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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

An Introduction to Atomic Layer Deposition

Atomic Layer Deposition has been instrumental in providing a deposition method for multiple space flight applications. It is well known that ALD is a cost effective nanoadditive-manufacturing technique that allows for the conformal coating of substrates with atomic control in a benign temperature and pressure environment. Through the introduction of paired precursor gases, thin films can be deposited on a myriad of substrates from flat surfaces to those with significant topography. By providing atomic layer control, where single layers of atoms can be deposited, the fabrication of metal transparent films, precise nano-laminates, and coatings of nano-channels, pores and particles is achievable. The feasibility of this technology for NASA line of business applications range from thermal systems, optics, sensors, to environmental protection. An overview of this technology will be presented.

ALD↗
NASA NTRS2019

Applications of Atomic Layer Deposition in the Modification of Carbon Nanotubes

Atomic Layer Deposition (ALD) is a cost-effective nanoadditive-manufacturing technique that allows for conformal coating of substrates with atomic control in a benign temperature and pressure environment. Using paired precursor gases, thin films can be deposited on flat or textured surfaces ranging from glass, polymers, aerogels, and metals. Through atomic layer control, where single layers of atoms are deposited, fabrication of metal transparent films, nano-laminates, and coatings of nano-channels and pores is achievable. Reaction mechanisms in ALD are normally self-limiting, allowing for atomically accurate control of nanometer (nm) thicknesses. Therefore, high uniformity and precise thickness control make ALD an attractive process for the creation of novel nano-scale devices. Decreases in resistivity and density of electrical wire are needed to improve the function of electronics, electric motors and cables. Such improvements may be accomplished by adding ballistically conducting, metallic carbon nanotubes (CNT) to Cu. ALD was used to coat multiple substrates including CNT with Cu in an effort to make CNT-Cu composites which is more conductive and less dense than Cu. In addition, ALD can be used to as a method to deposit the catalyst layer seed layer for CNT growth using Ni. The ALD of copper metallic films can follow multiple reaction pathways depending on the ALD precursors used. For this work the reaction pathway was deposition of copper oxide and then post process annealing in a hydrogen environment. Copper(II) diacetylacetonate (Cu(acac)2) and ozone are used as precursors for copper oxide. As-deposited copper oxide films prepared at 180°C resulted in a growth per cycle of 1.0 A/cycle with low film resistivity.

Dwivedi, Vivek H.↗
NASA NTRS2015

An Introduction to Atomic Layer Deposition with Thermal Applications

Atomic Layer Deposition (ALD) is a cost effective nano-manufacturing technique that allows for the conformal coating of substrates with atomic control in a benign temperature and pressure environment. Through the introduction of paired precursor gases thin films can be deposited on a myriad of substrates ranging from glass, polymers, aerogels, and metals to high aspect ratio geometries. This talk will focus on the utilization of ALD for engineering applications.

0000↗
NASA NTRS2018

Modification of Radiator Pigments by Atomic Layer Deposition (ALD)

The optical and physical properties of spacecraft radiator coatings are dictated by orbital environmental conditions. For example, coatings must adequately dissipate charge buildup when orbital conditions, such as polar, geostationary or gravity neutral, result in surface charging. Current dissipation techniques include depositing a layer of ITO (indium tin oxide) on the radiator surface in a high temperature process. Other examples include the application of variable emittance coatings such as the use of VO2 to optimize radiator size, allowing for a decrease in heater power budget. The application of these enhanced coatings must be such that the properties in question are tailored to mission-specific requirements. Modification of these coatings can be accomplished during coating application preprocessing by using a deposition technique prevalent in the semiconductor micro processing industry called Atomic Layer Deposition (ALD). The preprocessing is rendered directly on the coating dry pigment before binding. ALD is a cost effective nano-manufacturing technique that allows for the conformal coating of substrates with atomic-level thickness control in a benign temperature and pressure environment. Through the introduction of paired precursor gases, thin films can be deposited on a myriad of substrates ranging from glass, polymers, aerogels, metals, powders, and other high aspect-ratio micro- and nano-structures. By providing atomic-level control, where single layers of atoms can be deposited, the fabrication of metal transparent films, precise nano-laminates, and coatings of nano-channels and pores is achievable. We have demonstrated a method for the ALD of In2O3 and ITO films on a variety of substrates from Si(100) wafers, glass slides, and on Z93P pigments (patent pending). The results indicate excellent growth of 4-22 nm thick films demonstrating an order of magnitude decrease in resistivity on the pigments.

