The Rockets for Extended-source X-ray Spectroscopy (tREXS) are a series of suborbital rocket payloads designed to collect spectral emission from extended astronomical sources of soft X-rays. The tREXS spectrograph uses mechanical beam-shaping modules and reflection gratings to passively focus and then disperse incident X-rays to an array of Teledyne/e2v CIS 113 CMOS X-ray sensors. Designed to achieve a moderate spectral resolution, R ⪆ 50, from ≈15 to 40 Å over a large field of view (>10 deg ^2 ), the tREXS instrument is sensitive to line emission from key ion species over the soft-X-ray band. Here we present the complete end-to-end design of the tREXS spectrograph and discuss its significance and expected performance, using simulated observations of the Cygnus Loop supernova remnant and an enhanced region in the soft X-ray background.

Broadband high-efficiency diffraction gratings play a crucial role in the pulse stretcher and compressor of high-energy ultrafast lasers. Nevertheless, conventional grating manufacturing techniques, including mechanical ruling and holographic recording, face challenges in creating accurate blazed groove profiles necessary for the fabrication of broadband, high-efficiency mid-infrared gratings. In this work, we utilized combined electron-beam lithography and anisotropic wet etching technology to fabricate nearly perfect blazed grooves, producing high efficiency broadband mid-infrared (IR) grating for 4.3 µm 100 femtosecond laser. Global optimization was performed to achieve a design of > 90% efficiency over spectral range of 3.6 µm – 6.6 µm. Hybrid metal-dielectric coating (Au-Al2O3) is employed and optimized to minimize absorption and to enhance diffraction efficiency and laser-induced damage threshold (LIDT). Prototype gratings undergo testing at a desired application wavelengths of 4.3 µm in a tunable range of 0.2 µm, revealing that the optimal sample achieves a diffraction efficiency of 92%, closely approaching the theoretical value of 94.2%

Modern grating manufacturing techniques suffer from inherent issues that limit their peak efficiencies. We describe work in collaboration with the Nanofabrication Lab at Penn State University to design and characterize etched silicon gratings optimized for the extreme (EUV; 10 { 90 nm) and far ultraviolet (FUV; 90 { 180 nm) bandpasses. We develop this technology by fabricating a variety of gratings that operate over these bandpasses. We present analyses for two different grating designs in this work. The first is an FUV echelle that has similar parameters to the grating own on the CHESS sounding rocket. CHESS was an FUV spectrograph that utilized a mechanically ruled echelle grating. We compare the efficiency and in-instrument performance of the gratings, finding a ~ 50% increase in groove efficiency and an 80% decrease in inter-order scatter for the etched gratings compared to their mechanically ruled counterpart. The FUV echelle improvements can ultimately benefit the faint source sensitivity and high-resolution performance of future UV observatories, such as LUVOIR, by reducing the non-uniform inter-order backgrounds that have historically plagued echelle spectrographs. We additionally provide a description of how this lithographic process can be extended to gratings with holographic solutions by discussing our procedure for generating a map of groove traces from holographic recording parameters. This discussion is provided in the context of the creation of a grating sample that was developed in support of the ESCAPE Small Explorer Phase A study.

Diffraction gratings used in ultraviolet astronomical spectrographs have been made using mechanical ruling or interference lithography. However, required performance for newly developed EUV (10-90 nm) and FUV (100-180 nm) spectrographs can benefit from groove densities, blaze angles, and low-scatter enabled with electron-beam lithography patterning and chemical etching. We report on the fabrication of custom grating prototypes developed at the Nanofabrication Laboratory at Penn State University. The gratings in development for the ESCAPE NASA Small Explorer (Univ. of Colorado/Boulder) involve writing specific patterns of curved grooves with variable line density on flat substrates. The design of the grating within the DEUCE sounding rocket payload involves writing straight grooves on a spherically curved substrate. All gratings are subsequently etched to achieve the specified blaze in the silicon. These efforts are enabling new applications in the field of astronomical UV spectroscopy.

