2D Heterostructures Research Articles

Interlayer Friction and Adhesion Effects in Penta-PdSe2-Based van der Waals Heterostructures.

Due to their inherent lattice mismatch characteristics, 2D heterostructure interfaces are considered ideal for achieving stable and sustained ultralow friction (superlubricity). Despite extensive research, the current understanding of how interface adhesion affects interlayer friction remains limited. This study focused on graphene/MoS2 and graphene/PdSe2 heterostructure interfaces, where extremely low friction coefficients of ≈10-3 are observed. In contrast, the MoS2/PdSe2 heterostructure interfaces exhibit higher friction coefficients, ≈0.02, primarily due to significant interfacial interactions driven by interlayer charge transfer, which is closely related to the ionic nature of 2D material crystals. These findings indicate that the greater the difference in ionicity between the two 2D materials comprising the sliding interfaces is, the lower the interlayer friction, providing key criteria for designing ultralow friction pairs. Moreover, the experimental results demonstrate that interlayer friction in heterostructure systems is closely associated with the material thickness and interface adhesion strength. These experimental findings are supported by molecular dynamics simulations, further validating the observed friction behavior. By integrating experimental observations with simulation analyses, this study reveals the pivotal role of interface adhesion in regulating interlayer friction and offers new insights into understanding and optimizing the frictional performance of layered solid lubricants.

Investigation on the carrier dynamics and energy band of the CVD-grown large area WS2/Bi2O2Se heterostructure

Bismuth oxyselenide (Bi2O2Se) emerged as a prominent member of the quasi-2D layered material family, possesses appealing characteristics for optoelectronic applications including impressive environmental stability and high carrier mobility. Recently, although significant advancements have been made in the initial research on the optoelectronic characteristics of Bi2O2Se-based heterostructures, there remains a lack of comprehensive study on the carrier dynamics and energy band within these structures. In this work, large-area (1 cm × 1 cm) continuous Bi2O2Se and monolayer WS2 films were grown by chemical vapor deposition (CVD) method, and the related WS2/Bi2O2Se heterostructures were successfully constructed. Triple decay processes with lifetimes ofτ1 ∼ 298 ps, τ2∼37 ps andτ3 ∼ 1.58 ns are observed through time-resolved photoluminesce (TRPL), which were attributed to the recombination of neutral excitons, trions, and interlayer excitons, respectively. Then, the energy band structure was investigated through x-ray photoelectron spectroscopy, revealing a type-Ⅱ band alignment at the heterointerface. The valence band offset was 0.19 eV, while conduction band offset was approximately 1.09 eV as confirmed by ultraviolet photoelectron spectroscopy. As a result, the WS2/Bi2O2Se junction enhances charge transfer and interlayer interactions by the aid of interface build-in electric field. These results showcase the potential of integrating Bi2O2Se with other 2D semiconductors to form heterostructures possessing novel charge dynamic behaviors, and provide valuable understanding into the functionality of optoelectronic devices that rely on these 2D heterostructures.

A Deterministic Method to Construct a Common Supercell Between Two Similar Crystalline Surfaces.

Here, a deterministic algorithm is proposed, that is capable of constructing a common supercell between two similar crystalline surfaces without scanning all possible cases. Using the complex plane, the 2D lattice is defined as the 2D complex vector. Then, the relationship between two surfaces becomes the eigenvector-eigenvalue relation where an operator corresponds to a transformation matrix. It is shown that this transformation matrix can be directly determined from the lattice parameters and rotation angle of the two given crystalline surfaces with O(log Nmax) time complexity, where Nmax is the maximum index of repetition matrix elements. This process is much faster than the conventional brute force approach ( ). By implementing the method in Python code, experimental 2D heterostructures and their moiré patterns and additionally find new moiré patterns that have not yet been reported are successfully generated. According to the density functional theory (DFT) calculations, some of the new moiré patterns are expected to be as stable as experimentally-observed moiré patterns. Taken together, it is believed that the method can be widely applied as a useful tool for designing new heterostructures with interestingproperties.

