Two-dimensional (2D) materials are promising for next-generation photo detection because of their exceptional properties such as a strong interaction with light, electronic and optical properties that depend on the number of layers, and the ability to form hybrid structures. However, the intrinsic detection ability of 2D material-based photodetectors is low due to their atomic thickness. Photogating is widely used to improve the responsivity of devices, which usually generates large noise current, resulting in limited detectivity. Here, we report a molybdenum-based phototransistor with MoS₂ channel and α-MoO_3-x contact electrodes. The device works in a photo-induced barrier-lowering (PIBL) mechanism and its double heterojunctions between the channel and the electrodes can provide positive feedback to each other. As a result, a detectivity of 9.8 × 10¹⁶ cm Hz^1/2 W⁻¹ has been achieved. The proposed double heterojunction PIBL mechanism adds to the techniques available for the fabrication of 2D material-based phototransistors with an ultrahigh photosensitivity.

Straining to make a transistor: The use of carbon nanotubes (CNTs) as short-channel-length transistors will require control of their chirality, which determines whether they are semiconducting or metallic and if they form strong, low-resistance contacts. Tang et al . fabricated CNT intramolecular transistors by progressive heating and straining of individual CNTs within a transmission electron microscope. Changes to chirality along sections of the nanotube created metallic-to-semiconducting transitions. A semiconducting nanotube channel was covalently bonded to the metallic nanotube source and drain regions. The resulting CNT intramolecular transistors had channel lengths as short as 2.8 nanometers. —PDS

High–melting point alloy catalysts have been reported to be effective for the structure-controlled growth of single-wall carbon nanotubes (SWCNTs). However, some fundamental issues remain unclear because of the complex catalytic growth environment. Here, we directly investigated the active catalytic phase of Co-W-C alloy catalyst, the growth kinetics of CNTs, and their interfacial dynamics using closed-cell environmental transmission electron microscopy at atmospheric pressure. The alloy catalyst was precisely identified as a cubic η-carbide phase that remained unchanged during the whole CNT growth process. Rotations of the catalyst nanoparticles during CNT growth were observed, implying a weak interfacial interaction and undefined orientation dependence for the solid catalyst. Theoretical calculations suggested that the growth kinetics are determined by the diffusion of carbon atoms on the surface of the η-carbide catalyst and through the interface of the catalyst-CNT wall.

Carbon nanotubes (CNTs) have attracted intense research interest owing to their unique one-dimensional structure and exceptional properties. However, when individual CNTs are assembled to macrostructures such as films and fibers, their electrical performance often deteriorates significantly. This review offers a comprehensive look at the recent progress in the electrical properties and measurement techniques of CNTs, ranging from individual nanotubes to their assemblies. Firstly, we explore the methods for measuring the electrical properties of individual CNTs, including scanning tunnelling microscopy, electron microscope-based nanoprobes, and measurements using nanodevices. Secondly, we examine how structural characteristics of CNTs (e.g., chirality, diameter, and defects) influence their electrical behaviors. A critical comparison between individual CNTs and their assemblies reveals the difficulties in transferring the electrical properties from nanoscale to bulk materials. Finally, we put forward strategies to boost the electrical conductivity of CNT assemblies and also sketch out future research and development directions.