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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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108 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Pick-and-Place Transfer of Arbitrary-Metal Electrodes for van der Waals Device Fabrication

Van der Waals electrode integration is a promising strategy to create nearly perfect interfaces between metals and 2D materials, with advantages such as eliminating Fermi-level pinning and reducing contact resistance. However, the lack of a simple, generalizable pick-and-place transfer technology has greatly hampered the wide use of this technique. Here, we demonstrate the pick-and-place transfer of prefabricated electrodes from reusable polished hydrogenated diamond substrates without the use of any sacrificial layers due to the inherent low-energy and dangling-bond-free nature of the hydrogenated diamond surface. The technique enables transfer of arbitrary-metal electrodes and an electrode array, as demonstrated by successful transfer of eight different elemental metals with work functions ranging from 4.22 to 5.65 eV. We also demonstrate the electrode array transfer for large-scale device fabrication. The mechanical transfer of metal electrodes from diamond to van der Waals materials creates atomically smooth interfaces with no interstitial impurities or disorder, as observed with cross-section high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy. As a demonstration of its device application, we use the diamond transfer technique to create metal contacts to monolayer transition metal dichalcogenide semiconductors with high-work-function Pd, low-work-function Ti, and semimetal Bi to create n- and p-type field-effect transistors with low Schottky barrier heights. We also extend this technology to air-sensitive materials (trilayer 1T’ WTe 2 ) and other applications such as ambipolar transistors, Schottky diodes, and optoelectronics. This highly reliable and reproducible technology paves the way for new device architectures and high-performance devices.

2D materials↗
DOE OSTI2025

Strong-coupling quantum dot microscope

Here, we report the development and fabrication of a novel cryogenic instrument, a scanning quantum dot microscope (SQDM), capable of positioning a quantum dot to within tunneling range of a sample surface. The microscope is strong-coupling in the sense that electron wavefunctions in the quantum dot can directly overlap with electron wavefunctions in the sample, in contrast to probes based on electric-field coupling. The SQDM consists of a sharp glass probe with two asymmetric electrodes leading to an aluminum quantum dot at the apex. One electrode is capacitively coupled to the quantum dot, while the other lead is connected to the dot via a tunneling junction. A charge sensing circuit constructed from a high-electron-mobility transistor is attached to the capacitance lead to measure the charge state of the dot. The last key feature of the design is a tilted-apex geometry. This design feature, in conjunction with the capacitive sensing scheme, results in a robust quantum-dot probe capable of operating within angstrom distances of the sample surface while protecting the single tunnel junction responsible for electron transport onto the quantum dot. We demonstrate that our instrument can detect single-electron tunneling events and can also be operated as a standard scanning tunneling microscope capable of nanometer-scale resolution of the surface topography.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Enhanced ferroelectricity in ultrathin films grown directly on silicon

Ultrathin ferroelectric materials could potentially enable low-power logic and nonvolatile memories. As ferroelectric materials are made thinner, however, the ferroelectricity is usually suppressed. Size effects in ferroelectrics have been thoroughly investigated in perovskite oxides—the archetypal ferroelectric system. Perovskites, however, have so far proved unsuitable for thickness scaling and integration with modern semiconductor processes. In this paper we report ferroelectricity in ultrathin doped hafnium oxide (HfO 2 ), a fluorite-structure oxide grown by atomic layer deposition on silicon. We demonstrate the persistence of inversion symmetry breaking and spontaneous, switchable polarization down to a thickness of one nanometre. Our results indicate not only the absence of a ferroelectric critical thickness but also enhanced polar distortions as film thickness is reduced, unlike in perovskite ferroelectrics. This approach to enhancing ferroelectricity in ultrathin layers could provide a route towards polarization-driven memories and ferroelectric-based advanced transistors. This work shifts the search for the fundamental limits of ferroelectricity to simpler transition-metal oxide systems—that is, from perovskite-derived complex oxides to fluorite-structure binary oxides—in which ‘reverse’ size effects counterintuitively stabilize polar symmetry in the ultrathin regime.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Wide-Bandgap Semiconductor Amplifiers for Fusion Plasma Heating and Control

