Ambipolar conduction in gated tungsten disulphide nanotube.

Devices based on transition metal dichalcogenide nanotubes hold great potential for electronic and optoelectronic applications. Herein, the electrical transport and photoresponse characteristics of a back-gate device with a channel made of a single tungsten disulfide (WS) nanotube are investigated as functions of electric stress, ambient pressure, and illumination. As a transistor, the device exhibits p-type conduction, which can be transformed into ambipolar conduction at a high drain-source voltage.

The Superconducting Mechanism in BiS-Based Superconductors: A Comprehensive Review with Focus on Point-Contact Spectroscopy.

The family of BiS-based superconductors has attracted considerable attention since their discovery in 2012 due to the unique structural and electronic properties of these materials. Several experimental and theoretical studies have been performed to explore the basic properties and the underlying mechanism for superconductivity. In this review, we discuss the current understanding of pairing symmetry in BiS-based superconductors and particularly the role of point-contact spectroscopy in unravelling the mechanism underlying the superconducting state.

Field enhancement induced by surface defects in two-dimensional ReSe field emitters.

The field emission properties of rhenium diselenide (ReSe) nanosheets on Si/SiO substrates, obtained through mechanical exfoliation, have been investigated. The n-type conduction was confirmed by using nano-manipulated tungsten probes inside a scanning electrode microscope to directly contact the ReSe flake in back-gated field effect transistor configuration, avoiding any lithographic process. By performing a finite element electrostatic simulation of the electric field, it is demonstrated that the use of a tungsten probe as anode, at a controlled distance from the ReSe emitter surface, allows the collection of emitted electrons from a reduced area that furtherly decreases by reducing the tip-sample distance, allowing a local characterization of the field emission properties.

WS Nanotube Transistor for Photodetection and Optoelectronic Memory Applications.

Nanotube and nanowire transistors hold great promises for future electronic and optoelectronic devices owing to their downscaling possibilities. In this work, a single multi-walled tungsten disulfide (WS) nanotube is utilized as the channel of a back-gated field-effect transistor. The device exhibits a p-type behavior in ambient conditions, with a hole mobility µ ≈  1.

Multilayer WS for low-power visible and near-infrared phototransistors.

Mechanically exfoliated multilayer WS flakes are used as the channel of field effect transistors for low-power photodetection in the visible and near-infrared (NIR) spectral range. The electrical characterization as a function of the temperature reveals devices with n-type conduction and slightly different Schottky barriers at the drain and source contacts. The WS phototransistors can be operated in self-powered mode, yielding both a current and a voltage when exposed to light.

Memory effect and coexistence of negative and positive photoconductivity in black phosphorus field effect transistor for neuromorphic vision sensors.

Black phosphorus (BP) field-effect transistors with ultrathin channels exhibit unipolar p-type electrical conduction over a wide range of temperatures and pressures. Herein, we study a device that exhibits mobility up to 100 cm V s and a memory window up to 1.3 μA.

Fully printed memristors made with MoS and graphene water-based inks.

2-Dimensional materials (2DMs) offer an attractive solution for the realization of high density and reliable memristors, compatible with printed and flexible electronics. In this work we fabricate a fully inkjet printed MoS-based resistive switching memory, where graphene is used as top electrode and silver is used as bottom electrode. Memristic effects are observed only after annealing of each printed component.

Subthreshold Current Suppression in ReS Nanosheet-Based Field-Effect Transistors at High Temperatures.

Two-dimensional rhenium disulfide (ReS), a member of the transition-metal dichalcogenide family, has received significant attention due to its potential applications in field-effect transistors (FETs), photodetectors, and memories. In this work, we investigate the suppression of the subthreshold current during the forward voltage gate sweep, leading to an inversion of the hysteresis in the transfer characteristics of ReS nanosheet-based FETs from clockwise to anticlockwise. We explore the impact of temperature, sweeping gate voltage, and pressure on this behavior.

Manipulation of the electrical and memory properties of MoS field-effect transistors by highly charged ion irradiation.

Field-effect transistors based on molybdenum disulfide (MoS) exhibit a hysteresis in their transfer characteristics, which can be utilized to realize 2D memory devices. This hysteresis has been attributed to charge trapping due to adsorbates, or defects either in the MoS lattice or in the underlying substrate. We fabricated MoS field-effect transistors on SiO/Si substrates, irradiated these devices with Xe ions at a kinetic energy of 180 keV to deliberately introduce defects and studied the resulting changes of their electrical and hysteretic properties.

Spatially Resolved Photo-Response of a Carbon Nanotube/Si Photodetector.

Photodetectors based on vertical multi-walled carbon nanotube (MWCNT) film-Si heterojunctions are realized by growing MWCNTs on n-type Si substrates with a top surface covered by SiN layers. Spatially resolved photocurrent measurements reveal that higher photo detection is achieved in regions with thinner MWCNT film, where nearly 100% external quantum efficiency is achieved. Hence, we propose a simple method based on the use of scotch tape with which to tune the thickness and density of as-grown MWCNT film and enhance device photo-response.

Etch and Print: Graphene-Based Diodes for Silicon Technology.

The graphene-silicon junction is one of the simplest conceivable interfaces in graphene-integrated semiconductor technology that can lead to the development of future generation of electronic and optoelectronic devices. However, graphene's integration is currently expensive and time-consuming and shows several challenges in terms of large-scale device fabrication, effectively preventing the possibility of implementing this technology into industrial processes. Here, we show a simple and cost-effective fabrication technique, based on inkjet printing, for the realization of printed graphene-silicon rectifying devices.

Graphene-Silicon Device for Visible and Infrared Photodetection.

The fabrication of a graphene-silicon (Gr-Si) junction involves the formation of a parallel metal-insulator-semiconductor (MIS) structure, which is often disregarded but plays an important role in the optoelectronic properties of the device. In this work, the transfer of graphene onto a patterned n-type Si substrate, covered by SiN, produces a Gr-Si device, in which the parallel MIS consists of a Gr-SiN-Si structure surrounding the Gr-Si junction. The Gr-Si device exhibits rectifying behavior with a rectification ratio up to 10.

Electron Irradiation of Metal Contacts in Monolayer MoS Field-Effect Transistors.

Metal contacts play a fundamental role in nanoscale devices. In this work, Schottky metal contacts in monolayer molybdenum disulfide (MoS) field-effect transistors are investigated under electron beam irradiation. It is shown that the exposure of Ti/Au source/drain electrodes to an electron beam reduces the contact resistance and improves the transistor performance.

WS Nanotubes: Electrical Conduction and Field Emission Under Electron Irradiation and Mechanical Stress.

This study reports the electrical transport and the field emission properties of individual multi-walled tungsten disulphide (WS ) nanotubes (NTs) under electron beam irradiation and mechanical stress. Electron beam irradiation is used to reduce the nanotube-electrode contact resistance by one-order of magnitude. The field emission capability of single WS NTs is investigated, and a field emission current density as high as 600 kA cm is attained with a turn-on field of ≈100 V μm and field-enhancement factor ≈50.

Field Emission Characterization of MoS Nanoflowers.

Nanostructured materials have wide potential applicability as field emitters due to their high aspect ratio. We hydrothermally synthesized MoS nanoflowers on copper foil and characterized their field emission properties, by applying a tip-anode configuration in which a tungsten tip with curvature radius down to 30-100 nm has been used as the anode to measure local properties from small areas down to 1-100 µm. We demonstrate that MoS nanoflowers can be competitive with other well-established field emitters.