The tunable wavelength and amplitude of mono-mode instability-induced conformal self-assembled structures of 2D materials at spin-coating 6000 rpm with different IML concentrations.
Abstract
Self-assembled mechanical instabilities can offer a new technology roadmap for micro/nanopatterns of two-dimensional (2D) materials, which depends on the deterministic regulation of mechanical instability-induced self-assemblies. However, due to atomic thinness and ultra-low bending stiffness, different types of non-designable and non-deterministic multimode coupling mechanical instabilities, such as multimode-coupled crumpling, chaotic thermal-fluctuation-induced rippling, and unpredictable wrinkling, are extremely easy to be triggered in 2D materials. The above mode-coupled instabilities make it exceedingly difficult to controllably self-assemble 2D nanocrystals into designed morphologies. In this chapters, we will introduce a novel micro/nanopatterning technology of 2D materials based on mechanical self-assemblies. Firstly, a post-curing transfer strategy is proposed to fabricate multiscale conformal wrinkle micro/nanostructures of 2D materials. Secondly, we report a deterministic self-assembly for programmable micro/nanopatterning technology of atomically thin 2D materials via constructing novel 2D materials/IML/substrate trilayer systems. Finally, based on the micro/nanopatterning technology of 2D materials, we proposed a new fabrication method for the flexible micro/nano-electronics of deterministically self-assembled 2D materials including three-dimensional (3D) tactile and gesture sensors. We fundamentally overcome the key problem of self-assembly manipulation from randomness to determinism mode by decoupling mono-mode mechanical instability, providing new opportunities for programmable micro/nanopatterns of 2D materials. Moreover, mechanical instability-driven micro/nanopatterning technology enables simpler fabrication methods of self-assembled electronics based on 2D materials.
Keywords
- 2D nanomaterials
- self-assembly
- mechanical instability
- nanopatterning
- self-assembled electronics
1. Introduction
Mechanical self-assemblies in two-dimensional (2D) materials have aroused great scientific interest due to their significant promotion of basic understanding of special physical and chemical phenomena, spanning selective chemical reactivity, abnormal thickness fluctuations, fusion-fission behaviors, and anisotropic friction [1, 2, 3, 4, 5, 6, 7], as well as exciting applications such as strain sensors, photodetectors, anticounterfeiting, and energy storage [8, 9, 10, 11, 12, 13]. Compared to three-dimensional (3D) bulk materials, the atomically thin and inherently planar 2D materials are more susceptible to being self-assembled into complex 3D architectures
As an interesting self-assembly behavior, mechanical instability is expected to develop a micro/nanopatterning technology driven by deterministic mechanical self-assembly. However, 2D materials are very sensitive to external stimuli external stimuli due to the ultrathin thickness and exceptionally low-bending rigidity nature, such as thermal vibration [24, 25], high-temperature growth-induced lattice mismatch [26, 27], built-in tension [28, 29], van der Waals interactions [30], and compressive stress [31, 32, 33]. Therefore, it is very challenging to controllably assemble 2D materials into designed 3D morphologies, which often results in unavoidable restacking and aggregation. 2D materials are randomly corrugated in 3D
Mechanical instabilities in 2D materials can be utilized to introduce non-invasively tunable out-of-plane 3D topological deformations [39, 40, 41], further adjust charge transfer and carrier scattering [42, 43], and even create flat bands in 2D materials [44]. The key point to realizing deterministic self-assembly technology is to make mechanical instabilities in 2D materials controllable. Nevertheless, complex coupled multimodal mechanical instabilities, such as crumpling, rippling, wrinkling, folding, and buckling-induced delamination, can easily be triggered at the same time [27]. They result in the corresponding self-assembled morphologies suffer poor designability. The ripples caused by thermal fluctuations [24, 25] and the inherent random wrinkles generated during the growth and transfer process [26, 27] are random behaviors, making it difficult to predict and control the instability modes, scales, and directions of self-assembly morphologies [26]. Uniaxial strain can trigger quasi one-dimensional (1D) ordered self-assembled structures, but they are still uncontrollable multidirectional structures [31, 32, 33]. In addition, by coupling folding mode instabilities with wrinkle mode instabilities at an uncertain rate, crumpling is easily formed in 2D materials, which can lead to multidirectional and multiscale 3D self-assembly morphologies [31, 33]. The chaotic self-assembled structures induced by multimode coupling mechanical instabilities with uncontrollable scales and directions cannot precisely adjust the deformation of 3D structures in any way, which largely restrict the potential applications of self-assembled 2D materials. Consequently, decoupling multimode coupling mechanical instabilities and obtaining deterministic self-assembly with controlled structural configurations in 2D materials are crucial, but highly challenging.
