Search NASA⌕ Search

SEARCH · Search NASA

Results for “Diamond growth”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Strongly Interacting, Two-Dimensional, Dipolar Spin Ensembles in (111)-Oriented Diamond

Systems of spins with strong dipolar interactions and controlled dimensionality enable new explorations in quantum sensing and simulation. In this work, we investigate the creation of strong dipolar interactions in a two-dimensional ensemble of nitrogen-vacancy (NV) centers generated via plasma-enhanced chemical vapor deposition on (111)-oriented diamond substrates. We find that diamond growth on the (111) plane yields high incorporation of spins, both nitrogen and NV centers, where the density of the latter is tunable via the miscut of the diamond substrate. Our process allows us to form dense, preferentially aligned, 2D NV ensembles with volume-normalized ac sensitivity down to η ac = 810 pT μ m 3 / 2 Hz − 1 / 2 . Furthermore, we show that (111) affords maximally positive dipolar interactions among a 2D NV ensemble, which is crucial for leveraging dipolar-driven entanglement schemes and exploring new interacting spin physics. Published by the American Physical Society 2025

Hughes, Lillian B. (ORCID:0000000210201661)↗
NASA NTRS1997

High growth rate homoepitaxial diamond film deposition at high temperatures by microwave plasma-assisted chemical vapor deposition

The deposition of high quality diamond films at high linear growth rates and substrate temperatures for microwave-plasma chemical vapor deposition is disclosed. The linear growth rate achieved for this process is generally greater than 50 .mu.m/hr for high quality films, as compared to rates of less than 5 .mu.m/hr generally reported for MPCVD processes.

Vohra, Yogesh K.↗
DOE OSTI2022

Melting of the Fe–C–H System and Earth's Deep Carbon–Hydrogen Cycle

The occurrences and cycling of slab-originated carbon and hydrogen are considered to be controlled by their reactions with metallic iron from mantle disproportionation and slab serpentinization, to form Fe alloys containing carbon and hydrogen. In this work, we show experimental results on the phase relations and melting of the Fe-C-H system using laser-heated diamond anvil cell and X-ray diffraction techniques up to 72 GPa. The incorporation of hydrogen was found to lower the eutectic melting temperatures of Fe-C alloy by ~50–178 K at 20–70 GPa, facilitating the formation of metallic liquids in the deep mantle and thus enhancing the mobility and deep cycling of subducted carbon and hydrogen. Hydrogen also substitutes with carbon in Fe-C metal to form hydride and diamond at relatively high-temperature conditions (e.g., 42.6 GPa, >1885 K and 71.8 GPa, >1798 K). The hydrogen-carbon-enriched metallic liquids provide the necessary fluid environment for superdeep diamond growth.

58 GEOSCIENCES↗
DOE OSTI2024

Identification of Defects and the Origins of Surface Noise on Hydrogen–Terminated (100) Diamond

Near-surface nitrogen vacancy centres are critical to many diamond-based quantum technologies such as information processors and nanosensors. Surface defects play an important role in the design and performance of these devices. The targeted creation of defects is central to proposed bottom-up approaches to nanofabrication of quantum diamond processors, and uncontrolled surface defects may generate noise and charge trapping which degrade shallow NV device performance. Surface preparation protocols may be able to control the production of desired defects and eliminate unwanted defects, but only if their atomic structure can first be conclusively identified. This work uses a combination of scanning tunnelling microscopy (STM) imaging and first-principles simulations to identify several surface defects on H:C(100)—2 × 1 surfaces prepared using chemical vapour deposition (CVD). The atomic structure of these defects is elucidated, from which the microscopic origins of magnetic noise and charge trapping are determined based on the modeling of their paramagnetic properties and acceptor states. Rudimentary control of these deleterious properties is demonstrated through STM tip-induced manipulation of the defect structure. Furthermore, the results validate accepted models for CVD diamond growth by identifying key adsorbates responsible for the nucleation of new layers.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Record-Low Thermal Boundary Resistance between Diamond and GaN-on-SiC for Enabling Radiofrequency Device Cooling

