Bridging Synthesis and Controllable Doping of Monolayer 4 in. Length Transition-Metal Dichalcogenides Single Crystals with High Electron Mobility

Understanding Iron-Doping Modulating Domain Orientation and Improving the Device Performance of Monolayer Molybdenum Disulfide

Domain orientation modulation and controlled doping of two-dimensional (2D) transition-metal dichalcogenides (TMDCs) are two pivotal tasks for synthesizing wafer-scale single crystals and boosting device performances. However, realizing two such targets and uncovering internal physical mechanisms remain daunting challenges. We develop an accurate Fe doping strategy, which enables domain orientation control and electron mobility improvement of monolayer MoS2. By tuning of the Fe dopant dosages, parallel steps with different heights are formed, which induce edge-nucleation of unidirectionally aligned monolayer MoS2. In parallel, Fe doping induces the down shift of the conduction band minimum of monolayer MoS2 and matches well with the work function of an electrode, which reduces Schottky barrier height and delivers ultralow contact resistance (561 Ω μm) and excellent electron mobility (37.5 cm2 V-1 s-1). The modulation mechanism is clarified by combining theory calculations and electronic structure characterizations. This work hereby provides a new paradigm for synthesizing wafer-scale 2D TMDC single crystals and constructing high-performance devices.

Epitaxial Growth of Monolayer WS2 Single Crystals on Au(111) Toward Direct Surface-Enhanced Raman Spectroscopy Detection

The epitaxial growth of wafer-scale two-dimensional (2D) semiconducting transition metal dichalcogenides (STMDCs) single crystals is the key premise for their applications in next-generation electronics. Despite significant advancements, some fundamental factors affecting the epitaxy growth have not been fully uncovered, e.g., interface coupling strength, adlayer-substrate lattice matching, substrate step-edge-guiding effects, etc. Herein, we develop a model system to tackle these issues concurrently, and realize the epitaxial growth of wafer-scale monolayer tungsten disulfide (WS2) single crystals on the Au(111) substrate. This epitaxial system is featured with good adlayer-substrate lattice matching, obvious step-edge-guiding effect for the unidirectionally aligned nucleation/growth, and relatively weaker interfacial interaction than that of monolayer MoS2/Au(111), as evidenced by the evolution of a uniform Moiré pattern and an intrinsic band gap, according to on-site scanning tunneling microscopy/spectroscopy (STM/STS) characterizations and density functional theory calculations. Intriguingly, the unidirectionally aligned monolayer WS2 domains along the Au(111) steps can behave as ultrasensitive templates for surface-enhanced Raman scattering detection of organic molecules, due to the obvious charge transfer occurred at substrate step edges. This work should hereby deepen our understanding of the epitaxy mechanism of 2D STMDCs on single-crystal substrates, and propel their wafer-scale production and applications in various cutting-edge fields.

Large-Area Epitaxial Growth of Transition Metal Dichalcogenides

Over the past decade, research on atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs) has expanded rapidly due to their unique properties such as high carrier mobility, significant excitonic effects, and strong spin-orbit couplings. Considerable attention from both scientific and industrial communities has fully fueled the exploration of TMDs toward practical applications. Proposed scenarios, such as ultrascaled transistors, on-chip photonics, flexible optoelectronics, and efficient electrocatalysis, critically depend on the scalable production of large-area TMD films. Correspondingly, substantial efforts have been devoted to refining the synthesizing methodology of 2D TMDs, which brought the field to a stage that necessitates a comprehensive summary. In this Review, we give a systematic overview of the basic designs and significant advancements in large-area epitaxial growth of TMDs. We first sketch out their fundamental structures and diverse properties. Subsequent discussion encompasses the state-of-the-art wafer-scale production designs, single-crystal epitaxial strategies, and techniques for structure modification and postprocessing. Additionally, we highlight the future directions for application-driven material fabrication and persistent challenges, aiming to inspire ongoing exploration along a revolution in the modern semiconductor industry.

Two-Dimensional Semiconductors for State-of-the-Art Complementary Field-Effect Transistors and Integrated Circuits

As the trajectory of transistor scaling defined by Moore's law encounters challenges, the paradigm of ever-evolving integrated circuit technology shifts to explore unconventional materials and architectures to sustain progress. Two-dimensional (2D) semiconductors, characterized by their atomic-scale thickness and exceptional electronic properties, have emerged as a beacon of promise in this quest for the continued advancement of field-effect transistor (FET) technology. The energy-efficient complementary circuit integration necessitates strategic engineering of both n-channel and p-channel 2D FETs to achieve symmetrical high performance. This intricate process mandates the realization of demanding device characteristics, including low contact resistance, precisely controlled doping schemes, high mobility, and seamless incorporation of high- κ dielectrics. Furthermore, the uniform growth of wafer-scale 2D film is imperative to mitigate defect density, minimize device-to-device variation, and establish pristine interfaces within the integrated circuits. This review examines the latest breakthroughs with a focus on the preparation of 2D channel materials and device engineering in advanced FET structures. It also extensively summarizes critical aspects such as the scalability and compatibility of 2D FET devices with existing manufacturing technologies, elucidating the synergistic relationships crucial for realizing efficient and high-performance 2D FETs. These findings extend to potential integrated circuit applications in diverse functionalities.

