Ferroelectric Tunneling Junctions for Edge Computing

Covi, Erika; T., Duong, Quang; Lancaster, Suzanne; Havel, Viktor; Coignus, J.; Barbot, J.; Richter, Ole; Klein, P.; Chicca, Elisabetta; Grenouillet, L.; Mikolajick, Thomas; Slesazeck, Stefan

doi:10.1109/iscas51556.2021.9401800

Cited by 17 publications

(14 citation statements)

References 26 publications

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“…The measurement gives important insights into how polarization is stabilized in ferroelectric films, particularly when integrated with an intentional dielectric layer. A rapid polarization loss is seen in the first 100 ms after switching, which is a critical time frame for applications of bilayer FTJs (Covi et al, 2021) or FeFETs (Ni et al, 2018). Indeed, the current arising from backswitching which can be extracted from the rate of polarization loss in Figure 4 is critical when compared to the read current of an FTJ device.…”

Section: Discussionmentioning

confidence: 99%

Investigating charge trapping in ferroelectric thin films through transient measurements

Lancaster

Lomenzo

Engl

et al. 2022

Front. Nanotechnol.

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Section: Discussionmentioning

confidence: 99%

Investigating charge trapping in ferroelectric thin films through transient measurements

Lancaster

Lomenzo

Engl

et al. 2022

Front. Nanotechnol.

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“…The measurement gives important insights into how polarization is stabilized in ferroelectric films, particularly when integrated with an intentional dielectric layer. A rapid polarization loss is seen in the first 100 ms after switching, which is a critical time frame for applications of bilayer FTJs [6] or FeFETs [30]. Indeed, the current arising from backswitching which can be extracted from the rate of polarization loss in figure 4 is critical when compared to the read current of an FTJ device.…”

Section: Discussionmentioning

confidence: 99%

Investigating charge trapping in ferroelectric thin films through transient measurements

Lancaster,

Lomenzo,

Engl

et al. 2022

Preprint

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A measurement technique is presented to quantify the polarization loss in ferroelectric thin films as a function of delay time during the first 100s after switching. This technique can be used to investigate charge trapping in ferroelectric thin films by analyzing the magnitude and rate of polarization loss.Exemplary measurements have been performed on Hf0.5Zr0.5O2 (HZO) and HZO/Al2O3 films, as a function of pulse width and temperature. It is found that the competing effects of the depolarization field, internal bias field and charge trapping lead to a characteristic Gaussian dependence of the rate of polarization loss on the delay time. From this, a charge trapping and screening model could be identified which describes the dynamics of polarization loss on short timescales. IntroductionCharge trapping at the interfaces of ferroelectric (FE) HfO 2 -based thin films plays an important role in both the dynamics of polarization switching and FE device operation. Charge trapping has a significant impact on device operation in the case of FE field-effect transistors (FeFETs) [22,1] as well as ferroelectric tunnel junctions (FTJs) [9]. In both of these devices, an intentional dielectric (DE) layer is added to a metal-ferroelectric-metal (MFM) stack, which will modulate the impact of charge trapping due to the additional FE-DE interface. Assuming fixed and trapped charge densities is necessary in order to fully model the switching behavior of ferroelectric devices with DE layers [8,14]. Nonetheless, charge trapping is also involved in the switching of HfO 2 ferroelectrics without any intentional interfacial layer (IL) [25,16], due to the unavoidable presence of non-switching 'dead layers' at the FE-electrode interfaces [36]. It has been shown that even after switching, the injection of charges can continue to modify switching behaviour by shifting the coercive voltage through a so-called 'fluid imprint ' effect [4]. As such, a thorough understanding of charge trapping, including its origin, how it can be characterized and how it can be improved or harnessed, is clearly necessary, in order to optimize the operation of FE films in real devices.When a non-switching DE layer is introduced between a FE layer and an electrode, numerous impacts on the FE switching need to be considered. Non-switching layers generate a depolarization field which destabilizes 1

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“…26 Thus, spintronic and skyrmion-based devices offer promise for fast, power efficient, nonvolatile inmemory logic operation, which is imperative for the next generation of computing architectures. 27,28 To date, the integration of ferroelectrics on graphene mainly focuses on spin-coated polymers 29 or the exfoliation of graphene onto ferroelectric substrates, 30 either perovskites 31 or, most recently, ferroelectric HZO thin films. 32 For the chemical vapor deposition (CVD) of graphene, where largescale, single-layer graphene (SLG) can be reliably deposited on various metal substrates, 18 subsequent transfer of the film can lead to a deterioration in material quality, 33 while also losing any scaling benefits and the precise control over interface properties.…”

Section: Introductionmentioning

confidence: 99%

Toward Nonvolatile Spin–Orbit Devices: Deposition of Ferroelectric Hafnia on Monolayer Graphene/Co/HM Stacks

Lancaster

Arnay

Guerrero

et al. 2023

ACS Appl. Mater. Interfaces

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While technologically challenging, the integration of ferroelectric thin films with graphene spintronics potentially allows the realization of highly efficient, electrically tunable, nonvolatile memories through control of the interfacial spin−orbit driven interaction occurring at graphene/Co interfaces deposited on heavy metal supports. Here, the integration of ferroelectric Hf 0.5 Zr 0.5 O 2 on graphene/Co/heavy metal epitaxial stacks is investigated via the implementation of several nucleation methods in atomic layer deposition. By employing in situ Al 2 O 3 as a nucleation layer sandwiched between Hf 0.5 Zr 0.5 O 2 and graphene, the Hf 0.5 Zr 0.5 O 2 demonstrates a remanent polarization (2Pr) of 19.2 μC/cm 2 . Using an ex situ, naturally oxidized sputtered Ta layer for nucleation, we could control 2Pr via the interlayer thickness, reaching maximum values of 28 μC/cm 2 with low coercive fields. Magnetic hysteresis measurements taken before and after atomic layer deposition show strong perpendicular magnetic anisotropy, with minimal deviations in the magnetization reversal pathways due to the Hf 0.5 Zr 0.5 O 2 deposition process, thus pointing to a good preservation of the magnetic stack including single-layer graphene. X-ray diffraction measurements further confirm that the highquality interfaces demonstrated in the stack remain unperturbed by the ferroelectric deposition and anneal. The proposed graphenebased ferroelectric/magnetic structures offer the strong advantages of ferroelectricity and ferromagnetism at room temperature, enabling the development of novel magneto-electric and nonvolatile in-memory spin−orbit logic architectures with low power switching.

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Ferroelectric Tunneling Junctions for Edge Computing

Cited by 17 publications

References 26 publications

Investigating charge trapping in ferroelectric thin films through transient measurements

Investigating charge trapping in ferroelectric thin films through transient measurements

Investigating charge trapping in ferroelectric thin films through transient measurements

Toward Nonvolatile Spin–Orbit Devices: Deposition of Ferroelectric Hafnia on Monolayer Graphene/Co/HM Stacks

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