Investigating On Preparation And Electrical Properties Of Sm And Mn Doped PMN-Pt Ferroelectric Thin Films

Ferroelectric materials having excellent dielectric,piezoelectric,ferroelectric,and pyroelectric properties,are widely utilized in actuator,energy transducers,sensors,and detectors and other microelectronic devices.With the integration,miniaturization and multi-function of microelectronic devices,the preparation and performance analysis of ferroelectric thin films have attracted much attention.(1-x)Pb(Mg_1/3Nb_2/3)O₃-x PbTiO₃(PMN-PT)exhibits a high electromechanical coupling coefficient and giant electrostrictive effect,especially in the vicinity of the morphotropic phase boundary,it has extremely high dielectric,piezoelectric and other electrical properties.In comparison with PMN-PT bulk materials,the phase structures are convenient to be tuned around the MPB in PMN-PT thin films through the misfit strain from the substrate,chemical composition,or external fields,etc.Due to the simple operation and low cost,sol-gel method has been considered as one of the most popular methods on preparation of ferroelectric thin films,however,there still remains huge challenges to achieve the epitaxial growth of ferroelectric thin films.In this thesis,the high quality PMN-PT thin films have been prepared through the sol-gel method.Moreover,the Sm and Mn were succefully doped into the MPB PMN-PT thin film,which can suppress the generation of the oxygen vacancy and further improve the electrical properties.The main works are presented as the follows.(1)The y Sm-Pb(Mg_1/3Nb_2/3)O₃-0.32PbTiO₃(y=0,1%,1.5%,2%,2.5%,3%)precursor solutions were prepared by the sol-gel method,and the corresponding doped thin films were prepared on the Pt/Ti/Si O₂/Si substrate by the spin-coated method.The results show that the relatively smoothest surface of the thin film was obtained,where the solution concentration,the annealing temperature and oxygen flux are 0.3 mol/L,800°C and 1.5 L/min,respectively.The best electrical properties were observed in2%Sm doped thin film,including ferroelectric,piezoelectric and dielectric,which also have relatively small dielectric loss and leakage current.And the reversion of the locally electrical domains was also found in 2%Sm doped thin film.(2)z Mn-2%Sm-Pb(Mg_1/3Nb_2/3)O₃-0.32PbTiO₃(z=0,0.5%,1%,1.5%,2%)thin films were prepared on Pt/Ti/Si O₂/Si substrates by sol-gel method and spin coating method.The results show that the addition of Mn can refine the grain size and increase the density.The ferroelectric,piezoelectric and dielectric properties of the films are the largest when Mn=1%,and the leakage currents of the films were found to be the smallest.(3)Based on the sol-gel method combined with spin coating process,the epitaxial films of m Sm-Pb(Mg_1/3Nb_2/3)O₃-0.32PbTiO₃(m=0,1%,2%,3%)were prepared on niobium-doped strontium titanate(Nb STO).The results show that the ferroelectric properties of the thin film are most excellent when the doped Sm content is 2%.