Purpose: The purpose of this project was to evaluate the filtration efficiency of selected household materials and commercial fabrics for use in mask construction to provide protection from the SARS-CoV-2 virus (COVID-19). Methods: A particle counter was utilized to measure particle penetration through each of the material samples and filtration efficiencies were calculated for the following particle sizes: 0.3 µm, 0.5 µm, 1 µm, 3 µm, 5 µm, 10 µm. Samples included a N95 respirator, KN95 respirator, cleanroom mask, MERV 13 and 15 HVAC filters, paper towels, polypropylene shop towels, meltblown fabric, surgical sterilization wrap, cotton, and various wools. Some samples were measured in multiple layers. Results: The N95 respirator, meltblown fabric samples that were layered in 4 or more plys, and 2-ply MERV 15 bag filter had a filtration efficiency consistent with the NIOSH requirements for an N95 respirator with filtration efficiencies at 0.3 µm of 98.0%, 95.4%, and 95.1%, respectively. Of the samples tested that did not meet the N95 specifications, the cleanroom mask and KN95 respirator were the closest, with a filtration efficiency at 0.3 µm of 86.3% and 83.9%, respectively. Of the non-traditional filter materials tested, the sterilization wrap layered in 2 or more plys, paper towels in 3 or more plys, and some of the wool felt samples had filtration efficiencies that were markedly superior to those of the cotton and shop towel samples. Conclusions: While some of the filter materials tested had a filtration efficiency that met NIOSH N95 respirator requirements, most of the non-traditional filter materials tested were inferior to commercially manufactured masks. However, when used in multiple plys, some did provide superior filtration to the materials currently recommended to the public for mask use. Therefore, they may be beneficial for use in homemade masks for the public or as a layer in a composite mask for healthcare workers. Further testing of these materials for filter parameters such as pressure drop, durability, and safety is recommended before using them to produce masks.

Gratings enable dispersive spectroscopy from the X-ray to the optical, and feature prominently in proposed flagships and SmallSats alike. The exacting performance requirements of these future missions necessitate assessing whether the present state-of-the-art in grating manufacture will limit spectrometer performance. In this work, we manufacture a 1.5 mm thick, 1000 nm period at grating using electron-beam lithography (EBL), a promising lithographic technique for patterning gratings for future astronomical observatories. We assess the limiting spectral resolution of this grating by interferometrically measuring the diffracted wavefronts produced in +/-1st order. Our measurements show this grating has a performance of at least R ~ 14,600, and that our assessment is bounded by the error of our interferometric measurement. The impact of EBL stitching error on grating performance is quantifed, and a path to measuring the period error of customized, curved gratings is presented.

The soft X-ray grating spectrometer on board the Off-plane Grating Rocket Experiment (OGRE) hopes to achieve the highest resolution soft X-ray spectrum of an astrophysical object when it is launched via suborbital rocket. Paramount to the success of the spectrometer are the performance of the [Formula: see text] reflection gratings populating its reflection grating assembly. To test current grating fabrication capabilities, a grating prototype for the payload was fabricated via electron-beam lithography at The Pennsylvania State University’s Materials Research Institute and was subsequently tested for performance at Max Planck Institute for Extraterrestrial Physics’ PANTER X-ray Test Facility. Bayesian modeling of the resulting data via Markov chain Monte Carlo (MCMC) sampling indicated that the grating achieved the OGRE single-grating resolution requirement of [Formula: see text] at the 94% confidence level. The resulting [Formula: see text] posterior probability distribution suggests that this confidence level is likely a conservative estimate though, since only a finite [Formula: see text] parameter space was sampled and the model could not constrain the upper bound of [Formula: see text] to less than infinity. Raytrace simulations of the tested system found that the observed data can be reproduced with a grating performing at [Formula: see text]. It is therefore postulated that the behavior of the obtained [Formula: see text] posterior probability distribution can be explained by a finite measurement limit of the system and not a finite limit on [Formula: see text]. Implications of these results and improvements to the test setup are discussed.

We report on resolving power measurements of an X-ray reflection grating designed for use in an astronomical soft X-ray spectrograph. The grating was patterned via electron-beam lithography (EBL) to have fanned grooves to match the convergence of an illuminating beam. Grating measurements were conducted in an echelle-like mounting, which yields access to high diffraction orders in the soft X-ray bandpass (0.2-2.0 keV). By comparing the zeroth-order line-spread function to the telescope focus, we find evidence for minimal broadening (<1 '') introduced by the figure of the grating. In addition, we fit for the spectral resolution (R = lambda/Delta lambda) intrinsic to this grating using a Bayesian Markov Chain Monte Carlo approach. Using an ensemble fitting technique, we find that the grating resolutionRexceeds 2200 (3 sigma lower bound). This current grating resolution meets the performance required for a notional soft X-ray grating spectroscopy mission measuring hot baryonic material in the extended halos of galaxies. Using ray-trace simulations, we identify a geometric aberration resulting from path length differences across the width of the grating as a limiting factor in assessing the resolution of these gratings and discuss methods for placing better constraints on the inherent resolution of X-ray astronomical reflection gratings fabricated using EBL.

