mismatch. Besides, metal electrode have many other disadvantages. Conductive metallic oxide SrRuO3(SRO) have received continuous attention due to its interesting electrical and magnetic properties. SRO is an ideal bottom electrode in devices incorporating oriented ferroelectric films due to its outstanding thermal conductivity and stability, high resistance to chemical erosion, and good compatibility in structure with perovskite type ferroelectric materials. In this paper, the growth of SRO thin films on different substrates and the integration of ferroelectric thin films with SRO electrodes have been systematically studied.
首先，利用脉冲激光沉积法（PLD）分别在 STO、LAO、MgO 基片上制备 SRO 薄膜，研究了生长温度、氧分压、激光能量密度等工艺参数对 SRO 薄膜的晶相结 构、表面形貌、电阻率的影响。在优化的工艺参数下，在 MgO 基片上制备了外延 SRO 薄膜，薄膜面外为(110)和（001）取向，面内分别也各有两种取向，形成 X、 Y、Z、Z’型畴并存的多畴结构，SRO/MgO 外延薄膜具有良好的导电性，是良好的 薄膜电极材料。
Then, ferroelectric BTO thin films were deposited on SRO/STO and SRO/MgO electrodes by PLD. When grown on SRO/STO, BTO films were preferentially c-axis oriented. Using MgO as a substrate,produced a mixture of a-axis and c-axis oriented grains of BTO. The PFM analysis and P-E tests indicated that epitaxial BTO films with c-axis orientation on STO substrate exhibited stronger ferroelectricity as compared to the MgO one. Epitaxial BST films were fabricated on SRO/MgO by sputtering. Using the SRO films deposited at a temperature of 700℃ as electrode, the BST films exhibited a dielectric constant and loss tangent measured at 100KHz and 300K of 270 and 5%,respectively.
其次，分别用 PLD 法在 SRO/STO 和 SRO/MgO 底电极上制备了 BTO 外延薄 膜，在 SRO/STO 上制备的 BTO 薄膜为 c 轴取向，铁电性较强，测得其剩余极化 值 2Pr=7.3μC/cm2，并用 PFM 能观察到明显的电畴。而在 SRO/MgO 上制备的 BTO 薄膜为 a 轴取向和 c 轴取向并存的结构，铁电性较弱。用溅射法在 SRO/MgO 底电 极上制备了外延 BST 薄膜，在测试频率为 100KHz，无外加偏压时，在 700℃制备 的 SRO 薄膜电极上的 BST 薄膜的介电常数为 270,损耗约为 5%。
Keywords:SRO, BST, pulse laser deposition, thin film
III
目录
目录
第一章 概述 .................................................................................................................. 1 1.1 铁电材料的研究历史及性质 ......................................................................... 1 1.2 BST 类材料的结构及性质............................................................................. 3 1.3 集成铁电薄膜器件的电极材料 ..................................................................... 4 1.4 SRO 材料的结构与性质 ................................................................................ 6 1.5 SRO 薄膜制备的方法 .................................................................................... 7 1.6 SRO 薄膜的研究现状 .................................................................................... 8 1.7 本论文的主要工作 ....................................................................................... 12
Firstly, SRO films were deposited on SrTiO3 (STO),LaAlO3(LAO),MgO substrates by pulse laser deposition(PLD). The effect of growth temperature、oxygen pressure and pulse laser energy intensity on crystal structure 、 surface morphology 、 electrical resistivity of SRO thin films were studied. SRO thin films grow epitaxially on MgO substrate exhibiting two out-of-plane orientations,[110]SRO//[100]MgO and 45 ° -rotated cube-on-cube [001]SRO//[100]MgO, which are formed by two in-plane arrangements each. The epitaxial SRO thin films on MgO substrate were highly conductive, making these materials excellent candidates for use as thin-film electrodes.
ABSTRACT
Finally, SRO thin films were deposited on Pt/Ti/SiO2/Si substrates. The effect of growth temperature and pulse laser energy on crystal structure and surface morphology of SRO thin films were studied. It was found that amorphous films were obtained when the pulse laser energy intensity was lower than 130mj/pulse while crystalline films were obtained when the pulse laser energy intensity was higher than 130mj/pulse. BST films fabricated on SRO/Pt composite electrode by sputtering were polycrystalline, exhibiting a dielectric constant and loss tangent measured at 100KHz and 300K of 1030 and 3%, respectively.