2. Deterministic mode mechanical self-assembly
A complementary metal oxide semiconductor-compatible programmable tuning strategy has been developed to decouple uncontrollable multimode-coupled mechanical instabilities into controllable mode-decoupled mechanical instability, and to achieve deterministic mode self-assembly of 2D materials (Figure 1A). As shown in Figure 1A, II, the key point that realizes mode decoupling of mechanical instability in 2D nanosheets is to introduce designable intermediate multifunctional layers (IMLs) into bilayer systems. IMLs, including hydrogen silsesquioxane (HSQ) and poly(methyl methacrylate) (PMMA), play a variety of roles in generating and controlling deterministic self-assemblies driven by mono-mode mechanical instability, including deterministic mode, direction, and scale self-assemblies. First, IMLs work as carrier materials to avoid unwanted mode mechanical instability that triggers deterministic mode self-assembly in 2D materials during transfer. Second, IMLs work as a structural layer to enhance the effective bending stiffness of 2D materials/IML structures for self-assembly with deterministic dimensions. Third, IMLs also work as a functional layer and protective layer to manufacture programmable deterministic directional self-assembly patterns of 2D materials.
Decoupled mono-mode instability and corresponding self-assembled patterns with deterministic wavelength of MoS2 are observed in the designed three-layer systems in Figure 1B and C. Further, Figure 1D indicates that the deterministic self-assembly morphologies driven by mono-mode instability are mono-scale wrinkles with amplitude of
The results indicate that the mode-decoupled mechanical instability of 2D materials is achieved by constraining unwanted multimode instability (folding, collapsed folding, and buckling induced delamination in Figure 1A, I) to mono-mode instability (wrinkling in Figure 1A, II). As shown in Figure 5, the wavelength and amplitude of the self-assembly morphologies induced by mono-mode instability in three-layer systems can be given by
where
A new low-temperature post-curing transfer strategy is developed to achieve desirable and controllable mode decoupling mechanical instability in atomic thin 2D materials. The transfer strategy has three key points. It is extremely difficult to decouple and control the multimode-coupled mechanical instability of single-layer or even few layer 2D materials due to the extremely low bending stiffness [27, 39, 45]. Firstly, the well-designed IMLs we introduced to build 2D material/IML/substrate three-layer systems instead of two-layer 2D material/substrate systems to tackle the problem of extremely low flexural stiffness of 2D materials (Figures 6, 7, and 8A–E).
However, it also presents a new challenge that the interface strength among 2D materials, IMLs, and substrate is too low. The interfacial liquid introduced during the pre-curing transfer significantly lowers the interfacial adhesion energy between the pre-curing substrate and the 2D material, which cannot transfer stress (Figure 9). Note that the low-temperature post-curing transfer process of CVD-grown h-BN on Cu foil is similar to that of the CVD-grown graphene, the only difference is the grown substrate etching, in which the etchant is replaced by FeCl3 solution. Unlike the conventional wet transfer methods of 2D materials [45], the carrier material in the graphene/IML laminate is not removed after they are transferred onto substrates, which is used as a structure layer to increase the bending stiffness of surface film.
Therefore, producing sufficient interfacial adhesion energy after transfer is the second key point, which can make the interface enable to subject to critical strain to generate the wanted mode mechanical instabilities. To improve interfacial strength between the 2D material and the substrate, we propose a post-curing transfer method for 2D materials, where the uncured beGr-PDMS is directly poured and then cured on the upper surface of IMLs (Figure 10B and C). However, the accelerated diffusion of uncured PDMS polymers by high temperatures can introduce an inevitable gradient interface between beGr-PDMS and IMLs during the post-curing process, which can lead to uncontrollable multiscale self-assemblies of 2D material in the three-layer system (Figure 11).
