應(yīng)力對LaAlO3/BaTiO3超晶格結(jié)構(gòu)及性能的影響

采用激光脈沖分子束外延技術(shù)，在(100)取向SrTiO3或Nb:SrTiO3單晶基片上成功外延生長不同結(jié)構(gòu)的LaAlO3/BaTiO3超晶格。利用高能電子衍射技術(shù)和X射線衍射技術(shù)對LaAlO3/BaTiO3超晶格的生長過程和微結(jié)構(gòu)進(jìn)行了表征。發(fā)現(xiàn)由于LaAlO3和BaTiO3晶格常數(shù)的不匹配，在LaAlO3/BaTiO3超晶格中存在應(yīng)變，該應(yīng)變又對超晶格的鐵電性能具有很大的影響。而不同的結(jié)構(gòu)存在的應(yīng)變不同，非對稱結(jié)構(gòu)的LaAlO3/BaTiO3超晶格的應(yīng)變隨每個周期中LaAlO3層厚度的增加、BaTiO3層厚度的減少而增大，其剩余極化強度不僅未減少，反而增加。

LaAlO3/BaTiO3 superlattices were prepared on (100) oriented SrTiO3 or Nb-doped SrTiO3 substrates by laser molecular beam epitaxy. The change of diffraction streaks observed in reflection high-energy electron diffraction during the growth of LaAlO3 and BaTiO3 illustrated the different epitaxial growth for LaAlO3 and BaTiO3 . The X-ray diffraction spectra of the superlattices with different thickness of LaAlO3 and BaTiO3 layers within a period showed that the c-axis lattice constants changed with layer thickness due to the strain induced by lattice mismatch between LaAlO3 and BaTiO3. The remanent polarization of the superlattices increased with decreasing the thickness of BaTiO3 layers and increasing the thickness of LaTiO3 layers. This suggests that the remanent polarization is closely related with the lattice strain in the superlattices.