“…[8][9][10][11][12][13][14][15] Ferroelectric materials, in particular, perovskites ferroelectrics [8] such as Pb(Zr,Ti)O 3 (PZT), [16][17][18] BaTiO 3 , [19][20][21] and SrBi 2 Ta 2 O 9 [22,23] have been widely studied. However, due to integration challenges with modern complementary metal oxide semiconductor (CMOS) technologyetching, hydrogen sensitivity, thickness, and scaling beyond the 130 nm technology node, [24] industrial applications of perovskite oxides have never been materialized.…”
Hafnia thin films have been under intensive research during the past few years due to its robust ferroelectricity under very thin limit and good compatibility with silicon. The polar crystal structure critical to ferroelectricity in hafnia thin films is metastable, and is generally obtained in polycrystalline thin films, coexisting with other nonpolar phases. Recently, much attention has been focused on epitaxial ferroelectric hafnia thin films to get rid of the nonpolar phases, to investigate the more intrinsic factors to ferroelectricity, and its potential applications. Herein, recent progress on the growth of epitaxial hafnia thin films is reviewed. The epitaxial growth mechanism is explored, in particular, the interface matching, phase stability under temperature and oxygen pressure, followed by discussions on thickness dependency of ferroelectricity, and wake-up effect in hafnia. Finally, an outlook on ferroelectric hafnia both on fundamental studies and future applications is discussed.
“…[8][9][10][11][12][13][14][15] Ferroelectric materials, in particular, perovskites ferroelectrics [8] such as Pb(Zr,Ti)O 3 (PZT), [16][17][18] BaTiO 3 , [19][20][21] and SrBi 2 Ta 2 O 9 [22,23] have been widely studied. However, due to integration challenges with modern complementary metal oxide semiconductor (CMOS) technologyetching, hydrogen sensitivity, thickness, and scaling beyond the 130 nm technology node, [24] industrial applications of perovskite oxides have never been materialized.…”
Hafnia thin films have been under intensive research during the past few years due to its robust ferroelectricity under very thin limit and good compatibility with silicon. The polar crystal structure critical to ferroelectricity in hafnia thin films is metastable, and is generally obtained in polycrystalline thin films, coexisting with other nonpolar phases. Recently, much attention has been focused on epitaxial ferroelectric hafnia thin films to get rid of the nonpolar phases, to investigate the more intrinsic factors to ferroelectricity, and its potential applications. Herein, recent progress on the growth of epitaxial hafnia thin films is reviewed. The epitaxial growth mechanism is explored, in particular, the interface matching, phase stability under temperature and oxygen pressure, followed by discussions on thickness dependency of ferroelectricity, and wake-up effect in hafnia. Finally, an outlook on ferroelectric hafnia both on fundamental studies and future applications is discussed.
“…On the other hand, FeFET and FTJ could provide large dynamic ranges (G On /G Off †10 2 ) with numerous intermediate states. Hence, multi-level spintronic devices can be well suited for implementing frequently updated components such as neurons, while ferroelectric devices are considered to be more suitable for implementing analog synapses, given the device characteristics of large memory windows between states, low read/write energy, fast switching, and superior CMOS compatibility (Khan et al, 2020 ). In the following, we will elaborate particular challenges of implementing crossbar in-memory computing based on ReRAM and PCM materials, and highlight the strength in spintronic and ferroelectric device characteristics that could potentially address some of the challenges.…”
Achieving multi-level devices is crucial to efficiently emulate key bio-plausible functionalities such as synaptic plasticity and neuronal activity, and has become an important aspect of neuromorphic hardware development. In this review article, we focus on various ferromagnetic (FM) and ferroelectric (FE) devices capable of representing multiple states, and discuss the usage of such multi-level devices for implementing neuromorphic functionalities. We will elaborate that the analog-like resistive states in ferromagnetic or ferroelectric thin films are due to the non-coherent multi-domain switching dynamics, which is fundamentally different from most memristive materials involving electroforming processes or significant ion motion. Both device fundamentals related to the mechanism of introducing multilevel states and exemplary implementations of neural functionalities built on various device structures are highlighted. In light of the non-destructive nature and the relatively simple physical process of multi-domain switching, we envision that ferroic-based multi-state devices provide an alternative pathway toward energy efficient implementation of neuro-inspired computing hardware with potential advantages of high endurance and controllability.
“…[4][5][6][7] Ferroelectric field-effect transistor (FeFET) containing a ferroelectric thin film within the gate stack has received extensive interest for the next-generation nonvolatile memory applications, featuring low power consumption, fast write/read speed, and simple structure. [8][9][10] In principle, the memory state or channel conductance is modulated by the polarization of ferroelectric thin film in FeFET, which can be retained after removing gate voltage (i.e., nonvolatility). Multiple nonvolatile memory states could be readily achieved in the FeFETs with multi-domain ferroelectric thin films possessing multipolarization states.…”
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confidence: 99%
“…Multiple nonvolatile memory states could be readily achieved in the FeFETs with multi-domain ferroelectric thin films possessing multipolarization states. [10,11] Indeed, the capability of multilevel programming has been widely reported in the FeFETs gated with Pb(Zr,Ti)O 3 , SrBi 2 Ta 2 O 9 , and PVDF-TrFE ferroelectric thin films, demonstrating attractive potential in the abovementioned multilevel memory and neuromorphic applications. [12][13][14][15] However, because of the poor compatibility with…”
The ferroelectric field-effect transistor (FeFET) is a promising memory technology due to its high switching speed, low power consumption, and high capacity. Since the recent discovery of ferroelectricity in Si-doped HfO 2 thin films, HfO 2 -based materials have received considerable interest for the development of FeFET, particularly considering their excellent complementary metal-oxide-semiconductor (CMOS) compatibility, relatively low permittivity, and high coercive field. However, the multilevel capability is limited by the device size, and multidomain switching tends to vanish when the channel length of the HfO 2 -based FeFET approaches 30 nm. Here, multiple nonvolatile memory states are realized by tuning the electric field gradient across the Hf 0.5 Zr 0.5 O 2 (HZO) ferroelectric thin film along the channel direction of FeFET. The multi-step domain switching can be readily and directionally controlled in the HZO-FeFETs, with a very low variation. Moreover, multiple nonvolatile memory states or multi-step domain switching can be effectively controlled in the FeFETs with a channel length less than 20 nm. This study suggests the possibility to implement multilevel memory operations and mimic biological synapse functions in highly scaled HfO 2 -based FeFETs.
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