Giant anisotropic piezoresponse of layered ZrSe.

We investigated the effect of uniaxial strain on the electrical properties of few-layer ZrSe devices under compressive and tensile strains applied up to ±0.62% along different crystal directions. We observed that the piezoresponse, the change in resistance upon application of strain, of ZrSe strongly depends on both the direction in which electrical transport occurs and the direction in which uniaxial strain is applied.

Air-stable, aluminium oxide encapsulated graphene phototransistors.

Graphene has garnered significant interest in optoelectronics due to its unique properties, including broad wavelength absorption and high mobility. However, its weak stability in ambient conditions requires encapsulation for practical applications. In this study, we investigate graphene CVD-grown field-effect transistors fabricated on Si/SiOwafers, encapsulated with aluminum oxide (AlO) of different thicknesses.

Chemically-Linked Heterostructures of Palladium Nanosheets and 2H-MoS.

The burgeoning field of 2D heterostructures targets the combination of 2D materials with 3D, 1D, or 0D nanomaterials. Among the most popular 2D materials, the 2H polytype of molybdenum disulfide (MoS) features a well-defined bandgap that becomes direct at the monolayer level, which can be exploited for photodetection. A notable limitation of 2H-MoS is its curtailed absorbance beyond the visible range.

Influence of vacuum thermal annealing and air exposure on the performance of single-layer MoSdevices.

Two-dimensional semiconducting materials such as MoShave gained significant attention for potential applications in electronic components due to their reduced dimensionality and exceptional electrical and optoelectronic properties. However, when reporting the performance of such 2D-based devices, one needs to consider the effect of the environment in which the characterization is carried out. Air exposure has a non-negligible impact on the electronic performance and vacuum thermal annealing is an established method to decrease the effects of adsorbates.

Modulation of the Superconducting Phase Transition in Multilayer 2H-NbSe Induced by Uniform Biaxial Compressive Strain.

Strain is a powerful tool for tuning the properties of two-dimensional materials. Here, we investigated the effects of large, uniform biaxial compressive strain on the superconducting phase transition of multilayered 2H-NbSe flakes. We observed a consistent decrease in the critical temperature of NbSe flakes induced by the large thermal compression of a polymeric substrate (>1.

Improved Strain Transfer Efficiency in Large-Area Two-Dimensional MoS Obtained by Gold-Assisted Exfoliation.

Strain engineering represents a pivotal approach to tailoring the optoelectronic properties of two-dimensional (2D) materials. However, typical bending experiments often encounter challenges, such as layer slippage and inefficient transfer of strain from the substrate to the 2D material, hindering the realization of their full potential. In our study, using molybdenum disulfide (MoS) as a model 2D material, we have demonstrated that layers obtained through gold-assisted exfoliation on flexible polycarbonate substrates can achieve high-efficient strain transfer while also mitigating slippage effects, owing to the strong interfacial interaction established between MoS and gold.

Electrical properties of disordered films of van der Waals semiconductor WS on paper.

One of the primary objectives in contemporary electronics is to develop sensors that are not only scalable and cost-effective but also environmentally sustainable. To achieve this goal, numerous experiments have focused on incorporating nanomaterial-based films, which utilize nanoparticles or van der Waals materials, on paper substrates. In this article, we present a novel fabrication technique for producing dry-abraded van der Waals films on paper, demonstrating outstanding electrical characteristics.

Strain-Enhanced Large-Area Monolayer MoS Photodetectors.

In this study, we show a direct correlation between the applied mechanical strain and an increase in monolayer MoS photoresponsivity. This shows that tensile strain can improve the efficiency of monolayer MoS photodetectors. The observed high photocurrent and extended response time in our devices are indicative that devices are predominantly governed by photogating mechanisms, which become more prominent with applied tensile strain.

Large Biaxial Compressive Strain Tuning of Neutral and Charged Excitons in Single-Layer Transition Metal Dichalcogenides.

The absorption and emission of light in single-layer transition metal dichalcogenides are governed by the formation of excitonic quasiparticles. Strain provides a powerful technique to tune the optoelectronic properties of two-dimensional materials and thus to adjust their exciton energies. The effects of large compressive strain in the optical spectrum of two-dimensional (2D) semiconductors remain rather unexplored compared to those of tensile strain, mainly due to experimental constraints.

High-Throughput Mechanical Exfoliation for Low-Cost Production of van der Waals Nanosheets.

A method is presented for scaling up the production of flakes of van der Waals materials via mechanical exfoliation. Using a roll-to-roll setup and an automatized, massive parallel exfoliation process, adhesive tapes with a high density of nanosheets of van der Waals materials are produced. The technique allows for obtaining a good trade-off between large lateral size and excellent area scalability, while also maintaining low cost.

Approaching the Intrinsic Properties of Moiré Structures Using Atomic Force Microscopy Ironing.

Stacking monolayers of transition metal dichalcogenides (TMDs) has led to the discovery of a plethora of new exotic phenomena, resulting from moiré pattern formation. Due to the atomic thickness and high surface-to-volume ratio of heterostructures, the interfaces play a crucial role. Fluctuations in the interlayer distance affect interlayer coupling and moiré effects.

Direct Magnetic Evidence, Functionalization, and Low-Temperature Magneto-Electron Transport in Liquid-Phase Exfoliated FePS.

