Suppressing Fine-Frequency Modes in Aluminum Nitride Microresonators.
Abstract not provided.
Branch, Darren W.↗
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Results for “nitrides”
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Comparing directed efficiency of III-nitride nanowire light-emitting diodes
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solar (photovoltaic), solid state lighting, photos↗
III-Nitride Nanowires: Emerging Materials for Lighting and Energy Applications (invited).
Abstract not provided.
Wang, George T.↗
Cryogenic characterization of titanium nitride thin films
Not Available
Vertchenko, Larissa (ORCID:0000000227605750)↗
LDRD 191204: Optimization of Sputtered Aluminum Nitride for the Seeding of Metal Organic Chemical Vapor Deposition Gallium Nitride Films
GaN-on-Si combines the wide bandgap advantages of GaN with the cost and scaling advantages of Si. Sputtered A1N is an attractive nucleation layer material because it reduces Al diffusion into the Si and eliminates a time-intensive preconditioning step in the GaN growth process, but is limited by the poor film quality of PVD A1N films deposited on Si substrates. Sputtering also offers a large degree of control over A1N film properties, including control of the intrinsic stress using substrate biasing. Doping the A1N films with Sc improves the lattice match to A1GaN and GaN films by expanding the a-axis and c-axis lattice parameters. A1N and A1 0.88 Sc 0.12 N films have been grown on silicon, metal, and sapphire substrates and characterized for properties such as stress, grain size, roughness, and film orientation for use as nucleation layers for MOCVD GaN growth.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Hot isostatic pressing of silicon nitride with boron nitride, boron carbide, and carbon additions
Si3N4 test bars containing additions of BN, B4C, and C, were hot isostatically pressed in Ta cladding at 1900 and 2050 C to 98.9 percent to 99.5 percent theoretical density. Room-temperature strength data on specimens containing 2 wt pct BN and 0.5 wt pct C were comparable to data obtained for Si3N4 sintered with Y2O3, Y2O3 and Al2O3, or ZrO2. The 1370 C strengths were less than those obtained for additions of Y2O3 or ZrO2 but greater than those obtained from a combination of Y2O3 and Al2O3. SEM fractography indicated that, as with other types of Si3N4, room-temperature strength was controlled by processing flaws. The decrease in strength at 1370 C was typical of Si3N4 having an amorphous grain-boundary phase. The primary advantage of nonoxide additions appears to be in facilitating specimen removal from the Ta cladding.
Mieskowski, Diane M.↗
Reduction in interface state density of Al{sub 2}O{sub 3}/InGaAs metal-oxide-semiconductor interfaces by InGaAs surface nitridation
We report the decrease in interface trap density (D{sub it}) in Al{sub 2}O{sub 3}/InGaAs metal-oxide-semiconductor (MOS) capacitors by using electron cyclotron resonance plasma nitridation of the InGaAs surfaces. The impact of the nitridation process on the MOS interface properties is quantitatively examined. The plasma nitridation process is observed to form a nitrided layer at the InGaAs surface. The nitridation using microwave power (P{sub microwave}) of 250 W and nitridation time (t{sub nitridation}) of 420 s can form Al{sub 2}O{sub 3}/InGaAs MOS interfaces with a minimum D{sub it} value of 2.0 Multiplication-Sign 10{sup 11} cm{sup -2} eV{sup -1}. On the other hand, the nitridation process parameters such as P{sub microwave} and t{sub nitridation} are found to strongly alter D{sub it} (both decrease and increase are observed) and capacitance equivalent thickness (CET). It is found that the nitridation with higher P{sub microwave} and shorter t{sub nitridation} can reduce D{sub it} with less CET increase. Also, it is observed that as t{sub nitridation} increases, D{sub it} decreases first and increases later. It is revealed from XPS analyses that minimum D{sub it} can be determined by the balance between the saturation of nitridation and the progress of oxidation. As a result, it is found that the superior MOS interface formed by the nitridation is attributable to the existence of oxide-less InGaN/InGaAs interfaces.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Effect of nitriding on mechanical and microstructural properties of Direct Metal Laser Sintered 17-4PH stainless steel
In this work, the effect of the nitriding process on microstructure and mechanical properties of additively manufactured (AM) 17-4PH stainless steel is investigated. The nitriding was performed at 530 °C, 560 °C, and 580 °C for 2 h. The nitriding process improves the hardness and surface roughness of the AM 17-4PH steel. Detailed microstructural characterizations of both as-built and nitride samples are performed using an optical microscope, scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction technique. It reveals that the nitride layer thickness increases with nitriding temperature. A distinct transition layer between the substrate and nitride layer is observed in the 560 °C and 580 °C nitride samples. The nitriding process develops almost equiaxed grain microstructure with new secondary phase precipitates, whereas in the as-built material, the grains are primarily columnar along the AM process build direction. Specifically, the nitriding process introduces γ-Fe4N, ε-Fe3N, CrN, and Ni3N precipitates. The increase in Ni- and Cu-rich precipitates with the nitriding temperature explains the observed improvement in the hardness and surface roughness. Furthermore, the nitriding process does not alter the substrate's initial weak crystallographic texture.
