Microscopic structurte, electrical and optical properties of ferroelectric ultra-thin films

生长了铁电超薄膜，并用新颖的显微测量方法对其进行了表征。选择了适用于铁电存储器件的PZT(52/48)和适用于电光器件的PLZT(8/65/35)作为靶材。利用近场光学显微镜和压电扫描探针显微镜研究了PZT和PLZT超薄膜的微观、光学和铁电性质。研究结果如下：1.随着薄膜厚度的增加，PZT(52/48)和PLZT(8/65/35)薄膜的颗粒尺寸和剩余极化均增大。在PZT和PLZT薄膜的SNOM图像中观察到了特定的对比度。这种对比度可能与铁电性有关。在Pt/Ti/SiO_2和ITO/SiO_2衬底上制备的PZT和PLZT薄膜具有较好的(111)择优取向。薄膜中含有烧绿石相或PbO_2萃取物。另一方面，在STO(001)衬底上获得了高质量的(X射线衍射摇摆曲线半高宽小于200arcsec)(001)取向的P(L)ZT薄膜。通过压电扫描电子显微镜观察，证实了P(L)ZT超薄膜中铁电性的存在。磁区的尺寸小于1微米。然而，在超薄膜中观察到保留性的恶化。从实验和理论上对SNOM图像中观察到的伪影问题进行了讨论。采用多步沉积的方法，研制了一种阵列式PZT膜片微传感器。

Ferroelectric ultra-thin films were grown and characterized by means of novel microscopic measurement methods. PZT(52/48) which is suitable for ferroelectric memory devices and PLZT(8/65/35) which is suitable for electro-optic devices were chosen as the target materials. Near-field optical microscopy and piezoelectric SPM were applied to investigate microscopic optical and ferroelectric properties of the PZT and PLZT ultra-thin films. The results of the research project are as follows ;1. The both of the size of the grains and the remanent polarization of the PZT(52/48) and PLZT(8/65/35) thin films on Pt/Ti/Si0_2 increase with an increase of the film thickness.2. A specific contrast is observed in the SNOM images of the PZT and PLZT thin films. The contrast may be in relation to the ferroelectricity.3. The PZT and PLZT thin films are preferably (111)-oriented polycrystalline on Pt/Ti/Si0_2 and ITO/Si0_2 substrates. The films include pyrochbre phase or PbO_2 extraction. On the other hand, A high-quality (FWHM of XRD rocking curve is smaller than 200arcsec) (001)-oriented epitaxial P(L)ZT films are obtained on STO(001) substrates.4. By means of a piezoelectric SPM observation, the existence of ferroelectricity in P(L)ZT ultra-thin films was confirmed. The size of the domain is smaller than 1 um. However, the deterioration of the retention property was observed in ultra-thin films.5. The problem of the artifacts observed in SNOM images was discussed experimentally and theoretically.6. By means of a multi-step deposition, an arrayed PZT diaphragm micro sensor was developed.