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薄膜的结晶和电学性能。随着薄膜厚度的增加，多晶PZT薄膜的晶粒尺寸增大，电流密度减小。随着外延PZT薄膜厚度的增加，电流密度也会降低。由于晶粒尺寸和晶界的厚度依赖性，多晶PZT薄膜比外延PZT薄膜对介电常数和剩余极化的厚度依赖性更强。采用MOCVD法在Pt/SiO_2/Si上生长PZT薄膜，分别观察到voler - waber （V-W）生长模式、SrTiO_3的SrO平面上PZT的V-W生长模式、SrTiO_3的TiO_2平面上PZT的stranski - krstanov （S-K）生长模式和SrRuO_3/SrTiO_3上PZT薄膜的S-K生长模式。通过扫描探针显微镜（SPM）的压响应测量，发现纳米尺寸的PbTiO_3和PZT岛具有铁电性。采用种子两步生长法，在395℃下成功制备了PZT薄膜。通过两步生长过程，观察到PZT薄膜的晶粒尺寸增大，晶体性能和电学性能得到改善。采用SPM压电响应测量方法，观察了压电陶瓷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速度。采用MOCVD技术，在400℃下成功制备了具有Ir/PZT/Ir/SiO_2/Si结构的平面PZT电容器和三维PZT电容器。在SrRuO_3/SrTiO_3表面成功制备了20nm厚的具有铁电性的超薄PZT薄膜。

项目成果

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）。

M.Shimizu et al.: "Effects of Film Thickness and Grain Size on the Electrical Properties of Pb (Zr,Ti) O_3 Thin Films Prepared by MOCVD"Ferroelectrics. 241. 188-190 (2000)

M.Shimizu等人：“薄膜厚度和晶粒尺寸对MOCVD制备的Pb(Zr,Ti)O_3薄膜电性能的影响”铁电体。

H.Fujisawa et al.: "Low-Temperature Fabrication of Ir/Pb(Zr, Ti)O_3/Ir Capacitors Solely by Metalorganic Chemical vapor Deposition"Japanese Journal of Applied Physics. 40. 5551-5553 (2001)

H.Fujisawa等人：“仅通过金属有机化学气相沉积低温制造Ir/Pb(Zr,Ti)O_3/Ir电容器”，日本应用物理学杂志。

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。