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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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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Characterization of tribo-layer formed during sliding wear of SiC ball against nanocrystalline diamond coatings

Tribo-layer formation and frictional characteristics of the SiC ball were studied with the sliding test against nanocrystalline diamond coating under atmospheric test conditions. Unsteady friction coefficients in the range of 0.04 to 0.1 were observed during the tribo-test. Friction and wear characteristics were found to be influenced by the formation of cohesive tribo-layer (thickness ∼ 1.3 μm) in the wear track of nanocrystalline diamond coating. Hardness of the tribo-layer was measured using nanoindentation technique and low hardness of ∼ 1.2 GPa was observed. The presence of silicon and oxygen in the tribo-layer was noticed by the energy dispersive spectroscopy mapping and the chemical states of the silicon were analyzed using X-ray photoelectron spectroscopy. Large amount of oxygen content in the tribo-layer indicated tribo-oxidation wear mechanism. - Highlights: • Sliding wear and friction characteristics of SiC were studied against NCD coating. • Silicon oxide tribo-layer formation was observed in the NCD coating wear track. • Low hardness 1.2 GPa of tribo-layer was measured using nanoindentation technique. • Chemical states of silicon were analyzed using X-ray photoelectron spectroscopy.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Development of diamond-based diagnostics for next-generation XFELs

The composition and performance of three different diamond sensor based pass-through diagnostics are presented. A position-sensitive quadrant sensor was designed and characterized using the XPP beam at the SLAC LCLS, demonstrating a generated-charge resolution of 0.025 pC and a position sensitivity of 2 μm, measurable pulse-by-pulse at a repetition rate of up to 50 MHz. A compact signal path capable of repetition rates up to 1 GHz was used to characterize the charge collection properties of diamond sensors as a function of the density of electron-hole pairs created within the sensor, finding a limit of approximately 10 16 electron-hole pairs per cm 3 beyond which the collection efficiency and time began to degrade. Finally, a proposed scheme for measuring ionizing radiation at multi-GHz rates is presented, along with results preliminarily demonstrating signal transport capability in excess of 5 GHz.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Challenging endeavor to integrate gallium and carbon via direct bonding to evolve GaN on diamond architecture

Here this paper depicts efforts for fabricating GaN on diamond microstructure through direct bonding between Ga and C, while excluding the use of adhesive interlayer during spark plasma sintering (SPS) process. The resulting GaN on diamond architecture is seemingly successful, as suggested by macroscopic morphological observations. The microscopic inspection using high-resolution transmission electron microscopy (HRTEM), however, shows a unique, off-the-chart interlayer configuration, wherein the components are migrated, etched, or fused to tentatively form multiple crystal phases. These phases can be constructed based on their utmost stabilities among all possible phases thermodynamically driven under or near the SPS conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Probing Charge Dynamics in Diamond with an Individual Color Center

Control over the charge states of color centers in solids is necessary to fully utilize them in quantum technologies. However, the microscopic charge dynamics of deep defects in wide-band-gap semiconductors are complex, and much remains unknown. We utilize a single-shot charge-state readout of an individual nitrogen-vacancy (NV) center to probe the charge dynamics of the surrounding defects in diamond. We show that the NV center charge state can be converted through the capture of holes produced by optical illumination of defects many micrometers away. With this method, we study the optical charge conversion of silicon-vacancy (SiV) centers and provide evidence that the dark state of the SiV center under optical illumination is SiV 2– . These measurements illustrate that charge carrier generation, transport, and capture are important considerations in the design and implementation of quantum devices with color centers and provide a novel way to probe and control charge dynamics in diamond.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Pressurizing Field-Effect Transistors of Few-Layer MoS 2 in a Diamond Anvil Cell

