This work was supported in part by National Natural Science Foundation of China (Grant Nos. 61804003, 61674008) and in part by China Postdoctoral Science Foundation (Grant Nos. 2019T120017, 2018M630034).
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Figure 1
(Color online) (a) MFM and (b) MFIM structures, where top electrode is biased by $V_{\rm~App}\sin(2\pi~f\cdot~t)$, and bottom electrode is grounded. (c) Measured and simulated $P$-$E$ characteristics of MFM capacitor with 10 nm HZO film, showing the model calibration. Notice that measured slow switching of FE can be obtained by considering distribution of FE parameters.
Figure 2
(Color online) $P$-$E$ characteristics in the MFIM structure with (a) $T_F$ = 50 nm, (b) $T_F$ = 40 nm, (c) $T_F$ = 30 nm,protect łinebreak (d) $T_F$ = 15 nm, (e) $T_F$ = 5 nm, and (f) $T_F$ = 3 nm. Black square is the $P_F$-$E_F$, red circle is the $P_D$-$E_D$, blue triangle is the overall $P$-$E$ of FE-DE bilayer, green dash is the $P_F$-$E_F$ based on the LGD theory. All the simulation parameters are from Table
Figure 3
(Color online) (a) Critical ferroelectric thickness $T_{{\rm~cri},{\rm~A}}$ and $T_{{\rm~cri},{\rm~C}}$ for phase transition of MFIM with various gradient coefficient at equilibrium state ($V_{\rm~App}=0$). (b) Domain patterns at $V_{\rm~App}=0$ at the specified $T_F$ in (a) within region A, B and C, respectively.
Figure 4
(Color online) (a) Domain width versus ferroelectric thickness with different gradient coefficient at equilibrium state ($V_{\rm~App}=0$) for the region B in Figure
Figure 5
(Color online) (a) Voltages ($V_{\rm~DE}$and $V_{\rm~App}$, (b) electric fields, and (c) polarization charges as a function of time in MFIM with $T_F=30$ nm operated at frequency of 1 MHz as shown in Figure
Figure 6
(Color online) (a) $V_{\rm~DE}$-$V_{\rm~App}$ and (b) $A_{v}$-$V_{\rm~App}$ characteristics with different $T_F$.
Figure 7
(Color online) (a) Voltage window and (b) voltage amplification factor for hysteresis-free operation versus $T_F$ with different $k$.
Figure 8
(Color online) $P$-$E$ characteristics in the MFIM structure with different $T_D$ and $\varepsilon_{D}$, accounting for SiO$_2$, Al$_2$O$_3$, and HfO$_2$, respectively. (a)–(c) and (d)–(f) are the $T_D=1$ nm and 5 nm cases. All the simulation parameters are taken from Table
Figure 9
(Color online) (a), (b) $P$-$E$ and (c), (d) $V_{\rm~DE}$-$V_{\rm~App}$ characteristics in the MFIM structure with different values of $\varepsilon_{D}/T_D$ respectively. (a), (c) are the $\varepsilon_{D}/T_D$$\propto{3.9}$cases, and (b), (d) are the $\varepsilon_{D}/T_D$$\propto{10}$cases.
Figure 10
(Color online) (a)–(c) $P$-$E$ characteristics in the MFIM structure with different conductivity ($\Gamma=10$, 0.1 and 0.01 S/m)protect łinebreak operated at $f$ = 1M Hz. (d)–(f) $P$-$E$ characteristics with $\Gamma=10$ S/m operated at $f$ = 1k, 10M and 100M Hz. All the simulation parameters are taken from Table
Figure 11
(Color online) (a) Voltage window and (b) voltage amplification for hysteresis-free operation versus frequency with different $\Gamma$.
Symbol | Quantity | Value |
$\alpha$ | Landau constant of ferroelectric | $-2.9\times10^{8}$ V$\cdot~$m/C |
$\beta$ | Landau constant of ferroelectric | $-4.0\times10^{8}$ V$\cdot$m$^{5}$/C$^{3}$ |
$\gamma$ | Landau constant of ferroelectric | $6.0\times10^{10}$ V$\cdot~$m$^{9}$/C$^{5}$ |
ıtshapek | Gradient coefficient of ferroelectric | $1\times10^{-10}$ V$\cdot~$m$^{3}$/C |
ıtshape$\Gamma$ | Conductivity of polarization switching | 10 S/m |
$\varepsilon_{\rm~Fb}$ | Dielectric constant of ferroelectric | 25 |
$\varepsilon_{D}$ | Dielectric constant of dielectric | 25 |
ıtshapeT$_F$ | Thickness of ferroelectric | 10 nm |
ıtshapeT$_D$ | Thickness of dielectric | 5 nm |
ıtshapeL | Lateral size of simulation region | 50 nm |
ıtshapeV$_{\rm~App}$ | Amplitude of external applied voltage | 10 V |
ıtshapef | Sweep frequency of applied voltage | $10^{6}$ Hz |