We report on outstanding photo-responsivity, R > 10³ A/W, fast response (~0.1 s), and broadband sensitivity ranging from the UV to the NIR in two terminal graphene/MoS₂ photodetectors. Our devices are based on the deterministic transfer of MoS₂ on top of directly grown graphene on sapphire, and their performance outperforms previous similar photodetectors using large-scale grown graphene. Here we devise a protocol for the direct growth of transparent (transmittance, Tr > 90%), highly conductive (sheet resistance, R_□ < 1 kΩ) uniform and continuous graphene films on sapphire at 700 °C by using plasma-assisted chemical vapor deposition (CVD) with C₂H₂/H₂ gas mixtures. Our study demonstrates the successful use of plasma-assisted low-temperature CVD techniques to directly grow graphene on insulators for optoelectronic applications.

Integrating free‐standing complex oxides with two‐dimensional (2D) materials has recently attracted great interest, due to the rich physics evolving from such structures. Enhancing and tuning the opto–electronic properties of these systems is of high importance for a multitude of applications, such as sensors, memory devices or optical communications. The electrostatic control of photoluminescence of monolayer MoS₂ at room temperature via integration of free‐standing BaTiO₃ (BTO), a ferroelectric perovskite oxide is presented. It is shown that the use of BTO leads to highly tunable exciton emission of MoS₂ in a minimal range of gate voltages. Due to BTO's ferroelectric polarization‐induced doping, large peak emission shifts as well as a large and tunable A trion binding energy in the range of 40–100 meV are observed. These measurements are compared with those carried out when the BTO is replaced by a hexagonal boron nitride (hBN) dielectric layer, confirming BTO's superior gating properties and thus lower power consumption. Additionally, advantage of the ferroelectric switching of BTO is taken by fabricating devices where the BTO layer is decoupled from the gate electrode with a SiO₂ layer. Choosing to isolate the BTO allows to induce large remanent behavior of MoS₂’s excitonic features.

We present adaptive, strain-engineered photodetectors based on 2D semiconductors. Our devices present a footprint of only about 40 × 20 μm², and they are fabricated on transparent polypropylene substrates and integrate lithographically designed microheaters that induce controllable biaxial strain via thermal actuation, thus leading to a red shift in their spectral response. This strain-induced tunability is combined with a machine learning-based spectral reconstruction approach, where a neural network is trained on an extensive data set of synthetic spectra and corresponding photocurrents generated from measured device responsivities under varying strain conditions. Although the system demonstrates spectral reconstruction over a relatively narrow range, it provides a compelling proof-of-concept for a miniaturized adaptive spectrometer.

We present two approaches for fabricating shadow masks for the evaporation of electrodes onto nanomaterials. In the first one, we combine the use of a commercial fiber laser engraving system with readily available aluminum foil. This method is suitable for fabricating shadow masks with line widths of 50 µm and minimum feature separation of 20 µm, and using it to create masks with complex patterns is very straightforward. In the second approach, we use a commercially available vinyl cutting machine to pattern a vinyl stencil mask, and we use a glass fiber to define the separation between the electrodes. With this approach, we achieve well-defined electrodes separated by 15 µm, but this technique is less versatile in creating complex masks as compared with the laser-based one. We demonstrate the potential of these techniques by fabricating field-effect transistor devices based on MoS₂. Our approach is a cost-effective and easily accessible method for fabricating shadow masks with high resolution and accuracy, making it accessible to a wider range of laboratories.

The integration of high-dielectric-constant (high-κ) materials with two-dimensional (2D) semiconductors is promising to overcome performance limitations and reach their full theoretical potential. Here, we show that naturally occurring phlogopite mica, exfoliated into ultrathin flakes, can serve as a robust high-κ dielectric layer for transition metal dichalcogenide-based 2D electronics and optoelectronics. The wide band gap (∼4.8 eV), high dielectric constant (∼11), and large breakdown field (>10 MV cm^-1) of phlogopite enable transistors with subthreshold swings down to 100 mV dec^-1, minimal hysteresis (∼30-60 mV), and interface trap densities comparable to those of state-of-the-art oxide dielectrics. Moreover, phototransistors built upon monolayer molybdenum disulfide (MoS₂) and phlogopite exhibit responsivities up to 3.3 × 10⁴ AW^-1 and detectivities close to 10¹⁰ Jones, surpassing devices based on conventional gate insulators. We further demonstrate the versatility of this natural dielectric by integrating phlogopite/MoS₂ heterostructures into NMOS inverters, showcasing robust voltage gains and low-voltage operation. Our findings establish phlogopite as a promising, earth-abundant dielectric for next-generation 2D transistor technologies and high-performance photodetection.

This work demonstrates the fabrication and characterization of single-layer MoS₂ field-effect transistors using biodegradable albumen (chicken eggwhite) as gate dielectric. By introducing albumen as an insulator for MoS₂ transistors high carrier mobilities (up to ~90 cm² V⁻¹ s⁻¹) are observed, which is remarkably superior to that obtained with commonly used SiO₂ dielectric which we attribute to ionic gating due to the formation of an electric double layer in the albumen MoS₂ interface. In addition, the investigated devices are characterized upon illumination, observing responsivities of 4.5 AW⁻¹ (operated in photogating regime) and rise times as low as 52 ms (operated in photoconductivity regime). The presented study reveals the combination of albumen with van der Waals materials for prospective biodegradable and biocompatible optoelectronic device applications. Furthermore, the demonstrated universal fabrication process can be easily adopted to fabricate albumen-based devices with any other van der Waals material.