The implementation of 5G-and-beyond networks requires faster, high-performance, and power-efficient semiconductor devices, which are only possible with materials that can support higher frequencies. Gallium nitride (GaN) power amplifiers are essential for 5G-and-beyond technologies since they provide the desired combination of high frequency and high power. These applications along with terrestrial hub and backhaul communications at high power output can present severe heat removal challenges. The cooling of GaN devices with diamond as the heat spreader has gained significant momentum since device self-heating limits GaN’s performance. However, one of the significant challenges in integrating polycrystalline diamond on GaN devices is maintaining the device performance while achieving a low diamond/GaN channel thermal boundary resistance. In this study, we achieved a record-low thermal boundary resistance of around 3.1 ± 0.7 m 2 K/GW at the diamond/Si 3 N 4 /GaN interface, which is the closest to theoretical prediction to date. The diamond was integrated within ~1 nm of the GaN channel layer without degrading the channel’s electrical behavior. Furthermore, we successfully minimized the residual stress in the diamond layer, enabling more isotropic polycrystalline diamond growth on GaN with thicknesses >2 μm and a ~1.9 μm lateral grain size. More isotropic grains can spread the heat in both vertical and lateral directions efficiently. Using transient thermoreflectance, the thermal conductivity of the grains was measured to be 638 ± 48 W/m K, which when combined with the record-low thermal boundary resistance makes it a leading-edge achievement.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Creation of depth-confined, shallow nitrogen-vacancy centers in diamond with tunable density

Engineering shallow nitrogen-vacancy (NV) centers in diamond holds the key to unlocking new advances in nanoscale quantum sensing. We find that the creation of near-surface NVs through delta doping during diamond growth allows for tunable control over both NV depth confinement (with a twofold improvement relative to low-energy ion implantation) and NV density, ultimately resulting in highly sensitive single defects and ensembles with coherence limited by NV–NV interactions. Additionally, we demonstrate the utility of our shallow delta-doped NVs by imaging magnetism in few-layer CrSBr, a two-dimensional magnet. Here, we anticipate that the control afforded by near-surface delta doping will enable new developments in NV quantum sensing from nanoscale nuclear magnetic resonance to entanglement-enhanced metrology.

Chemical vapor deposition↗
NASA NTRS2009

Method of plasma enhanced chemical vapor deposition of diamond using methanol-based solutions

Briefly described, methods of forming diamond are described. A representative method, among others, includes: providing a substrate in a reaction chamber in a non-magnetic-field microwave plasma system; introducing, in the absence of a gas stream, a liquid precursor substantially free of water and containing methanol and at least one carbon and oxygen containing compound having a carbon to oxygen ratio greater than one, into an inlet of the reaction chamber; vaporizing the liquid precursor; and subjecting the vaporized precursor, in the absence of a carrier gas and in the absence in a reactive gas, to a plasma under conditions effective to disassociate the vaporized precursor and promote diamond growth on the substrate in a pressure range from about 70 to 130 Torr.

Tzeng, Yonhua↗
NASA NTRS1991

Applications of diamond films and related materials; Proceedings of the 1st International Conference, Auburn, AL, Aug. 17-22, 1991

The present conference discusses the nucleation and growth of diamond from hydrocarbons, the cutting tool performance of CVD thick-film diamond, the characterization of CVD diamond grinding powder, industrial applications of crystalline diamond-coated tools, standardized SEM tribometry of diamond-coated substrates, residual stress in CVD diamond films, the optical properties of CVD diamond films, polycrystalline diamond films for optical applications, and diamond growth on ferrous metals. Also discussed are ion beam-irradiation smoothing of diamond films, electronic circuits on diamond substrates, diamond-laminated surfaces for evaporative spray cooling, electron devices based on the unique properties of diamond, diamond cold cathodes, thin-film diamond microstructure applications, Schottky diodes from flame-grown diamond, diamond films for thermionic applications, methods of diamond nucleation and selective deposition, high-rate/large-area diamond film production, halogen-assisted diamond growth, the economics of diamond technology, and the optical and mechanical properties of diamondlike films.

Tzeng, Yonhua↗
DOE OSTI2023

Analysis of the High-Pressure High-Temperature (HPHT) growth of single crystal diamond

A multi-scale, computational model is developed to describe the growth characteristics of single-crystal diamond in the High-Pressure, High-Temperature (HPHT) process. This model is the first to connect phase-change kinetics governing crystal growth to the continuum transport of carbon through the growth cell. Results show the importance of convective transport driven by buoyant flow in the metallic solvent, which increases the growth rate by nearly an order of magnitude over that obtained under diffusion alone. Parametric studies show how crystal growth may be kinetically-limited or transport-limited, depending on the value of the macroscopic kinetic coefficient. Estimating this kinetic coefficient from growth experiments yields a phase-change Damköhler number of unity, indicating a mixed regime where phase-change kinetics and transport are comparable and strongly coupled in this system. Mechanisms responsible for slowing growth as the crystal size increases are explained. Finally, supersaturation inhomogeneities along the facets of larger crystals are predicted, which may be relevant to solvent inclusion formation during growth.

