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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Methods for low-temperature p-CVD and thermal ALD of magnesium diboride

ALD and p-CVD methods to generate MgB 2 and MgB 2 -containing films in the growth temperature range of 250-300° C. The thermal ALD and p-CVD methods shown herein ensure that the high-temperature-induced roughening, which causes high surface resistances in MgB2 coatings grown by the mentioned conventional techniques, is avoided. The MgB 2 and MgB 2 -containing films exhibit superconductive properties at above 20° K.

Mandia, David Joseph↗
DOE OSTI2020

Improving stability of ALD ZrN thin film coatings over U-Mo dispersion fuel

Atomic layer deposition (ALD) of ZrN is a candidate technology for coating U-Mo dispersion fuel as a diffusion barrier coating. During the early development stages of the coating the ZrN deposition showed to be mechanically unstable and ultimately resulted in spalling. Based on experimental outcomes it was found that instabillity can be eliminated through the introduction of a thin amorphous (a) Al 2 O 3 interlayer coating deposited in between the ~1-μm thick ZrN and the U-Mo. substrate. To elucidate these findings simulations were performed with density functional theory (DFT) to measure work of adhesions at different interfaces while finite element modeling (FEM) was performed to measure the residual stress distribution. DFT indicated that the ZrN coating deposited over (a)-Al 2 O 3 is ~2.5 times stronger when compared to direct deposition over U or UO 2 substrate. While calculations from FEM recognized; (1) large stress concentrations can originate from the irregularly distributed native surface oxides (UO 2 ) over U-Mo and (2) stress concentrations can be reduced if those surface UO 2 can be modified to a uniform layer (achieved after application of a 8 nm (a)-Al 2 O 3 interlayer). These results provided explanations and confirmed the role played by interlayer in eliminating the original mechanical instability of the ZrN.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

A Study of Support Effects for CH 4 and CO Oxidation over Pd Catalysts on ALD-Modified Al 2 O 3

Interactions between a metal and its oxide support can influence CO and CH 4 oxidation, but promotion by the support can be difficult to study because oxides can have different surface structures and surface areas. To focus on the chemical aspects of support promotion for CO and CH 4 oxidation, this study investigated the effect of support composition on Pd catalysts by preparing uniform films of NiO, Co 3 O 4 , Fe 2 O 3 , MnO 2 , CeO 2 , and ZrO 2 on γ-Al 2 O 3 using Atomic Layer Deposition (ALD). The structure of the films was characterized by XRD and STEM, and catalysts with ~ 1-wt% Pd were examined for CO and CH 4 oxidation. CeO 2 /γ-Al 2 O 3 was unique among the supports in greatly stabilizing the Pd dispersion to 1173 K. Rates for CO oxidation were enhanced by the presence of CeO 2 , Fe 2 O 3 , and MnO 2 , while the other oxides had no promotional effect. For CH 4 oxidation, only NiO and Co 3 O 4 were modest promoters, while the other reducible oxides even showed a negative effect on rates. Finally, possible reasons for the differences between CH 4 and CO oxidation activities are discussed.

42 ENGINEERING↗
DOE OSTI2018

Interaction between Al and atomic layer deposited (ALD) ZrN under high-energy heavy ion irradiation

Uranium-molybdenum (U-Mo) particles dispersed in an aluminum matrix is the most promising candidate fuel to convert high-power research and test reactors in Europe from using high-enriched to using low-enriched fuel. However, chemical interaction between the U-Mo and the Al matrix leads to undesirable fuel behavior. Zirconium nitride (ZrN) is used as a diffusion barrier between the U-Mo fuel particles and the Al matrix. To understand the potential microstructural evolution of ZrN during irradiation, a high-energy heavy ion (84 MeV Xe) irradiation experiment was performed on atomic layer deposited (ALD) nanocrystalline ZrN deposited on an Al plate. A fluence of 1.86 x 10 17 ions/cm 2 , or 90.3 dpa was reached during this experiment. Both analytic transmission electron microscopy (TEM) and synchrotron microbeam X-ray diffraction (ARD) techniques were utilized to investigate the kinetics of radiation-induced grain growth of ZrN at various radiation doses based on the Williamson-Hall analyses. The grain growth kinetics can be described by a power law expression, D n - D$n\atop{0}$ = K phi, with n = 5.1. The Al-ZrN interaction products (Al 3 Zr and AIN) created by radiation-induced ballistic mixing/radiation-enhanced diffusion and their corresponding formation mechanism were determined from electron diffraction and elemental composition analysis. These experimental results were confirmed by first principle thermodynamic density functional theory (DFT) calculations. The results from this ion irradiation study were also compared to in-pile irradiation data from physical vapor deposited (PVD) ZrN samples for a comprehensive evaluation of the interaction between Al and ZrN and its influence on diffusion barrier performance.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Ultra-thin on-chip ALD LiPON capacitors for high frequency application

