Selective Electron Beam Patterning of Oxygen-Doped WSe2 for Seamless Lateral Junction Transistors

Surface charge transfer doping (SCTD) using oxygen plasma to form a p-type dopant oxide layer on transition metal dichalcogenide (TMDs) is a promising doping technique for 2D TMDs field-effect transistors (FETs). However, patternability of SCTD is a key challenge to effectively switch FETs. Herein, a simple method to selectively pattern degenerately p-type (p⁺ )-doped WSe₂ FETs via electron beam (e-beam) irradiation is reported. The effect of the selective e-beam irradiation is confirmed by the gate-tunable optical responses of seamless lateral p⁺ -p diodes. The OFF state of the devices by inducing trapped charges via selective e-beam irradiation onto a desired channel area in p⁺ -doped WSe₂ , which is in sharp contrast to globally p⁺ -doped WSe₂ FETs, is realized. Selective e-beam irradiation of the PMMA-passivated p⁺ -WSe₂ enables accurate control of the threshold voltage (V_th ) of WSe₂ devices by varying the pattern size and e-beam dose, while preserving the low contact resistance. By utilizing hBN as the gate dielectric, high-performance WSe₂ p-FETs with a saturation current of -280 µA µm^-1 and on/off ratio of 10⁹ are achieved. This study's technique demonstrates a facile approach to obtain high-performance TMD p-FETs by e-beam irradiation, enabling efficient switching and patternability toward various junction devices.

Effect of E-Beam Irradiation on Thermal and Mechanical Properties of Ester Elastomers Containing Multifunctional Alcohols

The aim of this work was to investigate the thermal and mechanical properties of novel, electron beam-modified ester elastomers containing multifunctional alcohols. Polymers tested in this work consist of two blocks: sebacic acid-butylene glycol block and sebacic acid-sugar alcohol block. Different sugar alcohols were utilized in the polymer synthesis: glycerol, sorbitol, xylitol, erythritol, and mannitol. The polymers have undergone an irradiation procedure. The materials were irradiated with doses of 50 kGy, 100 kGy, and 150 kGy. The expected effect of using ionizing radiation was crosslinking process and improvement of the mechanical properties. Additionally, a beneficial side effect of the irradiation process is sterilization of the affected materials. It is also worth noting that the materials described in this paper do not require either sensitizers or cross-linking agent in order to perform radiation modification. Radiation-modified poly(polyol sebacate-co-butylene sebacate) elastomers have been characterized in respect to the mechanical properties (quasi-static tensile tests), cross-link density, thermal properties (Differential Scanning Calorimetry (DSC)), chemical properties: Fourier transform infrared spectroscopy (FTIR), and wettability (water contact angle). Poly(polyol sebacate-co-butylene sebacate) preopolymers were characterized with nuclear magnetic resonance spectroscopy (¹H NMR and ¹³C NMR) and gel permeation chromatography (GPC). Thermal stability of cross-linked materials (directly after synthesis process) was tested with thermogravimetric analysis (TGA).

Electron Beam Irradiation-Induced Deoxidation and Atomic Flattening on the Copper Surface

Electron beam (e-beam) has been developed for nanomaterial observation and moreover to induce structural evolutions in atomic scale. In this work, we demonstrate the deoxidation of cuprous oxide (Cu₂O) and the formation of an atomically flat surface on a Cu nanowire by e-beam irradiation. To develop e-beam irradiation applications, the relation between e-beam radiation and the atomic surface is significant. Through the density functional theory simulation of atomic sputtering, an obvious disparity in the sputtering threshold has been found under different structural conditions, which leads to different structural evolutions. Both surface deoxidation and atomic surface flattening reactions have been identified as self-limiting and irreversible processes via in situ transmission electron microscope observation. Under e-beam irradiation, the dynamic mechanism of atomic surface flattening is driven by the convergence of total surface energy and confirmed by climbing-image nudged elastic band (ci-NEB) calculations. With precise control, e-beam irradiation reveals enormous potentials in atomic surface engineering.