Hydrostatic pressure applied using diamond anvil cells (DAC) has been widely explored to modulate physical properties of materials by tuning their lattice degree of freedom. Independently, electrical field is able to tune the electronic degree of freedom of functional materials via, for example, the field-effect transistor (FET) configuration. Combining these two orthogonal approaches would allow discovery of new physical properties and phases going beyond the known phase space. Such experiments are, however, technically challenging and have not been demonstrated. In this paper, we report a feasible strategy to prepare and measure FETs in a DAC by lithographically patterning the nanodevices onto the diamond culet. Multiple-terminal FETs were fabricated in the DAC using few-layer MoS 2 and BN as the channel semiconductor and dielectric layer, respectively. It is found that the mobility, conductance, carrier concentration, and contact conductance of MoS 2 can all be significantly enhanced with pressure. Finally, we expect that the approach could enable unprecedented ways to explore new phases and properties of materials under coupled mechano-electrostatic modulation.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Extreme Temperature Cryptography Based On Nitrogen-Incorporated Ultrananocrystalline Diamond

Physical entropy sources that remain stable under extreme temperatures are essential for cryptography in emerging technological frontiers in deep space exploration, geothermal energy harvesting, and nuclear energy. However, conventional semiconductor platforms fail to generate stable and reliable cryptographic keys above 200 degrees C due to performance degradation. Here, we report a diamond-based cryptographic primitive that exploits the defect-rich sp 2 -bonded grain boundary network in nitrogen-incorporated ultrananocrystalline diamond (n-UNCD) film as a robust entropy source to generate cryptographic keys that remain operationally stable even after enduring extreme temperatures of 700 degrees C for 54 h while also surviving thermal cycling between room temperature and 700 degrees C for 48 h. The strength of the generated keys is assessed through several cryptographic metrics such as bit uniformity, entropy, hamming distances, and correlation coefficients, all of which are found to be near their respective ideal values. Moreover, the generated keys pass the NIST SP 800 and SP 800-90B tests and are also resilient to supply bias variations and a regression-based machine learning attack model based on the Fourier series. The robustness of the keys is attributed to the better thermal stability and chemical inertness of the n-UNCD film. This is supported by high-resolution energy-dispersive X-ray spectroscopy (EDS), which shows no significant lateral diffusion of metal atoms into the n-UNCD layer, and by Raman spectroscopy, which reveals no significant changes in the bonding configuration of the n-UNCD structure. Our findings highlight the remarkable potential of n-UNCD film for extreme environment cryptography by expanding the operational limits of conventional hardware security platforms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Efficient photon coupling from a diamond nitrogen vacancy center by integration with silica fiber

A central goal in quantum information science is to efficiently interface photons with single optical modes for quantum networking and distributed quantum computing. Here, we introduce and experimentally demonstrate a compact and efficient method for the low-loss coupling of a solid-state qubit, the nitrogen vacancy (NV) center in diamond, with a single-mode optical fiber. In this approach, single-mode tapered diamond waveguides containing exactly one high quality NV memory are selected and integrated on tapered silica fibers. Numerical optimization of an adiabatic coupler indicates that near-unity-efficiency photon transfer is possible between the two modes. Experimentally, we find an overall collection efficiency between 16% and 37% and estimate a single photon count rate at saturation above 700 kHz. This integrated system enables robust, alignment-free, and efficient interfacing of single-mode optical fibers with single photon emitters and quantum memories in solids.

Optics↗
DOE OSTI2013

Interfacial chemical bonding state and band alignment of CaF{sub 2}/hydrogen-terminated diamond heterojunction

CaF{sub 2} films are deposited on hydrogen-terminated diamond (H-diamond) by a radio-frequency sputter-deposition technique at room temperature. Interfacial chemical bonding state and band alignment of CaF{sub 2}/H-diamond heterojunction are investigated by X-ray photoelectron spectroscopy. It is confirmed that there are only C-Ca bonds at the CaF{sub 2}/H-diamond heterointerface. Valence and conductance band offsets of the CaF{sub 2}/H-diamond heterojunciton are determined to be 3.7 {+-} 0.2 and 0.3 {+-} 0.2 eV, respectively. It shows a type I straddling band configuration. The large valence band offset suggests advantage of the CaF{sub 2}/H-diamond heterojunciton for the development of high power and high frequency field effect transistors.

