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SHG on 1L/2L MoS2/PZT and bare PZT. a,b) R‐SHG mapping of a) bare PZT and b) the MoS2/PZT sample in Figure 1e. The open arrows show the incident light polarization direction. Scale bars: 3 µm. c) SHG intensity profiles taken on the same MoS2/PZT sample with the background signal subtracted. T‐SHG intensity for MoS2/PZT along the dashed arrow in Figure 1e (top panel); R‐SHG intensity for MoS2/PZT and bare PZT along the vertical arrows (middle panel) and horizontal arrows (bottom panel) in (a,b). The dashed lines indicate the DW positions.
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Two-dimensional transition metal dichalcogenides (TMDCs) such as MoS2 exhibit exceptionally strong nonlinear optical responses, while nanoscale control of the ampltiude, polar orientation, and phase of the nonlinear light in TMDCs remains challenging. In this work, by interfacing monolayer MoS2 with epitaxial PbZr0.2 Ti0.8 O3 (PZT) thin films and f...
Citations
... 8 The flexible nature also facilities strain engineering via stretchable or corrugated base layers, which leads to substantial modulation of their bandgap, 10 coercive field (E c ), 11,12 dielectric permittivity, 12 ferroelastic domains, 13 and photovoltaic response. 14 Unlike epitaxial complex oxide heterostructures, whose preparation imposes stringent requirements for the structural similarity between the constituent layers, 15 ferroelectric oxide membranes can be easily integrated with the mainstream Si platform 12,16,17 and two-dimensional (2D) van der Waals materials 18,19 for developing flexible nanoelectronics, optics, and energy applications. 3,20,21 It also possesses distinct advantages compared with ferroelectric polymers 22 and 2D van der Waals ferroelectrics 23 for its high Curie temperature (T C ), large polarization (P), and scalable synthesis. ...
... 3,20,21 It also possesses distinct advantages compared with ferroelectric polymers 22 and 2D van der Waals ferroelectrics 23 for its high Curie temperature (T C ), large polarization (P), and scalable synthesis. A wide range of device concepts have been realized based on ferroelectric oxide membranes, including ferroelectric tunnel junctions, 16,17,24 ferroelectric field effect transistors (FETs), 19 reconfigurable optical filters, 18 DW memories, 25 and supercapacitors. 26 For perovskite oxides, the type of electrode has a significant impact on T C , polarization dynamics, domain formation, and size scaling because the ferroelectric instability depends sensitively on the depolarization field, 27,28 strain, 29 and defect states. ...
We report the effects of screening capacity, surface roughness, and interfacial epitaxy of the bottom electrodes on the polarization switching, domain wall (DW) roughness, and ferroelectric Curie temperature (TC) of PbZr0.2Ti0.8O3 (PZT)-based free-standing membranes. Singe crystalline 10–50 nm (001) PZT and PZT/La0.67Sr0.33MnO3 (LSMO) membranes are prepared on Au, correlated oxide LSMO, and two-dimensional (2D) semiconductor MoS2 base layers. Switching the polarization of PZT yields nonvolatile current modulation in the MoS2 channel at room temperature, with an on/off ratio of up to 2 × 10⁵ and no apparent decay for more than 3 days. Piezoresponse force microscopy studies show that the coercive field Ec for the PZT membranes varies from 0.75 to 3.0 MV cm–1 on different base layers and exhibits strong polarization asymmetry. The PZT/LSMO membranes exhibit significantly smaller Ec, with the samples transferred on LSMO showing symmetric Ec of about −0.26/+0.28 MV cm–1, smaller than that of epitaxial PZT films. The DW roughness exponent ζ points to 2D random bond disorder dominated DW roughening (ζ = 0.31) at room temperature. Upon thermal quench at progressively higher temperatures, ζ values for PZT membranes on Au and LSMO approach the theoretical value for 1D random bond disorder (ζ = 2/3), while samples on MoS2 exhibits thermal roughening (ζ = 1/2). The PZT membranes on Au, LSMO, and MoS2 show TC of about 763 ± 12, 725 ± 25, and 588 ± 12 °C, respectively, well exceeding the bulk value. Our study reveals the complex interplay between the electrostatic and mechanical boundary conditions in determining ferroelectricity in free-standing PZT membranes, providing important material parameters for the functional design of PZT-based flexible nanoelectronics.
... The ferroelectric field effect has previously been adopted to induce nonvolatile modulation of the resistance and quantum transport in graphene [27,28]. Combining it with nanoscale domain patterning further enables the design of reconfigurable functionalities [29][30][31][32] and directional conduction paths [33] in a 2D channel. For ferroelectrics such as oxide Pb(Zr,Ti)O3 [34] and copolymer P(VDF-TrFE) [33], the remnant polarization corresponds to a high 2D carrier density that well exceeds 10 13 cm -2 . ...
... Third, we work with finite numbers of the stripe domains (35-50) (SM Section 3) [35], and the convoluted effect of finite SL modulation also broadens the reconstructed band. On the other hand, the limitations associated with a PZT back-gate, including the compromised KP potential due to interfacial screening charges and the non-programmable domain structure after sample fabrication, can be overcome by adopting a suspended PZT membrane top-gate [32]. ...