This paper discusses power electronics developed under the ARPA-E GAMOW program to support nuclear fusion power production. The goal of this project was to develop and assess the potential for wide-bandgap (WBG) semiconductor devices in power electronics to enable high-efficiency and high-voltage solid-state systems for fusion plasma generation, heating, and control. The power electronics use an architecture in which multiple high-power boards can be combined to produce megawatt-level power, where using multiple boards provides high reliability. Two main areas of power electronics boards are developed in this project for fusion plasma heating and control applications: (1) pulse generation and control and (2) radiofrequency generation. The first area is for boards capable of driving high-voltage millisecond pulses at high duty cycles. The envisioned application of these pulses is in plasma control of magnetohydrodynamic instabilities, plasma position, and edge-localized modes. Pulse-width modulation allows for the implementation of a wide variety of linear and nonlinear control systems. The boards developed for this project could actuate control coils based on digital input signals and can be parallelized to provide megawatts of output power. The design of the pulse generator is a low-side load switch. A load switch was designed and constructed that utilized 2-kV-rated field-effect transistor (FET)-based cascodes developed by Qorvo under this project to perform initial testing of these cascodes. The second area is being implemented using class E amplifiers with WBG devices and a reactance steering network to handle inductive or capacitive plasma loads. Applications include ion cyclotron resonance heating (ICRH) and high-harmonic fast-wave (HHFW) heating. A class E reactance steering network is demonstrated in modeling and experiment with a resistive-inductive load that models an inductively-coupled plasma. Power combining of boards with class E reactance steering networks is also simulated and demonstrated experimentally, to enable scaling up to high power. Modeling of high-power-density cooling and remaining useful life is conducted to enable reliable, effectively cooled high-power electronics for fusion applications.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

Optical-Gating of Spin-based Quantum States (Final Report)

This project developed a generalizable strategy for optical control of spin-based quantum states through the Photoisomerization-Induced Spin–Charge Excited State (PISCES) process, in which a photochromic spirooxazine ligand bound to an electronically bistable metal complex enables reversible, room-temperature optical switching of spin states in both dilute matrices and the solid state. A multidisciplinary team integrated synthesis, spectroscopy, theory, and surface science to establish design principles for opto-spintronic quantum materials. Systematic structure–property studies across four spirooxazine series revealed that donor–π–acceptor interactions govern thermal isomerization, which proceeds via a rotational pathway. Pulsed EPR measurements demonstrated millisecond-scale coherence times in cobalt-dioxolene-spirooxazine complexes, establishing their promise as optically addressable molecular qubits; the approach was extended to Cu(II), Ni(II), and lanthanide complexes, including optical modulation of zero-field splittings and clock transitions. Two-dimensional IR spectroscopy resolved picosecond ground-state population exchange dynamics, while ab initio calculations elucidated photoisomerization mechanisms and parametrized Hamiltonians for spin relaxation and decoherence. Toward device integration, the team fabricated 2D polymer scaffolds for covalent qubit organization, developed tip-enhanced Raman imaging of molecular monolayers, and demonstrated optical gating of gate voltage in spirooxazine-graphene field-effect transistors. The project produced numerous publications, dissertations, and presentations, and trained over 30 researchers.

2D polymers↗
DOE OSTI2020

High yield production of ultrathin fibroid semiconducting nanowire of Ta 2 Pd 3 Se 8

Immediately after the demonstration of the high-quality electronic properties in various two dimensional (2D) van der Waals (vdW) crystals fabricated with mechanical exfoliation, many methods have been reported to explore and control large scale fabrications. Comparing with recent advancements in fabricating 2D atomic layered crystals, large scale production of one dimensional (1D) nanowires with thickness approaching molecular or atomic level still remains stagnant. Here, we demonstrate the high yield production of a 1D vdW material, semiconducting Ta 2 Pd 3 Se 8 nanowires, by means of liquid-phase exfoliation. The thinnest nanowire we have readily achieved is around 1 nm, corresponding to a bundle of one or two molecular ribbons. Transmission electron microscopy (TEM) and transport measurements reveal the as-fabricated Ta 2 Pd 3 Se 8 nanowires exhibit unexpected high crystallinity and chemical stability. Our low-frequency Raman spectroscopy reveals clear evidence of the existing of weak inter-ribbon bindings. The fabricated nanowire transistors exhibit high switching performance and promising applications for photodetectors.