36 MATERIALS SCIENCE↗
DOE OSTI2013

A spectrometer on chemical vapour deposition-diamond basis for the measurement of the charge-state distribution of heavy ions in a laser-generated plasma

This article reports on the development and the first applications of a new spectrometer which enables the precise and time-resolved measurement of both the energy loss and the charge-state distribution of ion beams with 10 < Z < 30 at energies of 4-8 MeV/u after their interaction with a laser-generated plasma. The spectrometer is based on five 20 Multiplication-Sign 7 mm{sup 2} large and 20 {mu}m thick polycrystalline diamond samples produced via the Chemical Vapour Deposition (CVD) process and was designed with the help of ion-optical simulations. First experiments with the spectrometer were successfully carried out at GSI using {sup 48}Ca ions at an energy of 4.8 MeV/u interacting with a carbon plasma generated by the laser irradiation of a thin foil target. Owing to the high rate capability and the short response time of the spectrometer, pulsed ion beams with 10{sup 3}-10{sup 4} ions per bunch at a bunch frequency of 108 MHz could be detected. The temporal evolution of the five main charge states of the calcium ion beams as well as the corresponding energy loss values could be measured simultaneously. Due to the outstanding properties of diamond as a particle detector, a beam energy resolution ({Delta}E/E) Almost-Equal-To 0.1% could be reached using the presented experimental method, while a precision of 10% in the energy loss and charge-state distribution data was obtained.

36 MATERIALS SCIENCE↗
DOE OSTI2013

The properties of photonic band gaps for three-dimensional plasma photonic crystals in a diamond structure

In this paper, the properties of photonic band gaps (PBGs) for two types of three-dimensional plasma photonic crystals (PPCs) composed of isotropic dielectric and unmagnetized plasma with diamond lattices are theoretically investigated for electromagnetic waves based on a modified plane wave expansion method. The equations for type-1 structure are theoretically deduced, which depend on the diamond lattices realization (dielectric spheres immersed in plasma background). The influences of dielectric constant of dielectric, plasma collision frequency, filling factor, and plasma frequency on PBGs are investigated, respectively, and some corresponding physical explanations and the possible methods to realize the three-dimensional PPCs in experiments are also given. From the numerical results, it has been shown that not only the locations but also the gap/midgap ratios of the PBGs for two types of PPCs can be tuned by plasma frequency, filling factor, and the relative dielectric constant, respectively. However, the plasma collision frequency has no effect on the frequency ranges and gap/midgap ratios of the PBGs for two types of PPCs.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Super-thin single crystal diamond membrane radiation detectors

We propose to use the non-electronic grade (nitrogen content 5 ppb < [N] < 5 ppm) single crystal (sc) chemical vapour deposited (CVD) diamond as a thin-membrane radiation detector. Using deep Ar/O{sub 2} plasma etching it is possible to produce self-supported few micrometres thick scCVD membranes of a size approaching 7 mm × 7 mm, with a very good surface quality. After metallization and contacting, electrical properties of diamond membrane detectors were probed with 5.486 MeV α-particles as an ionization source. Despite nitrogen impurity, scCVD membrane detectors exhibit stable operation, charge collection efficiency close to 100%, with homogenous response, and extraordinary dielectric strength up to 30 V/μm.

36 MATERIALS SCIENCE↗
DOE OSTI2013

An ultra-thin diamond membrane as a transmission particle detector and vacuum window for external microbeams

Several applications of external microbeam techniques demand a very accurate and controlled dose delivery. To satisfy these requirements when post-sample ion detection is not feasible, we constructed a transmission single-ion detector based on an ultra-thin diamond membrane. The negligible intrinsic noise provides an excellent signal-to-noise ratio and enables a hit-detection efficiency of close to 100%, even for energetic protons, while the small thickness of the membrane limits beam spreading. Moreover, because of the superb mechanical stiffness of diamond, this membrane can simultaneously serve as a vacuum window and allow the extraction of an ion microbeam into the atmosphere.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Spectroscopic ellipsometry of homoepitaxial diamond multilayers and delta-doped structures

The optimization of diamond-based unipolar electronic devices such as pseudo-vertical Schottky diodes or delta-doped field effect transistors relies in part on the sequential growth of nominally undoped (p{sup –}) and heavily boron doped (p{sup ++}) layers with well-controlled thicknesses and steep interfaces. Optical ellipsometry offers a swift and contactless method to characterize the thickness, roughness, and electronic properties of semiconducting and metallic diamond layers. We report ellipsometric studies carried out on delta-doped structures and other epitaxial multilayers with various boron concentrations and thicknesses (down to the nanometer range). The results are compared with Secondary Ion Mass Spectroscopy and transport measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Flexible electron field emitters fabricated using conducting ultrananocrystalline diamond pyramidal microtips on polynorbornene films

