ABSTRACT
PREPARATION OF PLZT THIN FILMS BY CHEMICAL SOLUTION DEPOSITION AND THEIR CHARACTERIZATION
Kaplan, Burkan
M.S., Department of Metallurgical and Materials Engineering
Supervisor: Prof. Dr. Macit Ö / zenbaS
November 2005, 125 pages
In this study, La3+ was substituted into lead zirconate titanate (PZT) system by Pb1-xLax(ZryTi1-y)1-x/4O3 nominal stochiometry and it was processed via chemical solution deposition on (111)-Pt/Ti/SiO2/Si-(100) substrate.PLZT solutions were prepared by mixing two solutions, one of which was obtained by dissolving lead acetate and lanthanum acetate hydrate in 2 methoxyethanol at high temperature. This solution was then mixed with the second solution containing zirconium propoxide and titanium isopropoxide. 40ml/0.4M solution was prepared and spin coated on Pt/Ti/SiO2/Si substrates at 3000 rpm for 30 seconds. After 4 coating cycles, film thickness was reached to 600 nm.
A systematic study was carried out in different regions of PLZT phase diagram tetragonal, rhombohedral and on the morphotropic phase boundry (MPB) to obtain optimized results of ferroelectric, dielectric and optical properties of the material.
During the period of the work, effect of parameters on these properties such as heat treatment conditions, chemical composition of the film, microstructure and thickness of the film was investigated.
The films were characterized structurally and electrically. For structural properties, X-ray diffraction technique (XRD), energy dispersive spectrometry (EDS) and Scanning Electron Microscope (SEM) were used to observe phases and surface characterization. For electrical measurements, ferroelectric tester was used to obtain dielectric constant, loss tangent and hysteresis curves. Optical transmittance of the films was also investigated by UV-VIS Spectrophotometer and optical film constants were calculated by modified envelope method.
It was observed that the optimum heat treatment conditions were achieved at 7500C for 3 hours. The highest ferroelectric and dielectric properties such as remanent polarization and dielectric constant were obtained using that temperature.
The dielectric constant of the films was measured in the frequency range of 1kHz-1MHz and remained almost constant in this region. The change of dielectric constant and ferroelectric hysteresis loops were obtained as a function of Zr/Ti ratio and La content.
The grain size as a function of sintering temperature and La content was investigated. It was seen that as the sintering temperature was increased, the grain size of the films increased. The same tendency was also observed when the La content was increased.
Fatigue behavior of PLZT thin films was also investigated by Radiant Ferroelectric Tester at 50 kHz and ± / 15V. Change of remanent polarization (Pr) as a function of cumulative switching cycles (N) was drawn with the log scale of x-axis. Furthermore, leakage current characteristics of the films were also obtained by the ferroelectric tester at & / #61617 / 15V. It has been observed that as the La content of the film was increased, leakage current of the PLZT films decreased.
Keywords: PLZT, (111)-Pt/Ti/SiO2/Si-(100) substrate, Chemical Solution Deposition.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/2/12606738/index.pdf |
| Date | 01 December 2005 |
| Creators | Kaplan, Burkan |
| Contributors | Ozenbas, Macit |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for METU campus |
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