1D semiconductor↗
DOE OSTI2021

Solvent-Free Coating of Organic Semiconductor Membranes with Centimetric Crystalline Domains

Organic semiconductors (OSCs) have shown great promise in a variety of applications. Although solution processing of OSCs has resulted in high-quality films, exquisite control of structural development to minimize defect formation during large-scale fabrication remains formidable. Compounding this challenge is the use of halogenated organic solvents, which poses significant health and environmental hazards. However, the solvent-free techniques introduced thus far impose additional limitations on solidification kinetics; the resulting OSC thin films are often more defective than those processed from solution. Here, a solvent-free technique is reported to prepare OSC membranes with centimetric crystalline domains. Leveraging the tendency for liquid crystalline materials to preferentially orient, OSCs are “prealigned” by depositing them from the melt over a metal frame to form a freely suspended membrane. Additionally, crystallization from this prealigned phase affords membranes with unprecedented structural order across macroscopic distances. Field-effect transistors comprising membranes of dioctyl[1]-benzothieno[3,2-b][1]benzothiophene (C8BTBT) and didodecyl[1]-benzothieno[3,2-b][1]benzothiophene (C12BTBT) having centimeter-sized domains as active layers exhibit a hole mobility of ≈8.6 cm2 V -1 s -1 , superseding the mobility of any transistors whose active layers are deposited from melt. This technique is scalable to yield membranes with large crystalline domains over wafer dimensions, making it amenable for broad applications in large-area organic electronics.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A New Class of SiC Power MOSFETs with Record-Low Resistance

Silicon carbide (SiC) power transistors are used in the main traction inverter of electric vehicles (EVs). Tesla began installing SiC power MOSFETs in 2017, and has now produced 4.8 million EVs containing over 169 million SiC power MOSFETs. Looking ahead, the worldwide EV market is projected to exceed 50 million vehicles per year by 2030 (Reuters, Oct. 25, 2022). This will create a demand for over two billion SiC power MOSFETs per year. Our program aims to double the efficiency of today's commercial power MOSFETs. This will cut the number of MOSFETs per EV in half, reducing cost, simplifying assembly, decreasing weight, and increasing vehicle reliability through reduced parts count. Our approach is to apply innovative design and advanced processing to increase the density of current-controlling channels in SiC power MOSFET. We have developed two new MOSFET devices, each of which increases the channel density by a factor of six over today's best commercial MOSFETs. This required implementing new fabrication processes, creating new device designs, and integrating the processing steps and device designs into a manufacturable technology. In this project we have developed two innovative devices: (i) a novel three-dimensional structure, the "tri-gate MOSFET," and (ii) a deeply-scaled, fully self-aligned trench MOSFET, the "IMOSFET". Both products were experimentally demonstrated during this project and meet the program goals of increased efficiency relative to the current state-of-the art commercial products. In the process we have generated significant IP, with two US patents issued and three applications pending. We have also published three journal articles and given reports on this technology at seven international conferences. The success of this program has led to significant follow-on funding from industry. In May 2023 Purdue University signed a five-year R&D contract with GlobalFoundries to transfer our novel technology to commercial production. With headquarters in Malta, NY, Global Foundries is one of the largest pure-play silicon foundries in the world, with annual revenue of $\$$8.1B. Their SiC foundry will be built around the next-generation 200-mm diameter SiC wafers, which will double the number of die per wafer and reduce per-die production cost.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Design-Technology Co-Optimization for NVM-based Neuromorphic Processing Elements

An emerging use-case of machine learning (ML) is to train a model on a high-performance system and deploy the trained model on energy-constrained embedded systems. Neuromorphic hardware platforms, which operate on principles of the biological brain, can significantly lower the energy overhead of a machine learning inference task, making these platforms an attractive solution for embedded ML systems. In this paper, we present a design-technology tradeoff analysis to implement such inference tasks on the processing elements (PEs) of a Non-Volatile Memory (NVM)-based neuromorphic hardware. Through detailed circuit-level simulations at scaled process technology nodes, we show the negative impact of technology scaling on the information-processing latency, which impacts the quality-of-service (QoS) of an embedded ML system. At a finer granularity, the latency inside a PE depends on 1) the delay introduced by parasitic components on its current paths, and 2) the varying delay to sense different resistance states of its NVM cells. Based on these two observations, we make the following three contributions. First, on the technology front, we propose an optimization scheme where the NVM resistance state that takes the longest time to sense is set on current paths having the least delay, and vice versa, reducing the average PE latency, which improves the QoS. Second, on the architecture front, we introduce isolation transistors within each PE to partition it into regions that can be individually power-gated, reducing both latency and energy. Finally, on the system-software front, we propose a mechanism to leverage the proposed technological and architectural enhancements when implementing a machine-learning inference task on neuromorphic PEs of the hardware. Evaluations with a recent neuromorphic hardware architecture show that our proposed design-technology co-optimization approach improves both performance and energy efficiency of machine-learning inference tasks without incurring high cost-per-bit.

