Controlled Ferroelastic Domains In Pb(Zr_0.1Ti_0.9O₃ Thin Films

Ferroelectric materials, with excellent dielectric, ferroelctric, piezoelectric, pyroelectric properties and electro-optic effects, acousto-optic effects, have been widely studied due to their huge potentials in applications of micro-mechanical system, ultra-fast sensors and memories. Pb(Zr,Ti)O3, as one of the most promising ferroelectric materials, has already played an important role in these field. However, it is still necessary to explore the way to decrease its device size, minimize the power consumption and processing cost. Besides, domain structures of Pb(Zr,Ti)O3 thin films determines the performance in the memory devices. Hence, it is particularly important to research and regulate domain structures.In this thesis, high-quality epitaxial Pb(Zr0.1Ti0.9)O3 thin films are prepared on different substrates by pulsed laser deposition. Scanning probe microscope and X-ray diffraction are used to characterize surface morphology, domain structure and crystal structure of thin films. This thesis mainly studies three aspects of contents:(1)the preparation of high-quality epitaxial Pb(Zr0.1Ti0.9)O3 thin films; (2)formation mechanism and regulation of ferroelastic domains in Pb(Zr0.iTi0.9)O3 thin films; (3)effects of domain structure on polarization reversal in Pb(Zr0.iTi0.9)O3 thin films.High-quality epitaxial Pb(Zr0.1Ti0.9)O3 thin films are obtained by optimizing the targets’ quality, wet chemical etching process of single crystal substrates and growth parameters of thin film by pulsed laser deposition.Pb(Zr0.1Ti0.9)C3 thin films with different thickness were prepared on (110) DyScO3 and (001)SrTiO3 substrates with SrRuO3 as bottom electrodes and buffer layer. The domain structures of films were characterized respectively. The strain in epitaxial thin films are controlled by thickness of thin films and lattice mismatching of substrates. It is noted that ferroelastic domains only appear in 70 nm thick Pb(Zr0.iTi0.9)O3 thin films which are deposited on (110)DyScO3 substrates. Ferroelastic domains can be controlled by the epitaxial strain in thin films. The appearances of ferroelastic domains are considered as a mechanism to alleviate the elastic energy in films.In Pb(Zr0.1Ti0.9)O3 thin films with ferroelastic domains, multiple step reversal is detected as the polarization is reversed electrically or mechanically, where ferroelastic domains is an intermediate state. However, in Pb(Zr0.1Ti0.9)O3 thin films with only c domains, there is no such an intermediate state when ferroelectric polarization reverses. As compared to disposable polarization reversal, multiple step reversal is much easier. It is the existence of ferroelastic domains that leads to the easier performance.In a word, studying on ferroelastic domains in Pb(Zr0.1Ti0.9)O3 thin films allows the regulation of ferroelastic domains. The exploration on the preparation of high quality epitaxial Pb(Zr0.1Ti0.9)O3 thin films and the discovery of multiple step ferroelectric polarization reversal are both significantly important to applications of ferroelectric thin films.