Study on the Influence of Grain Boundary of Ferroelectric Thin Films on Elelectrical Properties and Its Application to Memory Devices

铁电薄膜晶界对电性能的影响及其在存储器件中的应用研究

• 批准号: 12450131
• 负责人: SHIMIZU Masaru
• 金额: $ 3.33万
• 依托单位: Himeji Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12450131/
• 关键词: MOCVD; Pb(Zr,Ti)O_3(PZT) thin films; grain size; grain boundary; ferroelectricity; piezoresponse; polarization reversal process; ultra thin PZT films; 強誘電体薄膜; 強誘電体メモリ; Pb(Zr, Ti)O_3(PZT); グレインサイズ制御; 圧電応答顕微鏡; エピタキシャルPZT薄膜; 強誘電体PZT薄膜; グレインサイズ

1. Crystalline and electrical properties of polycrystalline Pb(Zr,Ti)O_3 (PZT) thin films on SrRuO_3/SiO_2/Si and epitaxial PZT thin films on SrRuO_3/SrTiO_3 were investigated. Increase in grain size and decrease in current density of polycrystalline PZT films were observed as film thickness increased. Decrease in current density was also observed as film thickness increased for epitaxial PZT films. Polycrystalline PZT films showed stronger thickness dependence of dielectric constant and remanent polarization than that of epitaxial PZT films due to thickness dependence of grain size and grain boundary.2. The Volmer-Waber (V-W) growth mode for PZT thin films grown on Pt/SiO_2/Si by MOCVD, the V-W growth mode for PZT on SrO plane of SrTiO_3, the Stranski-Krastanov (S-K) mode for PZT on TiO_2 plane of SrTiO_3 and the S-K mode for PZT films on SrRuO_3/SrTiO_3 were observed, respectively. From piezoresponse measurements using scanning probe microscopy(SPM), it was found that nano-size PbTiO_3 and PZT islands showed ferroelectricity.3. PZT thin films were successfully obtained at 395 ℃ by two step growth rocess using seeds. Increase in grain size and improvements in crystalline and electrical properties were observed for PZT films by two step growth process.4. Polarization reversal process of PZT thin films was observed by piezoresponse measurements using SPM. Velocity of polarization reversal in in-plane direction and out-of plane direction were measured.5. Planer and three dimensional PZT capacitors with Ir/PZT/Ir/SiO_2/Si structure were successfully fabricated solely by MOCVD only at 400 ℃.6. The 20nm-thick ultra thin PZT films which showed ferroelectricity were successfully obtained on SrRuO_3/SrTiO_3.

1.研究了SrRuO_3/SiO_2/Si上多晶Pb(Zr,Ti)O_3(PZT)薄膜和SrRuO_3/SrTiO_3上外延PZT薄膜的晶粒尺寸增大和电流密度减小的影响。随着外延薄膜厚度的增加，还观察到电流密度的降低由于晶粒尺寸和晶界的厚度依赖性，多晶PZT薄膜的介电常数和剩余极化比外延PZT薄膜表现出更强的厚度依赖性。2． MOCVD Pt/SiO_2/Si，PZT 在 SrTiO_3 SrO 平面上的 V-W 生长模式，利用扫描探针显微镜(SPM)测量压电响应，分别观察到SrTiO_3的TiO_2平面上的PZT的S-K模式和SrRuO_3/SrTiO_3上的PZT薄膜的S-K模式。 PZT岛表现出铁电性。3．通过两步生长工艺，在395℃下观察到PZT薄膜晶粒尺寸的增加以及晶体和电学性能的改善。4．通过SPM压电响应测量观察PZT薄膜的极化反转过程。测量了面内方向和面外方向的极化反转。 5．仅在400℃下通过MOCVD成功制备了Ir/PZT/Ir/SiO_2/Si结构。6．在SrRuO_3/SrTiO_3上成功获得了具有铁电性的20nm厚的超薄PZT薄膜。

项目成果

Masaru Shimizu, Hironori Fujisawa, Hirohiko Niu et al.,: "Low Temperature Growth Of Pb(Zr, Ti)O_3 Thin Films by Two Step MOCVD Using Seeds"Ferroelectrics. (in press). (2002)

Masaru Shimizu、Hironori Fujisawa、Hirohiko Niu 等人：“使用种子通过两步 MOCVD 低温生长 Pb(Zr, Ti)O_3 薄膜”铁电体。

Hironori Fujisawa, Masaru Shimizu, Hirohiko Niu et al.,: "Observation of Polarization Reversal Processes in Pb(Zr, Ti)O_3 Thin Films Using Atomic Force"Proceedings of the 12th IEEE International Symposium on the Applications of Ferroelectrics. (in press).

Hironori Fujisawa、Masaru Shimizu、Hirohiko Niu 等人：“利用原子力观察 Pb(Zr, Ti)O_3 薄膜中的极化反转过程”第 12 届 IEEE 铁电体应用国际研讨会论文集。

M.Shimizu et al.: "Preparation of Ir-Based Thin Film Electrodes by MOCVD"Materials Research Society Symposium Proceedings. 596. 259-264 (2000)

M.Shimizu 等人：“通过 MOCVD 制备 Ir 基薄膜电极”材料研究学会研讨会论文集。

Hironori Fujisawa, Masaru Shimizu, Hirohiko Niu et al.,: "Piezoresponse Measurements for Pb(Zr, Ti)O_3 Island Structure Using Scanning Probe Microscopy"Materials Research Society Symposium Proceedings. 655. CC10101-10 (2001)

Hironori Fujisawa、Masaru Shimizu、Hirohiko Niu 等人，“使用扫描探针显微镜对 Pb(Zr, Ti)O_3 岛结构进行压电响应测量”材料研究会研讨会论文集。

H.Fujisawa: "Investigation of Polarization Switching Processes in Pb(Zr,Ti)O_3 Capacitors Using Piezoresponse Imaging"Ferroelectrics. (印刷中). (2002)

H.Fujisawa：“使用压电响应成像研究 Pb(Zr,Ti)O_3 电容器的极化切换过程”（出版中）。