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

采用新的显微测量方法对铁电超薄膜进行了生长和表征。选择适合铁电存储器件的PZT（52/48）和适合电光器件的PLZT（8/65/35）作为目标材料。采用近场光学显微镜和压电SPM技术研究了PZT和PLZT超薄膜的显微光学和铁电性能。本课题的研究成果如下：1。Pt/Ti/Si0_2表面的PZT（52/48）和PLZT（8/65/35）薄膜的晶粒尺寸和残余极化均随着薄膜厚度的增加而增大。在PZT和PLZT薄膜的SNOM图像中观察到特殊的对比。这种对比可能与铁电性有关。PZT和PLZT薄膜在Pt/Ti/Si0_2和ITO/Si0_2衬底上优选为（111）取向多晶。膜包括热解相或PbO_2萃取。另一方面，在STO（001）衬底上获得了高质量的（XRD摆动曲线FWHM小于200arcsec）（001）取向外延P(L)ZT薄膜。通过压电SPM观察，证实了P(L)ZT超薄膜中铁电性的存在。域的尺寸小于1um。然而，在超薄薄膜中观察到保留性能的恶化。从实验和理论两方面讨论了SNOM图像中观察到的伪影问题。采用多步骤沉积的方法，研制了一种阵列PZT薄膜微传感器。

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.