Experimental Observation of Negative Capacitance in Ferroelectrics at Room Temperature

Appleby, Daniel J. R.; Ponon, Nikhil; Kwa, Kelvin S. K.; Zou, Bin; Petrov, Peter K.; Wang, Tianle; Alford, Neil McN.; O'Neill, AG

doi:10.1021/nl5017255

Cited by 220 publications

(121 citation statements)

References 17 publications

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“…In the presence of the intermediate metal electrode between the ferroelectric and the dielectric capacitor, the dielectric capacitor does not result in a depolarizing field in the ferroelectric at V S ¼ 0-this is unlike the cases in ferroelectric-dielectric heterostructures without intermediate metallic layers. 7,8,11,12,15 As such, the ferroelectric can be polarized even at V S ¼ 0. 22 For the homogeneous switching simulations (details in Sec.…”

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confidence: 99%

“…The fact that the ferroelectric material can exhibit such a state of negative capacitance has already been demonstrated. 3,4,[6][7][8][9][10][11][12][13][14][15][16][17][18] Therefore, if another dielectric capacitor is placed in series with the ferroelectric [as shown schematically in Fig. 1(b)], a voltage amplification is expected across the dielectric capacitor.…”

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confidence: 99%

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Differential voltage amplification from ferroelectric negative capacitance

Khan

Hoffmann

Chatterjee

et al. 2017

Applied Physics Letters

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It is well known that one needs an external source of energy to provide voltage amplification. Because of this, conventional circuit elements such as resistors, inductors or capacitors cannot provide amplification all by themselves. Here, we demonstrate that a ferroelectric can cause a differential amplification without needing such an external energy source. As the ferroelectric switches from one polarization state to the other, a transfer of energy takes place from the ferroelectric to the dielectric, determined by the ratio of their capacitances, which, in turn, leads to the differential amplification. This amplification is very different in nature from conventional inductor-capacitor based circuits where an oscillatory amplification can be observed. The demonstration of differential voltage amplification from completely passive capacitor elements only, has fundamental ramifications for next generation electronics. Free Energy Charge C<0 a Time Source Voltage Ferroelectric Capacitor Voltage Amplification b FIG. 1: Voltage amplification due to ferroelectric negative capacitance: (a) Energy landscape of a ferroelectric capacitor. The capacitance, C, is negative in the region enclosed by the dashed box. (b) The experimental setup.

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confidence: 99%

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Differential voltage amplification from ferroelectric negative capacitance

Khan

Hoffmann

Chatterjee

et al. 2017

Applied Physics Letters

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“…The NC concept is obviously very attractive because it could enable low-voltage/low-power operation in field effect transistors [50][51][52]. Experimental work on Pb(Zr 0.2 Ti 0.8 )O 3 /SrTiO 3 (STO) [51], Ba 0.8 Sr 0.2 TiO 3 /LaAlO 3 (LAO) [52], and BaTiO 3 (BTO)/STO [53] shows that the capacitance of the constituent FE layer could be negative because the composite capacitance is larger than the capacitance of the STO or LAO layer. We note that NC and a negative dielectric constant from the FE layer can indeed be obtained if the CIS methodology is applied to a FE/DE or FE/PE bilayer or superlattice.…”

Section: Discussionmentioning

confidence: 99%

Are ferroelectric multilayers capacitors in series?

et al. 2015

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We show that ferroelectric multilayers are not simple capacitors in series (CIS) and treating these as CIS may lead to misinterpretation of experimental results and to erroneous conclusions. Here, we present a theoretical model of ferroelectric bilayers using basic thermodynamics taking into account the appropriate electrical boundary conditions and electrostatic fields. The spontaneous polarization mismatch in ferroelectric/ferroelectric (FE/FE), FE/paraelectric (FE/PE), and FE/dielectric (FE/DE) bilayers results in a non-linear electrostatic coupling which produces significant deviations in the overall dielectric response if it is computed using the simple capacitor-inseries (CIS) model. Our results show that the CIS approach is a good approximation only for DE/DE multilayers and for FE heterostructures if the individual layers are electrostatically screened from each other.

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“…The key to hysteresis-free FeFET design, which is required for analog and digital applications, is capacitance matching: positive capacitance of intrinsic MOSFET below the ferroelectric should stabilize its negative capacitance. To our knowledge, so far the non-hysteretic electrical characteristics can be experimentally observed in ferroelectric-dielectric bilayer [5,6]. Integration of well-known perovskite-type ferroelectrics on intrinsic MOSFET is very challenging due to issues like low-quality interface, mismatch of thermal expansion coefficients between ferroelectric oxide and Si, and incomplete screening, which have not been addressed [7].…”

Section: Introductionmentioning

confidence: 99%