Modulation of 1 MeV electron irradiation on ultraviolet response in MoS2FET.

The material, electrical and ultraviolet optoelectronic properties of few layers bottom molybdenum disulfide (MoS2) field effect transistors (FETs) device was investigated before and after 1 MeV electron irradiation. Due to the participation of SiO2in conduction, we discovered novel photoelectric properties and a relatively long photogenerated carrier lifetime (several tens of seconds). Electron irradiation causes lattice distortion, the decrease of carrier mobility, and the increase of interface state. It leads to the degradation of output characteristics, transfer characteristics and photocurrent of the MoS2FET.

Tailoring physical properties of WS2 nanosheets by defects control.

The controllable growth of high-quality transition metal dichalcogenides (TMDs) is crucial for their device applications, which rely on the atomic and quantitative understanding of the growth mechanism of TMDs. In this work, we propose a comprehensive picture of the growth of WS2 nanosheets via Monte Carlo simulation, and an extension of diffusion-limited growth under transition state theory is developed to describe heteroepitaxy growth of WS2. Theoretical results are in good agreement with the results of chemical vapor deposition that growth temperature dominates growth processes leading to samples with various densities of vacancy defects. The vacancy defects modify the photoluminescence and ferromagnetic behavior. Our work provides a pathway toward realizing controllable physical properties in 2D materials.

Electron radiation effects on the structural and electrical properties of MoS2 field effect transistors.

The effects of space radiation on the structural and electrical properties of MoS2 field effect transistors (FETs) were investigated. The 1 MeV electronically equivalent International Space Station (ISS) track was used to apply fluence equivalent to the orbital for 10 (1.0 × 1012 cm-2) and 30 years (3.0 × 1012 cm-2) using the AP8 and AE8 models. X-ray photoelectron spectroscopy (XPS), Raman and photoluminescence (PL) spectra were recorded before and after irradiation. Electron irradiation produced strong desulfurization effects in MoS2 FETs. The PL spectra before and after irradiation did not change significantly, while the [Formula: see text] and A1g Raman modes were red- and blue-shifted, respectively. The XPS results demonstrated a strong desulfurization effect of the electron beam on MoS2. This reduction indicates a much higher amount of irradiation-induced S vacancies compared to Mo vacancies. The electrical characteristics of the device were measured before and after irradiation. The increase in the channel leakage current after irradiation was attributed to the oxide trapping positive charges. MoS2 FETs irradiated by the electron-beam demonstrated a decreased current. This phenomenon can be attributed to the combination of the states at the SiO2/MoS2 interfaces and Coulomb scattering. Our study provides a deeper understanding of the influence of 1 MeV electron-beam irradiation on MoS2-based nano-electronic devices for future space applications.

Modulation of electronic and optical properties by surface vacancies in low-dimensional ß-Ga2O3.

Calculations using the Heyd-Scuseria-Ernzerhof screened hybrid functional reveal the detailed influence that surface vacancies have on the electronic and optical properties of low-dimensional (LD) ß-Ga2O3. Vacancies manifest subtle changes to the electronic characteristics as oxygen states predominate the valence band at the surface. Dielectric functions at the surface are found to increase with vacancies and defects. A broad impact on optical properties, such as absorption coefficients, reflectivity, refractive indices, and electron loss, is seen with increased vacancy defects. Both visible and infrared regions show direct correlation with vacancies while there is a marked decrease in the deep ultraviolet (UV) region. These calculations on the ß-Ga2O3 model system may guide the rational design of two-dimensional optical devices with minimized van der Waals forces.

The elemental 2D materials beyond graphene potentially used as hazardous gas sensors for environmental protection.

The intrinsic and electronic properties of elemental two-dimensional (2D) materials beyond graphene are first introduced in this review. Then the studies concerning the application of gas sensing using these 2D materials are comprehensively reviewed. On the whole, the carbon-, nitrogen-, and sulfur-based gases could be effectively detected by using most of them. For the sensing of organic vapors, the borophene, phosphorene, and arsenene may perform it well. Moreover, the G-series nerve agents might be efficiently monitored by the bismuthene. So far, there is still challenge on the material preparation due to the instability of these 2D materials under atmosphere. The synthesis or growth of materials integrated with the technique of surface protection should be associated with the device fabrication to establish a complete process for particular application. This review provides a complete and methodical guideline for scientists to further research and develop the hazardous gas sensors of these 2D materials in order to achieve the purpose of environmental protection.