Therefore, the third point is avoiding the formation of diffusion-induced gradient interfaces between IMLs and beGr-PDMS substrate. To reduce polymer diffusion caused by Brownian motion, we cured the beGr-PDMS at low temperature (Figure 10C). To confirm this, we conducted cross-sectional characterization, which indicates that a sharp interface between IMLs and beGr-PDMS substrate was observed instead of a gradient interface in the samples prepared by the low-temperature post-curing transfer method (Figure 9). In additions, Raman characterizations indicate that high-quality 2D materials with low defects are well transferred to target substrates (Figures 8–14). The results indicate that the low-temperature post-curing process can not only generate sufficient interface adhesion strength to withstand the critical interfacial stresses triggering mode-coupled mechanical instabilities, but also effectively avoid gradient interfaces induced by high temperatures-accelerated PDMS polymer diffusion.
We revealed the potential mechanism of the post-curing transfer-induced interfacial strength enhancement effect after solidification (Figure 10F–H). The enhanced interfacial strength between 2D materials and IMLs is caused by the thermal evaporation-driven topological entanglement of IMLs polymer chains during the high-temperature baking process (Figure 10F). Similarly, the interface strength enhancement between beGr-PDMS and IMLs is benefited by the topological entanglement between the IML and beGr-PDMS polymer network during the post-curing process (Figure 10G). The results indicate that the micro-mechanical interlocking induced by topological entanglement is the micro-mechanism of the interface strength enhancement [46]. Furthermore, a sharp decrease in interface strength during substrate etching is effectively prevented due to the liquid-free interfaces between beGr-PDMS, IML, and 2D materials (Figure 10D and H).
Moreover, more types of 2D materials grown by CVD, including insulator (h-BN), semi-conductors (2H-WS2) and semi-metals (graphene, 1 T-WSe2, 1 T-MoS2), were transferred to prove the versatility of the transfer strategy (Figure 10A). As shown in Figures 15–17, the experimental data indicate that our transfer strategy has good universality and can be extended to other diverse 2D materials.
3. Cross-scale mechanical self-assembly
In order to achieve cross-scale self-assembly of 2D materials, IML was introduced as a structural layer to control the scale of deterministic mode self-assembly morphological features.
The IMLs are introduced to work as structural layers to control the characteristic scale of deterministic mode self-assembled patterns and achieve cross-scale self-assembly of 2D materials. The amplitude and wavelength of self-assembled micro/nanostructures in 2D materials can be controlled by the thickness of IMLs, judging from Eqs. (1)–(3). Furthermore, the thickness of IMLs can be programmatically regulated by spin-coating speeds
PMMA | 0.5%, 6kr | 1%, 6kr | 2%, 6kr | 4%, 6kr | 6%, 6kr | 10%, 6kr |
---|---|---|---|---|---|---|
PMMA | 0.5%, 3kr | 1%, 3kr | 2%, 3kr | 4%, 3kr | 6%, 3kr | 10%, 3kr | 10%, 1kr |
---|---|---|---|---|---|---|---|
The wavelength and amplitude of mono-mode instability-induced conformal self-assembled 2D materials can be tuned by selecting different IML concentrations
where
4. Directed mechanical self-assembly
As shown in Eqs. (1) and (2), the deformation orientation, anisotropic structural stiffness, and functionalization of 2D materials in three-layer systems of 2D materials/IMLs/substrate can be adjusted through directed self-assembly. Therefore, it is important for the applications of deterministic self-assembly to transform non-directed into directed self-assembly with designed directions, especially for self-assembly-driven directed micro/nanopatterning technology and 2D materials-based flexible devices.
The above mechanical boundaries can be used to direct 2D materials self-assemble into ordered structures. Figures 18B–D and 22–24 show directed self-assembly morphologies of “MoS2” and “SJTU”-alphabetic-shaped MoS2, and “Gr”-alphabetic-shaped graphene, in which IMLs, as electron beam resists, are used to programmatically fabricate ordered patterns. In the 2D oriented self-assembled graphene and MoS2 nanosheets, the orientations of structural peaks are perpendicular to the EBL-defined boundaries (Figure 18B and D). Note that the EBL-defined “Gr” letter pattern was well transferred onto the target substrates by the low-temperature post-curing method without quality degradation. Moreover, the stress concentration-induced local self-assembly phenomenon can be harnessed to local strain engineering with large strains on demand by designing different curvature corners to control stress concentration and stress relaxation. We developed a revised shear-lag model reveals the mechanical mechanism of directed self-assembly structures induced by finite width soft constrained mechanical boundaries, indicating that mechanical boundaries can lead to asymmetric stress relaxation and asymmetric in-plane stress distribution.
