Transparent Large-Area MoS₂ Phototransistors with Inkjet-Printed Components on Flexible Platforms

Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have gained considerable attention as an emerging semiconductor due to their promising atomically thin film characteristics with good field-effect mobility and a tunable band gap energy. However, their electronic applications have been generally realized with conventional inorganic electrodes and dielectrics implemented using conventional photolithography or transferring processes that are not compatible with large-area and flexible device applications. To facilitate the advantages of 2D TMDCs in practical applications, strategies for realizing flexible and transparent 2D electronics using low-temperature, large-area, and low-cost processes should be developed. Motivated by this challenge, we report fully printed transparent chemical vapor deposition (CVD)-synthesized monolayer molybdenum disulfide (MoS₂) phototransistor arrays on flexible polymer substrates. All the electronic components, including dielectric and electrodes, were directly deposited with mechanically tolerable organic materials by inkjet-printing technology onto transferred monolayer MoS₂, and their annealing temperature of <180 °C allows the direct fabrication on commercial flexible substrates without additional assisted-structures. By integrating the soft organic components with ultrathin MoS₂, the fully printed MoS₂ phototransistors exhibit excellent transparency and mechanically stable operation

Electrical and Optical Characterization of MoS₂ with Sulfur Vacancy Passivation by Treatment with Alkanethiol Molecules

We investigated the physical properties of molybdenum disulfide (MoS₂) atomic crystals with a sulfur vacancy passivation after treatment with alkanethiol molecules including their electrical, Raman, and photoluminescence (PL) characteristics. MoS₂, one of the transition metal dichalcogenide materials, is a promising two-dimensional semiconductor material with good physical properties. It is known that sulfur vacancies exist in MoS₂, resulting in the n-type behavior of MoS₂. The sulfur vacancies on the MoS₂ surface tend to form covalent bonds with sulfur-containing groups. In this study, we deposited alkanethiol molecules on MoS₂ field effect transistors (FETs) and then characterized the electrical properties of the devices before and after the alkanethiol treatment. We observed that the electrical characteristics of MoS₂ FETs dramatically changed after the alkanethiol treatment. We also observed that the Raman and PL spectra of MoS₂ films changed after the alkanethiol treatment. These effects are attributed to the thiol (−SH) end groups in alkanethiols bonding at sulfur vacancy sites, thus altering the physical properties of the MoS₂. This study will help us better understand the electrical and optical properties of MoS₂ and suggest a way of tailoring the properties of MoS₂ by passivating a sulfur vacancy with thiol molecules