Thickness Of Nitrided Layer Research Articles

Nitride Induced Stress Affecting Crystallinity of Sidewall Damascene Gate-All-Around Nanowire Poly-Si FETs

In this article, poly-Si gate-all-around (GAA) field effect transistors (FETs) using sidewall damascene method are successfully demonstrated. By manipulating the stress which is imposed by nitride layer, the crystallinity of poly-Si channels can be modified easily by changing the thickness of nitride layer. The better crystallinity of the devices with 60 nm top nitride is attributed to larger average grain size and fewer defects, leading to higher field-effect carrier mobility compared to 40 and 80 nm top nitride layer devices. Both n-type and p-type devices exhibit superior electrical characteristics including higher on-state current of 40 μA/μm (n-type) and 26 μA/μm (p-type), steep subthreshold swing of 82 mV/dec. (n-type) and 104 mV/dec. (p-type), an extremely low drain-induced barrier lowering (DIBL) of 4.6 mV/V (n-type) and 16.6 mV/V (p-type), and high Ion/Ioff current ratio larger than seven orders of magnitude. The thermal stability and gate stress reliability measurement of sidewall damascene GAA nanowire poly-Si devices were also investigated. With better crystallinity, electrical characteristics of GAA nanowire poly-Si devices degrade less under same elevated temperature condition. Devices characteristics remain unchanged after long gate stress time. This simple fabrication process makes it a potential candidate for future three-dimensional integrated-circuit (3D-IC) and low-cost Internet of Things (IoTs) applications.

Cutting tools hardening and sharpening by fast argon and nitrogen atoms

A reamer made of AISI M2 high-speed steel was heated by ions accelerated from the plasma by a bias voltage applied to it and kept at 500°C for 120 min. Microhardness of the reamer surface increased by 1.75 times and the nitride layer thickness reached 130 μm. Nevertheless, radii of the cutting edges increased by 5 times up to ~ 40 μm, which made the tool blunt. Another reamer was heated by a converging beam of fast atoms produced by an immersed in the same plasma concave grid under a negative voltage of 5 kV. Due to uniform removal of the reamer material by the beam, the radii of cutting edges decreased from the initial value ~ 8 μm down to ~ 6 μm.

Investigation of Low-Temperature Liquid Nitriding Conditions for 316 Stainless Steel for Improved Mechanical and Corrosion Response

Combined influence of liquid nitriding time and liquid nitriding temperature on the properties of nitrided region developed on 316 stainless steel was investigated. Studies were restricted to low temperatures of 425 °C and 475 °C while the nitriding time was varied from 4 to 16 h. Developed nitrided layers were characterized by optical microscopy, scanning electron microscopy and X-ray diffraction. Mechanical and electrochemical properties of the nitrided layers were characterized, respectively, by Vickers micro-hardness measurements and cyclic polarization studies in 3.5 wt% NaCl solution. After 4-h nitriding at 425 °C or at 475 °C, the developed expanded austenite started to contract with simultaneous decrease in nitrided layer thickness, hardness and corrosion resistance. These prolonged nitriding time effects have been attributed to the decreased chemical potential of nitrogen in salt bath leading to the outward diffusion of N (from sample to salt bath). However, the 4-h nitriding at 475 °C resulted in larger expansion of austenite as compared to 4-h nitriding at 425 °C. Due to this, better mechanical and electrochemical property was realized after 4-h nitriding at 475 °C suggesting that the increased amount of N solubility in sample led to simultaneous increase in hardness and corrosion resistance of stainless steels.

Improved broadband dispersion engineering in coupled silicon nitride waveguides with a partially etched gap.

