We present the first study of the intrinsic electrical properties of WS2 transistors fabricated with two different dielectric environments WS2 on SiO2 and WS2 on h-BN/SiO2, respectively. A comparative analysis of the electrical characteristics of multiple transistors fabricated from natural and synthetic WS2 with various thicknesses from single- up to four-layers and over a wide temperature range from 300 K down to 4.2 K shows that disorder intrinsic to WS2 is currently the limiting factor of the electrical properties of this material. These results shed light on the role played by extrinsic factors such as charge traps in the oxide dielectric thought to be the cause for the commonly observed small values of charge carrier mobility in transition metal dichalcogenides.
We present a fabrication process for high quality suspended and double gated
trilayer graphene devices. The electrical transport measurements in these
transistors reveal a high charge carrier mobility (higher than 20000 cm^2/Vs)
and ballistic electric transport on a scale larger than 200nm. We report a
particularly large on/off ratio of the current in ABC-stacked trilayers, up to
250 for an average electric displacement of -0.08 V/nm, compatible with an
electric field induced energy gap. The high quality of these devices is also
demonstrated by the appearance of quantum Hall plateaus at magnetic fields as
low as 500mT.Comment: to appear in Applied Physics Letters. Typos corrected and references
update
Suspended superconducting nanostructures of MoRe 50%/50% by weight are fabricated employing commonly used fabrication steps in micro-and nano-meter scale devices followed by wet-etching with Hydro-fluoric acid of a SiO2 sacrificial layer. Suspended superconducting channels as narrow as 50 nm and length 3 µm have a critical temperature of ≈ 6.5 K, which can increase by 0.5K upon annealing at 400 • C. A detailed study of the dependence of the superconducting critical current and critical temperature upon annealing and in devices with different channel width reveals that desorption of contaminants is responsible for the improved superconducting properties. These findings pave the way for the development of superconducting electromechanical devices using standard fabrication techniques.
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