In this thesis, Bi4Ti3O12 thin films are deposited on ITO/glass and Pt/Ti/SiO2/Si substrates using RF magnetron sputtering at room temperature and two kinds of targets with different compositions of Bi4Ti3O12 and Bi4Ti3O12+4wt% Bi2O3, respectively, and then heated by a rapid thermal annealing (RTA) process in an oxygen atmosphere. Three topics are focused in this research, they are: (1) to study the effects of different fabricated conditions and substrates on the physical and electrical characteristics of Bi4Ti3O12; (2) to investigate the influence of bismuth evaporation during thermal process on the characteristics of thin films, and seeking for the methods of bismuth compensation; and (3) applying the Bi4Ti3O12 film as the insulting layer of AC thin film electroluminescence device with the phosphor layer of ZnS:TbOF, and investigating the interaction between the two films.
The experimental results indicate that intensities of X-ray diffraction (XRD) peaks of the films are evident when annealing at 650¢J for 15 min or at 700¢J for 10 min using RTA process, and the optimal properties of polycrystalline Bi4Ti3O12 thin films can be obtained at 700¢J for 15 min. No dielectric breakdown phenomenon of the films is detected in the filed of 500 kV/cm, and the leakage current density was lower than 10-6 A/cm2. The dielectric constant can attain to 307, and the loss factor is 0.02 at 1 kHz. The residual polarization and coercive field are 3.7 £gC/cm2 and 80 kV/cm with a sinusoidal wave of 500 Hz, respectively. The optical transmittance of the film is close to 100% at the wavelength of 550 nm.
Scanning electronic microscopy (SEM) observation reveals that the microstructures, grain sizes and thicknesses of the thin films strongly dependent on the substrates, that is, the Pt/Ti/SiO2/Si substrate provides a more suitable interface layer than ITO/glass substrate for the growth of Bi4Ti3O12 thin films. The energy dispersive spectrometer (EDS) results indicate that the Bi/Ti atomic ratio of the films is less than that of target, which suggests that evaporation loss of bismuth occurs during the heating process. Whereas, this phenomenon occurs near the surface of thin film, it is not apparent in the inner of film. Excess 4wt% Bi2O3 additive in the target or additional Bi2O3 powder in the annealing process can compensate the loss of bismuth in the films, and improve the characteristics of thin films. Finally, the interdiffusion and chemical reactions take place among the element Bi, S and O at the interface during the deposition of ZnS:TbOF on Bi4Ti3O12 films, which degrades the optical transmittance of thin films. A 100 nm SiO2 buffer layer sandwiched between the ZnS:TbOF and Bi4Ti3O12 films can prevent the interdiffusion of the two layers, and enhance the optical transmittance and dielectric breakdown of Bi4Ti3O12 films.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0731106-162411 |
| Date | 31 July 2006 |
| Creators | Chia, Wei-kuo |
| Contributors | Meiso YOKOYAMA, Ying-Chung CHEN, Cheng-Fu YANG |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0731106-162411 |
| Rights | unrestricted, Copyright information available at source archive |
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