4 research outputs found
Atomic Scale Dynamics of Contact Formation in the Cross-Section of InGaAs Nanowire Channels
Alloyed and compound contacts between
metal and semiconductor transistor channels enable self-aligned gate
processes which play a significant role in transistor scaling. At
nanoscale dimensions and for nanowire channels, prior experiments
focused on reactions along the channel length, but the early stage
of reaction in their cross sections remains unknown. Here, we report
on the dynamics of the solid-state reaction between metal (Ni) and
semiconductor (In<sub>0.53</sub>Ga<sub>0.47</sub>As), along the cross-section
of nanowires that are 15 nm in width. Unlike planar structures where
crystalline nickelide readily forms at conventional, low alloying
temperatures, nanowires exhibit a solid-state amorphization step that
can undergo a crystal regrowth step at elevated temperatures. In this
study, we capture the layer-by-layer reaction mechanism and growth
rate anisotropy using in situ transmission electron microscopy (TEM).
Our kinetic model depicts this new, in-plane contact formation which
could pave the way for engineered nanoscale transistors
Bilayer Metasurfaces for Dual- and Broadband Optical Antireflection
Optical antireflection has long been
pursued for a wide range of applications, but existing approaches
encounter issues in the performance, bandwidth, and structure complexity,
particularly in the long-wavelength infrared regime. Here we present
the demonstration of bilayer metasurfaces that accomplish dual- and
broadband optical antireflection in the terahertz and mid-infrared
spectral ranges. By simply tailoring the structural geometry and dimensions,
we show that subwavelength metal/dielectric structures enable dramatic
reduction of Fresnel reflection and significant enhancement of transmission
at a substrate surface, operating either at two discrete narrow bands
or over a broad bandwidth up to 28%. We also use a semianalytical
interference model to interpret the obtained results, in which we
find that the dispersion of the constituent structures plays a critical
role in achieving the observed broadband optical antireflection
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High Density Individually Addressable Nanowire Arrays Record Intracellular Activity from Primary Rodent and Human Stem Cell Derived Neurons
We report a new hybrid
integration scheme that offers for the first time a nanowire-on-lead
approach, which enables independent electrical addressability, is
scalable, and has superior spatial resolution in vertical nanowire
arrays. The fabrication of these nanowire arrays is demonstrated to
be scalable down to submicrometer site-to-site spacing and can be
combined with standard integrated circuit fabrication technologies.
We utilize these arrays to perform electrophysiological recordings
from mouse and rat primary neurons and human induced pluripotent stem
cell (hiPSC)-derived neurons, which revealed high signal-to-noise
ratios and sensitivity to subthreshold postsynaptic potentials (PSPs).
We measured electrical activity from rodent neurons from 8 days in
vitro (DIV) to 14 DIV and from hiPSC-derived neurons at 6 weeks in
vitro post culture with signal amplitudes up to 99 mV. Overall, our
platform paves the way for longitudinal electrophysiological experiments
on synaptic activity in human iPSC based disease models of neuronal
networks, critical for understanding the mechanisms of neurological
diseases and for developing drugs to treat them