Astronomical X-ray diffraction gratings are a key technology under development for current and future NASA missions. X-ray reflection gratings, developed at Penn State University, have recently demonstrated both leading diffraction efficiency and high spectral resolving power. However, recent results are the result of different fabrication techniques and a single technique has not yet been developed to yield a grating that satisfies both the diffraction efficiency and resolving power required by future missions. Here we seek to leverage exiting electron-beam lithographic techniques to produce a grating with groove groove pattern capable of high resolving power. We then introduce new ion-milling techniques to create custom groove profiles capable of high diffraction efficiency. The goal is to produce a radial groove pattern with precisely blazed facets that are customizable based on ion mill input parameters. The process should be insensitive to groove density (ranging from ~150 nm to 400+ nm), facet size, and desired facet angle. Initial efforts in this study have concentrated on constraining various parameters in ion milling to fully characterize the effect of each parameter on the grating groove profile. We present here initial results and discuss experimental verification and future work.

The Water Recovery X-Ray Rocket (WRXR) was a suborbital rocket payload that was launched and recovered in April 2018. The WRXR flew two technologies being developed for future large x-ray missions: x-ray reflection gratings and a hybrid CMOS detector (HCD). The large-format replicated gratings on the WRXR were measured in ground calibrations to have absolute single-order diffraction efficiency of similar to 60%, similar to 50%, and similar to 35% at CVI, OVII, and OVIII emission energies, respectively. The HCD was operated with similar to 6 e(-) read noise and similar to 88 eV energy resolution at 0.5 keV. The WRXR was also part of a two-payload campaign that successfully demonstrated NASA sounding rocket water recovery technology for science payloads. The primary instrument, a soft x-ray grating spectrometer, targeted diffuse emission from the Vela supernova remnant over a field-of-view >10 deg(2). The flight data show that the detector was operational during flight and detected x-ray events from an on-board calibration source, but there was no definitive detection of x-ray events from Vela. Flight results are presented along with a discussion of factors that could have contributed to the null detection. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE)

Thermally activated selective topography equilibration (TASTE) enables the creation of 3D structures in resist using grayscale electron-beam lithography followed by a thermal treatment to induce a selective polymer reflow. A blazed grating topography can be created by reflowing repeating staircase patterns in resist into wedge-like structures. Motivated by astronomical applications, such patterns with periodicities 840 nm and 400 nm have been fabricated in 130 nm-thick PMMA using TASTE to provide a base for X-ray reflection gratings. A path forward to integrate this alternative blazing technique into grating fabrication recipes is discussed.

We present the methodology used to fabricate an X-ray reflection grating and describe a technique for grating replication. Further, we present the experimental procedure and results of a study to measure the diffraction efficiency of a replicated X-ray reflection grating in an extreme off-plane geometry. The blazed grating demonstrates a total diffraction efficiency of similar to 60% from 0.34 to 1.2 keV at a grazing angle of similar to 1 degrees.5, with single-order efficiency ranging from similar to 35% to 65% for energies within the blaze envelope. The diffraction efficiency of the grating measured relative to the reflectivity of the metal coating averages similar to 90% above 0.34 keV. Data collected as a function of beam position on the grating indicate a relative variation in total efficiency of <1% rms across the grating surface.