Magnetism and the existence of magnetic order in a material is determined by its dimensionality. In this regard, the recent emergence of magnetic layered van der Waals (vdW) materials provides a wide playground to explore the exotic magnetism arising in the two-dimensional (2D) limit. The magnetism of 2D flakes, especially antiferromagnetic ones, however, cannot be easily probed by conventional magnetometry techniques, being often replaced by indirect methods like Raman spectroscopy.

Biodegradable albumen dielectrics for high-mobility MoS phototransistors.

This work demonstrates the fabrication and characterization of single-layer MoS field-effect transistors using biodegradable albumen (chicken eggwhite) as gate dielectric. By introducing albumen as an insulator for MoS transistors high carrier mobilities (up to ~90 cm V s) are observed, which is remarkably superior to that obtained with commonly used SiO dielectric which we attribute to ionic gating due to the formation of an electric double layer in the albumen MoS interface. In addition, the investigated devices are characterized upon illumination, observing responsivities of 4.

Improving the conductivity of graphite-based films by rapid laser annealing.

We present a method to anneal devices based on graphite films on paper and polycarbonate substrates. The devices are created using four different methods: spray-on films, graphite pencil-drawn films, liquid-phase exfoliated graphite films, and graphite powder abrasion-applied films. We characterize the optical properties of the films before and after laser annealing and report the two-terminal resistance of the devices for increased laser power density.

Waveguide-Integrated MoTe -- Homojunction Photodetector.

Two-dimensional (2D) materials, featuring distinctive electronic and optical properties and dangling-bond-free surfaces, are promising for developing high-performance on-chip photodetectors in photonic integrated circuits. However, most of the previously reported devices operating in the photoconductive mode suffer from a high dark current or a low responsivity. Here, we demonstrate a MoTe -- homojunction fabricated directly on a silicon photonic crystal (PC) waveguide, which enables on-chip photodetection with ultralow dark current, high responsivity, and fast response speed.

An ultraminiaturized spectrometer.

Scaling down spectrometers could allow their application in consumer devices.

Broadband-tunable spectral response of perovskite-on-paper photodetectors using halide mixing.

Paper offers a low-cost and widely available substrate for electronics. It possesses alternative characteristics to silicon, as it shows low density and high flexibility, together with biodegradability. Solution processable materials, such as hybrid perovskites, also present light and flexible features, together with a huge tunability of the material composition with varying optical properties.

Combining Freestanding Ferroelectric Perovskite Oxides with Two-Dimensional Semiconductors for High Performance Transistors.

We demonstrate the fabrication of field-effect transistors based on single-layer MoS and a thin layer of BaTiO (BTO) dielectric, isolated from its parent epitaxial template substrate. Thin BTO provides an ultrahigh-κ gate dielectric effectively screening Coulomb scattering centers. These devices show mobilities substantially larger than those obtained with standard SiO dielectrics and comparable with values obtained with hexagonal boron nitride, a dielectric employed for fabrication of high-performance two-dimensional (2D) based devices.

Paper-based broadband flexible photodetectors with van der Waals materials.

Layered metal chalcogenide materials are exceptionally appealing in optoelectronic devices thanks to their extraordinary optical properties. Recently, their application as flexible and wearable photodetectors have received a lot of attention. Herein, broadband and high-performance paper-based PDs were established in a very facile and inexpensive method by rubbing molybdenum disulfide and titanium trisulfide crystals on papers.

Fiber-coupled light-emitting diodes (LEDs) as safe and convenient light sources for the characterization of optoelectronic devices.

Optoelectronic device characterization requires to probe the electrical transport changes upon illumination with light of different incident powers, wavelengths, and modulation frequencies. This task is typically performed using laser-based or lamp + monochromator-based light sources, that result complex to use and costly to implement. Here, we describe the use of multimode fiber-coupled light-emitting diodes (LEDs) as a simple, low-cost alternative to more conventional light sources, and demonstrate their capabilities by extracting the main figures of merit of optoelectronic devices based on monolayer MoS , i.

Chip-integrated van der Waals PN heterojunction photodetector with low dark current and high responsivity.

Two-dimensional materials are attractive for constructing high-performance photonic chip-integrated photodetectors because of their remarkable electronic and optical properties and dangling-bond-free surfaces. However, the reported chip-integrated two-dimensional material photodetectors were mainly implemented with the configuration of metal-semiconductor-metal, suffering from high dark currents and low responsivities at high operation speed. Here, we report a van der Waals PN heterojunction photodetector, composed of p-type black phosphorous and n-type molybdenum telluride, integrated on a silicon nitride waveguide.

Eco-Friendly Disposable WS Paper Sensor for Sub-ppm NO Detection at Room Temperature.

We developed inexpensive and disposable gas sensors with a low environmental footprint. This approach is based on a biodegradable substrate, paper, and features safe and nontoxic electronic materials. We show that abrasion-induced deposited WS nanoplatelets on paper can be employed as a successful sensing layer to develop high-sensitivity and selective sensors, which operate even at room temperature.

Strongly Anisotropic Strain-Tunability of Excitons in Exfoliated ZrSe.

The effect of uniaxial strain on the band structure of ZrSe , a semiconducting material with a marked in-plane structural anisotropy, is studied. By using a modified three-point bending test apparatus, thin ZrSe flakes are subjected to uniaxial strain along different crystalline orientations monitoring the effect of strain on their optical properties through micro-reflectance spectroscopy. The obtained spectra show excitonic features that blueshift upon uniaxial tension.