Nd0.7Sr0.3MnO3陶瓷EPIR效应的起源

用两线法和四线法对球磨合成后热处理的Nd_0.7Sr_0.3MnO₃陶瓷样品的电脉冲诱导电阻转变(EPIR)效应进行了测试.结果表明:在Nd_0.7Sr_0.3MnO₃块体中用四线法测得的I-V曲线为非线性,说明Nd_0.7Sr_0.3MnO₃样品在晶(相)界处存在空间电荷层和界面电阻.但用四线法测量EPIR效应时,没有EPIR效应发生,表明晶(相)界处的空间电荷层和肖特基势垒不能产生EPIR效应;对同一样品采用直流两线法测量,其I-V曲线也为非线性,但却发生明显的EPIR效应.说明在Nd_0.7Sr_0.3MnO₃陶瓷中发现的EPIR效应起源于样品与电极之间的接触界面,块体内的晶(相)界处虽能产生相似I-V特性,但却不能发生EPIR效应. 关键词： 电脉冲诱导电阻转变(EPIR) 亚锰酸盐 空间电荷层 I-V非线性')" href="#">I-V非线性     

La0.5Ca0.5MnO3内禀与界面电脉冲诱导电阻转变效应的比较

一般地,钛矿结构锰氧化物的电脉冲诱导电阻转变(EPIR) 效应源于非内禀界面处的肖特基势垒. 本文采用固相烧结法制备了La_0.5Ca_0.5MnO₃ (LCMO)陶瓷样品, 用四线测量模式对样品电输运性质, 特别对其内禀EPIR效应和忆阻器行为进行了研究. 室温下, 尽管样品在四线测量模式下的I-V特性曲线呈欧姆线性规律, 但在适当的脉冲电压刺激下, 仍能诱导产生明显、稳定的EPIR效应. 通过与二线模式的界面EPIR比较, 发现LCMO内禀EPIR效应具有更小的脉冲临界电压、更好的稳定性和抗疲劳特性, 是稀土掺杂锰氧化物中观察到的一类新颖的EPIR效应. 关键词： 钙钛矿结构锰氧化物 电致电阻效应 电脉冲诱导电阻转变效应 肖特基势垒     

Nd0.7Sr0.3MnO3陶瓷中界面“陷阱态”相关电阻转变行为

通过固相烧结和高能球磨后热处理两种方法分别得到不具晶(相)界和具有明显晶(相)界的两种Nd_0.7Sr_0.3MnO₃陶瓷样品, 并用两线法和四线法分别对这两种样品的电极-块体接触界面和晶(相)界界面的I-V和电脉冲诱导电阻转变效应(EPIR)进行研究. 结果发现, 在两线法测试下, 电极-块体界面具有回滞的非线性I-V特征, 并能产生稳定的EPIR效应, EPIR的稳定性随温度的升高逐渐减弱并消失; 而对具有明显晶(相)界的陶瓷样品, 四线法测试结果表明, 虽然其I-V行为也具有非线性和回滞性特点, 但不能产生EPIR 效应. 这些奇特的界面输运行为与界面中的各种缺陷充当“陷阱”并实现对载流子的捕捉和释放过程密切相关. 而大量的晶(相)界界面及其复杂的连接方式导致较大的漏导则是晶(相)界不能出现EPIR效应的主要原因.     

Nd1-xSrxMnO3中掺杂浓度对电脉冲诱导电阻转变效应的影响

采用两线测量模式对固相烧结方法制备的Nd_1-xA_xMnO₃ (A= Ba, Ca, Sr,x= 0-0.9) 陶瓷样品电脉冲诱导电阻转变(EPIR)效应和I-V特性进行了测量. 结果表明, 与Nd_0.7Sr_0.3MnO₃一样, 相同浓度掺杂的Nd_0.7Ba_0.3MnO₃和Nd_0.7Ca_0.3MnO₃ 样品也能诱发稳定的室温EPIR效应. 进一步对Nd_1-xSr_xMnO₃系列样品的EPIR研究表明, 这种界面相关的EPIR效应与样品中电子或空穴掺杂浓度密切相关, 在半掺杂 (x= 0.5)附近, 样品与电极接触界面能诱发稳定的EPIR效应. 然而, 随掺杂浓度的进一步增大或降低, EPIR效应逐渐出现减弱、不明显到完全消失的过程. 产生这种现象的原因可能与锰氧化物中由于掺杂浓度差异所导致的界面缺陷在不同极性脉冲激励下重新分布而产生的内电场强弱有关.     