17-4PH steel↗
A proper assessment of TEM diffraction patterns originating from CrN nitrides in a ferritic matrix
Highlights: • A proper assessment of TEM diffraction pattern along the [001]{sub α-Fe} of a nitrided Fe-Cr alloy is proposed • Diffraction pattern results from the diffraction of the ferritic matrix and the three nitrides variants • Thin foil’s thickness plays a key role in the obtained diffraction pattern • Relrods located in the first layer of the reciprocal lattice can provide extra reflections in the diffraction patterns - Abstract: Upon nitriding of a Fe-3%Cr alloy at 550 °C during 48 h at a nitriding potential K{sub N} = 5 atm{sup −1/2}, finely dispersed CrN grains precipitate. Considering that the nitrides developing within the nitrided layer adopt a cubic, rock-salt structure, Transmission Electron Microscopy (TEM) investigations revealed the Bain orientation relationships (also called Baker-Nutting) existing between the matrix and the precipitates. Given the latter and the structures of both ferrite (bcc) and nitrides (fcc), we have shown that group theory predicts the existence of three nitrides variants, orthogonal to each other, developing in ferrite along the <001>{sub α-Fe} directions, which is in agreement with our experimental observations. The nitrides adopt a very thin platelet-like morphology, energetically corresponding to an absolute extremum. Diffraction patterns obtained along the [001]{sub α-Fe} result from the simultaneous diffraction of the ferritic matrix and the three nitrides variants. The platelet-like nitride precipitates give birth to diffuse intensity lines, originating from the two families developing along the (100) and (010) ferrite planes, as well as possible appearance of additional reflections, located at the forbidden positions {100}{sub α-Fe} and {110}{sub CrN} of the remaining variant, driving the interpretation of such diffraction patterns complicated. Foil thickness has proven to play a key role in the occurrence of this phenomenon. When the geometric diffraction conditions are favorable (i.e. very thin foil along the zone axis and very fine precipitates platelets), TEM analysis permitted to attribute these extra reflections to the nodes located in the first layer of the third variant's reciprocal space.
36 MATERIALS SCIENCE↗
Substrate nitridation induced modulations in transport properties of wurtzite GaN/p-Si (100) heterojunctions grown by molecular beam epitaxy
Phase pure wurtzite GaN films were grown on Si (100) substrates by introducing a silicon nitride layer followed by low temperature GaN growth as buffer layers. GaN films grown directly on Si (100) were found to be phase mixtured, containing both cubic ({beta}) and hexagonal ({alpha}) modifications. The x-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy studies reveal that the significant enhancement in the structural as well as in the optical properties of GaN films grown with silicon nitride buffer layer grown at 800 deg. C when compared to the samples grown in the absence of silicon nitride buffer layer and with silicon nitride buffer layer grown at 600 deg. C. Core-level photoelectron spectroscopy of Si{sub x}N{sub y} layers reveals the sources for superior qualities of GaN epilayers grown with the high temperature substrate nitridation process. The discussion has been carried out on the typical inverted rectification behavior exhibited by n-GaN/p-Si heterojunctions. Considerable modulation in the transport mechanism was observed with the nitridation conditions. The heterojunction fabricated with the sample of substrate nitridation at high temperature exhibited superior rectifying nature with reduced trap concentrations. Lowest ideality factors ({approx}1.5) were observed in the heterojunctions grown with high temperature substrate nitridation which is attributed to the recombination tunneling at the space charge region transport mechanism at lower voltages and at higher voltages space charge limited current conduction is the dominating transport mechanism. Whereas, thermally generated carrier tunneling and recombination tunneling are the dominating transport mechanisms in the heterojunctions grown without substrate nitridation and low temperature substrate nitridation, respectively.
