Enhancement of Ferroelectric Polarization Stability by Interface Engineering

Lu, Haidong; Liu, X.; Burton, John; Bark, Chung Wung; Wang, Y.; Zhang, Y.; Kim, D. J.; Stamm, Alexander; Lukashev, Pavel; Felker, D. A.; Folkman, C. M.; Gao, Peng; Rzchowski, M. S.; Pan, Xiaoqing; Eom, C. B.; Tsymbal, Evgeny Y.; Gruverman, Alexei

doi:10.1002/adma.201104398

Cited by 127 publications

(105 citation statements)

References 36 publications

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“…We can use the relationship between T and the spin current in Eq. (15) to elucidate the origin of the effect. In Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Fairly recently the persistence of ferroelectricity down to nanometer-thick films was confirmed theoretically 9,10 and experimentally 11,12 . Moreover, the ferroelectric polarization can be stabilized and enhanced via lateral strain and/or interface engineering [13][14][15] . These developments have opened new possibilities to use ferroelectric materials as active barriers in ferroelectric and multiferroic tunnel junctions (FTJs and MFTJs) 16,17 .…”

Section: Introductionmentioning

confidence: 99%

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Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions

et al. 2015

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Based on model calculations we predict electric-field control of the spin transfer torque (STT) in magnetic tunnel junctions with ferroelectric barriers. We demonstrate that the bias dependence of the in-plane, T , and out-of-plane, T ⊥ , components of the STT can be dramatically modified by the ferroelectric polarization. In particular, the magnitude of the STT can be enhanced or suppressed by switching the polarization direction and in some cases the sign of STT can be toggled. The underlying mechanism is the combination of polarization-induced symmetry breaking and the interplay of the bias-induced and polarization-induced spin-dependent screening giving rise to a rich behavior of the electrostatic potential energy profile. These properties could lead to enhanced switching efficiency in STT-based devices and open a new avenue for applications of multiferroic devices.

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“…We can use the relationship between T and the spin current in Eq. (15) to elucidate the origin of the effect. In Fig.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions

et al. 2015

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“…Moreover, we anticipate the possibility of spin-polarization control over a broader range of values, including a change between positive and negative. This additional tunability can be achieved by changing the doping level on the ferroelectric, as well as using interface engineering to adjust the Schottky barrier at the interface [34,35] and/or enhance ferroelectric polarization stability [36]. The detection of spin polarization may be achieved using methods similar to those adopted in the studies of spin injection into semiconductors [3][4][5][6][7][8].…”

Section: Fig 1 (Color Online)mentioning

confidence: 99%

Electric Control of Spin Injection into a Ferroelectric Semiconductor

et al. 2015

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“…An ultrathin barrier results in a large tunneling current, which facilitates easy signal readout and device scaling. However, serious undesirable effects, including the FE dead layer, 22 pinned interface dipole, [23][24][25] and leakage current, 11,18,26 arise and degrade the device performance.…”

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confidence: 99%

Overcoming the Fundamental Barrier Thickness Limits of Ferroelectric Tunnel Junctions through BaTiO₃/SrTiO₃ Composite Barriers

et al. 2016

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ABSTRACT:Ferroelectric tunnel junctions (FTJs) have attracted increasing research interest as a promising candidate for non-volatile memories. Recently, significant enhancements of tunneling electroresistance (TER) have been realized through modifications of electrode materials.However, direct control of the FTJ performance through modifying the tunneling barrier has not been adequately explored. Here, adding a new direction to FTJ research, we fabricated FTJs with Ferroelectric tunnel junctions (FTJs), composed of a thin ferroelectric (FE) layer sandwiched in between two metallic electrodes, have been intensively investigated in recent years. This device is considered to be a promising candidate for next-generation nonvolatile memories, because it combines the advantages of both ferroelectric random-access-memory and resistiveswitching memory. 1-3 The concept of FTJ was first proposed by Esaki in 1971, 4 but the research activities have not flourished untixl this decade. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] The operation of FTJs has been mainly explained in terms of interfacial screening of polarization charges. [5][6][7][8] In a metal 1(M1)/FE/metal 2 (M2) structured FTJ (Figure 1a), the two asymmetric electrodes lead to unequal screen lengths and potential changes at metal/FE interfaces. Depending on the polarizations, the electrostatic potential profile of tunneling barrier will be varied. As a result, the tunneling resistance can be switched between low (ON) and high (OFF) values by polarization reversal, leading to the socalled tunneling electroresistance (TER) effect.Extensive experimental works based on this asymmetric screening scenario have been reported during the last decade. In 2009, the TER effect was first demonstrated using conducting atomic force microscopy (CAFM). 9-11 Subsequently, FTJs with highly reproducible performance were realized in capacitor geometry, which will be useful for practical applications. 12,13 Up to recently, most studies of FTJs have focused on improving device performance by modifying the electrode materials. [14][15][16][17][18][19][20] Typical examples include the use of lightly doped semiconductors, [14][15][16] For a thick barrier, these obstacles can be avoided, but the tunneling current becomes too small for realizing a practically useful device. As an alternative, several groups have theoretically proposed a new kind of FTJ using an FE/paraelectric (FE/PE) composite barrier. 27,28 The PE layer provides a new route to control the tunneling barrier potentials, and thus the TER can be tuned and significantly enhanced. However, there have been few experimental efforts to systematically attest this theoretical prediction. 29 In this paper, we report experimental control of the TER effect by directly manipulating the tunneling barrier thickness and composition. For this purpose, we fabricated two types of FTJs: Figure S5), which further confirm good epitaxial film qualities.We estimated the lattice constants of the oxide layers from XRD reci...

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Enhancement of Ferroelectric Polarization Stability by Interface Engineering

Abstract: By using theoretical predictions based on first-principle calculations, we explore an interface engineering approach to stabilize polarization states in ferroelectric heterostructures with a thickness of just several nanometers.

Cited by 127 publications

References 36 publications

Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions

Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions

Electric Control of Spin Injection into a Ferroelectric Semiconductor

Overcoming the Fundamental Barrier Thickness Limits of Ferroelectric Tunnel Junctions through BaTiO₃/SrTiO₃ Composite Barriers

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Enhancement of Ferroelectric Polarization Stability by Interface Engineering

Abstract: By using theoretical predictions based on first-principle calculations, we explore an interface engineering approach to stabilize polarization states in ferroelectric heterostructures with a thickness of just several nanometers.

Cited by 127 publications

References 36 publications

Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions

Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions

Electric Control of Spin Injection into a Ferroelectric Semiconductor

Overcoming the Fundamental Barrier Thickness Limits of Ferroelectric Tunnel Junctions through BaTiO3/SrTiO3 Composite Barriers

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Overcoming the Fundamental Barrier Thickness Limits of Ferroelectric Tunnel Junctions through BaTiO₃/SrTiO₃ Composite Barriers