5. Dynamic mechanical self-assembly
In addition to the quasi-static above-mentioned cross-scale and directed self-assemblies, the dynamic self-assembly of 2D materials can be acquired through effective dynamic adjustment of mode-coupled instability.
During the dynamic operation of different NIR ON/OFF switches, the wavelength remains almost unchanged, indicating that the self-assembly morphology of 2D materials remains unchanged in the self-assembly mode and high mode-scale characteristics (Figure 25B). As indicated in Figure 25B, the amplitude of the self-assembled patterns can be dynamically adjusted by NIR light. When
where
As shown in Eqs. (4)–(6) and Figures 26 and 27, the time-varying amplitude of self-assembled structures can be tuned by the time-varying photothermal force and temperature difference. The ratio of beGr, and power density and incidence rate of NIR can be used to modulated the photothermal response speed of beGr-PDMS.
The photothermal performance of NIR-responsive beGr-PDMS can be well described by Eq. (4) As shown in Figure 25, beGr-PDMS heats rapidly under near-infrared radiation, indicating a high conversion rate of photothermal energy. After the NIR is closed
6. Self-assembled flexible devices
The deterministic self-assembled structures can bring some new unique properties into 2D materials, such as anisotropic piezoresistive, flexoelectric, piezoelectric, and mechanical optoelectronic coupling effects of 2D directed self-assembled 2D materials (Figure 18B–D). Moreover, the dynamic self-assembly can be used to realize the
In this work, as shown in Figure 28, a novel concept is proposed to manufacture deterministic self-assembled flexible electronic devices of 2D materials driven by deterministic mono-mode instability. A single self-assembled structure can be considered as an independently adjustable self-assembled electronic component, such as a transistor, a capacitor, a resistor, or a converter (Figure 28A). The independently adjustable electronic component can be assembled into complex circuits and interact with the external environment
As shown in Figure 28B, an ultra-fast response wearable flexible sensor for gesture detection was manufactured based on the deterministic self-assembly of 2D materials in 2D material/IML/substrate three-layer systems. When the hand is in the initial horizontal position, the sensor is connected to the arm near the wrist (Figure 28B). The amplitude and wavelength of initial self-assembled wrinkles are
Moreover, by utilizing directed self-assembly of 2D materials in 2D material/IMLs/substrate three-layer systems, we fabricated a new functional oriented flexible electronic device (Figure 28C) [47]. A 3D anisotropic tactile sensor with ultra-fast response is presented by employing the 1D directed self-assembly of 2D materials to effectively identify normal and shear forces. The 1D ordered self-assembled structure of 2D materials can work as sensing element, which is the key to the tactile sensing function of the anisotropic 3D tactile sensor. Each 1D ordered self-assembly structure can be equivalent to a resistor with the same resistance value, and the resistor is determined to be connected in parallel before being touched by fingers (Figure 28C, II). As shown in Figure 28C, III–V, the tactile sensor has three touch modes: normal force touch, x-direction shear force touch, and y-direction shear force contact. As indicated in Figure 28C, VI, the self-assembled structures are locally squeezed into a flat state, and the resistance
Furthermore, the sensor can also sense the shear force caused by finger sliding friction. Owing to 1D ordered self-assembly of 2D materials, the tactile sensors show anisotropic sensing characteristics. The self-assembled structure with a symmetrical sinusoidal shape undergoes significant deformation when the fingers slide along
7. Conclusions
We have fundamentally overcome the key problem of mechanical instability mode manipulation caused by the extremely low bending stiffness of atomically thin 2D crystals to realize the highly designable decoupled mono-mode mechanical instability and deterministic mode self-assembly of 2D materials. The key to decoupling multimode-coupled mechanical instabilities in ultra-thin 2D materials is to construct 2D material/IMLs-substrate three-layer systems by introducing a universal, programmable IMLs and micro-mechanical interlocking bonding.