Novel 2D heterostructure composites of V2C MXene/TiO2 and graphene/TiO2 for platinum replacement in dye-sensitized solar cells

This study evaluates the potential of V2C MXene/TiO2 and Graphene/TiO2 composites as alternatives to platinum for counter-electrodes in dye-sensitized solar cells (DSSCs). V2C MXene was synthesized by selectively etching the aluminum layer from V2AlC MAX phase powder, resulting in multilayered V2C MXene. The layered morphologies of MXene and graphene were confirmed via Scanning Electron Microscopy (SEM), while their crystalline structures were validated using X-ray diffraction (XRD) analysis. SEM analysis confirmed the delaminated layered structure of graphene and the distinct layers of V2C MXene. XRD findings showed that MXene has significantly greater interlayer spacing than graphene, offering more catalytic sites for charge injection. Electrocatalysts were prepared by incorporating TiO2 paste with MXene and graphene, with TiO2 serving as a binder. These composites were then employed as counter-electrode materials in dye-sensitized solar cells. The MXene-based counter electrode achieved a photoconversion efficiency of 1.625 %, surpassing graphene-based (1.149 %) and Pt-based (1.567 %) counterparts under standard illumination. The efficiency of cells was meticulously characterized over an extended period. The results indicated that the efficiency of these cells remained stable over time. This stability suggests that MXene/TiO2 and Graphene/TiO2 based catalysts are robust and do not degrade with time.

Rational design of 2D blue phosphorene/Ti2BT2 (T=Se, Te) heterostructures as high-performance anode materials for alkali-metal ion batteries: A first principles study

Blue phosphorene (BlueP) is extensively regarded as an attractive anode for the next generation of metal-ion batteries (MIBs) owing to the rapid ion diffusion and high storage capacity; however, its electrochemical performance is still seriously impeded by the intrinsically low conductivity and poor mechanical stiffness. To overcome the above obstacles, we theoretically designed BlueP/Ti2BSe2 and BlueP/Ti2BTe2 heterostructures, and explored their potential as the anodes of MIBs using first principles calculations. The computational results demonstrate that the resulting heterostructures have excellent thermal and mechanical stability. Moreover, the designed two heterostructures show low ion diffusion barrier (<0.30 eV) with inherent metallicity, which greatly contributes to the rate performance of MIBs. Remarkably, the BlueP/Ti2BSe2 (BlueP/Ti2BTe2) anode delivers high Li/Na/K storage capacities of 492.68 (379.54)/410.54 (379.54)/191.59 mA h/g, and suitable averaged open circuit voltages (OCVs) of 0.56 (0.33)/0.33 (0.10)/0.42 V. This work not only broadens the BlueP-based 2D heterostructures, but also lays a solid foundation for the theoretical design of exceptional anodes.

3D SERS substrate using silver nanoparticles decorated ZnO nanorods on silicon micropyramids hybrid heterostructure

3D hybrid heterostructure have been fabricated using Ag Nanoparticles decorated ZnO nanorods over textured Silicon Micropyramid for Surface Enhanced Raman Scattering (SERS) applications. Silicon texturing was performed using facile Alkaline texturing route followed by the growth of ZnO nanorods (ZnONR) array on the micropyramids over which, the Ag nanoparticles (AgNPs) were decorated. The phase and the surface of the heterostructure was studied by XRD and Field Emission Scanning Electron Microscope (FESEM), respectively. The SERS performance of the 3D heterostructure was evaluated using Rhodamine 6G (R6G) at various concentrations with a detection limit of 0.1 pM. The superior properties of SiMP/ZnONR/AgNP over ZnONR/AgND heterostructure has also been presented to understand the effect of the 3D pyramidal substrate for superior SERS performance. The recovery of the prepared heterostructure has also been demonstrated by photocatalytic degradation of Rhodamine 6G and Methylene Blue. Our work demonstrates a facile synthesis of 3D SERS heterostructure and sheds light on its superior SERS properties paving ways for wide range of applications in bio-sensors, detection of harmful chemicals, food adulterations, narcotic detection and many more.

