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We demonstrate an optimized fabrication process for electric field (voltage gate) controlled nano-constriction spin Hall nano-oscillators (SHNOs), achieving feature sizes of <30 nm with easy to handle ma-N 2401 e-beam...

Tungsten disulfide is an emerging 2D material with unique electrical and optical properties. Although chemical vapor deposition and mechanical exfoliation lead to large‐area layers, sonication solvent‐based exfoliation is a convenient method to realize mono‐ and few‐layer flakes. Herein, a mixture of dimethyl‐sulfoxide (DMSO) and water as a safe, facile, and user‐friendly exfoliation solvent for the synthesis of large‐scale WS2 sheets is investigated. While water molecules weaken the Van der Waals force between the stacked layers, DMSO molecules facilitate the exfoliation process. To improve exfoliation and achieve large‐area sheets, plasma pretreatment is exploited on bulk WS2 prior to the exfoliation process. For this purpose, O2 and H2 gases are used to carry out the plasma pretreatment. The oxygen plasma treatment is shown to be an effective strategy, leading to large‐area features. Moreover, inert gases as He and Ar are used to obtain small sheets. Transmission electron microscopy, atomic force microscopy, Raman spectroscopy, and dynamic light scattering analyses are used to understand the mechanism of exfoliation and study the effects of various parameters as water temperature, plasma power, and duration.

We report a novel strategy to stitch small WS2 flakes to form larger features in liquid-phase exfoliation. Owing to the initial granular size of the bulk WS2, which, is around 2 µm, the use of conventional liquid-based exfoliation techniques leads to small area nanoflakes with sizes around 1 μm. However, by joining smaller flakes through tin-oxide quantum dot (SnO2 QD) decoration during probe sonication, sheets up to 20 μm are achieved. The neighboring flakes could stitch together to form larger features through the Sn–S and Sn–O bonds at their lateral sides of their flakes and to realize mosaic arrangement of arbitrary shaped larger sheets. While the original WS2 flakes show n-type behavior, an interesting conversion into a p-channel behavior is observed upon addition of SnO2 QDs followed by additional SF6 plasma treatment process. Additionally, we have investigated the use of SF6 plasma treatment to enhance the carrier mobility and on-off ratio of the field effect transistors, yielding an effective field-effect-mobility of 80 cm2 V−1 s−1 and relatively high on/off current ratio of 105, indicating its superior electronic properties.

A novel hydrogen plasma treatment to convert an amorphous phosphorus film deposited on silicon substrates into a thin crystalline layer is successfully developed. The amorphous phosphorus layer is deposited on desired substrates as silicon using vacuum evaporation in a direct-current plasma reactor in a controllable fashion. The formation of 2D phosphorene layers is based on the phase transition of a previously deposited amorphous film into the crystalline black phosphorus flakes. Direct transformation from red phosphorus to black can be achieved at a temperature of 300 C on desired substrates as silicon, although mica and glass can also be used. This allotrope transformation can be achieved without any high pressure or high temperature. Apart from hydrogen plasma treatment, ultraviolet (UV) exposure to see any possible improvement in the 2D layer formation is also used herein. Various characterization techniques including scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and Raman spectroscopy are used to study the crystallinity and morphology of the samples. In addition, the plasma-treated flakes are used to realize photodetectors which show excellent response to illuminating light. While the hydrogen plasma treatment leads to crystalline phosphorene sheets, the UV treatment results in granular and partially crystalline nanostructures.The world of 2D materials has witnessed a growing path to apply this appealing family in various applications including electronics, optoelectronics, bioelectronics, and sensing and energy devices. [1][2][3][4][5] Owing to its unique properties, phosphorene (few layers or monolayers of black phosphorus (BP)) has grasped the researchers' attention around the globe. [6,7] High-pressure and high-temperature procedures, sonication-based methods, and even phase transition using the presence of SnI 4 /Sn are the most common techniques used to realize few-or monolayer phosphorene through a complete phase transition from red phosphorus (RP) to its BP allotrope. Mechanical exfoliation of phosphorene flakes and their transfer to desired substrates is a main line of research for the fabrication of phosphorenebased electronic and optical devices. Owing to an unstable and sensitive nature of phosphorene, its successful transfer onto the target substrate is a challenge and requires extreme precautions to avoid extended exposure to air and humidity. [8][9][10][11][12][13] Direct formation of the crystalline phosphorene flakes on desired substrates has always been a technological challenge. Recently various bottom-up techniques have been demonstrated to realize 2D materials including phosphorene flakes. As reported, there is no successful fabrication of phosphorene by means of the chemical vapor deposition (CVD) technique or wet chemical methods. The most successful bottom-up method which has been introduced recently is pulsed laser deposition (PLD) which requires a bulk target. [14] Accordingly, the evolution of a bottom-up growth method, which does not nee...