第二章 实验方法和装置 ............................................................................................ 13 2.1 脉冲激光沉积(PLD) ..................................................................................... 13 2.1.1 脉冲激光沉积的过程 ........................................................................ 13 2.1.2 PLD 镀膜的工艺参数........................................................................ 14 2.1.3 脉冲激光沉积(PLD)的特点 .............................................................. 16 2.2 薄膜的微观结构分析方法 ........................................................................... 16 2.2.1 XRD 原理........................................................................................... 16 2.2.2 AFM 原理 .......................................................................................... 17 2.3 电性能测试方法 ........................................................................................... 19 2.3.1 四探针法测量原理 ............................................................................ 19 2.3.2 介电性能测试方法 ............................................................................ 20
最后，用 PLD 法在 Pt/Ti/SiO2/Si 基片上制备 SRO 薄膜，研究了激光能量密度 和沉积温度对 SRO 薄膜表面形貌和微结构的影响。结果表明，激光能量密度过低 时（小于 130mj/Pulse），得到的是非晶薄膜，增大激光能量密度，得到（200）择 优取向的多晶薄膜。用溅射法在 SRO/Pt 复合电极上制备的 BST 薄膜为多晶结构。 在测试频率为 100KHz，无外加偏压时，在 700℃制备的 SRO 薄膜电极上的 BST 薄膜的介电常数为 1030,损耗小于 3%。
摘要
摘要Байду номын сангаас
铁电薄膜由于具有一系列重要的特性而应用广泛，目前铁电薄膜在其各种功 能器件的应用中电极材料主要是 Pt 等贵金属。由于金属电极与铁电材料在结构上 不匹配，难以在电极上生长外延铁电薄膜，而且金属电极存在易氧化，附着能力 差，与薄膜之间互扩散严重等缺点，因此人们开始研究与铁电薄膜具有相近结构， 且化学和热稳定性较好的导电金属氧化物。具有金属导电性的钙钛矿结构氧化物 SrRuO3(简称 SRO)由于其优良的电学和磁学性能而备受关注。SRO 的室温电阻率 为 280µΩ.cm,具有高电导率、高化学稳定性和热稳定性，与目前广泛研究的铁电 薄膜(BST、PZT)具有类似的晶格结构和良好的晶格匹配性，是铁电薄膜器件理想 的电极材料之一。因此我们开展了 SRO 薄膜的制备及其与铁电薄膜集成的研究。
关键词：SRO，BST，脉冲激光沉积（PLD），薄膜
I
ABSTRACT
ABSTRACT
Ferroelectric thin films have been used in a lot of devices due to their important characteristics. The electrode of ferroelectric thin film devices mostly use precious metals such as Pt. Epitaxial ferroelectric thin film can not be obtained on metal electrode because of lattice mismatch. Besides, metal electrode have many other disadvantages. Conductive metallic oxide SrRuO3(SRO) have received continuous attention due to its interesting electrical and magnetic properties. SRO is an ideal bottom electrode in devices incorporating oriented ferroelectric films due to its outstanding thermal conductivity and stability, high resistance to chemical erosion, and good compatibility in structure with perovskite type ferroelectric materials. In this paper, the growth of SRO thin films on different substrates and the integration of ferroelectric thin films with SRO electrodes have been systematically studied.
首先，利用脉冲激光沉积法（PLD）分别在 STO、LAO、MgO 基片上制备 SRO 薄膜，研究了生长温度、氧分压、激光能量密度等工艺参数对 SRO 薄膜的晶相结 构、表面形貌、电阻率的影响。在优化的工艺参数下，在 MgO 基片上制备了外延 SRO 薄膜，薄膜面外为(110)和（001）取向，面内分别也各有两种取向，形成 X、 Y、Z、Z’型畴并存的多畴结构，SRO/MgO 外延薄膜具有良好的导电性，是良好的 薄膜电极材料。
Then, ferroelectric BTO thin films were deposited on SRO/STO and SRO/MgO electrodes by PLD. When grown on SRO/STO, BTO films were preferentially c-axis oriented. Using MgO as a substrate,produced a mixture of a-axis and c-axis oriented grains of BTO. The PFM analysis and P-E tests indicated that epitaxial BTO films with c-axis orientation on STO substrate exhibited stronger ferroelectricity as compared to the MgO one. Epitaxial BST films were fabricated on SRO/MgO by sputtering. Using the SRO films deposited at a temperature of 700℃ as electrode, the BST films exhibited a dielectric constant and loss tangent measured at 100KHz and 300K of 270 and 5%,respectively.
其次，分别用 PLD 法在 SRO/STO 和 SRO/MgO 底电极上制备了 BTO 外延薄 膜，在 SRO/STO 上制备的 BTO 薄膜为 c 轴取向，铁电性较强，测得其剩余极化 值 2Pr=7.3μC/cm2，并用 PFM 能观察到明显的电畴。而在 SRO/MgO 上制备的 BTO 薄膜为 a 轴取向和 c 轴取向并存的结构，铁电性较弱。用溅射法在 SRO/MgO 底电 极上制备了外延 BST 薄膜，在测试频率为 100KHz，无外加偏压时，在 700℃制备 的 SRO 薄膜电极上的 BST 薄膜的介电常数为 270,损耗约为 5%。
Keywords:SRO, BST, pulse laser deposition, thin film
III
目录
目录
第一章 概述 .................................................................................................................. 1 1.1 铁电材料的研究历史及性质 ......................................................................... 1 1.2 BST 类材料的结构及性质............................................................................. 3 1.3 集成铁电薄膜器件的电极材料 ..................................................................... 4 1.4 SRO 材料的结构与性质 ................................................................................ 6 1.5 SRO 薄膜制备的方法 .................................................................................... 7 1.6 SRO 薄膜的研究现状 .................................................................................... 8 1.7 本论文的主要工作 ....................................................................................... 12
Firstly, SRO films were deposited on SrTiO3 (STO),LaAlO3(LAO),MgO substrates by pulse laser deposition(PLD). The effect of growth temperature、oxygen pressure and pulse laser energy intensity on crystal structure 、 surface morphology 、 electrical resistivity of SRO thin films were studied. SRO thin films grow epitaxially on MgO substrate exhibiting two out-of-plane orientations,[110]SRO//[100]MgO and 45 ° -rotated cube-on-cube [001]SRO//[100]MgO, which are formed by two in-plane arrangements each. The epitaxial SRO thin films on MgO substrate were highly conductive, making these materials excellent candidates for use as thin-film electrodes.