ITO↗
NASA NTRS2019

Application and Development of Atomic Layer Deposition Techniques to Improve Thermo-Optical Coatings for Spacecraft Thermal Control and Advanced Optical Instruments

A key technology development driver in environmental control systems and next generation optics are discussed utilizing thin film development borrowed from the semiconductor industry. The optical and physical properties of spacecraft radiator coatings are dictated by orbital environmental conditions. For example, coatings must adequately dissipate charge buildup when orbital conditions, such as polar, geostationary or gravity neutral, result in surface charging. Current dissipation techniques include depositing a layer of ITO (indium tin oxide) on the radiator surface in a high temperature process. The application of these enhanced coatings must be such that the properties in question are tailored to mission-specific requirements. The multi-billion-dollar semiconductor industry has adopted Atomic Layer Deposition (ALD) for self-assembly and atomic-scale placement. ALD is a cost-effective nanoadditive-manufacturing technique that allows for the conformal coating of substrates with atomic control in a benign temperature and pressure environment. By using ALD, modification of these coatings can be accomplished during coating application preprocessing. The preprocessing is rendered directly on the coating dry pigment before binding. Through the introduction of paired precursor gases, thin films can be deposited on a myriad of substrates ranging from glass, polymers, aerogels, metals, powders, and other high aspect-ratio micro- and nano- structures. By providing atomic-level control, where single layers of atoms can be deposited, the fabrication of metal transparent films, precise nano-laminates, and coatings of nano-channels and pores is achievable. A method has been demonstrated for the ALD of In2O3 and films on a variety of substrates from Si(100) wafers, glass slides, and on Z93P pigments resulting in a direct spaceflight application. Results will be presented that verify the chemical composition of ALD pigments and charge dissipation properties when the pigment goes through its binding and coating process and we present early results of ALD for carbon nanotube formation and encapsulation.

Dwivedi, Vivek H.↗
NASA NTRS2012

Mirror coatings with atomic layer deposition : initial results

The new technology of Atomic Layer Deposition (ALD) holds promise to enable a future strategic mission that can address both ultraviolet (UV) astrophysics and optical exoplanet science with a shared telescope. The technology path to a shared telescope requires the development of a mirror coating with high reflectance from 100 nm to 1000 nm, and low polarization effects (i.e., s-p phase shifts that can vary with angle of incidence across a primary and secondary mirror) in the optical range. Currently, UV coatings have low reflectance, and conventional optical coatings have poor polarization properties for high-contrast coronagraph applications. In this paper we attempt to take a first step toward solving both problems simultaneously by using ALD, taking advantage of the fact that ALD can potentially produce mirror coatings with denser layers than conventional coatings (hence better reflectance, durability, and water resistance). In addition, ALD can potentially produce coatings with new composite materials (hence better control of polarization). We report here the results of our initial experiments with mirror coatings using ALD.

