Pt Department Of Ferroelectric Thin Film Growth And Performance Research

Owing to its excellent physical properties such as high remnant polarization, large pyroelectric coefficient, and large dielectric constant, Pb(Zr1-xTix)O3 and PbTiO3 thin films have promising applications in ferroelectric random access memories, ferroelectric field-effect transistors, pyroelectric infrared sensors, and so on. In this thesis, the Pb(Zr1-xTix)O3 and PbTiO3 thin films were prepared by RF magnetron sputtering and molecular beam epitaxy, respectively. The effects of the growth and annealing parameters on the crystalline structure, surface morphology, and electrical properties were systematically investigated, and the growth conditions to grow high-quality PTO films were optimized under low temperature and low oxygen partial pressure. The main results are as follows.i) Amorphous PZT thin films were prepared on the Pt/Si substrates by RF magnetron sputtering. Effects of temperature and heating rate of the rapid thermal annealing process on the crystallization quality of PZT thin film was studied. The results show that the optimal annealing temperature is between 600°C and 750°C. When the temperature is lower than 600°C, the PZT film can not be fully crystallized; while higher than 750°C, it will be non-stoichiometric because of the over-volatilization of Pb. This indicates that the annealing temperature is a key factor to provide the kinetic energy for crystallization. For the films grown at a moderate temperature, (100)-texture of PTO films was observed for low annealing temperature, with increasing annealing temperature, (110)-texture was observed and with further increasing temperature, (111)-texture were observed. Similarly, the thin films exhibit more obvious (100)-texture occurred under the slower heating rate, with increasing heating rate, (110)-texture was observed, with further increasing heating rate, (111)-texture were observed. This can be explained by the different nucleation mechanism of the PZT films.ii) In order to obtain high-quality ferroelectric PTO thin films on Pt/Si and SrTiO3 substrates, molecular beam epitaxy system was performed and the growth was in situ monitored by RHEED. XRD results shows that the PbTiO3 thin films with (111)-texture were grown on the Pt/Si substrates. And PTO films were epitaxially grown on SrTiO3 and Nb: SrTiO3 substrates. It is noted that the FWHM of PTO(001) is as low as 0.054°, suggesting very high crystal-quality, and better than ever reported. Such single-crystal PTO films exhibit good ferroelectric hysteretic loops.iii) The TiO2 buffer layer inducing the growth of PTO on GaN substrates in situ monitored by RHEED. The results show that layer-by-layer growth mode is predominant and island growth mode is also observed. XRD results show that (00l)PTO film was grown. This suggests that the TiO2 buffer layer is effectively to induce the PTO growth and finally realize the integration growth of ferroelectric PTO with GaN.