LiFe0.3Mn0.7PO4-on-MXene heterostructures as highly reversible cathode materials for Lithium-ion batteries

Two-dimensional (2D) heterostructure materials, incorporating the collective strengths and synergetic properties of individual building blocks, have attracted great interest as a novel paradigm in electrode materials science. The family of 2D transition metal carbides and nitrides (e.g., MXenes) has become an appealing platform for fabricating functional materials with strong application performance. Herein, a 2D LiFe0.3Mn0.7PO4 (LFMP)–on-MXene heterostructure composite is prepared through an electrostatic self-assembly procedure. The functional groups on the surface of MXenes possess highly electronegative properties that facilitate the incorporation of LFMPs into MXenes to construct heterostructure composites. The special heterostructure of nanosized-LiFe0.3Mn0.7PO4 and MXene provides rapid Li+ and electron transport in the cathodes. This LiFe0.3Mn0.7PO4-3.0 wt% MXene composite can exhibit an excellent rate capability of 98.3 mAh g−1 at 50C and a very stable cycling performance with a capacity retention of 94.3 % at 5C after 1000 cycles. Furthermore, NaFe0.3Mn0.7PO4-3.0 wt% MXene with stable cyclability can be obtained by an electrochemical conversion method with LiFe0.3Mn0.7PO4-3.0 wt% MXene. Ex-situ XRD suggests that LiFe0.3Mn0.7PO4-on-MXene achieves a highly reversible structural evolution with a solid solution phase transformation (LFMP→LixFe0.3Mn0.7PO4 (LxFMP), LxFMP→LFMP) and a two-phase reaction (LxFMP←→Fe0.3Mn0.7PO4 (FMP)). This work provides a new direction for the use of MXenes to fabricate 2D heterostructures for lithium-ion batteries.

Revealing Enhanced Optical Nonlinearity and Robust Ferromagnetism in Atomically Sharp Stacking Binary-Ternary Magnetic Heterostructures.

Two-dimensional (2D) materials provide a versatile platform for the integration of diverse crystals, enabling the formation of heterostructures with intriguing functionalities. Coherently growing 2D heterostructures are highly desirable for property manipulation due to their strong interfacial interaction. In this work, we propose a general synthesis approach and provide insight into well-designed 2D binary-ternary magnetic heterostructures. Atomically sharp interfaces were achieved in typical lateral and vertical Cr1+mSe2(001)/CuCr2Se4(111) heterostructures owing to their similar lattice arrangement, with the observation of a significant enhancement of optical second-harmonic generation. Further magnetism measurements revealed a Curie temperature up to 360 K and thickness- and temperature-dependent magnetism in this heterostructure. Additionally, we synthesized three analogous 2D magnetic heterostructures in Fe-Cr-S, Co-Cr-S, and Cu-Cr-S systems, demonstrating the ubiquitous nature of the coherent heteroepitaxy. Our work involves the development of an innovative platform for investigating the underlying physics and potential applications of 2D binary-ternary heterostructures as well as the fabrication of associated functional devices.

Modulation of Electrostatic Potential in 2D Crystal Engineered by an Array of Alternating Polar Molecules.