Nanoscale Lacing by Electrons

The ability to harness the optical or electrical properties of nanoscale particles depends on their assembly in terms of size and spatial characteristics which remains challenging due to lack of size focusing. Electrons provide a clean and focusing agent to initiate the assembly of nanoclusters or nanoparticles. Here an intriguing route is demonstrated to lace gold nanoclusters and nanoparticles in string assembly through electron-initiated nucleation and aggregative growth of Au(I)-thiolate motifs on a thin film substrate. This size-focused assembly is demonstrated by controlling the electron dose under transmission electron microscopic imaging conditions. The Au(I)-thiolate motifs, in combination with the molecularly mediated alignment, facilitate the interstring electrostatic and intrastring aurophilic interactions, which functions as a molecular template to aid electron-initiated 1D lacing. The findings demonstrate a hierarchical route for the 1D assemblies with size and spatial tunable catalytic, optical, sensing, and diagnostic properties.

Misorientation-Angle-Dependent Phase Transformation in van der Waals Multilayers via Electron-Beam Irradiation

Misorientation-angle dependence on layer thickness is an intriguing feature of van der Waals materials, which causes stark optical gain and electrical transport modulation. However, the influence of misorientation angle on phase transformation is not determined yet. Herein, this phenomenon in a MoS₂ multilayer via in situ electron-beam irradiation is reported. An AA'-stacked MoS₂ bilayer undergoes structural transformation from the 2H semiconducting phase to the 1T' metallic phase, similar to a MoS₂ monolayer, which is confirmed via in situ transmission electron microscopy. Moreover, non-AA' stacking, which has no local AA' stacking order in the Moiré pattern, does not reveal such a phase transformation. While a collective sliding motion of chalcogen atoms easily occurs during the transformation in AA' stacking, in non-AA' stacking it is suppressed by the weak van der Waals strength and by the chalcogen atoms interlocked at different orientations, which disfavor their kinetics by the increased entropy of mixing.

Determination of free cholesterol oxide products in food samples by gas chromatography and accelerated solvent extraction: influence of electron-beam irradiation on cholesterol oxide formation

BACKGROUND

The aim of this study was to develop an efficient method for cholesterol oxide product (COP) determination in irradiated and non-irradiated ready-to-eat foods with high water content by gas chromatography-flame ionisation detector after accelerated solvent extraction (ASE), and derivatisation with a silylating reagent.

RESULTS

The ASE solvent was an 85:15 v/v petroleum ether/chloroform mixture at 40 °C and 1500 psi followed by solid phase extraction. The ASE method was compared with the established lixiviation method, proving an advantageous alternative which reduces analysis time by a factor of 15 and solvent volume by 50%, and minimises the use of chlorinated solvents. COP derivative structures were identified by gas chromatography coupled with mass spectrometry. Analytical characteristics were determined from standards and recoveries were 63-95%, establishing the validity of the method.

CONCLUSION

The results obtained and their analysis by chemometric techniques established COP formation in food samples after e-beam irradiation. Increase in COP concentration depended on both irradiation doses and food composition, mainly water and fat content, although linear correlations among variables were not found. © 2016 Society of Chemical Industry.

Stability of a second-generation cephalosporin veterinary mastitis formulation after electron beam irradiation

This study focused on the chemical stability of the cephalosporin (6R, 7R)-7-(1-pentafluorophenoxyacetamido)-3-[2-(5-methyl-1,3,4-thiodiazolyl)thiomethyl]-Delta(3)-cephem-4-carboxylic acid, sodium salt (cephem 1) formulation after electron beam (e-beam) irradiation. The cephem 1 concentrations of samples irradiated at 5, 10, and 15 kilograys for glass vials and low-density polyethylene (LDPE) cannula syringes were not statistically different from the concentrations of the nonirradiated control samples. Samples from each irradiation dose stored in controlled-temperature chambers at 5 degrees C and 30 degrees C for 24 months did not show any concentration changes within statistical limits compared with the nontreated samples. Samples from each irradiation dose stored at 40 degrees C for 12 months also did not show any concentration changes within statistical limits compared with the nontreated samples. The percentage of related substances increased slightly with the increase in e-beam irradiation level and storage temperature, but this increase was within the proposed label claim of 90% to 110% (45-55 mg/g). In conclusion, e-beam sterilization did not affect the chemical stability of cephem 1 intramammary formulation in LDPE cannula syringes, suggesting that e-beam irradiation may be a feasible method for terminal sterilization of this cephem 1 formulation.