42 ENGINEERING↗
DOE OSTI2022

Graphene nanoribbons initiated from molecularly derived seeds

Abstract Semiconducting graphene nanoribbons are promising materials for nanoelectronics but are held back by synthesis challenges. Here we report that molecular-scale carbon seeds can be exploited to initiate the chemical vapor deposition (CVD) synthesis of graphene to generate one-dimensional graphene nanoribbons narrower than 5 nm when coupled with growth phenomena that selectively extend seeds along a single direction. This concept is demonstrated by subliming graphene-like polycyclic aromatic hydrocarbon molecules onto a Ge(001) catalyst surface and then anisotropically evolving size-controlled nanoribbons from the seeds along $$\left\langle 110\right\rangle$$ 110 of Ge(001) via CH 4 CVD. Armchair nanoribbons with mean normalized standard deviation as small as 11% (3 times smaller than nanoribbons nucleated without seeds), aspect ratio as large as 30, and width as narrow as 2.6 nm (tunable via CH 4 exposure time) are realized. Two populations of nanoribbons are compared in field-effect transistors (FETs), with off-current differing by 150 times because of the nanoribbons’ different widths.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Wafer-scale growth of two-dimensional, phase-pure InSe

Two-dimensional (2D) indium monoselenide (InSe) has attracted significant attention as an ultrathin III–VI semiconductor with a combination of favorable attributes that are comparable to those of III–V semiconductors and van der Waals 2D transition-metal dichalcogenides. Nevertheless, there has been no demonstration of large-area synthesis of 2D InSe due to the complexity of the binary In-Se system and the difficulties in promoting lateral growth. Here, we report the polymorph-selective synthesis of epitaxial 2D InSe by metal-organic chemical vapor deposition (MOCVD) over 2-in wafers. We achieve polymorph-selective epitaxial growth of InSe on c-plane sapphire via flow modulation to control the Se/In ratio. The layer-by-layer growth allows thickness control with tunable optical properties comparable to those of bulk crystals. We also demonstrate gate-tunable electrical transport with a field-effect mobility comparable to that of single-crystalline flakes. Importantly, these results indicate that InSe grown by MOCVD could be an effective channel material for back-end-of-line integration in logic transistors.

2D materials↗
DOE OSTI2021

Transfer-Free Synthesis of Atomically Precise Graphene Nanoribbons on Insulating Substrates

The rational bottom-up synthesis of graphene nanoribbons (GNRs) provides atomically precise control of widths and edges that give rise to a wide range of electronic properties promising for electronic devices such as field-effect transistors (FETs). Since the bottom-up synthesis commonly takes place on catalytic metallic surfaces, the integration of GNRs into such devices requires their transfer onto insulating substrates, which remains one of the bottlenecks in the development of GNR-based electronics. Herein, we report on a method for the transfer-free placement of GNRs on insulators. This involves growing GNRs on a gold film deposited onto an insulating layer followed by gentle wet etching of the gold, which leaves the nanoribbons to settle in place on the underlying insulating substrate. Scanning tunneling microscopy and Raman spectroscopy confirm that atomically precise GNRs of high density uniformly grow on the gold films deposited onto SiO 2 /Si substrates and remain structurally intact after the etching process. We have also demonstrated transfer-free fabrication of ultrashort channel GNR FETs using this process. A very important aspect of the present work is that the method can scale up well to 12 in. wafers, which is extremely difficult for previous techniques. Our work here thus represents an important step toward large-scale integration of GNRs into electronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High-performance 2D electronic devices enabled by strong and tough two-dimensional polymer with ultra-low dielectric constant