High performance flexible field emitters made of aligned pyramidal shaped conducting ultrananocrystalline diamond (C-UNCD) microtips on polynorbornene substrates is demonstrated. Flexible C-UNCD pyramidal microtips show a low turn-on field of 1.80 V/μm with a field enhancement factor of 4580 and a high emission current density of 5.8 mA/cm{sup 2} (at an applied field of 4.20 V/μm) with life-time stability of 210 min. Such an enhancement in the field emission is due to the presence of sp{sup 2}-graphitic sheath with a nanowire-like diamond core. This high performance flexible C-UNCD field emitter is potentially useful for the fabrication of diverse, flexible electronic devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Zr/oxidized diamond interface for high power Schottky diodes

High forward current density of 10{sup 3} A/cm{sup 2} (at 6 V) and a breakdown field larger than 7.7 MV/cm for diamond diodes with a pseudo-vertical architecture, are demonstrated. The power figure of merit is above 244 MW/cm{sup 2} and the relative standard deviation of the reverse current density over 83 diodes is 10% with a mean value of 10{sup −9} A/cm{sup 2}. These results are obtained with zirconium as Schottky contacts on the oxygenated (100) oriented surface of a stack comprising an optimized lightly boron doped diamond layer on a heavily boron doped one, epitaxially grown on a Ib substrate. The origin of such performances are discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Spectrally dependent photovoltages in Schottky photodiode based on (100) B-doped diamond

Spectrally and spatially resolved photovoltages were measured by Kelvin probe force microscopy (KPFM) on a Schottky photo-diode made of a 4 nm thin tungsten-carbide (WC) layer on a 500 nm oxygen-terminated boron-doped diamond epitaxial layer (O-BDD) that was grown on a Ib (100) diamond substrate. The diode was grounded by the sideways ohmic contact (Ti/WC), and the semitransparent Schottky contact was let unconnected. The electrical potentials across the device were measured in dark (only 650 nm LED of KPFM being on), under broad-band white light (halogen lamp), UV (365 nm diode), and deep ultraviolet (deuterium lamp) illumination. Illumination induced shift of the electrical potential remains within 210 mV. We propose that the photovoltage actually corresponds to a shift of Fermi level inside the BDD channel and thereby explains orders of magnitude changes in photocurrent.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Heteroepitaxial ZnO films on diamond: Optoelectronic properties and the role of interface polarity

We demonstrate the growth of heteroepitaxial ZnO films on (110) diamond substrates by molecular beam epitaxy and report on a major advance in structural quality, as confirmed by XRD and high-resolution TEM measurements. The growth direction is found to be along the polar c-axis with Zn-polarity, deduced from annular bright-field scanning transmission electron microscopy imaging. This is important information, as simulations of the electronic band structure reveal the ZnO polarity to dominate the electronic structure of the interface: the formation of a two-dimensional electron gas on the ZnO side or a two-dimensional hole gas on the diamond side are predicted for Zn- and O-polarity, respectively. In addition, photoluminescence and absorption studies exhibit good optical properties and reveal stimulated emission for optical excitation above a threshold of 30 kW/cm{sup 2}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Quasiparticle electronic structure and optical absorption of diamond nanoparticles from ab initio many-body perturbation theory

The excited states of small-diameter diamond nanoparticles in the gas phase are studied using the GW method and Bethe-Salpeter equation (BSE) within the ab initio many-body perturbation theory. The calculated ionization potentials and optical gaps are in agreement with experimental results, with the average error about 0.2 eV. The electron affinity is negative and the lowest unoccupied molecular orbital is rather delocalized. Precise determination of the electron affinity requires one to take the off-diagonal matrix elements of the self-energy operator into account in the GW calculation. BSE calculations predict a large exciton binding energy which is an order of magnitude larger than that in the bulk diamond.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