36 MATERIALS SCIENCE↗
NASA NTRS2005

Synthesizing Diamond from Liquid Feedstock

A relatively economical method of chemical vapor deposition (CVD) has been developed for synthesizing diamond crystals and films. Unlike prior CVD methods for synthesizing diamond, this method does not require precisely proportioned flows of compressed gas feedstocks or the use of electrical discharges to decompose the feedstocks to obtain free radicals needed for deposition chemical reactions. Instead, the feedstocks used in this method are mixtures of common organic liquids that can be prepared in advance, and decomposition of feedstock vapors is effected simply by heating. The feedstock used in this method is a solution comprising between 90 and 99 weight percent of methanol and the balance of one or more other oxyhydrocarbons that could include ethanol, isopropanol, and/or acetone. This mixture of compounds is chosen so that dissociation of molecules results in the desired proportions of carbon-containing radicals (principally, CH3) and of OH, H, and O radicals. Undesirably, the CVD temperature and pressure conditions thermodynamically favor the growth of graphite over the growth of diamond. The H radicals are desirable because they help to stabilize the growing surface of diamond by shifting the thermodynamic balance toward favoring the growth of diamond. The OH and O radicals are desirable because they preferentially etch graphite and other non-diamond carbon, thereby helping to ensure the net deposition of pure diamond. The non-methanol compounds are included in the solution because (1) methanol contains equal numbers of C and O atoms; (2) an excess of C over O is needed to obtain net deposition of diamond; and (3) the non-methanol molecules contain multiple carbon atoms for each oxygen atom and thus supply the needed excess carbon A typical apparatus used in this method includes a reservoir containing the feedstock liquid and a partially evacuated stainless-steel reaction chamber. The reservoir is connected to the chamber via tubing and a needle valve or other suitable flow controller. When the liquid enters the low-pressure environment inside the chamber, it evaporates to form a vapor mixture of the same chemical composition. In addition to the inlet for the feedstock liquid, the chamber is fitted with an outlet connected to a vacuum pump (not shown) through a throttle valve (also not shown) that is automatically controlled to keep the pressure at or near the required value throughout the deposition process. Inside the chamber, a spiral filament made of tungsten, tantalum, graphite, or other high-melting-temperature material is electrically heated to a temperature >2,000 C high enough to cause dissociation of vapor molecules into the aforementioned radicals. A deposition substrate typically, a diamond-polished silicon wafer about 2.5 cm square is positioned about 2 cm away from the filament. The exact location of the substrate is chosen so that the substrate becomes heated by the filament to a deposition temperature in the approximate range of 800 to 1,000 C.

Tzeng, Yonhua↗
NASA NTRS1993

Laser-enhanced synthesis and processing of diamond films from liquid hydrocarbons

We report synthesis of diamond films by pulsed laser irradiation on copper substrate immersed into liquid benzene. It is envisaged that carbon released from benzene at the liquid-solid interface is converted into diamond as a result of rapid quenching from a high temperature. The diamond crystallites were characterized using high resolution transmission electron microscopy imaging and electron diffraction techniques. Growth of thicker diamond films by subsequent chemical vapor deposition has been investigated by transmission and scanning electron microscopy techniques. Thin diamond film deposited during liquid phase provided seed for diamond growth during subsequent chemical vapor deposition.

Singh, Jogender↗
DOE OSTI2024

Atomistic evidence of nucleation mechanism for the direct graphite-to-diamond transformation

The direct graphite-to-diamond transformation mechanism has been a subject of intense study and remains debated concerning the initial stages of the conversion, the intermediate phases, and their transformation pathways. Here, we successfully recover samples at the early conversion stage by tuning high-pressure/high-temperature conditions and reveal direct evidence supporting the nucleation-growth mechanism. Atomistic observations show that intermediate orthorhombic graphite phase mediates the growth of diamond nuclei. Furthermore, we observe that quenchable orthorhombic and rhombohedra graphite are stabilized in buckled graphite at lower temperatures. These intermediate phases are further converted into hexagonal and cubic diamond at higher temperatures following energetically favorable pathways in the order: graphite → orthorhombic graphite → hexagonal diamond, graphite → orthorhombic graphite → cubic diamond, graphite → rhombohedra graphite → cubic diamond. Furthermore, these results significantly improve our understanding of the transformation mechanism, enabling the synthesis of different high-quality forms of diamond from graphite.

