We report on electron wakefield acceleration in the resonant bubble regime with few-millijoule near-single-cycle laser pulses at a kilohertz repetition rate. Using very tight focusing of the laser pulse in conjunction with microscale supersonic gas jets, we demonstrate a stable relativistic electron source with a high charge per pulse up to 24 pC/shot. The corresponding average current is 24 nA, making this kilohertz electron source useful for various applications.
Thin membranes are highly sought-after for nanopore-based
single-molecule
sensing, and fabrication of such membranes becomes challenging in
the ≲10 nm thickness regime where a plethora of useful molecule
information can be acquired by nanopore sensing. In this work, we
present a scalable and controllable method to fabricate silicon nitride
(Si
x
N
y
) membranes
with effective thickness down to ∼1.5 nm using standard silicon
processing and chemical etching using hydrofluoric acid (HF). Nanopores
were fabricated using the controlled breakdown method with estimated
pore diameters down to ∼1.8 nm yielding events >500,000
and
>1,800,000 from dsDNA and bovine serum albumin (BSA) protein, respectively,
demonstrating the high-performance and extended lifetime of the pores
fabricated through our membranes. We used two different compositions
of Si
x
N
y
for
membrane fabrication (near-stoichiometric and silicon-rich Si
x
N
y
) and compared
them against commercial membranes. The final thicknesses of the membranes
were measured using ellipsometry and were in good agreement with the
values calculated from the bulk etch rates and DNA translocation characteristics.
The stoichiometry and the density of the membrane layers were characterized
with Rutherford backscattering spectrometry while the nanopores were
characterized using pH-conductance, conductivity-conductance, and
power spectral density (PSD) graphs.
Small-angle x-ray scattering (SAXS) was used to quantitatively study the morphology of aligned, monodisperse conical etched ion tracks in thin films of amorphous SiO 2 with aspect ratios of around 6 : 1 and in polycarbonate foils with aspect ratios of around 1000 : 1. This paper presents the measurement procedure and methods developed for the analysis of the scattering images and shows results obtained for the two material systems. To enable accurate parameter extraction from the data collected from conical scattering objects, a model fitting the two-dimensional (2D) detector images was developed. The analysis involved fitting images from a sequence of measurements with different sample tilts to minimize errors, which may have been introduced due to the experimental setup. The model was validated by the exploitation of the geometric relationship between the sample tilt angle and the cone opening angle, to an angle observed in the features of the SAXS images. We also demonstrate that a fitting procedure for 1D data extracted from the scattering images using a hard cylinder model can also be used to extract the cone size. The application of these techniques enables us to reconstruct the cone morphologies with unprecedented precision.
In situ small angle X-ray scattering (SAXS) measurements of ion track etching of polycarbonate foils are used to directly monitor the selective dissolution of ion tracks with high precision, including...
New SAXS fitting models reveal the detailed morphology of cylindrical ion tracks in polymers composed of a highly damaged core with a gradual transition to the undamaged material.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.