As the feature size of microelectronic circuits is scaling down to nanometer order, the increasing interconnect crosstalk, resistance-capacitance (RC) delay and power consumption can limit the chip performance and reliability. To address these challenges, new low-k dielectric (k < 2) materials need to be developed to replace current silicon dioxide (k = 3.9) or SiCOH, etc. However, existing low-k dielectric materials, such as organosilicate glass or polymeric dielectrics, suffer from poor thermal and mechanical properties. Two-dimensional polymers (2DPs) are considered promising low-k dielectric materials because of their good thermal and mechanical properties, high porosity and designability. Here, we report a chemical-vapor-deposition (CVD) method for growing fluoride rich 2DP-F films on arbitrary substrates. We show that the grown 2DP-F thin films exhibit ultra-low dielectric constant (in plane k = 1.85 and out-of-plane k = 1.82) and remarkable mechanical properties (Young’s modulus > 15 GPa). We also demonstrated the improved performance of monolayer MoS 2 field-effect-transistors when utilizing 2DP-F thin films as dielectric substrates.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Tri-gate GaN junction HEMT

This work presents a tri-gate GaN junction high-electron-mobility transistor (JHEMT) concept in which the p–n junction wraps around the AlGaN/GaN fins in the gate region. This tri-gate JHEMT differs from all existing GaN FinFETs and tri-gate HEMTs, as they employ a Schottky or a metal-insulator-semiconductor (MIS) gate stack. A tri-gate GaN JHEMT is fabricated using p-type NiO with the gate metal forming an Ohmic contact to NiO. The device shows minimal hysteresis and a subthreshold slope of 63 ± 2 mV/decade with an on-off current ratio of 10 8 . Compared to the tri-gate MISHEMTs fabricated on the same wafer, the tri-gate JHEMTs exhibit higher threshold voltage (V TH ) and achieve positive V TH without the need for additional AlGaN recess. In addition, this tri-gate JHEMT with a fin width of 60 nm achieves a breakdown voltage (BV) > 1500 V (defined at the drain current of 1 μA/mm at zero gate bias) and maintains the high BV with the fin length scaled down to 200 nm. In comparison, the tri-gate MISHEMTs with narrower and longer fins show punch-through at high voltages. Moreover, when compared to planar enhancement mode HEMTs, tri-gate JHEMTs show significantly lower channel sheet resistance in the gate region. Finally, these results illustrate a stronger channel depletion and electrostatic control in the junction tri-gate compared to the MIS tri-gate and suggest great promise of the tri-gate GaN JHEMTs for both high-voltage power and low-voltage power/digital applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Low-thermal-budget synthesis of monolayer molybdenum disulfide for silicon back-end-of-line integration on a 200 mm platform

Two-dimensional (2D) materials are promising candidates for future electronics due to their excellent electrical and photonic properties. Although promising results on the wafer-scale synthesis (≤150 mm diameter) of monolayer molybdenum disulfide (MoS 2 ) have already been reported, the high-quality synthesis of 2D materials on wafers of 200 mm or larger, which are typically used in commercial silicon foundries, remains difficult. The back-end-of-line (BEOL) integration of directly grown 2D materials on silicon complementary metal–oxide–semiconductor (CMOS) circuits is also unavailable due to the high thermal budget required, which far exceeds the limits of silicon BEOL integration (<400 °C). This high temperature forces the use of challenging transfer processes, which tend to introduce defects and contamination to both the 2D materials and the BEOL circuits. Here we report a low-thermal-budget synthesis method (growth temperature < 300 °C, growth time ≤ 60 min) for monolayer MoS 2 films, which enables the 2D material to be synthesized at a temperature below the precursor decomposition temperature and grown directly on silicon CMOS circuits without requiring any transfer process. We designed a metal–organic chemical vapour deposition reactor to separate the low-temperature growth region from the high-temperature chalcogenide-precursor-decomposition region. We obtain monolayer MoS 2 with electrical uniformity on 200 mm wafers, as well as a high material quality with an electron mobility of ~35.9 cm 2 V -1 s -1 . Finally, we demonstrate a silicon-CMOS-compatible BEOL fabrication process flow for MoS 2 transistors; the performance of these silicon devices shows negligible degradation (current variation < 0.5%, threshold voltage shift < 20 mV). We believe that this is an important step towards monolithic 3D integration for future electronics.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Editorial: Neuroscience, computing, performance, and benchmarks: Why it matters to neuroscience how fast we can compute

