Investigation On The Dielectric, Electrical And Optical Properties Of Giant-dielectric Materials

Giant-dielectric materials are usually ferroelectrics. They show great dielectric constant, and they have many important and practical applications in electronic devices. This work is based on the preparation, characterization, and processing of giant-dielectric materials.The fast development of information technology requires integrated circuit to be greater integrated, faster functioned, and lower power-consumed, that lead to continuous shrinkage of MOS and DRAM feature size. And under this trend the thickness of MOS gate dielectrics would soon scale down to its physical limit. Substitution of SiO₂ gate and capacitor dielectrics with high-k dielectric is a promising solution for the future development of CMOS technology. PZT is a kind of giant-dielectric material with perovskite structure. It shows great dielectric constant normally above 100 and low loss tangent, therefore it can be used as gate dielectrics.In this article, PZT were made by traditional sol-gel way and annealed in the RTP at 650℃ for 120s. The phase structures of PZT film were measured by X-ray diffraction and the morphology was observed by scanning electron microscopy. Al/PZT/Si was measured by LCR meter at a frequency 10 KHz. The I-V property was measured by semiconductor parameter meter. We studied the influences of the experimental conditions on the dielectric and I-V properties of the Al/PZT/Si structure.The family of the layed perovskite structure ferroelectric is another kind of giant-dielectric materials. These materials, especially SBT, are the key candidates for a nonvolatile memory device because of their excellent fatigue resistance and electrical properties for submicron thickness with a simple Pt electrode. In these materials, SBT is most intensively studied. SBT has the general chemical formula of (Bi₂O₂)²⁺(A_m-1B_mO_3m+1)^2-, where A is Sr, and B is Ta. A and B are the standard A-site and B-site cations of the perovskite structure, and m is the number of perovskite unit cells between Bi₂O₂ layers.The solid-solution composition in SrBi₂Ta_1-xNb_xO₉ (SBTN) is expected to meet the requirements of large remanent polarization, low coercive field, and high ferroelectric phase temperature. The crystal structure and ferroelectric properties in the solid solution SBTN have been studied. The optical properties in the solid-solution system, however, rarely have been studied. The optical properties of the ferroelectric materials, on the other hand, are of interest for applications such as uncooled infrared detectors, optical sensor protection, and waveguides. We studied the optical constants and band-gap energies of SBTN solid-solution ferroelectric films and their dependence on the Nb content using spectroscopic ellipsometry. In addition, we studied the optically induced polarization fatigue in SBTN films. These results are helpful in understanding the fatigue-free response observed in electrical field, and are also necessary to fully characterize SBTN for memory applications.