In order to meet the targeted dispersion requirements of applications, hybridized modes of coupled waveguides, whose dispersion characteristics can be significantly altered around their mode cross-point, have been recently investigated. The applications have been applied to microresonators based on concentric waveguides with a thin silicon nitride layer. However, it is still challenging to achieve a low and flattened anomalous dispersion profile just by optimizing the gap width between the waveguides. We propose to investigate the dispersion characteristics of coupled silicon nitride waveguides with a partially etched gap. It is shown that low and broadband anomalous dispersion can be achieved based on relatively thin 515 nm thick silicon nitride layer waveguides. The mechanism of a partially etched gap on dispersion engineering can be attributed to the tuning of the coupling strength between the waveguides. Therefore, when combined with other design parameters, it offers an additional "tuning knob" of advanced dispersion engineering when designing such coupled-waveguide devices for nonlinear photonic applications.

Influence of temperature and duration on the nitriding behavior of 40Cr low alloy steel in mixture of NH3 and N2

40Cr low alloy steel samples was nitrided by plasma nitriding with hollow cathode discharge assistance in a gas mixture of N2 and NH3 with different ratios at temperatures ranging from 520 °C to 560 °C for processing time from 2 to 6 h. The influences of processing temperature and time on the thickness and phase composition of nitrided layer were researched. Nitrided layers were evaluated using scanning electron microscope (SEM), X-ray diffraction and microhardness tester. The thickness of white layer increased with the processing temperature and time increasing. For samples nitrided at 540 for 4 h, the white layer is 5.6 μm in ammonia and 10.2 μm in mixture gas respectively. The maximum thickness of white layer about 15 μm thick is obtained after nitrided at 560 °C for 6 h in this study. The phases of nitrided layer are mainly composed of ε-Fe2-3N with a small amount of Fe4N. Such nitrided layer was beneficial to reducing the friction coefficient. The corrosion resistance of the nitrided sample was improved with the increasing thickness of the white layer.

Effect of auxiliary cathode on plasma nitriding behavior of Cr12MoV alloy steel

Cr12MoV alloy steel was nitrided in a plasma chamber with and without an auxiliary cathode. The results indicate, that at an appropriate distance between the auxiliary cathode and the alloy steel, hollow cathode discharge (HCD) is generated. The HCD is effective and important to harden the alloy steel by promoting the formation of a harder and thicker nitrided layer, which not only contains a nitrogen diffusion zone, where nitridation of the chromium carbide of the alloy occurs as in the case without auxiliary cathode, but also a top compound layer. The distance between the auxiliary cathode and the alloy steel noticeably affected the plasma nitriding kinetics of the Cr12MoV alloy steel. As the distance increases, the thickness of the compound layer and the microhardness of the nitrided layer increase first followed by a decrease. The nitridation mechanisms of the alloy steel with and without auxiliary cathode are discussed.

Surface Hardening of Massive Steel Products in the Low-pressure Glow Discharge Plasma

A process vacuum chamber is filled with a homogeneous plasma of glow discharge with electrostatic electron confinement, which is used for surface hardening of massive products. At the current of 2–20 A and the gas pressure ranging from 0.1 to 1 Pa the discharge voltage amounts to 350–500 V. When a bias voltage of 2 kV is applied to an immersed in the plasma hollow cylinder with a mass of 15 kg, electrical power spent on heating it by accelerated ions exceeds by an order of magnitude the power spent on the discharge maintenance. The massive cylinder is heated up to 700 °C for 15 min. When argon mixture with nitrogen (30%) is used, the nitriding for 3h results in an increase in the surface hardness from 400 up to 1000 HV50 and the nitrided layer thickness grows to ~100 μm. The nitriding rate is enhanced by a high degree of nitrogen dissociation due to decomposition by fast electrons and surface structural defects due to bombardment by high-energy ions.

