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1/f noise represents the dominant source of noise in the low-frequency range in several physical systems, including field-effect transistors. Its investigation can provide very important information on the fabrication process, highlighting the steps that are more prone to the introduction of defects. Here, 1/f noise in bilayer MoS2 transistors on paper with inkjet-printed Ag contacts and hBN die- lectric is investigated. These devices are promising building blocks for future low-cost, flexible, and easily recyclable disposable electronics. The analysis of 1/f noise, performed following Hooge’s empirical approach, results in a Hooge parameter ≈1–10, which is comparable to those reported for bilayer MoS2 transistors on SiO2. The present results indicate that the noise properties of the investigated devices are stable against substrate bending and are mainly determined by the printing of the dielectric, while not being sensibly affected by the use of the paper substrate. These results are promising for the further development of low noise 2D material-based flexible electronics on paper.

Complementary electronics has represented the corner stone of the digital era, and silicon technology has enabled this accomplishment. At the dawn of the flexible and wearable electronics age, the seek for new materials enabling the integration of complementary metal-oxide semiconductor (CMOS) technology on flexible substrates, finds in low-dimensional materials (either 1D or 2D) extraordinary candidates. Here, we show that the main building blocks for digital electronics can be obtained by exploiting 2D materials like molybdenum disulfide, hexagonal boron nitride and 1D materials such as carbon nanotubes through the inkjet-printing technique. In particular, we show that the proposed approach enables the fabrication of logic gates and a basic sequential network on a flexible substrate such as paper, with a performance already comparable with mainstream organic technology.

Paper is the ideal substrate for the development of flexible and environmentally sustainable ubiquitous electronic systems, which, combined with two-dimensional materials, could be exploited in many Internet-of-Things applications, ranging from wearable electronics to smart packaging. Here we report high-performance MoS2 field-effect transistors on paper fabricated with a “channel array” approach, combining the advantages of two large-area techniques: chemical vapor deposition and inkjet-printing. The first allows the pre-deposition of a pattern of MoS2; the second, the printing of dielectric layers, contacts, and connections to complete transistors and circuits fabrication. Average ION/IOFF of 8 × 103 (up to 5 × 104) and mobility of 5.5 cm2 V−1 s−1 (up to 26 cm2 V−1 s−1) are obtained. Fully functional integrated circuits of digital and analog building blocks, such as logic gates and current mirrors, are demonstrated, highlighting the potential of this approach for ubiquitous electronics on paper., Paper is a promising substrate for flexible and environmentally sustainable electronic devices. Here, the authors combine chemical vapor deposition of MoS2 with inkjet printing of a hexagonal boron nitride (hBN) dielectric and silver electrodes, to fabricate flexible MoS2 field-effect transistors on paper, and then combine the latter with printed graphene resistors and silver interconnects to create inverters, logic gates and current mirrors.

Single-photon emitters play a key role in present and emerging quantum technologies. Several recent measurements have established monolayer ${\mathrm{WSe}}_{2}$ as a promising candidate for a reliable single-photon source. The origin and underlying microscopic processes have remained, however, largely elusive. We present a multiscale tight-binding simulation for the optical spectra of ${\mathrm{WSe}}_{2}$ under nonuniform strain and in the presence of point defects employing the Bethe-Salpeter equation. Strain locally shifts excitonic energy levels into the band gap where they overlap with localized intragap defect states. The resulting hybridization allows for efficient filling and subsequent radiative decay of the defect states. We identify intervalley defect excitonic states as the likely candidate for antibunched single-photon emission. This proposed scenario is shown to account for a large variety of experimental observations including brightness, radiative transition rates, the variation of the excitonic energy with applied magnetic and electric fields as well as the variation of the polarization of the emitted photon with the magnetic field.

Single quantum emitters (SQEs) are the basic building blocks for quantum optics and quantum information technology. Strain-induced defects in monolayer transition metal dichalcogenides (TMDs) have been shown to be a promising platform for the generation of SQEs. In particular, achieving optically active and electrically controlled quantum emitters make these materials attractive for applications ranging from quantum communication and optoelectronics to high resolution metrology. Here, we report the spectral photoresponse of monolayer WSe2 upon strain, where we observe a connection between single-photon emission and photocurrent (PC) generation in a p-n device. A strong antibunching in second-order correlation from this localized emitter unambiguously demonstrates the single-photon nature of the emission, whereas the PC is highly dominated by the absorption at such a localized state, showing an exponential dependence with the applied electric field. Furthermore, we can resolve narrow PC peaks with 1.0 meV spectral width.

Second-harmonic generation (SHG) is a powerful measurement technique to analyze the symmetry properties of crystals. Mechanical strain can reduce the symmetry of a crystal and even weak strain can have a considerable impact on the SHG intensity along different polarization directions. The impact of strain on the SHG can be modeled with a second-order nonlinear photoelastic tensor. In this work, we determined the photoelastic tensors at a fundamental wavelength of 800 nm for four different transition metal dichalcogenide (TMD) monolayers: MoS2, MoSe2, WS2, and WSe2. Strain is applied using a three-point bending scheme, and the polarization-resolved SHG pattern is measured in backscattering geometry. Furthermore, we connected the strain dependent SHG with the strain dependence of the A-exciton energy. With the second-order nonlinear photoelastic tensor, full strain information can be accurately extracted from polarization-resolved SHG measurements. Accordingly, uniaxial strain, induced by polydimethylsiloxan (PDMS) exfoliation and transfer, is measured. We find that TMD monolayers fabricated with PDMS are strained by ∼0.2%. With the experimentally determined nonlinear photoelastic tensors, it will be possible to optically probe arbitrary strain fields in TMD monolayers.

Digital electronics are ubiquitous in the modern world, but analogue electronics also play a crucial role in many devices and applications. Analogue circuits are typically manufactured using silicon as the active material. However, the desire for improved performance, new devices and flexible integration has—as for their digital counterparts—led to research into alternative materials, including the use of two-dimensional (2D) materials. Here, we show that operational amplifiers—a basic building block of analogue electronics—can be created using the 2D semiconductor molybdenum disulfide (MoS2) as the active material. The device is capable of stable operation with good performance, and we demonstrate its use in feedback circuits including inverting amplifiers, integrators, log amplifiers and transimpedance amplifiers. We also show that our 2D platform can be used to monolithically integrate an analogue signal preconditioning circuit with a MoS2 photodetector. An operational amplifier that uses the two-dimensional semiconductor molybdenum disulfide as the active material can be used to create complex analogue circuits, including inverters, integrators and amplifiers.