The integration of two-dimensional (2D) van der Waals semiconductors into silicon electronics technology will require the production of large-scale, uniform, and highly crystalline films. We report a route for synthesizing wafer-scale single-crystalline 2H molybdenum ditelluride (MoTe2) semiconductors on an amorphous insulating substrate. In-plane 2D-epitaxy growth by tellurizing was triggered from a deliberately implanted single seed crystal. The resulting single-crystalline film completely covered a 2.5-centimeter wafer with excellent uniformity. The 2H MoTe2 2D single-crystalline film can use itself as a template for further rapid epitaxy in a vertical manner. Transistor arrays fabricated with the as-prepared 2H MoTe2 single crystals exhibited high electrical performance, with excellent uniformity and 100% device yield.

Materials with a quasi-one-dimensional stripy magnetic order often exhibit low crystal and magnetic symmetries, thus allowing the presence of various energy coupling terms and giving rise to macroscopic interplay between spin, charge, and phonon. In this work, we performed optical, electrical and magnetic characterizations combined with first-principles calculations on a van der Waals antiferromagnetic insulator chromium oxychloride (CrOCl). We detected the subtle phase transition behaviors of exfoliated CrOCl under varying temperature and magnetic field and clarified its controversial spin structures. We found that the antiferromagnetism and its air stability persist down to few-layer samples, making it a promising candidate for future 2D spintronic devices. Additionally, we verified the magnetoelastic coupling effect in CrOCl, allowing for the potential manipulation of the magnetic states via electric field or strain. These virtues of CrOCl provide us with an ideal platform for fundamental research on spin-charge, spin-phonon coupling, and spin-interactions.

Quantum interference gives rise to the asymmetric Fano resonance line shape when the final states of an electronic transition follow within a continuum of states and a discrete state, which has significant applications in optical switching and sensing. The resonant optical phenomena associated with the Fano resonance have been observed by absorption spectra, Raman spectra, transmission spectra, etc., but have rarely been reported in photoluminescence (PL) spectroscopy. In this work, we performed spectroscopic studies on layered chromium thiophosphate (CrPS4), a promising ternary antiferromagnetic semiconductor with PL in the near-infrared wavelength region and observed a Fano resonance when CrPS4 experiences phase transition into the antiferromagnetic state below the Néel temperature (38 K). The photoluminescence of the continuum states results from the d band transitions localized at Cr3+ ions, whereas the discrete state is formed by an impurity level, the electronic transition of which is enabled by symmetry breaking. Our findings provide insights into the photon-emitting coherent electronic transitions of CrPS4 and their connection to the magnetism-related broken symmetry.

Because of atomic thickness and non-zero band gap, two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have become promising candidates for post-silicon nanoelectronic materials. In the process of realizing 2D electronic devices for scaling down modern integrated circuitry, contact engineering suitable for large-scale manufacturing is crucial, but it remains elusive. Here, we demonstrated the large-scale chemical assembly of van der Waals heterostructures, with metallic 1T′-MoTe2 on top of semiconducting 2H-MoTe2, via a spatial-controlled phase-engineered growth method. Based on the heterophase structure, a large-scale field-effect transistor (FET) array was fabricated, in which 1T′-MoTe2 was used as the contact electrode and 2H-MoTe2 was used as the semiconducting channel. The vertical nanosheet-based heterophase FET exhibits ohmic contact behavior with distinctively low contact resistance. A total of 120 FETs were measured, and the measured average field-effect mobility was as high as 15 cm2 V–1 s–1 (comparable to that of exfoliated single-crystalline 2H-MoTe2). The superior electrical properties are attributed to the atomic clean interface that leads to an ideal contact between top 1T′- and bottom 2H-MoTe2. This spatially controlled large-scale chemical assembly of vertical 2D metal–semiconductor heterostructures with low contact resistance provides a new route toward the practical application of high-performance electronic and optoelectronic devices based on the atomically thin TMDCs.

netic layered transition-metal oxyhalides in a low-symmetry orthorhombic structure provide a new degree of freedom to modulate magnetism, [3] increasing the attention to explore their low-dimensional properties. [4][5][6] Recently, magnetic superstructures and optical anisotropies have been explored in layered single-crystal CrOCl. [4] Additionally, the atomic structure, work function, and magnetism of VOCl have been investigated. [5] Interestingly, relatively high Néel temperatures in monolayer FeOX (X = F, Cl, Br, or I) have recently been predicted by theoretical calculations, indicating that they are robust antiferromagnets. [7] Bulk FeOCl was first synthesized by Goldsztaub in 1935 [8] and it was reported to have the highest Néel temperature of 92 K among transition-metal oxyhalides. [4,5,9,10] It has been widely studied, specifically for its structure, [8,11,12] intercalation, [13][14][15][16][17] magnetism, [6,9,12,18] phase transition, [18,19] and catalytic performance. [20][21][22][23] Over the past decade, various methods, including chemical vapor transport (CVT), [8,[11][12][13][14][15][16][17][18][19][20][21][24][25][26] chemical vapor deposition, [27] partial pyrolysis, [22,23,28] liquid exfoliation, [29] chemical exfoliation, [6] and rapid thermal annealing, have been developed to 2D van der Waals (vdW) transition-metal oxyhalides with low symmetry, novel magnetism, and good stability provide a versatile platform for conducting fundamental research and developing spintronics. Antiferromagnetic FeOCl has attracted significant interest owing to its unique semiconductor properties and relatively high Néel temperature. Herein, good-quality centimeter-scale FeOCl single crystals are controllably synthesized using the universal temperatureoscillation chemical vapor transport (TO-CVT) method. The crystal structure, bandgap, and anisotropic behavior of the 2D FeOCl are explored in detail. The absorption spectrum and electrical measurements reveal that 2D FeOCl is a semiconductor with an optical bandgap of ≈2.1 eV and a resistivity of ≈10 −1 Ω m at 295 K, and the bandgap increases with decreasing thickness. Strong in-plane optical and electrical anisotropies are observed in 2D FeOCl flakes, and the maximum resistance anisotropic ratio reaches 2.66 at 295 K. Additionally, the lattice vibration modes are studied through temperature-dependent Raman spectra and first-principles density functional calculations. A significant decrease in the Raman frequencies below the Néel temperature is observed, which results from the strong spin−phonon coupling effect in 2D FeOCl. This study provides a highquality low-symmetry vdW magnetic candidate for miniaturized spintronics.