The moiré potential in rotationally misfit two-dimensional (2D) heterostructures has been used to build artificial exciton and electron lattices, which have become platforms for realizing exotic electronic phases. Here, we demonstrate a different approach to create a superlattice potential in 2D crystals by using the near field of an array of polar molecules. A bilayer of titanyl phthalocyanine (TiOPc), consisting of alternating out-of-plane dipoles, is deposited on monolayer MoS2. Time-resolved two-photon photoemission spectroscopy reveals a pair of interlayer exciton states with an energy difference of ∼0.1 eV, which is consistent with the electrostatic potential modulation induced by the TiOPc bilayer as determined by density functional theory calculations. Because the symmetry and the period of this potential superlattice can be changed readily by using molecules of different shapes and sizes, molecule/2D heterostructures can be promising platforms for designing artificial exciton and electron lattices.

(Invited) Two-Dimensional Organic-Perovskite Hybrid Materials and Heterostructures

Epitaxial heterostructures based on oxide perovskites and III–V, II–VI and transition metal dichalcogenide semiconductors form the foundation of modern electronics and optoelectronics. Halide perovskites—an emerging family of tunable semiconductors with desirable properties—are attractive for applications such as solution-processed solar cells, light-emitting diodes, detectors and lasers. Their inherently soft crystal lattice allows greater tolerance to lattice mismatch, making them promising for heterostructure formation and semiconductor integration. Atomically sharp epitaxial interfaces are necessary to improve performance and for device miniaturization. However, epitaxial growth of atomically sharp heterostructures of halide perovskites has not yet been achieved, owing to their high intrinsic ion mobility and their poor chemical stability. Therefore, understanding the origins of this instability and identifying effective approaches to suppress ion diffusion are of great importance. In this talk I will present an effective strategy to substantially inhibit in-plane ion diffusion in two-dimensional halide perovskites by incorporating rigid π-conjugated organic ligands. Highly stable and tunable lateral and vertical epitaxial heterostructures, multiheterostructures and superlattices will be demonstrated. Furthermore, using these 2D heterostructures as a new platform, I will present our recent efforts in 1) quantitatively understanding the anion inter-diffusions and migrations, and 2) controlling and manipulating exciton transport and light-emission in halide perovskites.

3D high-temperature resistance BaTiO3/EG hybrids with enhanced EMWs absorption capacity

BaTiO3 is a promising electromagnetic waves (EMWs) absorption material due to its chemical stability and large dielectric constant. However, the high reflection coefficient of pure BaTiO3 at high frequencies reduced its EMWs absorption capacity. To resolve the issue, BaTiO3/expanded graphite (EG) hybrids were successfully synthesized by high-energy ultrasound assisted heat treatment technology. The combination of BaTiO3 particles and layered EG formed three-dimensional (3D) heterostructure of BaTiO3/EG hybrids, which optimized the impedance matching. Abundant conductive network enhanced interfacial polarization, numerous interface defects and multiple reflections together promoted the attenuation of EMWs. At the molar ratio of 0.2:0.8 between BaTiO3 and EG, the BaTiO3/EG sample with 1.5 mm match thickness displayed −100.6 dB of minimum reflection loss (RLmin) and 5.9 GHz of effective absorption bandwidth (EAB). In addition, the ceramic character of BaTiO3/EG hybrids endowed them excellent high-temperature stability.

Synergetic interface engineering and space-confined effect in CoSe2@Ti3C2Tx heterostructure for high power and long life sodium ion capacitors

The intriguing characteristics of two-dimensional (2D) heterostructures stem from their unique interfaces, which can improve ion storage capability and rate performance. However, there are still challenges in increasing the proportion of heterogeneous interfaces in materials and understanding the complex interaction mechanisms at these interfaces. Here, we have successfully synthesized confined CoSe2 within the interlayer space of Ti3C2Tx through a simple solvothermal method, resulting in the formation of a superlattice-like heterostructures of CoSe2@Ti3C2Tx. Both density functional theory (DFT) calculations and experimental results show that compared with CoSe2 and Ti3C2Tx, CoSe2@Ti3C2Tx can significantly improve adsorption of Na+ ions, while maintaining low volume expansion and high Na+ ions migration rate. The heterostructure formed by MXene and CoSe2 is a Schottky heterostructure, and its interfacial charge transfer induces a built-in electric field that promotes rapid ion transport. When CoSe2@Ti3C2Tx was used as an anode material, it exhibits a high specific capacity of up to 600.1 mAh/g and an excellent rate performance of 206.3 mAh/g at 20 A/g. By utilizing CoSe2@Ti3C2Tx as the anode and activated carbon (AC) as the cathode, the sodium-ion capacitor of CoSe2@Ti3C2Tx//AC exhibits excellent energy and power density (125.0 Wh kg−1 and 22.5 kW kg−1 at 300.0 W kg−1 and 37.5 Wh kg−1, respectively), as well as a long service life (86.3 % capacity retention over 15,300 cycles at 5 A/g), demonstrating its potential for practical applications.

