Research Of Highly-oriented Growth And Properties Of Barium Zirconate Titanate Ferroelectric Thin Films On SrTiO₃ Substrates

Barium zirconate titanate(Ba Zr_xTi_1-xO₃,BZT)ferroelectric thin film is a kind of BTO-based ferroelectric thin film.It not only has excellent piezoelectric,ferroelectric,and nonlinear optical,but also has higher dielectric constant and lower leakage current than BTO thin film.At the same time,BZT ferroelectric thin film is easy to make components due to it's small volume,easy integration and low driving voltage,which is conducive to the miniaturization and integration of electronic components.As a result,it has broad application prospects in the fields of microelectronics,micromachining,nonlinear optical devices and so on.It is well known that ferroelectric thin films are anisotropic,and the electrical properties of polycrystalline ferroelectric thin films are poor.Therefore,the preparation of highly preferred or epitaxial oriented BZT ferroelectric thin films is of great significance for their properties optimization and practical applications.In this paper,Ba Zr_0.2Ti_0.8O₃(BZT)ferroelectric thin films were deposited on Sr Ti O₃(STO)substrates by RF magnetron sputtering method,and their microstructure and electrical properties were analyzed.The main contents of this paper are summarized as follows:(1)BZT ferroelectric thin films were grown on(100)-STO single crystal substrates by RF magnetron sputtering method with LNO as the bottom electrodes.The effects of sputtering atmosphere,sputtering pressure,deposition temperature and cooling rate on the crystal structure of BZT thin films were analyzed and discussed.The results show that(00l)highly preferred orientation of BZT thin films can be achieved on LNO/STO substrates when the sputtering atmosphere is Ar/O₂=32:8,sputtering pressure is 1.2 Pa,deposition temperature is 700?and cooling rate is7?8?/min.(2)Based on the optimized preparation conditions,the effects of thin film thickness,substrate material,bottom electrode material and zirconium content on the microstructure and electrical properties of BZT ferroelectric thin films were investigated.The results show that the thin film thickness has no effect on the crystal orientation of BZT thin films grown on LNO/STO substrates,which are(00l)highly preferred orientation.However,with the increase of thin film thickness,the crystallinity of BZT thin films is better and the electrical properties are enhanced.The BZT thin films grown on Si substrates have(00l)preferred orientation,compared with BZT/LNO/STO heterostructure,whose dielectric constant is smaller and hysteresis loop is close to a linear slender curve.The BZT thin films grown on SRO or LNO bottom electrodes are(00l)preferred orientation,while the BZT thin films grown on Pt bottom electrodes are polycrystalline orientation.Meanwhile,the dielectric constant of BZT/Pt/STO heterostructure is larger,and the remanent polarization(P_r)is about 4.8?C/cm².BTO and BZT-20 thin films were deposited on LNO/STO substrates,respectively.Compared with BTO thin films,the(00l)diffraction peak of BZT-20 thin films shifts to the left and the dielectric properties are better.(3)The effects of STO substrate orientations on the orientation growth and electrical properties of BZT ferroelectric thin films were investigated.The results show that with LNO as the bottom electrodes,STO substrates with different orientations strongly control the highly preferred orientation growth of LNO bottom electrodes and BZT thin films.The dielectric constant of(110)-BZT thin films is the largest,and that of(001)-BZT thin films is the smallest.At the same time,the energy storage efficiency of(001)-BZT thin films can reach 92.2%.In addition,with(100)-STO as substrates,the effects of texture orientations of Pt bottom electrodes on BZT thin films were analyzed.The results show that the deposition temperature of Pt bottom electrodes affects it's texture orientation.At 200?and 500?,the bottom electrode Pt shows(111)preferred orientation,while at 800?,the bottom electrode Pt shows(200)preferred orientation.The BZT thin films grown on the PT bottom electrodes are all polycrystalline,among which the dielectric constant of BZT/Pt(200?)/STO heterostructure is the largest,and the energy storage efficiency of BZT/Pt(800?)/STO heterostructure is the highest.