36 MATERIALS SCIENCE↗
Discontinuous Inter-Granular Separations (DIGS) in the Gas Nitride Layer of ISS Race Rings
The starboard solar alpha rotary joint (SARJ) race ring on the International space station (ISS) failed due to severe spalling of the outer diameter, 45 degree (outer canted) nitrided surface. Subsequent analysis at NASA-KSC revealed that almost all of the debris generated due to the failure was nitrided 15-5 stainless steel. Subsequent analysis of the nitride control coupons (NCC) at NASA-JSC revealed the presence of discontinuous inter-granular separations (DIGS) in the gas nitride layer. These DIGS were present in the inter-granular networking located in the top 2 mils of the nitride layer. The manufacturer's specification requires the maximum white structure to be 0.0003 inches and intergranular networking below the allowable white structure depth to be cause for rejection; a requirement that the NCCs did not meet. Subsequent testing and analysis revealed that lower DIGS content significantly lowered the probability of nitride spalling in simulated, dry condition runs. One batch of nitride samples with DIGS content similar to the port SARJ (did not fail on orbit) which exhibited almost no nitride spalling after being run on one test rig. Another batch of nitride samples with DIGS content levels similar to the starboard SARJ exhibited significant nitride spalling on the same test rig with the same load under dry conditions. Although DIGS were not the root cause of starboard race ring failure, testing indicates that increased DIGS reduced the robustness of the gas nitride layer under dry operating conditions.
Figert, John↗
Methods of forming boron nitride
A method of forming a boron nitride. The method comprises contacting a metal article with a monomeric boron-nitrogen compound and converting the monomeric boron-nitrogen compound to a boron nitride. The boron nitride is formed on the same or a different metal article. The monomeric boron-nitrogen compound is borazine, cycloborazane, trimethylcycloborazane, polyborazylene, B-vinylborazine, poly(B-vinylborazine), or combinations thereof. The monomeric boron-nitrogen compound is polymerized to form the boron nitride by exposure to a temperature greater than approximately 100.degree. C. The boron nitride is amorphous boron nitride, hexagonal boron nitride, rhombohedral boron nitride, turbostratic boron nitride, wurzite boron nitride, combinations thereof, or boron nitride and carbon. A method of conditioning a ballistic weapon and a metal article coated with the monomeric boron-nitrogen compound are also disclosed.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
RF sputtered silicon and hafnium nitrides: Properties and adhesion to 440C stainless steel
Silicon nitride and hafnium nitride coatings were deposited by reactive RF sputtering on oxidized and unoxidized 440C stainless steel substrates. Sputtering was done in mixtures of argon and nitrogen gases from pressed powder silicon nitride and from hafnium metal targets. Depositions were at two background pressures, 8 and 20 mtorr, and at two different fractions (f) of nitrogen in argon, 0.25 and 0.60, for hafnium nitride and at f = 0.25 for silicon nitride. The coatings and the interface between the coating and substrates were investigated by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis and Auger electron spectroscopy. A Knoop microhardness of 1650 + or - 100 kg/sq mm was measured for hafnium nitride and 3900 + or - 500 kg/sq mm for silicon nitride. The friction coefficients between a 440C rider and the coatings were measured under lubricated conditions. Scratch test results demonstrate that the adhesion of hafnium nitride to both oxidized and unoxidized 440C is superior to that of silicon nitride. Oxidized 440C is found to have increased adhesion, to both nitrides, over that of unoxidized 440C.