High Temperature Oxidation Behaviors of CrNx and Cr-Si-N Thin Films at 1000 °C

The high temperature oxidation performance of nitride thin films has become an important issue when they are used as protective coatings on dry cutting tools or on die casting molds. In this study, the high temperature oxidation behaviors of CrNx and Cr-Si-N thin films were investigated at 1000 °C for 6 h in ambient air. The CrNx and Cr-Si-N thin films were prepared by a bipolar asymmetric pulsed direct-current (DC) magnetron sputtering system. Cr-Si-N films with silicon content ranging from 3.9 to 12.2 at.% were deposited by adjusting the Si target power. A thermogravimeter was adopted to study the oxidation kinetics of thin films. The weight gains were measured to calculate the parabolic rate constants of thin films. X-ray diffraction, X-ray mapping, and Auger electron spectroscopy were employed to study the microstructure and elemental redistributions of oxidized thin films. The as-deposited CrNx and Cr-Si-N thin films consisted of CrN and Cr2N mixed phases. The faceted Cr2O3 surface oxides, porous inner oxide layer, and oxygen-containing CrSi2 phases were found for the CrN film after oxidation test. On the other hand, the Cr-Si-N film containing 12.2 at.% Si showed a dense surface oxide layer and a thick and compact nitride layer, which indicates its best oxidation resistance. The high temperature oxidation resistance of Cr-Si-N thin films was improved by increasing Si content, due to the amorphous matrix contained nanocomposite microstructure and the formation of amorphous silicon oxide to retard the diffusion paths of oxygen, chromium, silicon, and nitrogen. The lowest parabolic rate constant of 1.48 × 10–2 mg2/cm4/h was obtained for the 12.2 at.% Si contained Cr-Si-N thin films, which provided the best oxidation resistance at 1000 °C for 6 h in this work. It should be noted that the residual tensile stress of thin film had a detrimental effect on the adhesion property during the oxidation test.

Standing contact fatigue behavior of nitrided AISI 316L steels

In this work, an experimental-numerical evaluation of the standing contact fatigue testing of a nitrided AISI 316L steel was developed. The nitride layers were formed at the surface of an AISI 316L steel by a salt bath nitriding process at a temperature of 580 °C for 1, 3 and 5 h of exposure time, obtaining three different layer thicknesses. In order to know the mechanical response and the different mechanisms of damage associated with the standing contact fatigue test, Hertzian tests were performed on a MTS machine by cyclic loading of a sphere on a flat surface formed by the layer/substrate system. The standing contact fatigue test was developed through two main stages. First, the critical loads for each treatment condition were determined by monotonic tests, where the appearance of circular cracks was considered as the failure criterion. Subsequently, cyclic subcritical loads were applied at a frequency of 5 Hz. A numerical model based on the finite element method was developed to evaluate the stress field generated in the system by cyclic contact loads. The results indicate that the thinnest thickness of nitride layer exhibits better resistance to standing contact fatigue.

Effect of Quench Polish Quench Nitriding Temperature on the Microstructure and Wear Resistance of SAF2906 Duplex Stainless Steel

The effect of quench polish quench (QPQ) nitriding temperature on the microstructure and wear resistance of SAF2906 duplex stainless steel was investigated. Results showed the surface of the nitrided samples was composed of an oxidized layer, a loose compound layer, a compact compound layer, and a diffusion layer. The oxidized layer was composed of Fe3O4. The main phases of the loose compound layer were CrN, αN, Fe2–3N, and Fe3O4. The compact compound layer was composed of CrN, αN, and Fe2–3N. In the diffusion layer, CrN and expanded austenite (S) were the main phases. The nitrided layer thickness increased from 20 to 41 μm with an increasing temperature of 570 to 610 °C. When the nitriding temperature was above 590 °C, the precipitates in the diffusion layer became coarsened, and their morphologies gradually changed from spherical particulate to rod-like and flocculent-like. Tribotests showed the cumulative mass loss of QPQ-treated samples was much lower than that of the substrate. The cumulative mass loss of the samples nitrided at 610 °C was higher than that at 570 °C during the first 29 h. When the test time was over 29 h, the former was lower than the latter.