Multi-layer ceramic capacitors have been used for high frequency decoupling application due to a lower overall impedance leading to fast current response. However, high parasitic inductance limits the application of these capacitors in ultra-high frequency domain. Thus, Multlayer Ceramic Capacitors (MLCCs) are placed close to the IC to improve circuit efficiency and reduce inductance. With next generation applications, the demand for frequency range has further increased which not only requires enhanced capacitor material but improved manufacturing techniques to limit the inductive path. Here, we demonstrate ALD of two different polymorphs of ultra-thin film lithium phosphorus oxynitride (LiPON) as an inorganic solid state electrolyte (SSE) for on chip capacitors for decoupling application. Both the LiPON capacitors shows an electric double layer behavior with a capacitance of 15 μF/cm 2 and a low leakage current (<20 nA/cm 2 ) at 2V. The LiPON shows EDLC behavior up to 10 kHz and beyond, both the polymorphs show an electrostatic behavior with a high dielectric constant (14). Furthermore, this dual frequency behavior along with low parasitic inductance and on chip integration allows for operation in extended frequency ranges.

25 ENERGY STORAGE↗
DOE OSTI2016

Amorphous TiO 2 Compact Layers via ALD for Planar Halide Perovskite Photovoltaics

A low temperature (< 120 °C) route to pinhole-free amorphous TiO 2 compact layers may pave the way to more efficient, flexible, and stable inverted perovskite halide device designs. Toward this end, we utilize low-temperature thermal atomic layer deposition (ALD) to synthesize ultra-thin (12 nm) compact TiO 2 underlayers for planar halide perovskite PV. While device performance with as-deposited TiO 2 films is poor, we identify room temperature UV-O 3 treatment as a route to device efficiency comparable to crystalline TiO 2 thin films synthesized by higher temperature methods. Here, we further explore the chemical, physical, and interfacial properties 2 that might explain the improved performance through x-ray diffraction, spectroscopic ellipsometry, Raman spectroscopy, and x-ray photoelectron spectroscopy. These findings challenge our intuition about effective electron selective layers as well as point the way to a greater selection of flexible substrates and more stable inverted device designs.

14 SOLAR ENERGY↗
DOE OSTI2014

Multiscale Simulations of ALD in Cross Flow Reactors

In this study, we have developed a multiscale simulation code that allows us to study the impact of surface chemistry on the coating of large area substrates with high surface area/high aspect-ratio features. Our code, based on open-source libraries, takes advantage of the ALD surface chemistry to achieve an extremely efficient two-way coupling between reactor and feature length scales, and it can provide simulated quartz crystal microbalance and mass spectrometry data at any point of the reactor. By combining experimental surface characterization with simple analysis of growth profiles in a tubular cross flow reactor, we are able to extract a minimal set of reactions to effectively model the surface chemistry, including the presence of spurious CVD, to evaluate the impact of surface chemistry on the coating of large, high surface area substrates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Preliminary results from Low Pressure Steam Oxidation Testing of ALD ZrN and ZrO2 Coating Deposited over UCN Fuel Kernels

Steam oxidation testing was used to investigate as-developed 100 nm ALD ZrN and 1000 nm ZrO 2 coatings deposited over UC1-xNx fuel kernels. The results of these tests were compared against oxidation of uncoated kernels. This work was performed to support development of coatings which both provide high temperature Zr metal diffusion barrier and also provide resistance against oxidation, especially against high temperature steam and/or air. This work was performed in collaboration with Oak Ridge National Laboratory (ORNL), using ORNL-provided samples. The oxidation tests yielded valuable information, including relative differences in performance of different coating materials and coating thicknesses.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Studies as a function of different ALD capping layers on cavity losses for QIS and accelerators