Photon-beam-inducing synthesis of a tunable porous graphene/Ti3C2T x heterostructure for energy conversion-storage system

Flexible electronic device requires a novel micro-supercapacitors (MSCs) energy conversion-storage system based on two-dimensional (2D) materials to solve the problems of stiffness and complexity. Herein, we report a novel catalytic introduction method of graphene with adjustable porosity by high-energy photon beam. The graphene/Ti3C2T x heterostructure was constructed by electrostatic self-assembly, has a high cycle life (98% after 8000 cycles), energy density (11.02 mWh cm−3), and demonstrate excellent flexible alternating current line-filtering performance. The phase angle of −79.8° at 120 Hz and a resistance-capacitance constant of 0.068 ms. Furthermore, the porous graphene/Ti3C2T x structures produced by multiple catalytic inductions allowed ions to deeply penetrate the electrode, thereby increasing the stacking density. The special ‘pore-layer nesting’ graphene structure with adjustable pores effectively increased the specific surface area, and its superior matching with electrolyte solutions greatly improved surface-active site utilization. This work offers an alternative strategy for fabricating a 2D heterostructure for an MSC.

A Universal In-Situ Interfacial Growth Strategy for Various MXene-Based van der Waals Heterostructures with Uniform Heterointerfaces: The Efficient Conversion from 3D Composite to 2D Heterostructures.

Two-dimensional (2D) van der Waals heterostructures endow individual 2D material with the novel functional structures, intriguing compositions, and fantastic interfaces, which efficiently provide a feasible route to overcome the intrinsic limitations of single 2D components and embrace the distinct features of different materials. However, the construction of 2D heterostructures with uniform heterointerfaces still poses significant challenges. Herein, a universal in-situ interfacial growth strategy is designed to controllably prepare a series of MXene-based tin selenides/sulfides with 2D van der Waals homogeneous heterostructures. Molten salt etching by-products that are usually recognized as undesirable impurities, are reasonably utilized by us to efficiently transform into different 2D nanostructures via in-situ interfacial growth. The obtained MXene-based 2D heterostructures present sandwiched structures and lamellar interlacing networks with uniform heterointerfaces, which demonstrate the efficient conversion from 3D composite to 2D heterostructures. Such 2D heterostructures significantly enhance charge transfer efficiency, chemical reversibility, and overall structural stability in the electrochemical process. Taking 2D-SnSe2/MXene anode as a representative, it delivers outstanding lithium storage performance with large reversible capacities and ultrahigh capacity retention of over 97% after numerous cycles at 0.2, 1.0, and 10.0 Ag-1 current density, which suggests its tremendous application potential in lithium-ion batteries.

Visible Light-Activated Room Temperature NO2 Gas Sensing Based on the In2O3@ZnO Heterostructure with a Hollow Microtube Structure.