One-dimensional graphene superlattice subjected to strong Kronig-Penney (KP) potential is promising for achieving electron lensing effect, while previous studies utilizing the modulated dielectric gates can only yield a moderate, spatially dispersed potential profile. Here, we realize high KP potential modulation of graphene via nanoscale ferroelectric domain gating. Graphene transistors are fabricated on PbZr$_{0.2}$Ti$_{0.8}$O$_{3}$ back-gates patterned with periodic, 100-200 nm wide stripe domains. Due to band reconstruction, the h-BN top-gating induces satellite Dirac points in samples with current along the superlattice vector $\hat{s}$, a feature absent in samples with current perpendicular to $\hat{s}$. The satellite Dirac point position scales with the superlattice period ($L$) as $\propto L^{\beta}$, with $\beta = -1.18 \pm 0.06$. These results can be well explained by the high KP potential scenario, with the Fermi velocity perpendicular to $\hat{s}$ quenched to about 1% of that for pristine graphene. Our study presents a promising material platform for realizing electron supercollimation and investigating flat band phenomena.
... 16 Utilizing 2D/ferroelectric heterostructures, a variety of electronic devices including nonvolatile memories, steep-slope field-effect transistors, and FTJs have been demonstrated. [47][48][49][50]59,[61][62][63][64][65][66][68][69][70][71][72] The heterostructures of 2D/piezoelectrics and 2D/pyroelectrics also enable the development of pressure sensors and infrared bolometers. 75,77,89 Mbisike et al. demonstrated an integrated pyroelectric device based on WSe 2 and PZT, which significantly amplifies the output current as compared to the standalone device based on PZT only. ...
The integration of 2D ferroelectric materials with 2D photoelectric materials presents a promising avenue for addressing issues related to controlled doping and device integration in layered semiconductors. The reversible and non‐volatile residual polarization inherent to ferroelectrics can provide stable n ‐ or p ‐type doping for 2D semiconductors. Despite advances in doping strategies for 2D materials, existing techniques, and post‐doping characterization methodologies exhibit limitations, including the challenge of achieving high‐resolution graphical depictions of doped structures. Here, a WS 2 /CuInP 2 S 6 heterostructure is demonstarted whereby the residual polarization of ferroelectric CuInP 2 S 6 regions with anti‐parallel directions supplies screening charges of opposite signs to WS 2 monolayers. This notably alters the ratio of neutral excitons and negatively charged trions within the recombination luminescence of the direct‐gap semiconductor, thereby offering a viable approach for controllable, non‐volatile modulation in 2D systems. Beyond proposing a feasible strategy for patterned doping and effective regulation in 2D semiconductors through interface engineering, this work enhances the understanding of the interplay between ferroelectrics and semiconductors.
One-dimensional graphene superlattice subjected to strong Kronig-Penney (KP) potential is promising for achieving the electron-lensing effect, while previous studies utilizing the modulated dielectric gates can only yield a moderate, spatially dispersed potential profile. Here, we realize high KP potential modulation of graphene via nanoscale ferroelectric domain gating. Graphene transistors are fabricated on PbZr0.2Ti0.8O3 back gates patterned with periodic, 100–200 nm wide stripe domains. Because of band reconstruction, the h-BN top gating induces satellite Dirac points in samples with current along the superlattice vector s^, a feature absent in samples with current perpendicular to s^. The satellite Dirac point position scales with the superlattice period (L) as ∝Lβ, with β=−1.18±0.06. These results can be well explained by the high KP potential scenario, with the Fermi velocity perpendicular to s^ quenched to about 1% of that for pristine graphene. Our study presents a promising material platform for realizing electron supercollimation and investigating flat band phenomena.
Solid-state multilevel data storage devices based on ferroelectric materials possess significant potential for use as artificial synapses in building biomimetic neural networks with low energy consumption and efficient data processing capabilities. To enable multilevel data storage, precise control of the ferroelectric domain through voltage pulses is essential. In this study, we investigate the manipulation of ferroelectric nanodomain structures using a nanotip and demonstrate their evolution under controlled application of electric pulses with varying strength and duration. The results highlight the differences in electric-field-driven ferroelectric nanodomain structures between (001)-/(101)- and (111)-oriented PbZr0.2Ti0.8O3 thin films. Interestingly, the latter exhibits highly anisotropic domain wall motion characteristics. The (111)-oriented PbZr0.2Ti0.8O3/SrRuO3 heterostructure demonstrates the best performance in increasing the domain radius with respect to electric pulse strength and duration. It shows at least three resistance states with a high switching ratio, making it a promising candidate for multilevel data storage applications. Additionally, the self-reversal rates of upward and downward domains differ and must be considered in designing and implementing multilevel data storage systems for stability and effectiveness. These findings reveal the potential of ferroelectric nanodomain structures for data storage and pave the way for nanotip-controlled artificial synapses.