The decoupled mono-mode instability of atomic thin 2D materials opens up a new opportunity for the determination of third-order cross-scale and directed self-assemblies in 2D nanocrystals. Interestingly, a non-contact
Acknowledgments
We strongly appreciate discussions with Yu-Long Chen, Shuai-Chen, Shu-Zheng Yan, Tian-Jiao Ma, Zhong-Ying Xue. We also thank Guang-Yu Zhang’s group for providing 2D materials, Qi Sun for the EBL process, Gang Wang for providing beGr, and Tian-Tian Li for LCSM measurements. The authors would like to acknowledge the supports by the National Science Foundation (12121002, 12032015, 12172216), Science and Technology Innovation Action Plan of Shanghai (21190760100), the Program of Shanghai Academic/Technology Research Leader (19XD1421600), the State Key Laboratory of Mechanical System and Vibration (Grant No. MSVZD202105), and Double First-Class Construction project of Shanghai Jiaotong University (WH220402002).
References
- 1.
Meyer JC, Geim AK, Katsnelson MI, Novoselov KS, Booth TJ, Roth S. The structure of suspended graphene sheets. Nature. 2007; 446 (7131):60-63 - 2.
Xie S et al. Coherent, atomically thin transition-metal dichalcogenide superlattices with engineered strain. Science. 2018; 359 (6380):1131-1136 - 3.
Xue J et al. Scanning tunnelling microscopy and spectroscopy of ultra-flat graphene on hexagonal boron nitride. Nature Materials. 2011; 10 (4):282-285 - 4.
Choi JS et al. Friction anisotropy–driven domain imaging on exfoliated monolayer graphene. Science. 2011; 333 (6042):607-610 - 5.
Chang D et al. Reversible fusion and fission of graphene oxide-based fibers. Science. 2021; 372 (6542):614-617. DOI: 10.1126/science.abb6640 - 6.
Deng S et al. Graphene wrinkles enable spatially defined chemistry. Nano Letters. 2019; 19 (8):5640-5646 - 7.
Sun P et al. Limits on gas impermeability of graphene. Nature. 2020; 579 (7798):229-232 - 8.
Kang P, Wang MC, Knapp PM, Nam S. Crumpled graphene photodetector with enhanced, strain-tunable, and wavelength-selective photoresponsivity. Advanced Materials. 2016; 28 (23):4639-4645 - 9.
Xiong P et al. Strain engineering of two-dimensional multilayered heterostructures for beyond-lithium-based rechargeable batteries. Nature Communications. 2020; 11 (1):1-12. DOI: 10.1038/s41467-020-17014-w - 10.
Wang Y et al. Super-elastic graphene ripples for flexible strain sensors. ACS Nano. 2011; 5 (5):3645-3650 - 11.
Thomas AV et al. Controlled crumpling of graphene oxide films for tunable optical transmittance. Advanced Materials. 2015; 27 (21):3256-3265 - 12.
Jing L et al. Multigenerational crumpling of 2D materials for Anticounterfeiting patterns with deep learning authentication. Matter. 2020; 3 (6):2160-2180 - 13.
Dai C et al. Kirigami engineering of suspended graphene transducers. Nano Letters. 2022; 22 (13):5301-5306 - 14.
Zhao B et al. High-order superlattices by rolling up van der Waals heterostructures. Nature. 2021; 591 (7850):385-390 - 15.
Cui X et al. Rolling up transition metal dichalcogenide nanoscrolls via one drop of ethanol. Nature Communications. 2018; 9 (1):1-7 - 16.
Annett J, Cross GL. Self-assembly of graphene ribbons by spontaneous self-tearing and peeling from a substrate. Nature. 2016; 535 (7611):271-275 - 17.
Xu W et al. Ultrathin thermoresponsive self-folding 3D graphene. Science Advances. 2017; 3 (10):e1701084 - 18.
Blees MK et al. Graphene kirigami. Nature. 2015; 524 (7564):204-207 - 19.
Chen H et al. Atomically precise, custom-design origami graphene nanostructures. Science. 2019; 365 (6457):1036-1040 - 20.
Yang L-Z et al. Origami-controlled strain engineering of tunable flat bands and correlated states in folded graphene. Physical Review Materials. 2022; 6 (4):L041001 - 21.
Geringer V et al. Intrinsic and extrinsic corrugation of monolayer graphene deposited on SiO 2. Physical Review Letters. 2009; 102 (7):076102 - 22.
Hu J, Vanacore GM, Cepellotti A, Marzari N, Zewail AH. Rippling ultrafast dynamics of suspended 2D monolayers, graphene. Proceedings of the National Academy of Sciences of the USA. 2016; 113 (43):E6555-E6561 - 23.