Graphite-diamond phase transformation↗
DOE OSTI2025

Reduced thermal resistance of Al-rich AlGaN HEMTs via top-side diamond integration

We report back-end-of-line growth of nanocrystalline diamond (NCD) on ultrawide bandgap (UWBG) high Al content aluminum gallium nitride (AlGaN) channel high electron mobility transistors for thermal management. A thin (∼15 nm) silicon nitride (SiN x ) interlayer was deposited to protect the device surface before performing a low temperature (500 °C) NCD growth process in an attempt to protect the gates on these fully fabricated devices. Notably, atomic force microscopy showed that the maximum lateral grain size exceeded 300 nm even though the film thickness was ∼250 nm. Comparing electrical (DC) performance before and after NCD growth, the gate leakage increased by ∼10 2 after NCD growth. Despite the lower NCD growth temperature, intermixing of the Ni and Au was observed in the Schottky gate metal stack; however, we believe there is another mechanism, possibly hydrogen-related, that is responsible for the measured increase in gate leakage. Regarding thermal management, the device-level thermal resistance (quantified using the average gate temperature rise measured by thermoreflectance imaging) was reduced by 29% through the incorporation of the top-side diamond film. Using time-domain thermoreflectance, the thermal conductivity of the ≈250 nm thick NCD film was measured to be 45 ± 25 W m −1 K −1 . This is expected to be at least 5× greater than the thermal conductivity of the thin disordered AlGaN alloy. There could also be a coupled electrothermal component contributing to the reduced temperature rise from electric field spreading and consequent heat spreading. This study demonstrates a promising first step toward device-level thermal management of high power UWBG Al-rich AlGaN devices.

Lundh, James Spencer [U.S. Naval Research Laborato↗
NASA NTRS1998

In Situ Infrared Spectroscopy of the Gaseous Species Present in a Diamond Chemical Vapor Deposition System

We interfaced a Hot-Filament Chemical Vapor Deposition (HFCVD) system to the emission port of an FT-IR spectrometer, in order to study the gas phase species present during the deposition of diamond thin films. The implementation of the infrared (IR) emission technique in situ allowed the study of various carbon-containing species believed to be crucial in diamond film growth. The two IR-active vibrational fundamentals of methane, v(3)(f2) and v(4)(f2), were observed at three different filament temperatures: 1000, 1500 and 2000 C. However, the net signal of v(3) was emission, while that of v(4) was absorption. These results indicate that the v(4) fundamental is excited beyond equilibrium, while the v(3) fundamental remains mostly in the ground state. This is due to the small concentration of methane, the low energy of v(4) compared to v(3) or to the Hz vibrational mode, and symmetry considerations that forbid interaction among the four fundamentals of methane. Thus, the excitation of v(3) is more likely than its decay under HFCVD conditions, producing a non-equilibrium population. At a filament temperature of 2000 C, the v(3) (sigma(+)(3)) fundamental of acetylene and a band at 1328 cm-l also ascribed to acetylene (v5 (pi(U)) + v4) appear in net absorption. This correlates well with the onset of molecular hydrogen breaking by the filament, which occurs at temperatures around 2000 C and above. The hydrogen atoms produced in this heterogeneous reaction give rise to a chain of reactions that lead to acetylene, among other carbonaceous species.

Morell, G.↗
NASA NTRS1990

Status and applications of diamond and diamond-like materials: An emerging technology

Recent discoveries that make possible the growth of crystalline diamond by chemical vapor deposition offer the potential for a wide variety of new applications. This report takes a broad look at the state of the technology following from these discoveries in relation to other allied materials, such as high-pressure diamond and cubic boron nitride. Most of the potential defense, space, and commercial applications are related to diamond's hardness, but some utilize other aspects such as optical or electronic properties. The growth processes are reviewed, and techniques for characterizing the resulting materials' properties are discussed. Crystalline diamond is emphasized, but other diamond-like materials (silicon carbide, amorphous carbon containing hydrogen) are also examined. Scientific, technical, and economic problem areas that could impede the rapid exploitation of these materials are identified. Recommendations are presented covering broad areas of research and development.

Source record↗