A fast 2D MoS photodetector with ultralow contact resistance.

Two-dimensional (2D) transition metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS), hold great promise for next-generation nanoelectronic and nanophotonic devices. While high photoresponsivity and broad spectral coverage (UV-IR) have been reported, the slow response time of MoS photodetectors caused by their unfavorable RC characteristics is still a major limit in current devices. Once the RC limit issue is resolved, the intrinsic saturation drift velocity of electrons in TMDs (∼10 cm s) may enable GHz opto-electronic operations.

Electrically tunable non-radiative lifetime in WS/WSe heterostructures.

Van der Waals heterostructures based on transition metal dichalcogenides (TMDs) have emerged as excellent candidates for next-generation optoelectronics and valleytronics, due to their fascinating physical properties. The understanding and active control of the relaxation dynamics of heterostructures play a crucial role in device design and optimization. Here, we investigate the back-gate modulation of exciton dynamics in a WS/WSe heterostructure by combining time-resolved photoluminescence (TRPL) and transient absorption spectroscopy (TAS) at cryogenic temperatures.

Chemical Potential Characterization of Symmetry-Breaking Phases in a Rhombohedral Trilayer Graphene.

Rhombohedral trilayer graphene has recently emerged as a natural flat-band platform for studying interaction-driven symmetry-breaking phases. The displacement field () can further flatten the band to enhance the density of states, thereby controlling the electronic correlation that tips the energy balance between spin and valley degrees of freedom. To characterize the energy competition, chemical potential measurement─a direct thermodynamic probe of Fermi surfaces─is highly demanding to be conducted under a constant .

A Gate Programmable van der Waals Metal-Ferroelectric-Semiconductor Vertical Heterojunction Memory.

Ferroelectricity, one of the keys to realize non-volatile memories owing to the remanent electric polarization, is an emerging phenomenon in the 2D limit. Yet the demonstrations of van der Waals (vdW) memories using 2D ferroelectric materials as an ingredient are very limited. Especially, gate-tunable ferroelectric vdW memristive device, which holds promises in future multi-bit data storage applications, remains challenging.

Artificial Neuron Networks Enabled Identification and Characterizations of 2D Materials and van der Waals Heterostructures.

Two-dimensional (2D) materials and their in-plane and out-of-plane (.., van der Waals, vdW) heterostructures are promising building blocks for next-generation electronic and optoelectronic devices.

Correlated states in doubly-aligned hBN/graphene/hBN heterostructures.

Interfacial moiré superlattices in van der Waals vertical assemblies effectively reconstruct the crystal symmetry, leading to opportunities for investigating exotic quantum states. Notably, a two-dimensional nanosheet has top and bottom open surfaces, allowing the specific case of doubly aligned super-moiré lattice to serve as a toy model for studying the tunable lattice symmetry and the complexity of related electronic structures. Here, we show that by doubly aligning a graphene monolayer to both top and bottom encapsulating hexagonal boron nitride (h-BN), multiple conductivity minima are observed away from the main Dirac point, which are sensitively tunable with respect to the small twist angles.

In-Plane Magnetic Domains and Néel-like Domain Walls in Thin Flakes of the Room Temperature CrTe Van der Waals Ferromagnet.

The recent discovery of magnetic van der Waals (vdW) materials triggered a wealth of investigations in materials science and now offers genuinely new prospects for both fundamental and applied research. Although the catalog of vdW ferromagnets is rapidly expanding, most of them have a Curie temperature below 300 K, a notable disadvantage for potential applications. Combining element-selective X-ray magnetic imaging and magnetic force microscopy, we resolve at room temperature the magnetic domains and domain walls in micron-sized flakes of the CrTe vdW ferromagnet.

In-plane anisotropic electronics based on low-symmetry 2D materials: progress and prospects.

Low-symmetry layered materials such as black phosphorus (BP) have been revived recently due to their high intrinsic mobility and in-plane anisotropic properties, which can be used in anisotropic electronic and optoelectronic devices. Since the anisotropic properties have a close relationship with their anisotropic structural characters, especially for materials with low-symmetry, exploring new low-symmetry layered materials and investigating their anisotropic properties have inspired numerous research efforts. In this paper, we review the recent experimental progresses on low-symmetry layered materials and their corresponding anisotropic electrical transport, magneto-transport, optoelectronic, thermoelectric, ferroelectric, and piezoelectric properties.