Nd0.7Sr0.3MnO3中显微结构相关电致电阻效应

用固相反应和高能球磨合成后续热处理两种方法分别得到钙钛矿结构Nd_0.7Sr_0.3MnO₃氧化物.两种不同方法得到的多晶样品,虽然晶体结构相同,化学成分和晶粒大小相近,但它们电输运性质却表现出很大差异.用固相反应法制得的样品的电阻几乎不随负载电流的变化而变化,即不表现电致电阻行为;而通过高能球磨合成后续热处理方法得到的样品电阻随外加电流增大而急剧减小,出现显著电致电阻效应.产生这种截然不同电输运特性的原因可能与样品的显微结构和界面性质有关. 关键词： 电致电阻效应 显微结构 钙钛矿结构锰氧化物 界面电阻     

MgB2超导线和不同电极材料之间接触电阻的研究

我们用四引线法测量了MgB2超导线和不同电极材料之间的接触电阻,电极材料包括金,铟和银胶,实验数据显示,用热蒸发镀膜的方法制备上的金属材料电极和超导线之间有较小的接触电阻,对电极材料进行后期的退火处理可以有效的降低接触电阻的大小。     

点接触金属/Pr$lt;sub$gt;0.7$lt;/sub$gt;Ca$lt;sub$gt;0.3$lt;/sub$gt;MnO$lt;sub$gt;3$lt;/sub$gt;/Pt结构稳定的低电流电阻开关特性

利用自主开发的导电原子力显微镜控制Pt,W探针构成点接触金属/Pr_0.7Ca_0.3MnO₃（PCMO）/Pt三明治结构,对其电流-电压（I-V）及脉冲诱导电阻开关（EPIR）特性进行了研究.研究发现,在10 nA限流下两种电极对应结构的I-V都表现出相当稳定的双极性电阻开关特性,以及大于100的电阻开关比.进一步测试发现,点接触W/PCMO/Pt器件具有在10 nA限流下稳定的EPIR特性以及100 pA限流下重复的双极性电阻开关特性.此电流比已报道的电流低3个数量级,表明此结构在低功耗存储器件方面的潜在应用.通过对比样品不同位置、不同限流、不同接触面积点接触Pt/PCMO/Pt的I-V回滞特性,把点接触器件在低电流下稳定、显著的电阻开关效应归结于小的器件面积导致强的局域电场加强了O离子迁移效应. 关键词： 脉冲诱导电阻开关 电场下氧离子迁移 电阻开关     

Nd0.67Sr0.33MnOy(y<3.0)中的自旋相关电致电阻效应

用固相反应法制备系列Nd_0.67Sr_0.33MnO_y(y = 3.00—2.80)多晶样品.样品输运性质表现出自旋相关电致电阻特征.对氧含量等于化学计量样品，在测量温度范围内电阻不随负载电流变化，I-V曲线符合线性欧姆定律.对氧含量低于化学计量样品，当高于某一特征温度时，电阻变化符合线性欧姆定律；但低于这一特征温度时，电阻大小与负载电流有关，I-V曲线偏离线 关键词： 钙钛矿结构锰氧化物 电致电阻效应 自旋相关界面输运 氧缺陷     

钙钛矿结构Pr1－xCaxMnO3薄膜中电脉冲诱导电阻值变化的理论研究

建立一个有效的三明治隧穿模型研究在Pr_1-xCa_xMnO₃薄膜中电流脉冲引起的电阻改变(EPIR)性质，发现载流子在三明治结构各区域间的隧穿概率以及在不均匀界面层的导通概率对材料的EPIR值产生重要影响.还研究了电流-电压曲线中的迟滞效应，得到的结果与近年来的文献报道一致. 关键词： 强关联电子系统 金属-氧化物界面 隧穿     

点接触金属/Pr0.7Ca0.3MnO3/Pt结构稳定的低电流电阻开关特性

利用自主开发的导电原子力显微镜控制Pt,W探针构成点接触金属/Pr0.7Ca0.3MnO3(PCMO)/Pt三明治结构,对其电流-电压(I-V)及脉冲诱导电阻开关(EPIR)特性进行了研究.研究发现,在10 nA限流下两种电极对应结构的I-V都表现出相当稳定的双极性电阻开关特性,以及大于100的电阻开关比.进一步测试发现,点接触W/PCMO/Pt器件具有在10 nA限流下稳定的EPIR特性以及100 pA限流下重复的双极性电阻开关特性.此电流比已报道的电流低3个数量级,表明此结构在低功耗存储器件方面的潜在应用.通过对比样品不同位置、不同限流、不同接触面积点接触Pt/PCMO/Pt的I-V回滞特性,把点接触器件在低电流下稳定、显著的电阻开关效应归结于小的器件面积导致强的局域电场加强了O离子迁移效应.     