This work examines the isofocality of four commercially available positive resists for electron beam lithography (EBL) at 100 keV: AR-P 6200 (commercially known as CSAR 62) by AllResist GmbH, ZEP520A by Zeon Corp., polymethylmethacrylate 950 A4 (950k molecular weight in anisole) by MicroChem Corp., and mr-PosEBR 0.3 by Micro Resist Technology GmbH. Isofocality is the operating point in a given process where a specific dose (namely, the isofocal dose) results in the same feature size (isofocal feature) independent of the effective blur (blureff). The blureff is a lumped parameter that includes the effects of resist processing, spot size, beam focus, forward scattering, etc., which contributes to the final resist image. The isofocal feature is typically larger than the drawn target critical dimension (CD). The difference between the isofocal feature size and the CD target defines the isofocal bias. By analyzing the exposure latitudes across 0%, 25%, 50%, 75%, and 100% pattern densities (ρ) with feature sizes ranging from 100 to 400 nm, the approximate pattern density dependent isofocal doses (IFDρ) and isofocal biases (IFΔρ) are identified for a silicon substrate across all four resists given their fixed processes at 100 keV. Examining the trends in isofocality in these positive resist processes, the proximity effect correction is adjusted to provide the empirically found IFDρ for 100 keV EBL on a silicon substrate.

Neurotransmitter release in chemical synapses is fundamental to diverse brain functions such as motor action, learning, cognition, emotion, perception, and consciousness. Moreover, improper functioning or abnormal release of neurotransmitter is associated with numerous neurological disorders such as epilepsy, sclerosis, schizophrenia, Alzheimer's disease, and Parkinson's disease. We have utilized hysteresis engineering in a back-gated MoS2 field effect transistor (FET) in order to mimic such neurotransmitter release dynamics in chemical synapses. All three essential features, i.e., quantal, stochastic, and excitatory or inhibitory nature of neurotransmitter release, were accurately captured in our experimental demonstration. We also mimicked an important phenomenon called long-term potentiation (LTP), which forms the basis of human memory. Finally, we demonstrated how to engineer the LTP time by operating the MoS2 FET in different regimes. Our findings could provide a critical component toward the design of next-generation smart and intelligent human-like machines and human-machine interfaces.

We present reliability analysis of the two most critical interfaces in III-V Heterojunction Tunnel FET (HTFET) design: (1) Tunnel Heterojunction is characterized in three-dimensional atomic scale resolution using Atom Probe Tomography. We explore the impact of tunnel junction abruptness and source dopant fluctuations on HTFET performance; (2) Extremely scaled Hi-K gate dielectric (sub-0.8 nm EOT: HfO2, HfO2-ZrO2 bilayer, and ZrO2)/ III-V channel interface is evaluated using Positive Bias Temperature Instability (PBTI) measurements. HfO2 based HTFET exhibits superior PBTI performance over ZrO2 based HTFET and shows lifetime improvement over III-V FinFET.

It is well known that cold development yields higher contrast and improved exposure latitude particularly for ZEP520 from Zeon Chemicals. In this paper, the authors quantify the effective process blur as a function of temperature. The effective process blur for our development process conditions were found to be 10, 42, and 71 nm for developer temperatures at −12, 21, and 30 °C, respectively. Knowledge of how to tune the process blur can be used in a unique application. Instead of using the best possible process blur, exposure latitude is traded for improved exposure time. Optimizing the e-beam exposure time is always desired while maintaining a target critical dimension and desired shape at the wafer. In particular, the exposure time can be dominated by shape overhead delays stemming from the over digitization of curved shapes within a pattern. As such, it is better to expose a pattern with the least number of shapes as possible while obtaining the desired shape at the wafer. The authors demonstrate how e-beam simulation can be used to determine the optimal effective process blur to obtain a target desired shape while minimizing the fractured shape count to ultimately reduce overall exposure time.

Compressively strained Ge (s-Ge) quantum well (QW) FinFETs with Si 0.3 Ge 0.7 buffer are fabricated on 300mm bulk Si substrate with 20nm W Fin and 80nm fin pitch using sidewall image transfer (SIT) patterning process. We demonstrate (a) in-situ process flow for a tri-layer high-κ dielectric HfO 2 /Al 2 O 3 /GeO x gate stack achieving ultrathin EOT of 0.7nm with low D IT and low gate leakage; (b) 1.3% s-Ge FinFETs with Phosphorus doped Si 0.3 Ge 0.7 buffer on bulk Si substrate exhibiting peak μ h =700 cm 2 /V s , μ h =220 cm 2 /Vs at 10 13 /cm 2 hole density. The s-Ge FinFETs achieve the highest μ*C max of 3.1×10 -4 F/Vs resulting in 5x higher I ON over unstrained Ge FinFETs.