Layer-by-layer assembly is widely used for constructing two-dimensional van der Waals heterostructures, yet polymer-induced interfacial contamination in conventional transfer processes often limits device performance. Here, we show that ultraclean chromium oxychloride (CrOCl)/bilayer graphene (BLG) heterinterfaces, realized via a one-step transfer process, enable significantly enhanced electrical modulation. Precise control of the adhesion and release behavior of a polyvinyl butyral support effectively suppresses crack formation and minimizes interfacial residues, yielding uniform and contamination-free heterointerfaces. As a result, directly laminated CrOCl/BLG/boron nitride (BN) devices exhibit an exceptional switching ratio exceeding 10⁸ without post-annealing, outperforming layer-by-layer assembled counterparts by nearly seven orders of magnitude. These results highlight the critical role of interface cleanliness in governing the electrical performance of bilayer graphene heterostructures and provide a robust strategy for high-performance two-dimensional hetero-integration.

High-performance field-effect transistors (FETs) based on atomically thin two-dimensional (2D) semiconductors have demonstrated great promise in post-Moore integrated circuits. However, unipolar p-type 2D semiconductor transistors yet remain challenging and suffer from low saturation current density (less than 10 μA·μm^–1) and high contact resistance (larger than 100 kΩ·μm), mainly limited by the Schottky barrier induced by the mismatch of the work-functions and the Fermi level pinning at the metal contact interfaces. Here, we overcome these two obstacles through van der Waals (vdW) integration of high work-function metal palladium (Pd) as the contacts onto monolayer WSe₂ grown by chemical vapor deposition (CVD) method. We demonstrate unipolar p-type monolayer WSe₂ FETs with superior device performance: room temperature on-state current density exceeding 100 μA·μm^–1, contact resistance of 12 kΩ·μm, on/off ratio over 10⁷, and field-effect hole mobility of ~ 103 cm²·V^–1·s^–1. Electrical transport measurements reveal that the Fermi level pinning effect is completely effectively eliminated in monolayer WSe₂ with vdW Pd contacts, leading to a Schottky barrier-free Ohmic contact at the metal-semiconductor junctions. Combining the advantages of large-scale vdW contact strategy and CVD growth, our results pave the way for wafer-scale fabrication of complementary-metal-oxide-semiconductor (CMOS) logic circuits based on atomically thin 2D semiconductors.

Nanoscale light sources with high speed of electrical modulation and low energy consumption are key components for nanophotonics and optoelectronics. The record-high carrier mobility and ultrafast carrier dynamics of graphene make it promising as an atomically thin light emitter, which can be further integrated into arbitrary platforms by van der Waals forces. However, due to the zero bandgap, graphene is difficult to emit light through the interband recombination of carriers like conventional semiconductors. Here, we demonstrate ultrafast thermal light emitters based on suspended graphene/hexagonal boron nitride (Gr/hBN) heterostructures. Electrons in biased graphene are significantly heated up to 2800 K at modest electric fields, emitting bright photons from the near-infrared to the visible spectral range. By eliminating the heat dissipation channel of the substrate, the radiation efficiency of the suspended Gr/hBN device is about two orders of magnitude greater than that of graphene devices supported on SiO₂ or hBN. We further demonstrate that hot electrons and low-energy acoustic phonons in graphene are weakly coupled to each other and are not in full thermal equilibrium. Direct cooling of high-temperature hot electrons to low-temperature acoustic phonons is enabled by the significant near-field heat transfer at the highly localized Gr/hBN interface, resulting in ultrafast thermal emission with up to 1 GHz bandwidth under electrical excitation. It is found that suspending the Gr/hBN heterostructures on the SiO₂ trenches significantly modifies the light emission due to the formation of the optical cavity and showed a~440% enhancement in intensity at the peak wavelength of 940 nm compared to the black-body thermal radiation. The demonstration of electrically driven ultrafast light emission from suspended Gr/hBN heterostructures sheds the light on applications of graphene heterostructures in photonic integrated circuits, such as broadband light sources and ultrafast thermo-optic phase modulators.

Improving thermal transport between substrate and transistors has become a vital solution to the thermal challenge in nanoelectronics. Recently 2D WTe₂ has sparked extensive interest because of heavy atomic mass and low Debye temperature. Here, the thermal transport of supported WTe₂ was studied via Raman thermometry with electrical heating. The supported 30 nm WTe₂ encased with 70 nm Al₂O₃ delivered 4.8 W·m^-1·K^-1 in-plane thermal conductivity along zigzag direction at room temperature, which was almost 1.6 times larger than that along armchair direction (3.0 W·m^-1·K^-1). Interestingly, the superior and inferior directions for thermal transport are just opposite of those for electrical transport. Hence, a heat manipulation model in WTe₂ FET device was proposed. Within the designed configuration, waste heat in WTe₂ would be mostly dissipated to metal contacts located along zigzag, relieving the local temperature discrepancy in the channel effectively and preventing degradation or breakdown. Our study provides new insight into thermal transport of anisotropic 2D materials, which might inspire energy-efficient nanodevices in the future.