On a Novel Ferro Resistive Random Access Memory (FRRAM): Basic Model and First Experiments

Meyer, René; Contreras, J. Rodrı́guez; Petraru, A.; Kohlstedt, H.

doi:10.1080/10584580490893655

Cited by 28 publications

(31 citation statements)

References 8 publications

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“…[20][21][22][23]27,28 Nonetheless, from I-V characteristics alone it might be a risky task to conclude the nature of the underlying mechanism. 19,26,28,30 Therefore, it is critical to be able to distinguish a ferroelectric switching from that of a nonferroelectric origin, and this forms the motivation for this letter.…”

Section: Methods To Distinguish Ferroelectric From Nonferroelectric Ormentioning

confidence: 99%

“…[20][21][22][23][24][25][26][27][28] In the case of ferroelectrics, the issue is further complicated by characteristics such as interface properties, i.e., the barrier height and the sign of the remnant charge of the ferroelectric material. [20][21][22][23]27,28 Nonetheless, from I-V characteristics alone it might be a risky task to conclude the nature of the underlying mechanism. 19,26,28,30 Therefore, it is critical to be able to distinguish a ferroelectric switching from that of a nonferroelectric origin, and this forms the motivation for this letter.…”

Section: Methods To Distinguish Ferroelectric From Nonferroelectric Ormentioning

confidence: 99%

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Method to distinguish ferroelectric from nonferroelectric origin in case of resistive switching in ferroelectric capacitors

Kohlstedt

Petraru

Szot

et al. 2008

Applied Physics Letters

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We present investigations on the resistive switching effect in SrRuO3∕PbZr0.2Ti0.8O3∕Pt ferroelectric capacitors. Using a conductive atomic force microscope, the out-of-plane piezoelectric response and the capacitive and resistive current were simultaneously measured as a function of applied bias voltage. We observed two independent switching phenomena, one attributed to the ferroelectric switching process and the other to resistive switching.We show that I-V curves alone are not sufficient in ferroelectric materials to clarify the underlying switching mechanism and must be used with sufficient caution.

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Section: Methods To Distinguish Ferroelectric From Nonferroelectric Ormentioning

confidence: 99%

Section: Methods To Distinguish Ferroelectric From Nonferroelectric Ormentioning

confidence: 99%

Method to distinguish ferroelectric from nonferroelectric origin in case of resistive switching in ferroelectric capacitors

Kohlstedt

Petraru

Szot

et al. 2008

Applied Physics Letters

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“…As a result, different profiles of the inner electric potential and different local conductivities across the film give rise to a polarization dependent conductivity. In a recent paper, 13 we proposed a model of the resistive switching by taking into account nonferroelectric interfacial layers. The presence of nonferroelectric interface layers lead to an incomplete screening of the polarization charge.…”

Section: Type-i Ferroresistive Devicementioning

confidence: 99%

Hysteretic resistance concepts in ferroelectric thin films

Meyer

Waser

2006

Journal of Applied Physics

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Hysteretic resistance effects based on a correlation between ferroelectric polarization and conductivity might become of particular interest for nonvolatile memory applications, because they are not subject to the scaling restrictions of charge based memories such as the ferroelectric random access memory. Two basic concepts, a metal-ferroelectric-metal structure and a metal-ferroelectric-semiconductor structure are discussed in the literature. This contribution discusses the principle of operation of those concepts in terms of the band model. A generalized model is proposed, which is based on a conductive metal-ferroelectric-semiconductor-metal structure. Here, the existence of a low and a high conductive state originates from a switch of the polarization in the ferroelectric layer and a resulting positive or negative polarization charge at the ferroelectric-semiconductor interface. Charge carriers in the film are attracted by or depleted at the interface giving rise to different local conductivities. By simulation, the effect of internal screening caused by mobile charge carriers on the hysteretic current-voltage behavior and the depolarizing field in the ferroelectric are estimated. The simulation discloses a switching ratio up to several orders of magnitude and a conductivity window, which scales with the donor concentration. It may also explain resistive switching in systems consisting only of one ferroelectric layer by assuming the presence of nonferroelectric interface layers.