Niobium-based bulk SRF cavities have demonstrated exceptional performance. To further improve niobium cavity performance, we present studies involving a novel surface engineering process designed to prevent the formation of amorphous niobium oxides on the surface. This is achieved by encapsulating the niobium surface using thermal Atomic-Layer-Deposition (ALD). This technique has been shown to enhance the properties of niobium cavities and 2D resonators. This study not only aims to improve SRF performance at high fields but also has the potential to enhance the quality factor in low-field regimes, particularly for quantum applications. For the method to be effective, it is essential to have a clean interface between the encapsulating layer and the bulk niobium. Achieving this requires a uniform coating across the entire cavity surface and efficient removal of the underlying niobium oxides. To optimize the process, a variety of material characterization tools have been utilized to refine parameters such as thin film thickness and annealing conditions. Cavity RF measurements were performed at the vertical test facilities at FNAL to assess the Q vs. Eacc curves for accelerator applications, as well as at the SQMS dilution refrigerators to investigate the full two-level system (TLS) losses at milliKelvin and single-photon levels. Based on the results, we characterized the loss of different oxides in various regimes and applications, comparing them to natural niobium pentoxide.

Grassellino, L. [Fermilab]↗
DOE OSTI2020

Advances in Atomic Layer Deposition (ALD) Nanolaminate Synthesis of Thermoelectric Films in Porous Templates for Improved Seebeck Coefficient

Thermoelectrics is a green renewable energy technology which can significantly contribute to power generation due to its potential in generating electricity out of waste heat. The main challenge for the development of thermoelectrics is its low conversion efficiency. One key strategy to improve conversion efficiency is reducing the thermal conductivity of thermoelectric materials. In this paper, the state-of-the-art progresses made in improving thermoelectric materials are reviewed and discussed, focusing on phononic engineering via applying porous templates and ALD deposited nanolaminates structure. The effect of nanolaminates structure and porous templates on Seebeck coefficient, electrical conductivity and thermal conductivity, and hence in figure of merit zT of different types of materials system, including PnCs, lead chalcogenide-based nanostructured films on planar and porous templates, ZnO-based superlattice, and hybrid organic-inorganic superlattices, will be reviewed and discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Fast method for reactor and feature scale coupling in ALD and CVD

Transport and surface chemistry of certain deposition techniques is modeled. Methods provide a model of the transport inside nanostructures as a single-particle discrete Markov chain process. This approach decouples the complexity of the surface chemistry from the transport model, thus allowing its application under general surface chemistry conditions, including atomic layer deposition (ALD) and chemical vapor deposition (CVD). Methods provide for determination of determine statistical information of the trajectory of individual molecules, such as the average interaction time or the number of wall collisions for molecules entering the nanostructures as well as to track the relative contributions to thin-film growth of different independent reaction pathways at each point of the feature.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Revealing the Bonding Environment of Zn in ALD Zn(O,S) Buffer Layers through X-ray Absorption Spectroscopy

Zn(O,S) buffer layer electronic configuration is determined by its composition and thickness, tunable through atomic layer deposition. The Zn K and L-edges in the X-ray absorption near edge structure verify ionicity and covalency changes with S content. A high intensity shoulder in the Zn K-edge indicates strong Zn 4s hybridized states and a preferred c-axis orientation. 2–3 nm thick films with low S content show a subdued shoulder showing less contribution from Zn 4s hybridization. Here, a lower energy shift with film thickness suggests a decreasing bandgap. Further, ZnSO 4 forms at substrate interfaces, which may be detrimental for device performance.

36 MATERIALS SCIENCE↗
DOE OSTI2018

High Gain MCP ALD Films

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33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2017

Improved Performance in FeF 2 Conversion Cathodes through Use of a Conductive 3D Scaffold and Al 2 O 3 ALD Coating

FeF 2 is considered a promising conversion compound for the positive electrode in lithium-ion batteries due to its high thermodynamic reduction potential (2.66 V vs Li/Li + ) and high theoretical specific capacity (571 mA h g -1 ). However, the sluggish reaction kinetics and rapid capacity decay caused by side reactions during cycling limit its practical application. Here, the fabrication of Ni-supported 3D Al 2 O 3 -coated FeF 2 electrodes is presented, and it is shown that these structured electrodes significantly overcome these limitations. The electrodes are prepared by iron electrodeposition on a Ni support, followed by a facile fluorination process and Al 2 O 3 coating by atomic layer deposition. The 3D FeF 2 electrode delivers an initial discharge capacity of 380 mA h g -1 at a current density of 200 mA g -1 at room temperature. The 3D scaffold improves the reaction kinetics and enables a high specific capacity by providing an efficient electron pathway to the insulating FeF 2 and short Li diffusion lengths. The Al 2 O 3 coating significantly improves the cycle life, probably by preventing side reactions through limiting direct electrode–electrolyte contact. The fabrication method presented here can also be applied for synthesis of other metal fluoride materials on different 3D conductive templates.