Two-Dimensional Semiconductors and Transistors for Future Integrated Circuits

Silicon transistors are approaching their physical limit, calling for the emergence of a technological revolution. As the acknowledged ultimate version of transistor channels, 2D semiconductors are of interest for the development of post-Moore electronics due to their useful properties and all-in-one potentials. Here, the promise and current status of 2D semiconductors and transistors are reviewed, from materials and devices to integrated applications. First, we outline the evolution and challenges of silicon-based integrated circuits, followed by a detailed discussion on the properties and preparation strategies of 2D semiconductors and van der Waals heterostructures. Subsequently, the significant progress of 2D transistors, including device optimization, large-scale integration, and unconventional devices, are presented. We also examine 2D semiconductors for advanced heterogeneous and multifunctional integration beyond CMOS. Finally, the key technical challenges and potential strategies for 2D transistors and integrated circuits are also discussed. We envision that the field of 2D semiconductors and transistors could yield substantial progress in the upcoming years and hope this review will trigger the interest of scientists planning their next experiment.

Robust multiferroic in interfacial modulation synthesized wafer-scale one-unit-cell of chromium sulfide

Multiferroic materials offer a promising avenue for manipulating digital information by leveraging the cross-coupling between ferroelectric and ferromagnetic orders. Despite the ferroelectricity has been uncovered by ion displacement or interlayer-sliding, one-unit-cell of multiferroic materials design and wafer-scale synthesis have yet to be realized. Here we develope an interface modulated strategy to grow 1-inch one-unit-cell of non-layered chromium sulfide with unidirectional orientation on industry-compatible c-plane sapphire. The interfacial interaction between chromium sulfide and substrate induces the intralayer-sliding of self-intercalated chromium atoms and breaks the space reversal symmetry. As a result, robust room-temperature ferroelectricity (retaining more than one month) emerges in one-unit-cell of chromium sulfide with ultrahigh remanent polarization. Besides, long-range ferromagnetic order is discovered with the Curie temperature approaching 200 K, almost two times higher than that of bulk counterpart. In parallel, the magnetoelectric coupling is certified and which makes 1-inch one-unit-cell of chromium sulfide the largest and thinnest multiferroics.

Sheet-Isolated MoS2 Used for Dispersing Pt Nanoparticles and its Application in Methanol Fuel Cells

It is highly challenging to activate the basal plane and minimize the π-π stacking of MoS2 sheets, thus enhancing its catalytic performance. Here, we display an approach for making well-dispersed MoS2 . By using the N-doped multi-walled carbon nanotubes (NMWCNTs) as an isolation unit, the aggregation of MoS2 sheets was effectively reduced, favoring the dispersion of Pt nanoparticles (noted as Pt/NMWCNTs-isolated-MoS2 ). Excellent bifunctional catalytic performance for methanol oxidation and oxygen reduction reaction (MOR/ORR) were demonstrated by the produced Pt/NMWCNTs-isolated-MoS2 . In comparison to Pt nanoparticles supported on MoS2 (Pt/MoS2 ), the MOR activity (2314.14 mA mgpt -1 ) and stability (317.69 mA mgpt -1 after 2 h of operation) on Pt/NMWCNTs-isolatedMoS2 were 24 and 232 times higher, respectively. As for ORR, Pt/NMWCNTs-isolated-MoS2 holds large half-wave potential (0.88 V) and high stability (92.71 % after 22 h of operation). This work presents a tactic for activating the basal planes and reducing the π-π stacking of 2D materials to satisfy their applications in electrocatalysis. In addition, the proposed sheet-isolation method can be used for fabricating other 2D materials to promote the dispersion of nanoparticles, which assist its application in other fields of energy as well as the environment.

Controlled Synthesis and Accurate Doping of Wafer-Scale 2D Semiconducting Transition Metal Dichalcogenides

2D semiconducting transition metal dichalcogenide (TMDCs) possess atomically thin thickness, a dangling-bond-free surface, flexible band structure, and silicon-compatible feature, making them one of the most promising channels for constructing state-of-the-art field-effect transistors in the post-Moore's era. However, the existing 2D semiconducting TMDCs fall short of meeting the industry criteria for practical applications in electronics due to their small domain size and the lack of an effective approach to modulate intrinsic physical properties. Therefore, it is crucial to prepare and dope 2D semiconducting TMDCs single crystals with wafer size. In this review, the up-to-date progress regarding the wafer-scale growth of 2D semiconducting TMDC polycrystalline and single-crystal films is systematically summarized. The domain orientation control of 2D TMDCs and the seamless stitching of unidirectionally aligned 2D islands by means of substrate design are proposed. In addition, the accurate and uniform doping of 2D semiconducting TMDCs and the effect on electronic device performances are also discussed. Finally, the dominating challenges pertaining to the enhancement of the electronic device performances of TMDCs are emphasized, and further development directions are put forward. This review provides a systematic and in-depth summary of high-performance device applications of 2D semiconducting TMDCs.