Dobrik G et al. Large-area nanoengineering of graphene corrugations hosting visible-frequency graphene plasmons. Nature Nanotechnology. 2021; 17 (1):1-18 - 24.
Lui CH, Liu L, Mak KF, Flynn GW, Heinz TF. Ultraflat graphene. Nature. 2009; 462 (7271):339-341 - 25.
Fasolino A, Los JH, Katsnelson MI. Intrinsic ripples in graphene. Nature Materials. 2007; 6 (11):858-861. DOI: 10.1038/nmat2011 - 26.
Yuan G et al. Proton-assisted growth of ultra-flat graphene films. Nature. 2020; 577 (7789):204-208 - 27.
Wang M et al. Single-crystal, large-area, fold-free monolayer graphene. Nature. 2021; 596 (7873):519-524 - 28.
Calado V, Schneider G, Theulings A, Dekker C, Vandersypen L. Formation and control of wrinkles in graphene by the wedging transfer method. Applied Physics Letters. 2012; 101 (10):103116 - 29.
Zhao Y et al. Large-area transfer of two-dimensional materials free of cracks, contamination and wrinkles via controllable conformal contact. Nature Communications. 2022; 13 (1):1-10 - 30.
Ares P et al. Van der Waals interaction affects wrinkle formation in two-dimensional materials. Proceedings of the National Academy of Sciences of the USA. 2021; 118 (14):e2025870118 - 31.
Zang J et al. Multifunctionality and control of the crumpling and unfolding of large-area graphene. Nature Materials. 2013; 12 (4):321-325 - 32.
Lee W-K et al. Multiscale, hierarchical patterning of graphene by conformal wrinkling. Nano Letters. 2016; 16 (11):7121-7127 - 33.
Chen PY et al. Multiscale graphene topographies programmed by sequential mechanical deformation. Advanced Materials. 2016; 28 (18):3564-3571 - 34.
Novoselov KS, Geim A. The rise of graphene. Nature Materials. 2007; 6 (3):183-191 - 35.
Xu P et al. Unusual ultra-low-frequency fluctuations in freestanding graphene. Nature Communications. 2014; 5 :1-7. DOI: 10.1038/ncomms4720 - 36.
Deng J et al. Epitaxial growth of ultraflat stanene with topological band inversion. Nature Materials. 2018; 17 (12):1081-1086 - 37.
Deng B et al. Growth of Ultraflat graphene with greatly enhanced mechanical properties. Nano Letters. 2020; 20 (9):6798-6806 - 38.
Zheng F, Thi QH, Wong LW, Deng Q, Ly TH, Zhao J. Critical stable length in wrinkles of two-dimensional materials. ACS Nano. 2020; 14 (2):2137-2144 - 39.
Castellanos-Gomez A et al. Local strain engineering in atomically thin MoS2. Nano Letters. 2013; 13 (11):5361-5366 - 40.
Bao W et al. Controlled ripple texturing of suspended graphene and ultrathin graphite membranes. Nature Nanotechnology. 2009; 4 (9):562-566. DOI: 10.1038/nnano.2009.191 - 41.
Carbone MGP, Manikas AC, Souli I, Pavlou C, Galiotis C. Mosaic pattern formation in exfoliated graphene by mechanical deformation. Nature Communications. 2019; 10 (1):1-7 - 42.
Zhu W et al. Structure and electronic transport in graphene wrinkles. Nano Letters. 2012; 12 (7):3431-3436 - 43.
Pereira VM, Neto AC, Liang H, Mahadevan L. Geometry, mechanics, and electronics of singular structures and wrinkles in graphene. Physical Review Letters. 2010; 105 (15):156603 - 44.
Mao J et al. Evidence of flat bands and correlated states in buckled graphene superlattices. Nature. 2020; 584 (7820):215-220 - 45.
Hu KM et al. Tension-induced Raman enhancement of graphene membranes in the stretched state. Small. 2019; 15 (2):1804337 - 46.
He P et al. Kinetically enhanced bubble-exfoliation of graphite toward high-yield preparation of high-quality graphene. Chemistry of Materials. 2017; 29 (20):8578-8582 - 47.
Hu KM et al. Deterministically self-assembled 2D materials and electronics. Matter. 2023; 6 (5):1654-1668