25 ENERGY STORAGE↗
DOE OSTI2017

Controlled 3D Carbon Nanotube Architecture Coated with MoO x Material by ALD Technique: A High Energy Density Lithium‐Ion Battery Electrode

Due to its high theoretical capacity, energy density, and excellent reversibility with Li/Li + , molybdenum oxide is one of the vastly studied electrode material in lithium‐ion batteries. However, like most of the oxides, it also suffers from poor cyclic stability because of its low electrical conductivity. In 3D core–shell structure prepared by atomic layer deposition coating, it can provide superiority in nanoscale decoration than other deposition methods because of its extreme conformality and precise thickness control on high aspect ratio surfaces. This report illustrates the electrochemical activity of 3D core–shell type amorphous MoO x material coated by atomic layer deposition technique on conducting carbon nanotubes (CNT) scaffold which exhibits excellent overall cell capacity. The obtained capacity is manifold higher than its planar 2D counterpart and that can become an advanced nanoscale fabrication methodology of such 3D nanostructures for electrode preparation. Such binder free MoO x /CNT core–shell electrode structure shows very high and stable electrochemical activity toward Li/Li + system. An optimal thickness of MoO x on CNT is also found out in order to attain the most stable cyclic performance of this nanostructure. A stable reversible areal capacity of 645 µAh cm −2 with specific capacity of 915 mAh g −1 is achieved from optimized MoO x /CNT assembly.

Dhara, Arpan↗
DOE OSTI2025

High‐Performance Rechargeable Lithium‐Chlorine Batteries with ALD Conformal Starburst Porous Graphene Positive Electrodes

Abstract Rechargeable alkali metal‐chlorine batteries are emerging as a promising high‐energy‐density solution. However, they confront significant challenges, including the primary issue stemming from the weak binding affinity of cathode materials for Cl 2 , which leads to a sluggish and inadequate supply of Cl 2 during the redox reactions, resulting in a shortened cycle life and low Coulombic efficiency (CE), particularly when operating at ultrahigh specific capacity outputs. Herein, an Al 2 O 3 ‐skinned heterostructured starburst porous graphene with conformal metasurfaces (Al 2 O 3 @rGO) is reported, crafted from a hierarchical porous starburst graphene arranged in a unique layered structure by the PTFE microemulsion skin effect, leveraging subsequent fluidized bed atomic layer deposition (FBALD) of Al 2 O 3 groups. Al 2 O 3 @rGO features superhydrophilicity, effective adsorption, fast kinetics from stable dynamic respiratory interface, high electrical and thermal conductivity anisotropy, intelligent thermal management and safe operation over a wide temperature range. Consequently, the Li‐Cl 2 @Al 2 O 3 @rGO battery achieves an ultrahigh discharge specific capacity of 5000 mAh g −1 at ≈100% CE, and even delivers stable cycling over 200 cycles with 2000 mAh g −1 at an average CE of 99.8% under low temperature environment of ‐40 °C. The scalable heterostructure approach offers a sustainable perspective of the development of functionalized metamaterials and metasurfaces for next‐generation safe and energy‐dense batteries and broader applications.

Chemistry↗
DOE OSTI2018

Replication of SMSI via ALD: TiO2 Overcoats Increase Pt-Catalyzed Acrolein Hydrogenation Selectivity

The effects of sub-nanometer atomic layer deposition films of titania and alumina are compared for the acrolein hydrogenation selectivity of Pt/SrTiO3 catalysts. The titania-overcoated catalyst is similar to strong metal-support interaction catalysts formed by high temperature reduction, with a thin titania film on top of the supported Pt nanoparticles and an increase in allyl alcohol selectivity, neither of which are observed for the alumina-overcoated catalyst.

bio-inspired↗