Enhancing the mechanical and anticorrosion properties of 316L stainless steel via a cathodic plasma electrolytic nitriding treatment with added PEG

A cathodic plasma electrolytic nitriding (CPEN) treatment with a urea aqueous solution was performed on 316L stainless steel to rapidly improve its surface properties in this work. Test results show that the PEG2000 macromolecules increased the nitriding energy via enhancing the ability to bond the produced gas film to the metal/electrolyte interface. The cross-sectional morphologies indicate that a thick nitrided layer was obtained when the urea concentration was 543 g l−1, corresponding to a Vickers hardness 450 HV0.1, which was 3.5 times larger than that of the substrate. The nitrided layer mainly contained expanded austenite (γN), oxides and iron nitrides (e.g., Fe3O4 and FeN0.076). In terms of its performance, coefficient of friction (COF) of the nitride layer decreased to nearly two-thirds that of the untreated layer, and the passivation current densities of the nitrided sample in a 3.5% NaCl solution decreased by an order of magnitude compared to that of the substrate. Therefore, the approach presented herein provides an attractive way to modify the effect of CPEN in a urea aqueous solution.

Preparation of Graphene-Supported Microwell Liquid Cells for In Situ Transmission Electron Microscopy.

The fabrication and preparation of graphene-supported microwell liquid cells (GSMLCs) for in situ electron microscopy is presented in a stepwise protocol. The versatility of the GSMLCs is demonstrated in the context of a study about etching and growth dynamics of gold nanostructures from a HAuCl4 precursor solution. GSMLCs combine the advantages of conventional silicon- and graphene-based liquid cells by offering reproducible well depths together with facile cell manufacturing and handling of the specimen under investigation. The GSMLCs are fabricated on a single silicon substrate which drastically reduces the complexity of the manufacturing process compared to two-wafer-based liquid cell designs. Here, no bonding or alignment process steps are required. Furthermore, the enclosed liquid volume can be tailored to the respective experimental requirements by simply adjusting the thickness of a silicon nitride layer. This enables a significant reduction of window bulging in the electron microscope vacuum. Finally, a state-of-the-art quantitative evaluation of single particle tracking and dendrite formation in liquid cell experiments using only open source software is presented.

Effect of the carburized layer on the plasma nitriding behavior of duplex treated M50NiL steel

In this study, carburizing and nitriding duplex treatment was carried out at various carburizing pressures in the range of 1000–2500 Pa on M50NiL steel. The modified layers were characterized by laser scanning confocal microscopy (LSCM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD) and microhardness testing. The results show that increasing the carburizing pressure to 2000 Pa leads to a decrease in the thickness of compound layer and nitrided layer, and resulted in a great increase in the number of spherical precipitates M(C,N) in the nitrided layer. The compound layer consists of ε phase and γ′ phase as well as a trace of Fe3O4. The change of carbon content in the surface layer after carburizing and the increase in carbon content in the surface layer caused by the transformation from carbides into nitrides during nitriding greatly decreased the content of γ′ phase in the compound layer when the carburizing pressure increased from 1000 Pa to 1500 Pa. The effects of the solid solution by alloying elements, the precipitates and the diffusion of carbon atoms on the diffusion rate of nitrogen atoms are discussed.

LOW-TEMPERATURE NITRIDING BEHAVIOR OF COMPRESSIVE DEFORMED AISI 316Ti AUSTENITIC STAINLESS STEELS

The effects of compressive cold deformation under the quasi-static loads on the nitride formation, nitride layer growth and surface hardness properties were researched in this study. Martensite structure did not form in AISI 316Ti stainless steel as a result of quasi-static deformation. Diffusion layer did not form in all nitrided samples. Both the deformed and undeformed samples have only compound layer on the surfaces at the low-temperature nitriding conditions (400∘C, 7[Formula: see text]h). According to the X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS) and electron probe microanalysis (EPMA) results, S-phase and chromium nitride (CrN) were formed in the compound layers of the deformed samples. However, CrN did not form in the compound layer of the undeformed sample. The optical microscope (OM) results showed that the compressive cold deformation increased the nitrogen diffusion rate and led to thicker nitrided layer than the undeformed sample under the same plasma-nitriding conditions. All nitrided layers presented higher microhardness values ([Formula: see text][Formula: see text]HV) when compared with the untreated sample hardness. It was also verified that the deformation amount did not affect significantly the nitrided layer hardness.

