| With the development of modern industry and national economy,the demand for high-performance functional materials and devices increases greatly.The researches and development of functional materials play an increasingly important role in the national economy and high-tech fields.Ferroelectric film materials,as one of the hot topics of high and new technology research,have very good ferroelectric,piezoelectric,photoelectric and nonlinear optical properties,which can be widely used in microelectronics,optoelectronics,integrated optics,solar energy and other fields.In this work,Pb(Zr0.4Ti0.6)O3(PZT),(Na0.5Bi0.5)TiO3(NBT)and BiFeO3(BFO)ferroelectric thin film heterostructures were prepared by different methods.The structure,electrical properties and optical properties of film heterostructure were investigated.1?The SRO/PZT/SRO/Ti3Al/LAO heterostructure is constructed on LAO substrate by introducing 2 nm Ti3Al ultra-thin buffer/template.The effects of Ti3Al buffer on the structure and performance of SRO/PZT/SRO are studied.It is found that the ultra-thin Ti3Al layer greatly improves the epitaxial quality of SRO/PZT/SRO heterostructure.Compared with direct epitaxy on LAO,the(002)diffraction peak intensity of PZT is enhanced,and the full width at half height is reduced from 0.972° to 0.911°.According to the X-ray diffraction and transmission electron microscope analyses,the edge dislocation density NE in PZT film is effectively reduced by ultra-thin Ti3Al buffer layer and is reduced from 3.83×1010/cm2 to 3.10×1010/cm2.The remanent polarization 2Pr of SRO/PZT/SRO capacitor increased from 122.1 ?C/cm2 to 136.7 ?C/cm2,but 2V,decreased from 2.9 V to 2.6 V.It is found that the introduction of Ti3Al layer improves the short-circuit current Jsc,open circuit voltage Voc and conversion efficiency,which is attributed to the enhanced polarization of PZT film.The photovoltaic effect of SRO/PZT/SRO hetero structure is influenced by the interface barrier and ferroelectric polarization.Jsc increases linearly with the increase of light intensity,and Voc first decreases linearly with the increase of light intensity and then tends to a constant value of 0.27 V.2?The(00l)oriented epitaxial BFO/LSCO/STO hetero structure is fabricated on STO substrate by magnetron sputtering.X-ray photoelectron spectroscopy shows that iron in BFO films is Fe3+.It is found that Pt/BFO/LSCO heterostructures exhibit I-V resistive storage characteristics,which is caused by carrier filling and debonding in the interface potential well.The photoelectric effect of Pt/BFO/LSCO heterostructure can be controlled by external field polarization.With the increase of temperature,Voc decreases linearly.The photoelectric effect is closely related to the thickness of BFO.With the increase of the thickness,the dominant mechanism changes from the interface barrier to the ferroelectric polarization.3?The NBT/LSCO/STO structure is fabricated,in which LSCO film was prepared by magnetron sputtering and NBT film by pulsed laser deposition.The structure and properties of the heterostructure are studied.It is found that the NBT films prepared at the optimum temperature of 650? are single-phase(00l)epitaxial perovskite structure.The LSCO/NBT/LSCO heterostructure capacitor has a small coercive field of 47 kV/cm,a relatively large remanent polarization of 15.6 ?C/cm2,and an effective piezoelectric coefficient of d33 of 145 pm/V.The effects of orientation on the structure and physical properties of NBT/LSCO are studied.The results show that the 2Pr of(111),(110)and(001)NBT films are 87.5 ?C/cm2,62.6 ?C/cm2 and 28.5 ?C/cm2.(111)NBT film has the largest ferroelectric properties.The optical properties show that the polarization regulation of photoelectric effect is closely related to the orientation of NBT films,and the intensity of regulation is(111)NBT>(110)NBT>(001)NBT.4?The 200 nm epitaxial BFO:NBT composite films with BFO volume fraction of 3:25 are prepared on STO substrate by magnetron sputtering and pulsed laser co-deposition method.The results of XRD and AFM show that the introduction of BFO increases the c-axis lattice constant,grain size and reduces the surface roughness of NBT film.The doping of BFO increased the ferroelectric properties of NBT with increased Pr by 20.6?C/cm2.BFO:NBT film show a high recoverable energy storage density Wrec=44.0 J/cm3,which is 1.8 times of NBT film.The Wrec shows a good thermal stability and less frequency dependence.The photoelectric effect of BFO:NBT films is controlled by the external field polarization.Voc and Jsc are Voc=-0.44 V and Jsc=10.8 ?A/cm2,respectively.As compared with NBT films,Voc from BFO:NBT films was increases by 0.25 V. |
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