以氧化物底電極控制鐵電薄膜結晶方向之研究

Abstract

利用MOD法以及Sol-gel法製備SBT以及PTO、PZT鐵電薄膜，分別利用[110]優選方向之SRO以及BRO為底電極，以Pt為上電極得到MIM電容結構，做物性以及電性量測。鐵電薄膜厚度約2500Å，利用X-Ray以及SEM分析可得知其結晶狀況。探討在不同底材披覆不同鐵電薄膜狀態下，薄膜介面應變能以及電性關係。 由X-Ray量測顯示SRO與BRO對於SBT與PTO沒有控制成長方向能力，而BRO對於PZT有控制其朝特定生長方向的現象，由TEM晶格影像可以發現BRO介面原子排列與PZT介面相契合。PTO與PbZr0.2Ti0.8O3出現極大漏電流現象，由SEM觀察得知PTO 與PbZr0.2Ti0.8O3晶粒顆粒較大，並根據AFM得知PTO與PbZr0.2Ti0.8O3表面粗糙度較高，因此出現較大漏電流密度現象。

SBT and PTO, and PZT ferroelectric thin films were prepared by matelorganic and sol-gel method in this study. The physical and electrical properties of the dielectric films, sandwiched in a MIM structure with [110] oriented SRO or BRO as bottom electrode and Pt as top electrode, are investigated. The thicknesses of these thin films were about 2500Å. The crystal structure and surface morphology were analyzed by X-Ray and SEM measurement. Interface strain energy and electricity properties of these MIM structures were measured and their correlations were studied. X-Ray diffraction shows that SRO and BRO bottom electrode did not induce the SBT thin film growth in one direction. However, BRO bottom electrodes leaded to growth PZT ferroelectric thin film in (110) prefer direction.TEM lattice image showed an expitaxial relation between BRO and PZT at their interface. For typical PTO and PbZr0.2Ti0.8O3 films, the SEM images showed that the grain size and the roughness of PTO and PbZr0.2Ti0.8O3 were large than PZT(MPB).Therefore, the leakge current density of PTO and PbZr0.2Ti0.8O3 was larger than PZT(MPB).