The persistent challenge of poor recovery characteristics of NO2 sensors operated at room temperature remains significant. However, the development of In2O3-based gas sensing materials provides a promising approach to accelerate response and recovery for sub-ppm of NO2 detection at room temperature. Herein, we propose a simple two-step method to synthesize a one-dimensional (1D) In2O3@ZnO heterostructure material with hollow microtubes, by coupling metal-organic frameworks (MOFs) (MIL-68 (In)) and zinc ions. Meanwhile, the In2O3@ZnO composite-based gas sensor exhibits superior sensitivity performance to NO2 under visible light activation. The response value to 5 ppm of NO2 at room temperature is as high as 1800, which is 35 times higher than that of the pure In2O3-based sensor. Additionally, the gas sensor based on the In2O3@ZnO heterostructure demonstrates a significantly reduced response/recovery time of 30 s/67 s compared to the sensor based on pure In2O3 (74 s/235 s). The outstanding gas sensing properties of the In2O3@ZnO heterostructure-based sensors can be attributed to the enhanced photogenerated charge separation efficiency resulting from the heterostructure effect, and the improved receptor function toward NO2, which can increase the reactive sites and gas adsorption capacity. In summary, this work proposes a low-cost and efficient method to synthesize a 1D heterostructure material with microtube structures, which can serve as a fundamental technique for developing high-performance room-temperature gas sensors.

Epitaxial Integration of Transferable High-κ Dielectric and 2D Semiconductor.

The synthesis of high-dielectric-constant (high-κ) dielectric materials and their integration with channel materials have been the key challenges in the state-of-the-art transistor architecture, as they can provide strong gate control and low operating voltage. For next-generation electronics, high-mobility two-dimensional (2D) layered semiconductors with dangling-bond-free surfaces and an atomic-thick thickness are being explored as channel materials to achieve shorter channel lengths and less interfacial scattering. Nowadays, the integration of high-κ dielectrics with high-mobility 2D semiconductors mainly relies on atomic layer deposition or transfer stacking, which may cause several undesirable problems, such as channel damage and interface traps. Here, we demonstrate the integration of high-mobility 2D semiconducting Bi2O2Se with transferable high-κ SrTiO3 as a 2D field-effect transistor by direct epitaxial growth. Remarkably, such 2D heterostructures can be efficiently transferred from the water-soluble Sr3Al2O6 sacrificial layer onto arbitrary substrates. The as-fabricated 2D Bi2O2Se/SrTiO3 transistors exhibit an on/off ratio over 104 and a subthreshold swing down to 90 mV/dec. Furthermore, the 2D Bi2O2Se/SrTiO3 heterostructures can be easily transferred onto flexible polyethylene terephthalate (PET) substrates, and the as-fabricated transistors exhibit good potential in flexible electronics. Our study opens up a new avenue for the integration of high-κ dielectrics with high-mobility 2D semiconductors and paves the way for the exploration of multifunctional electronic devices.

Superlubric Sliding of Graphene Auto-Kirigami with Interfaces Containing Self-Assembled Stripe-Pattern Adsorbates.

Van der Waals heterostructures formed by stacked 2D materials show exceptional electronic, mechanical, and optical properties. Superlubricity, a condition where atomically flat, incommensurate planes of atoms result in ultra-low friction, is a prime example enabling, for example, self-assembly of optically visible graphene nanostructures in air via a sliding auto-kirigami process. Here, it is demonstrated that a subtle but ubiquitous adsorbate stripe structure found on graphene and graphitic surfaces in ambient conditions remains stable within the interface between twisted graphene layers as they slide over each other. Despite this contamination, the interface retains an exceptional superlubricious state with an estimated upper bound frictional shear strength of 10kPa, indicating that direct atomic incommensurate contact is not required to achieve ambient superlubricity for 2D materials. The results suggest that any phenomena depending on 2D heterostructure interfaces such as exotic electronic behavior may need to consider the presence of stripe adsorbate structures that remain intercalated.