Interface-engineered resistive switching in Ag/SrTiO3/Nd0.7Ca0.3MnO3/YBa2Cu3O7 heterostructures

For Ag/Nd_0.7Ca_0.3MnO₃/YBa₂Cu₃O₇ (Ag/NCMO/YBCO) heterostructures, we investigate effects of an SrTiO₃ (STO) buffer layer inserted into the Ag/NCMO interface upon the room-temperature resistive switching. In comparison with the non-buffered (Ag/NCMO/YBCO) structure, the insertion of the STO buffer layer can greatly enhance the electric-field-induced-resistance (EPIR) effect. The STO-buffered (Ag/STO/NCMO/ YBCO) device can be switched on-and-off between the higher to lower resistance states at an EPIR ratio of 253% with pulsed voltage ±1.5 V and 405% with pulsed voltage ±3.0 V. The enhanced EPIR ratio is attributed to a combined effect of the migration of oxygen vacancies near the interface and ferroelectric polarization of the STO buffer.     

Resistance switching in Fe-doped P0.7Ca0.3MnO3 thin films

An enhanced electric-pulse-induced resistance (EPIR) switching effect is observed in the Ag/P_0.7Ca_0.3Mn_1 − xFe_xO₃/YBa₂Cu₃O₇ (Ag/PCMFO/YBCO) and Ag/(PCMFO/PCMO)/YBCO structures. Unlike in the PCMO-based EPIR devices, where the Ag/PCMO interface plays a crucial role, both the Ag/PCMFO interface and the bulk PCMFO are found to have significant contributions to the EPIR switching of the PCMFO-based device. A possible explanation is to extend the pulse-driven oxygen ion/vacancy motion model at the metal/PCMO interface region to the bulk PCMFO.     

Electric pulse-induced resistive switching in ceramic interfaces

We show the existence of a reversible, complementary and polarity dependant electric pulse-induced resistance (EPIR) switching effects in Au/YBa₂Cu₃O_7-δ ceramic superconductor interfaces. Non-volatile high and low resistance states and transition regions between them are obtained as a function of the amplitude and polarity of the pulsing voltage. Relaxation processes of the resistivity after applying the pulses, not associated with heating effects, are also observed. We also report on the temperature sensitivity of these resistance hysteresis switching loops, where both the difference between high and low resistance states and the voltage needed to produce the switching decrease with increasing temperature. Our results are consistent with a mechanism for the EPIR effect based on oxygen electromigration.     

Electric-pulse-induced resistance switching in Nd0.7Sr0.3MnO3 ceramics

Nonlinear and hysteretic current–voltage characteristics and electric-pulse-induced resistance (EPIR) switching effects were found in Nd_0.7Sr_0.3MnO₃ ceramics. For samples measured using the two-wire method, a polarity-dependent, stable and reproducible EPIR effect occurs in the whole temperature range measured. The high and low resistive metastates vary with temperature and seemingly can be destroyed by temperatures larger than 400 K. However, for the same sample measured using the four-wire method, no EPIR effect is observed. The result indicates that the EPIR effect is intensively correlated with the interface between the Ag-electrodes and the bulk of the Nd_0.7Sr_0.3MnO₃ polycrystal.     

“Positive” and “negative” electric-pulse-induced reversible resistance switching effect in Pr<Subscript>0.7</Subscript>Ca<Subscript>0.3</Subscript>MnO<Subscript>3</Subscript> films

“Negative” electric-pulse-induced reversible resistance (EPIR) switching phenomenon was found in In/PCMO/Pt sandwich, in which the high resistance can be written with positive voltage pulses, and the low resistance can be reset using negative voltage pulses (the positive voltage direction is defined as going from the top electrode to the bottom electrode). This is just the opposite from the “positive” EPIR effect in Ag/PCMO/Pt sandwich, in which the high resistance can be written only with negative voltage pulses, and the low resistance can be reset using positive voltage pulses. The I–V hysteresis curves of In/PCMO/Pt and Ag/PCMO/Pt sandwiches also show opposite directions, i.e., counterclockwise and clockwise under a negative voltage region for indium and Ag electrode systems, respectively. C–V characteristics show that the barrier does not exist in Ag/PCMO/Pt sandwich, while In/PCMO/Pt sandwich exhibits an obvious Schottky-like barrier. We suggest that in the negative EPIR behavior in In/PCMO/Pt structure, the resistance states are mainly controlled changing the Schottky-like barrier at the interface with the weak effect of carrier trapping process, while the positive EPIR behavior in Ag/PCMO/Pt sandwich mainly depends on the carrier trapping process at the interface. PACS 72.80.-r; 73.40.-C; 75.70.-i