Effect of Surface Nanocrystallization Pretreatment on the Tribological Properties of Plasma Nitrided AISI 316 L Stainless Steel Under Boundary Lubrication

It has been proved that surface nanocrstallization pretreatment is beneficial to plasma nitriding of steel by enhancing nitrogen diffusion, while the tribological properties of the nitrided nanostructured steel under boundary lubrication are not clear. In this work, AISI 316 L stainless steel with and without ultrasonic cold forging technology (UCFT) pretreatment was plasma nitrided at 500 °C for 4 h. The effects of UCFT pretreatment on the microstructure and properties of the nitrided layer and the tribochemical interactions between the nitrided layer and friction modifier molybdenum dithiocarbamate (MoDTC) and antiwear additive zinc dialkyldithio-phosphate (ZDDP) were investigated using SRV tribometer, scanning electron microscopy (SEM), vickers hardness tester, optical microscope, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). Surface analyses confirm the formation of a 20 μm thick nitrided layer on the UCFT-pretreated sample and it had higher hardness than that on the unpretreated sample. Furthermore, the nitrided UCFT-pretreated sample presented better synergetic effect with MoDTC and ZDDP on tribological behaviors than the nitrided unpretreated sample. This is attributed to the higher contents of Mo, S, Zn, P, and MoS2/MoO3 ratio in the tribofilms on the nitrided UCFT-pretreated sample.

Effect of Nitride Layer Thickness on Reciprocating Sliding Wear Behavior of AlN Layers on Spray-Formed Al Alloys

Dry sliding friction and wear behavior of nitrided and non-nitrided spray-formed Al alloys against AISI52100 steel were investigated using a linear-reciprocating ball on flat configuration under different normal loads. In case of nitrided spray-formed Al alloys, an increase in the applied normal load leads to a steady reduction of the stationary stage of the coefficient of friction depending on the sustainability of the AlN/Al compound. With regard to the nitride layer, thickness-specific wear regimes are distinguished for both spray-formed Al alloys. Nitrided spray-formed AlSi alloys show mild abrasive wear independent of normal load in case of AlN layers with up to 3 µm thickness. The layers exhibit an increased wear resistance compared to the non-nitrided condition for all applied test loads. Thick AlN layers > 4 µm show a steep increase in wear rate at loads exceeding 10 N, indicating a severe adhesive wear. These layers fail due to nitride layer delamination. Nitrided spray-formed AlMg alloys show mild abrasive wear for thin AlN layers < 4 µm up to normal loads of 12 N. Thick AlN layers almost immediately fail upon the initiation of the sliding contact due to crack formation within the nitride layer.

Characterization of surface layers formed on DU10Mo ingots after processing steps and high humidity exposure

