39 research outputs found
3D-imaging of Printed Nanostructured Networks using High-resolution FIB-SEM Nanotomography
Networks of solution-processed nanomaterials are important for multiple
applications in electronics, sensing and energy storage/generation. While it is
known that network morphology plays a dominant role in determining the physical
properties of printed networks, it remains difficult to quantify network
structure. Here, we utilise FIB-SEM nanotomography to characterise the
morphology of nanostructured networks. Nanometer-resolution 3D-images were
obtained from printed networks of graphene nanosheets of various sizes, as well
as networks of WS2 nanosheets, silver nanosheets and silver nanowires.
Important morphological characteristics, including network porosity,
tortuosity, pore dimensions and nanosheet orientation were extracted and linked
to network resistivity. By extending this technique to interrogate the
structure and interfaces within vertical printed heterostacks, we demonstrate
the potential of this technique for device characterisation and optimisation.Comment: 6 figure
Quantifying the contribution of material and junction resistances in nano-networks
Networks of nanowires and nanosheets are important for many applications in
printed electronics. However, the network conductivity and mobility are usually
limited by the inter-particle junction resistance, a property that is
challenging to minimise because it is difficult to measure. Here, we develop a
simple model for conduction in networks of 1D or 2D nanomaterials, which allows
us to extract junction and nanoparticle resistances from
particle-size-dependent D.C. resistivity data of conducting and semiconducting
materials. We find junction resistances in porous networks to scale with
nanoparticle resistivity and vary from 5 Ohm for silver nanosheets to 25 GOhm
for WS2 nanosheets. Moreover, our model allows junction and nanoparticle
resistances to be extracted from A.C. impedance spectra of semiconducting
networks. Impedance data links the high mobility (~7 cm2/Vs) of aligned
networks of electrochemically exfoliated MoS2 nanosheets to low junction
resistances of ~670 kOhm. Temperature-dependent impedance measurements allow us
to quantitatively differentiate intra-nanosheet phonon-limited band-like
transport from inter-nanosheet hopping for the first time.Comment: 5 figure
First Dark Matter Search Results from the LUX-ZEPLIN (LZ) Experiment
The LUX-ZEPLIN experiment is a dark matter detector centered on a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA. This Letter reports results from LUX-ZEPLIN's first search for weakly interacting massive particles (WIMPs) with an exposure of 60 live days using a fiducial mass of 5.5 t. A profile-likelihood ratio analysis shows the data to be consistent with a background-only hypothesis, setting new limits on spin-independent WIMP-nucleon, spin-dependent WIMP-neutron, and spin-dependent WIMP-proton cross sections for WIMP masses above 9 GeV/c2. The most stringent limit is set for spin-independent scattering at 36 GeV/c2, rejecting cross sections above 9.2×10-48 cm at the 90% confidence level
The LUX-ZEPLIN (LZ) Experiment
We describe the design and assembly of the LUX-ZEPLIN experiment, a direct detection search for cosmic WIMP dark matter particles. The centerpiece of the experiment is a large liquid xenon time projection chamber sensitive to low energy nuclear recoils. Rejection of backgrounds is enhanced by a Xe skin veto detector and by a liquid scintillator Outer Detector loaded with gadolinium for efficient neutron capture and tagging. LZ is located in the Davis Cavern at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. We describe the major subsystems of the experiment and its key design features and requirements
First Dark Matter Search Results from the LUX-ZEPLIN (LZ) Experiment
The LUX-ZEPLIN (LZ) experiment is a dark matter detector centered on a
dual-phase xenon time projection chamber operating at the Sanford Underground
Research Facility in Lead, South Dakota, USA. This Letter reports results from
LZ's first search for Weakly Interacting Massive Particles (WIMPs) with an
exposure of 60 live days using a fiducial mass of 5.5 t. A profile-likelihood
ratio analysis shows the data to be consistent with a background-only
hypothesis, setting new limits on spin-independent WIMP-nucleon, spin-dependent
WIMP-neutron, and spin-dependent WIMP-proton cross-sections for WIMP masses
above 9 GeV/c. The most stringent limit is set at 30 GeV/c, excluding
cross sections above 5.9 cm at the 90\% confidence level.Comment: 9 pages, 6 figures. See https://tinyurl.com/LZDataReleaseRun1 for a
data release related to this pape
The LUX-ZEPLIN (LZ) radioactivity and cleanliness control programs
LUX-ZEPLIN (LZ) is a second-generation direct dark matter experiment with spin-independent WIMP-nucleon scattering sensitivity above 1.4×10−48cm2 for a WIMP mass of 40GeV/c2 and a 1000days exposure. LZ achieves this sensitivity through a combination of a large 5.6t fiducial volume, active inner and outer veto systems, and radio-pure construction using materials with inherently low radioactivity content. The LZ collaboration performed an extensive radioassay campaign over a period of six years to inform material selection for construction and provide an input to the experimental background model against which any possible signal excess may be evaluated. The campaign and its results are described in this paper. We present assays of dust and radon daughters depositing on the surface of components as well as cleanliness controls necessary to maintain background expectations through detector construction and assembly. Finally, examples from the campaign to highlight fixed contaminant radioassays for the LZ photomultiplier tubes, quality control and quality assurance procedures through fabrication, radon emanation measurements of major sub-systems, and bespoke detector systems to assay scintillator are presented
The LUX-ZEPLIN (LZ) experiment
We describe the design and assembly of the LUX-ZEPLIN experiment, a direct detection search for cosmic WIMP dark matter particles. The centerpiece of the experiment is a large liquid xenon time projection chamber sensitive to low energy nuclear recoils. Rejection of backgrounds is enhanced by a Xe skin veto detector and by a liquid scintillator Outer Detector loaded with gadolinium for efficient neutron capture and tagging. LZ is located in the Davis Cavern at the 4850’ level of the Sanford Underground Research Facility in Lead, South Dakota, USA. We describe the major subsystems of the experiment and its key design features and requirements
Understanding how junction resistances impact the conduction mechanism in nano-networks
Networks of nanowires, nanotubes, and nanosheets are important for many applications in printed electronics. However, the network conductivity and mobility are usually limited by the resistance between the particles, often referred to as the junction resistance. Minimising the junction resistance has proven to be challenging, partly because it is difficult to measure. Here, we develop a simple model for electrical conduction in networks of 1D or 2D nanomaterials that allows us to extract junction and nanoparticle resistances from particle-size-dependent DC network resistivity data. We find junction resistances in porous networks to scale with nanoparticle resistivity and vary from 5 Ω for silver nanosheets to 24 GΩ for WS2 nanosheets. Moreover, our model allows junction and nanoparticle resistances to be obtained simultaneously from AC impedance spectra of semiconducting nanosheet networks. Through our model, we use the impedance data to directly link the high mobility of aligned networks of electrochemically exfoliated MoS2 nanosheets (≈ 7 cm2 V−1 s−1) to low junction resistances of ∼2.3 MΩ. Temperature-dependent impedance measurements also allow us to comprehensively investigate transport mechanisms within the network and quantitatively differentiate intra-nanosheet phonon-limited bandlike transport from inter-nanosheet hopping.ChemE/Opto-electronic Material