铁电存储器及相关的物理问题

1、不同存储器性能比较不同存储器性能比较铁电存储器铁电存储器(2) 铁电纳米管铁电纳米管n极化开关：极化方向相极化开关：极化方向相反的铁电畴成核、成长、反的铁电畴成核、成长、合并过程合并过程n新畴首先在铁电新畴首先在铁电/电极界电极界面成核，再向前生长面成核，再向前生长（速度（速度103 m/s)t=d/v=10-6m/103m/s=1 ns再向側面生长并合并长大再向側面生长并合并长大直至全部反转直至全部反转（t=E-3/2=20ns to 1)n极化反转快慢是由畴极化反转快慢是由畴界运动速度（畴界动界运动速度（畴界动性）决定，与材料的性）决定，与材料的结构、应力、缺陷有结构、应力、缺陷有关。关。

2、n开关研究的意义：开关研究的意义：1。研究电畴的成核、成研究电畴的成核、成长、合并及与材料结长、合并及与材料结构、缺陷有关，开关构、缺陷有关，开关动力学。动力学。n2存储器读写速度存储器读写速度。APL 76,369 (2001)APL 80,2961 (2002)SrBi2Ta2O9其中，（a）反相畴；（b）180o畴；（c）90o畴； （d）180o反相畴；（e）90o反相畴。 J. of Phys. Cond. Matt. 12，3745（2000）Domain Structure in SrBi2Ta2O9Dark field image with super spot:“d” is

3、anti-phase boundaries (red lines); The boundary between white and dark is 90 domain (black line);“f” is 180 domain boundary (blue lines); “e” is anti-phase +90 domain; Between B and C, anti-phase boundary +180 domain.Appl. Phys. Lett., Vol 76(1), 103 (2000). Bi4Ti3O12 3 layers Oxygen Octahedron (m=3

4、)SrBi2Ta2O9 2 layers Oxygen Octahedron (m=2) (Bi2O2)2+(Am-1BmO3m+1)2-Where:A = Sr2+, Ba2+, Bi3+ et al，B=Ti4+,Ta5+, Nb5+et al，m = 1, 2, 3, 4,5et al。在在 Bi4Ti3O12的，位替代（掺杂）的，位替代（掺杂） Pr , Tc低低; 抗疲劳性好，三层钙态矿结构抗疲劳性好，三层钙态矿结构三层钙态矿结构三层钙态矿结构n铁电存储器铁电存储器(FeRAM)n磁存储器磁存储器 (MRAM)n相变型存储器相变型存储器(PRAM)203040506070 x=0.0

5、0 x=0.46x=0.852 (degree)Intensity (Arb. Units)Bi4-xNdxTi3O12/Pt-Si(0 0 6)(0 0 8)(1 1 1)(0 0 10)(1 1 7)(0 0 12)(0 0 14)Pt(2 2 0)(1 1 15)(0 0 16)(0 2 14)(3 1 7)/(1 3 7)0.00.20.40.60.81.00.29550.29560.29570.29580.29590.29600.29610.2962BiBi4-x4-xNdNdx xTiTi3 3O O1212 d(117) (nm)Nd content, x104105106107

6、10810910101011-30-20-100102030 +P*-(+P) -P*- (-P) Switched Polarization (C/cm2)Switching Cycles (Times)9.13%9.42%-600-400-2000200400600-40-30-20-1001020304010-1100101102103104105-60-40-200204060 Pr (C/cm2)Applied Field (kV/cm) befor after(b) Polarization (C/cm2)Retention Time (s)+P*+P*r-P*r-P*(a)102

7、030405060 Intensity (arb. unit)2q (deg.)BiTBLTBTN0.018BLTN0.018(006)(008)(117)(200)&(020)(0014)Pt (111)(2110)(0214)(2214)0.000.020.040.060.080.100510152025 Polarization(mC/cm2)Nb content (x) BLTN thin films BTN thin films BTN ceramics-400-2000200400-60-40-20020406001020300100200300400 Polarizati

8、on (mC/cm2)Electric field (kV/cm)(a) BLTN0.018 BTN0.018 BLT BiTPr (mC/cm2)Ec(kV/cm)BLTN0.018BTN0.018BLTBiT (b) 0246810-1.0-0.50.00.51.0 BLTN0.018 BLT BiT BTN0.018 Normalized DP (mC/cm2)Log (Switching cycles)0246810-1.5-1.0-0.50.00.51.01.5-1.0-0.50.00.51.01.5-1.5-1.0-0.50.00.51.01.5 Log (Switching cy

9、cles) BLTN0.09 BTN0.09 Normalized D P (mC/cm2) BLTN0.06 BTN0.06 BLTN0.03 BTN0.0310-1100101102103104-50-40-30-20-1001020304050 Polarization (mC/cm2)Rentention Time (s) +P* +P*r -P*r -P*名称缩写名称缩写/m数数材料名称材料名称原料原料烧结温度烧结温度(oC)BW(m=1)Bi2WO6B+WO3940CBT(m=2)CaBi2Ta2O9B+CaO+Ta2O51250SBT(m=2)SrBi2Ta2O9B+SrO+Ta

10、2O51230BBT(m=2)BaBi2Ta2O9B+BaO+Ta2O51050BTT(m=2)Bi3TiTaO9B+TiO2+Ta2O51200BTN(m=2)Bi3TiNbO9B+TiO2+Nb2O51180BTO(m=3)Bi4Ti3O12B+TiO21050BLT(m=3)Bi3.25La0.75Ti3O12B+TiO2+La2O31240BNT(m=3)Bi3.15Nd0.85Ti3O12B+TiO2+Nd2O31270BTO-Nb0.03(m=3)Nb0.03-doped Bi4Ti3O12B+TiO2+ Nb2O51120SBTi(m=4)SrBi4Ti4O15B+TiO2+Sr

11、O1100SBTi-BTO (m=4，3)Bi4Ti3O12- SrBi4Ti4O15B+TiO2+SrO1110SBTi-BLT (m=4，3)Bi3.25La0.75Ti3O12-SrBi4Ti4O15B+TiO2+SrO+ La2O31110SBT-BTN(m=2)(SrBi2Ta2O9 )-(Bi3TiNbO9)B+TiO2+SrO+ Ta2O5+ Nb2O51280材料名称90o畴界形态疲劳特性正交因子r=(a-b)/(a+b)BW(m=1)noneunknown3.610-3CBT(m=2)straightPoor506.0510-3SBT(m=2)high curvedGood16.8710-4BBT(m=2)室温顺电相 0BTT(m=2)straightPoor516.910-3BTN(m=2)straightgood?528.410-3BTO(m=3)straightPoor536.1510-3BLT(m=3)curvedGood353.1610-3BNT(m=3)curvedGood54unknownBTO-Nb(m=3)