Large-scale 2D heterostructures from hydrogen-bonded organic frameworks and graphene with distinct Dirac and flat bands

The current strategies for building 2D organic-inorganic heterojunctions involve mostly wet-chemistry processes or exfoliation and transfer, leading to interface contaminations, poor crystallizing, or limited size. Here we show a bottom-up procedure to fabricate 2D large-scale heterostructure with clean interface and highly-crystalline sheets. As a prototypical example, a well-ordered hydrogen-bonded organic framework is self-assembled on the highly-oriented-pyrolytic-graphite substrate. The organic framework adopts a honeycomb lattice with faulted/unfaulted halves in a unit cell, resemble to molecular “graphene”. Interestingly, the topmost layer of substrate is self-lifted by organic framework via strong interlayer coupling, to form effectively a floating organic framework/graphene heterostructure. The individual layer of heterostructure inherits its intrinsic property, exhibiting distinct Dirac bands of graphene and narrow bands of organic framework. Our results demonstrate a promising approach to fabricate 2D organic-inorganic heterostructure with large-scale uniformity and highly-crystalline via the self-lifting effect, which is generally applicable to most of van der Waals materials.

Two-dimensional iron oxide/graphene-based nanocomposites as high-performance solid lubricants

Beyond conventional 2D layered materials such as graphene and transition metal dichalcogenides, 2D metal oxides have also received much interest in recent years. They have unique electronic (such as 2D TiO2 and MoO2), catalytic (such as 2D CeO2 and MnO2), and magnetic properties (such as 2D Fe2O3) compared with bulk metal oxides due to their atomically thin structures. Certain types of 2D metal oxides also have the potential to be a new type of high-performance solid lubricants due to the tunable interlayer interaction and possibility for 2D heterostructure formation, but this remains largely unexplored. In this work, we developed a scalable microwave-assisted solid-state synthesis of 2D Fe2O3 and their nanocomposites with reduced graphene oxide (rGO). The 2D Fe2O3/rGO nanocomposites were systematically characterized by electron microscopies and spectroscopies, and their utilization as solid lubricants was studied by pin-on-disk tribometer on both silicon and steel substrates. The results show that due to the easy sliding between 2D Fe2O3 and rGO nanosheets and their unique magnetic-induced assembled morphology, low coefficient of friction (COF) can be achieved for both steel-silicon and steel-steel interfaces. Superlubricity (COF ∼ 0.007) can be achieved for the 2D Fe2O3/rGO nanocomposite with a GO primer layer on a steel substrate. This work provides new insights into the development of functional 2D nanocomposites and expands their applications to solid lubrication and beyond.

Imaging tunable Luttinger liquid systems in van der Waals heterostructures.

One-dimensional (1D) interacting electrons are often described as a Luttinger liquid1-4 having properties that are intrinsically different from those of Fermi liquids in higher dimensions5,6. In materials systems, 1D electrons exhibit exotic quantum phenomena that can be tuned by both intra- and inter-1D-chain electronic interactions, but their experimental characterization can be challenging. Here we demonstrate that layer-stacking domain walls (DWs) in van der Waals heterostructures form a broadly tunable Luttinger liquid system, including both isolated and coupled arrays. We have imaged the evolution of DW Luttinger liquids under different interaction regimes tuned by electron density using scanning tunnelling microscopy. Single DWs at low carrier density are highly susceptible to Wigner crystallization consistent with a spin-incoherent Luttinger liquid, whereas at intermediate densities dimerized Wigner crystals form because of an enhanced magneto-elastic coupling. Periodic arrays of DWs exhibit an interplay between intra- and inter-chain interactions that gives rise to new quantum phases. At low electron densities, inter-chain interactions are dominant and induce a 2D electron crystal composed of phased-locked 1D Wigner crystal in a staggered configuration. Increased electron density causes intra-chain fluctuation potentials to dominate, leading to an electronic smectic liquid crystal phase in which electrons are ordered with algebraical correlation decay along the chain direction but disordered between chains. Our work shows that layer-stacking DWs in 2D heterostructures provides opportunities to explore Luttinger liquid physics.