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  1. A helium gas field ion source has been demonstrated to be capable of realizing higher milling resolution relative to liquid gallium ion sources. One drawback, however, is that the helium ion mass is prohibitively low for reasonable sputtering rates of bulk materials, requiring a dosage that may lead to significant subsurface damage. Manipulation of suspended graphene is, therefore, a logical application for He+ milling. We demonstrate that competitive ion beam-induced deposition from residual carbonaceous contamination can be thermally mitigated via a pulsed laser-assisted He+ milling. By optimizing pulsed laser power density, frequency, and pulse width, we reduce the carbonaceous byproducts and mill graphene gaps down to sub 10 nm in highly complex kiragami patterns. 
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  2. Abstract

    Tailoring the electrical transport properties of two-dimensional transition metal dichalcogenides can enable the formation of atomically thin circuits. In this work, cyclic hydrogen and oxygen plasma exposures are utilized to introduce defects and oxidize MoS2in a controlled manner. This results in the formation of sub-stochiometric MoO3−x, which transforms the semiconducting behavior to metallic conduction. To demonstrate functionality, single flakes of MoS2were lithographically oxidized using electron beam lithography and subsequent plasma exposures. This enabled the formation of atomically thin inverters from a single flake of MoS2, which represents an advancement toward atomically thin circuitry.

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  3. Abstract A new optical delivery system has been developed for the (scanning) transmission electron microscope. Here we describe the in situ and “rapid ex situ ” photothermal heating modality of the system, which delivers >200 mW of optical power from a fiber-coupled laser diode to a 3.7 μ m radius spot on the sample. Selected thermal pathways can be accessed via judicious choices of the laser power, pulse width, number of pulses, and radial position. The long optical working distance mitigates any charging artifacts and tremendous thermal stability is observed in both pulsed and continuous wave conditions, notably, no drift correction is applied in any experiment. To demonstrate the optical delivery system’s capability, we explore the recrystallization, grain growth, phase separation, and solid state dewetting of a Ag 0.5 Ni 0.5 film. Finally, we demonstrate that the structural and chemical aspects of the resulting dewetted films was assessed. 
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