Development of Strain-induced ferroerectlic Thin Films Prepared by MOCVD

研究了应变对薄膜铁电性的影响。在(100)MgO衬底上沉积的Pb(Ti，Nb)O_3薄膜中，随着Nb含量的增加，c轴取向程度增加。C轴与a轴的晶格参数比(c/a)随Nb含量的增加而减小。Pb(Ti，Nb)O_3、Pb(Ti，Al)O_3和Pb(Zr，Ti)O_3薄膜的c轴取向度随c/a比的减小而增大。这可以用施加在薄膜上的应力来解释。还观察到了薄膜的取向对铁电性能的影响。极轴取向的(001)四方PZT和(111)三方PZT显示出最大的剩余极化(Pr)。而(101)和(111)取向的四方PZT以及(110)和(100)取向的三方相PZT，其Pr值均大于理论计算值。这种现象可以用施加在薄膜上的应力引起的磁畴结构来解释。

Strain effect on the ferroelectricity of the film was investigated. The degree of c-axis orientation increased when Nb content increased in Pb (Ti, Nb) O_3 film deposited on (100) MgO substrates. Lattice parameter ratio of c- to a-axis (c/a) decreased with increasing Nb content. Increase of the degree of c-axis orientation with decreasing c/a ratio which was commonly observed for Pb (Ti, Nb) O_3, Pb (Ti, Al) O_3 and Pb (Zr, Ti) O_3 films. These can be explained by the stress applied to the film.Effect of the orientation of the Pb (Zr, Ti) O_3 films on the ferroerectricity was also observed. Polar-axis oriented film, (001) tetragonal-PZT and (111) rhombohedral PZT, showed the largest remnant polarization (Pr). However, the other oriented films, (101) and (111)-oriented tetragonal PZT and (110) and (100)-oriented rhombohedral PZT, showed large Pr value compared with the expected value from the calculation. This phenomena can be explained by the domain structure induced by the stress applied to the film.