The design of monolithic UMo fuel elements fabricated from low-enriched uranium for use in high-power research reactors requires bonding of the fuel foil to either Al cladding or a Zr barrier layer. Processing of the UMo ingot to final foil form has the potential to generate surface layers on the foil that differ from the bulk, metallic UMo. The interfacial properties between the UMo and Zr or Al cladding layers will then be determined by these surface layers. We use x-ray photoelectron spectroscopy, cross-sectional scanning electron microscopy, and atomic force microscopy to characterize the composition, oxidation state, and morphology of the surface layers that form after hot rolling and cold rolling depleted U–10 wt% Mo alloy (DU10Mo). A thick uranium nitride layer is observed after hot rolling, although its origin is likely from a previous processing step. The efficacy of acid etching in HNO3 is compared to that of electropolishing in H2SO4 to remove surface nitride and oxide layers, and both methods are found to be similarly effective. Both laboratory (low humidity) air exposure and longer rinse times in water are shown to promote the formation of surface oxide layers. Exposure of both acid-etched and electropolished DU10Mo foils to humid air (97% relative humidity) for six weeks results in formation of a thick oxide layer due to corrosion. The oxide layer on the acid-etched foil is thicker and more highly oxidized than the oxide layer that forms on the electropolished foil, and these differences in oxidation behavior are attributed to higher surface roughness on the acid-etched foil. In general, Mo is found to play a role as a sacrificial element, typically exhibiting a larger ratio of Mo6+/Mo4+ than U6+/U4+. This is unexpected, given the greater thermodynamic driving force to form U oxides than Mo oxides.

AISI 5140 steel nitriding in a plasma of a non-self-sustaining arc discharge with a thermionic cathode under the pulse action of ions

Steel AISI 5140 was exposed to pulsed (50 kHz) low-energy (up to 1 kV) nitriding in the plasma of a non-self-sustained arc discharge with a hot hollow cathode in a pure nitrogen atmosphere. The aim was to investigate the effect of the ion energy (pulse amplitude) and ion current density on the nitride layer thickness and on the depth of diffusion saturation with nitrogen. Experiments were also performed to study the effect of the ion energy and ion current density on the efficiency of nitriding at a constant specimen temperature and constant process time.

Mechanical and microstructural aspects of C20-steel blades subjected to gas nitriding

The paper presents the investigation of conical blades made of unalloyed steel C20 gas-nitrided by the Nitreg method. On the surface of steel blades (with tip angles in the range of 20–170°) an approx. 15mm-thick nitride layer of was fabricated, which had a bizonal structure of: ɛ (Fe2–3N and Fe3(N,C)1–x) and ɛ+γ′(Fe4N) with a hardness of 1310HV and 910HV, respectively. Hardness tests carried out on blade cross-section showed that a 0.7–1mm thick diffusion layer occurred under the nitride layer. By applying the criterion of effective nitrided layer thickness, gc+50, it was demonstrated that blades with a tip angle of 20° and 30° had been through-nitrided (i.e. nitrided through and through). A static compression test showed that, as a result of nitriding, the compressive strength of the blades had increased by a factor of two.

Low-temperature gas nitriding of AISI 4140 steel accelerated by LaFeO3 perovskite oxide

Rare earth nitriding was considered as an effective method to accelerate the nitriding efficiency. However the catalytic mechanism was not clear due to the uncertainty of rare earth (RE) elements’ existence during nitriding. In the present work, the LaFeO3 perovskite oxide was attempted to use as a catalyst in the gas nitriding for the first time. The effect of nitriding temperature on the microstructure and properties of the RE nitrided layer was investigated and the catalytic mechanism of the RE was discussed. The microstructure, phase composition and microhardness profiles of nitrided layers were characterized by the optical microscope, X-ray diffraction and micro-hardness tester, respectively. The corrosion resistance of nitrided layers was tested by the potentiodynamic polarization technique. Pin-on-disc tribometer were applied to evaluate the wear property. The X-ray photoelectron spectroscopy and scanning electron microscope equipped with an energy dispersive X-ray spectroscopy were used to identify the catalytic mechanism of the RE by analyzing the chemical state and elemental distribution on the nitrided surface. The results show that a perovskite-type oxide, LaFeO3, would form after the gas nitriding, which presents an obvious catalytic activity and increases the thickness of nitrided layers. In addition, the mechanical and corrosion properties could also be improved after nitriding with RE addition. The LaFeO3 perovskite oxide could accelerate the nitriding rate by adjusting the ratio of the adsorbed nitrogen (N) and dissolved N. On the other hand, the sufficient oxygen vacancies in the LaFeO3 oxide could provide more diffusion routes for N atoms.