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“…Mechanisms under discussion are ͑i͒ trapping/detrapping effects and charge transfer processes via donor and acceptor levels ͑Cr 3+ /Cr 4+ ͒, 10,13 ͑ii͒ a Mott metal-insulator transition, 14 ͑iii͒ formation of local current domains, 12 ͑iv͒ redox processes of extended defects, 15 and ͑v͒ conductivity changes due to a reversal of a local spontaneous polarization. 16 Polarization changes might not be stringently of ferroelectric nature, but might also be due to defect dipoles, e.g., formed by acceptor/oxygen vacancy defect associates. 17 In our present work, we investigate resistive switching of 0.2% chromium-doped Ba 0.7 Sr 0.3 TiO 3 ͑BST͒ capacitorlike thin films of around 40 nm thickness at RT.…”

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confidence: 99%

Resistive switching and data reliability of epitaxial (Ba,Sr)TiO3 thin films

Oligschlaeger

Waser

Meyer

et al. 2006

Applied Physics Letters

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118

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We report on resistive switching of capacitor-like SrRuO 3 /Ba 0.7 Sr 0.3 TiO 3 / Pt thin films epitaxially grown on SrTiO 3 substrates. We observe a weak but stable hysteresis in the current-voltage curve. By applying short voltage pulses, a high or low resistive state as well as intermediate states can be addressed even at room temperature. We demonstrate a multiple-branch hysteresis curve corresponding to multilevel switching modus revealing different subloops for different write voltages. Furthermore reliability issues such as cycling endurance and data retention are presented. 10 Here, different resistance levels could be addressed by a variation of length and amplitude of the programming voltage pulse. There is still some debate about the physical mechanisms of the resistance change and about the key experimental parameters. Mechanisms under discussion are ͑i͒ trapping/detrapping effects and charge transfer processes via donor and acceptor levels ͑Cr 3+ /Cr 4+ ͒, 10,13 ͑ii͒ a Mott metal-insulator transition, 14 ͑iii͒ formation of local current domains, 12 ͑iv͒ redox processes of extended defects, 15 and ͑v͒ conductivity changes due to a reversal of a local spontaneous polarization. 16 Polarization changes might not be stringently of ferroelectric nature, but might also be due to defect dipoles, e.g., formed by acceptor/oxygen vacancy defect associates. 17 In our present work, we investigate resistive switching of 0.2% chromium-doped Ba 0.7 Sr 0.3 TiO 3 ͑BST͒ capacitorlike thin films of around 40 nm thickness at RT. We investigate in detail multibranch type I͑V͒ curves, which have not been reported for perovskites dielectrics so far. We will present detailed measurements of the multilevel switching and focus on reliability issues such as cycling endurance and data retention.SrRuO 3 ͑SRO͒ bottom electrodes of 100 nm thickness and BST layer of 40 nm thickness are grown in situ epitaxially on single crystalline ͑100͒ oriented SrTiO 3 ͑STO͒ substrates. The films are deposited by pulsed laser ablation while maintaining a substrate temperatur of 700°C and an oxygen base pressure of 0.25 mbar. The epitaxial growth of the bilayers is confirmed by x-ray diffraction measurements ͓Phil-ips PW 3020 ͑Cu K␣͔͒. Pt top electrodes are deposited by sputtering and patterned by optical lithography and a lift-off process to areas of 0.09 mm 2 down to 100 m 2 . The bottom electrode is contacted after removing the BST film from the sample edge by wet chemical etching. A postannealing step in oxygen is performed at 700°C for 5 min. The currentvoltage characteristics are measured with a Keithley 2410 source meter. To protect samples from damages due to high currents a current compliance is used. All samples reveal low initial resistances so that a high voltage treatment prior to quasistatic I͑V͒ characterization or pulse measurements to convert the sample from an insulating state into a low conductive state as described in Ref. 11 for SrTiO 3 single crystals ͑"forming process"͒ is not required here. The stable switching behavior r...

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On a Novel Ferro Resistive Random Access Memory (FRRAM): Basic Model and First Experiments

Cited by 28 publications

References 8 publications

Method to distinguish ferroelectric from nonferroelectric origin in case of resistive switching in ferroelectric capacitors

Method to distinguish ferroelectric from nonferroelectric origin in case of resistive switching in ferroelectric capacitors

Hysteretic resistance concepts in ferroelectric thin films

Resistive switching and data reliability of epitaxial (Ba,Sr)TiO3 thin films

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