At the turn of the millennium the computational neuroscience community realized that neuroscience was in a software crisis: software development was no longer progressing as expected and reproducibility declined. The International Neuroinformatics Coordinating Facility (INCF) was inaugurated in 2007 as an initiative to improve this situation. The INCF has since pursued its mission to help the development of standards and best practices. In a community paper published this very same year, Brette et al. tried to assess the state of the field and to establish a scientific approach to simulation technology, addressing foundational topics, such as which simulation schemes are best suited for the types of models we see in neuroscience. In 2015, a Frontiers Research Topic “Python in neuroscience” by Muller et al. triggered and documented a revolution in the neuroscience community, namely in the usage of the scripting language Python as a common language for interfacing with simulation codes and connecting between applications. The review by Einevoll et al. documented that simulation tools have since further matured and become reliable research instruments used by many scientific groups for their respective questions. Open source and community standard simulators today allow research groups to focus on their scientific questions and leave the details of the computational work to the community of simulator developers. A parallel development has occurred, which has been barely visible in neuroscientific circles beyond the community of simulator developers: Supercomputers used for large and complex scientific calculations have increased their performance from ~10 TeraFLOPS (10 13 floating point operations per second) in the early 2000s to above 1 ExaFLOPS (10 18 floating point operations per second) in the year 2022. This represents a 100,000-fold increase in our computational capabilities, or almost 17 doublings of computational capability in 22 years. Moore's law (the observation that it is economically viable to double the number of transistors in an integrated circuit every other 18–24 months) explains a part of this; our ability and willingness to build and operate physically larger computers, explains another part. It should be clear, however, that such a technological advancement requires software adaptations and under the hood, simulators had to reinvent themselves and change substantially to embrace this technological opportunity. It actually is quite remarkable that—apart from the change in semantics for the parallelization—this has mostly happened without the users knowing. The current Research Topic was motivated by the wish to assemble an update on the state of neuroscientific software (mostly simulators) in 2022, to assess whether we can see more clearly which scientific questions can (or cannot) be asked due to our increased capability of simulation, and also to anticipate whether and for how long we can expect this increase of computational capabilities to continue.

biophysically detailed models↗
DOE OSTI2020

Tilted fluctuation electron microscopy

Fluctuation electron microscopy (FEM) is a scanning nanodiffraction-based method that offers a unique approach to characterizing nanometer-scale medium-range order (MRO) in disordered materials. In addition to determining the degree of MRO, careful analysis of scanning nanodiffraction data can also be used to determine strain in thin film amorphous samples. We applied FEM to characterize the strain and MRO of magnetron sputtered amorphous tantalum (a-Ta) thin films over a range of tilt angles from 0° to 45° in order to measure any deviations between the in-plane and out-of-plane strain and MRO. We validate our approach using electron diffraction simulations of FEM experiments for a-Ta. We measure anisotropic strain in the simulated a-Ta diffraction patterns and find that the experimental a-Ta is isotropically strained within the accuracy of our method. Our approach provides a workflow for acquiring tilted scanning nanodiffraction data, determining the relative strain and ordering as a function of in- A nd out-of-plane directions, and removing any artifacts induced in FEM data due to strain. We also describe some limitations of the tilted FEM method when applied to thin films with very low strains.

36 MATERIALS SCIENCE↗
DOE OSTI2025

In-flight performance of the XRISM/Resolve detector system

The Resolve instrument was launched on board the XRISM observatory in early September 2023. The Resolve spectrometer is based on a high-sensitivity X-ray calorimeter detector system (DS) that has been successfully deployed in many ground and sub-orbital spectrometers. However, the Resolve instrument is the first long-term implementation in space. The instrument will provide essential diagnostics for nearly every class of X-ray emitting objects, from galactic supernova remnants to the outskirts of galaxy clusters, without degradation for spatially extended objects. The Resolve DS consists of a 36-pixel microcalorimeter array operated at a heat sink temperature of 50 mK. In pre-flight testing, the DS demonstrated a resolving power of better than 1300 at 6 keV with a simultaneous bandpass from below 0.3 keV to above 12 keV and a timing precision better than 100μs. An anti-coincidence detector placed directly behind the microcalorimeter array effectively suppresses background. The detector energy-resolution budget included terms for interference from the Resolve cooling system and the spacecraft. Additional terms for energy-scale stability, on-orbit effects, and use of mid-grade events were also included, predicting an end-of-life, on-orbit performance for high- and mid-resolution grade events that meet the requirement of 7 eV FWHM at 6 keV. Here, we discuss the actual on-orbit performance of the Resolve DS and compare this with the performance in pre-flight testing, on-orbit predictions, and the almost identical Hitomi/SXS instrument. We will also discuss the on-orbit gain stability, an assessment of on-orbit interference, and measurements of the on-orbit background.

Astronomy and AstroPhysics↗