Grill, A.↗
RF-sputtered silicon and hafnium nitrides - Properties and adhesion to 440C stainless steel
Silicon nitride and hafnium nitride coatings were deposited by reactive RF sputtering on oxidized and unoxidized 440C stainless steel substrates. Sputtering was done in mixtures of argon and nitrogen gases from pressed powder silicon nitride and from hafnium metal targets. Depositions were at two background pressures, 8 and 20 mtorr, and at two different fractions (f) of nitrogen in argon, 0.25 and 0.60, for hafnium nitride and at f = 0.25 for silicon nitride. The coatings and the interface between the coating and substrates were investigated by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis and Auger electron spectroscopy. A Knoop microhardness of 1650 + or 100 kg/sq mm was measured for hafnium nitride and 3900 + or 500 kg/sq mm for silicon nitride. The friction coefficients between a 440C rider and the coatings were measured under lubricated conditions. Scratch test results demonstrate that the adhesion of hafnium nitride to both oxidized and unoxidized 440C is superior to that of silicon nitride. Oxidized 440C is found to have increased adhesion, to both nitrides, over that of unoxidized 440C.
Grill, A.↗
Ion nitriding; Proceedings of the International Conference, Cleveland, OH, Sept. 15-17, 1986
The present conference discusses plasma-assisted surface coating/modification processes, the applications to date of ion nitriding, the effects of nitrogen on metal surfaces, ion nitriding mechanisms in Cr, Al and Cr + Al-containing 1040 steel, ion nitriding of Al and its alloys, life enhancement for forging dies, novel anode plasma nitriding developments, and a comparative study of the pulsed and dc ion-nitriding behavior in specimens with blind holes. Also discussed are the influence of heating method on ion nitriding, surface hardening of marage steels by ion nitriding without core hardness reduction, plasma nitriding of nodular cast iron sput gears, NbN composites for superconductors, the carburization of tungsten in a glow discharge methane plasma, economic considerations concerning plasma nitriding, and the corrosion properties obtained by ion nitriding.
Spalvins, T.↗
Corrosion Behavior of Plasma-Nitrided 904L Austenitic Stainless Steel in Hydrofluoric Acid
A new type of high-chromium nickel molybdenum super austenitic stainless steel, 904L, has excellent corrosion resistance in acidic environments. However, the service life of 904L decreases significantly in a mixed acid system that includes hydrogen fluoride and sulfuric acid. In this article, different plasma nitriding processes were used to modify the surface of 904L stainless steel. X-ray diffraction was used to analyze the phase composition after nitriding; scanning electron microscopy and atomic force microscopy were used to examine the surface morphology after nitriding; electrochemical noise and electrochemical methods were used to study the localized corrosion behavior and the damage mechanism of the ion nitride layer; and the effect of the plasma nitride layer on the corrosion resistance was explored. The results show that with increasing nitriding time, the thickness of the nitride layer increased. Ion nitriding resulted in the coarsening of the 904L austenitic stainless steel surface. A long nitriding treatment time resulted in the precipitation of CrN in the modified layer, depleting the chromium from the matrix and remarkably reducing the corrosion resistance.
36 MATERIALS SCIENCE↗
Structure refinement for tantalum nitrides nanocrystals with various morphologies
Graphical abstract: Tantalum nitrides nanocrystals with various phases and morphologies for the first time have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. Highlights: ► The spherical TaN, cuboidal TaN{sub 0.83} and TaN{sub 0.5} nanocrystals have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. ► The crystal structures of different tantalum nitrides were determined by Rietveld refinement on the X-ray diffraction data and the examinations of electron microcopies. ► The specific surface area of the tantalum nitrides powders was around 10 m{sup 2} g{sup −1}. ► Tantalum nitrides powders could be suitable for capacitor with high specific capacitance. -- Abstract: Tantalum nitrides (TaN{sub x}) nanocrystals with different phase and morphology have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. The crystal structures of tantalum nitrides were determined by Rietveld refinement based on the X-ray diffraction data. The morphologies of various tantalum nitrides nanocrystals in high quality were analyzed through the electron microcopies examinations. The spherical TaN nanoparticles, cuboidal TaN{sub 0.83} and TaN{sub 0.5} nanocrystals have been selectively prepared at different annealing temperatures. In addition, the specific surface areas of the tantalum nitrides nanocrystals measured by BET method were around 9.87–11.64 m{sup 2} g{sup −1}, indicating that such nano-sized tantalum nitrides could be suitable for capacitor with high specific capacitance.
36 MATERIALS SCIENCE↗