Traub, Wesley↗
NASA NTRS2019

Atomic Layer Deposition Josephson Junctions for Cryogenic Circuit Applications

Superconducting-insulating-superconducting (SIS) trilayers have been produced for Josephson Junction fabrication by thermal atomic layer deposition (ALD) processes. The trilayers are composed of alternating layers of Ti0.4N0.6/Al2O3/ Ti0.4N0.6, deposited at 450°C, in a thermal ALD reactor on Al2O3-coated silicon. The conformal nature of the ALD process provides excellent step coverage of superconducting and insulating films. The film thickness of a single ALD cycle being one mono-layer, allows us to precisely control the tunnel-barrier insulator thickness by counting the number of ALD cycles during the insulator deposition step. Tunnel-junctions with critical current 500 A/cm2 are reported. Fabrication of Josephson Junctions and progress toward development of a single-element ALD Superconducting Quantum Interference Device (SQUID) will be discussed

Atomic Layer Definition↗
NASA NTRS2014

Atomic Layer Deposition of Chemical Passivation Layers and High Performance Anti-Reflection Coatings on Back-Illuminated Detectors

A back-illuminated silicon photodetector has a layer of Al2O3 deposited on a silicon oxide surface that receives electromagnetic radiation to be detected. The Al2O3 layer has an antireflection coating deposited thereon. The Al2O3 layer provides a chemically resistant separation layer between the silicon oxide surface and the antireflection coating. The Al2O3 layer is thin enough that it is optically innocuous. Under deep ultraviolet radiation, the silicon oxide layer and the antireflection coating do not interact chemically. In one embodiment, the silicon photodetector has a delta-doped layer near (within a few nanometers of) the silicon oxide surface. The Al2O3 layer is expected to provide similar protection for doped layers fabricated using other methods, such as MBE, ion implantation and CVD deposition.

Hoenk, Michael E.↗
NASA NTRS2008

Using ALD To Bond CNTs to Substrates and Matrices

Atomic-layer deposition (ALD) has been shown to be effective as a means of coating carbon nanotubes (CNTs) with layers of Al2O3 that form strong bonds between the CNTs and the substrates on which the CNTs are grown. ALD is a previously developed vaporphase thin-film-growth technique. ALD differs from conventional chemical vapor deposition, in which material is deposited continually by thermal decomposition of a precursor gas. In ALD, material is deposited one layer of atoms at a time because the deposition process is self-limiting and driven by chemical reactions between the precursor gas and the surface of the substrate or the previously deposited layer.

Wong, Eric W.↗
NASA NTRS2019

Technology Development for the Modification of High Aspect Ratio Geometries for Thermal and Environmental Control

A key technology development driver in environmental control systems and next generation optics are discussed utilizing thin film development borrowed from the semiconductor industry. The optical and physical properties of spacecraft radiator coatings are dictated by orbital environmental conditions. For example, coatings must adequately dissipate charge buildup when orbital conditions, such as polar, geostationary or gravity neutral, result in surface charging. Current dissipation techniques include depositing a layer of ITO (indium tin oxide) on the radiator surface in a high temperature process. The application of these enhanced coatings must be such that the properties in question are tailored to mission-specific requirements. The multi-billion-dollar semiconductor industry has adopted Atomic Layer Deposition (ALD) for self-assembly and atomic-scale placement. ALD is a cost-effective nanoadditive-manufacturing technique that allows for the conformal coating of substrates with atomic control in a benign temperature and pressure environment. By using ALD, modification of these coatings can be accomplished during coating application preprocessing. The preprocessing is rendered directly on the coating dry pigment before binding. Through the introduction of paired precursor gases, thin films can be deposited on a myriad of substrates ranging from glass, polymers, aerogels, metals, powders, and other high aspect-ratio micro- and nano- structures. By providing atomic-level control, where single layers of atoms can be deposited, the fabrication of metal transparent films, precise nano-laminates, and coatings of nano-channels and pores is achievable. A method has been demonstrated for the ALD of In2O3 and films on a variety of substrates from Si(100) wafers, glass slides, and on Z93P pigments resulting in a direct spaceflight application. Results will be presented that verify the chemical composition of ALD pigments and charge dissipation properties when the pigment goes through its binding and coating process and we present early results of ALD for carbon nanotube formation and encapsulation.

Dwivedi, Vivek H.↗