Anisotropic Carrier Mobility from 2H WSe2

Achieving a Noise Limit with a Few-layer WSe2 Avalanche Photodetector at Room Temperature

We engineered a two-dimensional Pt/WSe2/Ni avalanche photodetector (APD) optimized for ultraweak signal detection at room temperature. By fine-tuning the work functions, we achieved an ultralow dark current of 10-14 A under small bias, with a noise equivalent power (NEP) of 8.09 fW/Hz1/2. This performance is driven by effective dark barrier blocking and a record-long electron mean free path (123 nm) in intrinsic WSe2, minimizing dark carrier replenishment and suppressing noise under an ultralow electric field. Our APD exhibits a high gain of 5 × 105 at a modulation frequency of 20 kHz, effectively balancing gain and bandwidth, a common challenge in traditional photovoltaic-based APDs. By addressing the typical challenges of high noise and low gain and minimizing dependence on high electric fields, this work highlights the potential of 2D materials in developing efficient, low-power, and ultrasensitive photodetections.

Temperature dependence of the dielectric function and critical points of monolayer WSe2

Monolayer materials typically display intriguing temperature-dependent dielectric and optical properties, which are crucial for improving the structure and functionality of associated devices. Due to its unique photoelectric capabilities, monolayer WSe2 has recently received a lot of attention in the fields of atomically thin electronics and optoelectronics. In this work, we focus on the evolution of the temperature-dependent dielectric function (ε = ε1 + i ε2) of monolayer WSe2 over energies from 0.74 to 6.40 eV and temperatures from 40 to 350 K. We analyze the second derivatives of ε with respect to energy to accurately locate the critical points (CP). The dependence of the observed CP energies on temperature is consistent with the alternative domination of the declining exciton binding energy as the temperature increases.

Structure modulation of two-dimensional transition metal chalcogenides: recent advances in methodology, mechanism and applications

Together with the development of two-dimensional (2D) materials, transition metal dichalcogenides (TMDs) have become one of the most popular series of model materials for fundamental sciences and practical applications. Due to the ever-growing requirements of customization and multi-function, dozens of modulated structures have been introduced in TMDs. In this review, we present a systematic and comprehensive overview of the structure modulation of TMDs, including point, linear and out-of-plane structures, following and updating the conventional classification for silicon and related bulk semiconductors. In particular, we focus on the structural characteristics of modulated TMD structures and analyse the corresponding root causes. We also summarize the recent progress in modulating methods, mechanisms, properties and applications based on modulated TMD structures. Finally, we demonstrate challenges and prospects in the structure modulation of TMDs and forecast potential directions about what and how breakthroughs can be achieved.

Electrical and magnetic anisotropies in van der Waals multiferroic CuCrP2S6

Multiferroic materials have great potential in non-volatile devices for low-power and ultra-high density information storage, owing to their unique characteristic of coexisting ferroelectric and ferromagnetic orders. The effective manipulation of their intrinsic anisotropy makes it promising to control multiple degrees of the storage "medium". Here, we have discovered intriguing in-plane electrical and magnetic anisotropies in van der Waals (vdW) multiferroic CuCrP₂S₆. The uniaxial anisotropies of current rectifications, magnetic properties and magnon modes are demonstrated and manipulated by electric direction/polarity, temperature variation and magnetic field. More important, we have discovered the spin-flop transition corresponding to specific resonance modes, and determined the anisotropy parameters by consistent model fittings and theoretical calculations. Our work provides in-depth investigation and quantitative analysis of electrical and magnetic anisotropies with the same easy axis in vdW multiferroics, which will stimulate potential device applications of artificial bionic synapses, multi-terminal spintronic chips and magnetoelectric devices.