Carbon Barrier Layer Research Articles

Double Nitrogenation Layer Formed Using Nitric Oxide for Enhancing Li+ Storage Performance, Cycling Stability, and Safety of Si Electrodes.

To enhance Li storage properties, nitrogenation methods are developed for Si anodes. First, melamine, urea, and nitric oxide (NO) precursors are used to nitrogenize carbon-coated Si particles. The properties of the obtained particles are compared. It is found that the NO process can maximize the graphitic nitrogen (N) content and electronic conductivity of a sample. In addition, optimized N functional groups and O─C species on the electrode surface increase electrolyte wettability. However, with a carbon barrier layer, NO hardly nitrogenizes the Si cores. Therefore, bare Si particles are reacted with NO. Core-shell Si@amorphous SiNx particles are produced using a facile and scalable NO treatment route. The effects of the NO reaction time on the physicochemical properties and charge-discharge performance of the obtained materials are systematically examined. Finally, the Si@SiNx particles are coated with N-doped carbon. Superior capacities of 2435 and 1280 mAh g-1 are achieved at 0.2 and 5Ag-1, respectively. After 300 cycles, 90% of the initial capacity is retained. In addition, differential scanning calorimetry data indicate that the multiple nitrogenation layers formed by NO significantly suppress electrode exothermic reactions during thermal runaway.

Tracking the chemically active Zn NPs to unravel the electrochemical activity evolution of Ta2O5 bone-like surface

Surface biofunctionalization has been researched for hard tissue implant applications. In this study, Zn nanoparticles (NPs) were deposited by magnetron sputtering onto CaP-enriched micro/nano-porous Ta2O5 surfaces. The electrochemical evolution of the surfaces through active Zn NPs (coated or not by a carbon delivery layer) was monitored in artificial saliva for 14 days. The Zn NPs led to a decrease in the corrosion resistance, as the surfaces became electrochemical active, revealing a diffusional behavior. The carbon barrier layer shows the ability to control the Zn NPs' mobility and, consequently, the ion release. These results open opportunities for the development of bio-multifunctional medical devices (osseointegration and antimicrobial functions) with controlled chemical activity.

Large‐Area Uniform 1‐nm‐Level Amorphous Carbon Layers from 3D Conformal Polymer Brushes. A “Next‐Generation” Cu Diffusion Barrier? (Adv. Mater. 15/2022)

Conformal Amorphous Carbon Ultrathin Cu diffusion barriers with high conformality have gained great attention for next-generation ultrahigh-density semiconductor device miniaturization. In article number 2110454, Sun Hwa Lee, Rodney S. Ruoff, Ki-Bum Kim, Sang Ouk Kim, and co-workers introduce a handy and reliable method for the preparation of conformal amorphous carbon (a-C) barrier layers with nanometer-level thickness. A polystyrene brush layer is grafted onto a 3D copper structure with self-limiting chemistry, and subsequent carbonization yields large-area uniform 1 nm-level a-C layers with excellent Cu blocking performance.

Regulating the interfacial reaction of Sc2W3O12/AgCuTi composite filler by introducing a carbon barrier layer

Negative thermal expansion (NTE) materials can offset the high expansion of metal brazing alloys, and play a key role in alleviating the residual stress and improving the mechanical properties of the joint. However, in Sc2W3O12 reinforced AgCuTi composite filler, the strong interfacial reaction between active Ti and Sc2W3O12 has become a bottleneck restricting the NTE behavior of Sc2W3O12. Herein, a novel strategy is proposed by designing a carbon barrier layer between active filler and Sc2W3O12 materials. Under the guidance of experimental results and theoretical analysis, the interface evolution mechanism is proposed. The results show that the carbon barrier layer increases the diffusion path of Ti atoms and weakens the interfacial reaction. With the help of carbon barrier layer, Sc2W3O12 gives full play to its NTE behavior during brazing, and the retention rate increases from 65.8% to 97.6%. Consequently, a highest shear strength of ∼77 MPa is achieved in the C/SiC-GH3536 joints by the designed composites filler, which is 1.3 times higher than that without carbon barrier layer and 3.2 times higher than that of AgCuTi filler. Our work opens the way for expanding the application of NTE materials in brazing process, and also provides new insights for the development of low-CTE composites.

Interface modification of Cr/Ti multilayers with C barrier layer for enhanced reflectivity in the water window regime.

The influence of a carbon barrier layer to improve the reflectivity of Cr/Ti multilayers, intended to be used in the water window wavelength regime, is investigated. Specular grazing-incidence X-ray reflectivity results of Cr/Ti multilayers with 10 bilayers show that interface widths are reduced to ∼0.24 nm upon introduction of a ∼0.3 nm C barrier layer at each Cr-on-Ti interface. As the number of bilayers increases to 75, a multilayer with C barrier layers maintains almost the same interface widths with no cumulative increase in interface imperfections. Using such interface-engineered Cr/C/Ti multilayers, a remarkably high soft X-ray reflectivity of ∼31.6% is achieved at a wavelength of2.77 nm and at a grazing angle of incidence of 16.2°, which is the highest reflectivity reported so far in the literature in this wavelength regime. Further investigation of the multilayers by diffused grazing-incidence X-ray reflectivity and grazing-incidence extended X-ray absorption fine-structure measurements using synchrotron radiation suggests that the improvement in interface microstructure can be attributed to significant suppression of inter-diffusion at Cr/Ti interfaces by the introduction of C barrier layers and also due to the smoothing effect of the C layer promoting two-dimensional growth of the multilayer.

Interface Study on the Effect of Carbon and Boron Carbide Diffusion Barriers in Sc/Si Multilayer System.

Sc/Si multilayers are one of the promising material combinations commonly used in the spectral range of 35-50 nm. However, diffusion and silicidation at the interfaces of Sc/Si multilayers limit widespread applications of this material combination. To improve the properties of Sc/Si multilayers, the scheme of barrier layers is utilized. In this work, a series of Sc/Si multilayers with boron carbide and carbon barrier layers were designed and fabricated to compare the properties including interface quality and thermal stability. The effect on the multilayer structure and quality before and after annealing were investigated by using grazing-incidence X-ray reflection, X-ray diffraction, rocking-curve X-ray diffuse scattering, transmission electron microscopy, and selected area electron diffraction. The results indicate that severe interdiffusion and crystallization occur in the multilayer with a carbon barrier after annealing. However, a boron carbide barrier layer improves thermal stability up to 550 °C since the interfaces remain abrupt and clear after annealing. The multilayer quality is confirmed to be improved significantly.

Tuning the Reactivity of Al/NiO@C Nanoenergetic Materials through Building an Interfacial Carbon Barrier Layer

Inspired by the crucial role of the interface layer in tuning the reactivity of nanoenergetic materials (nEMs), in this study, we report a new method to tune the energetic performances of Al/NiO@C nEMs by designing the interfacial barrier layer between the fuel and oxidizer. The carbon shell in special core-shell NiO@C nanorods derived from nickel-based metal-organic frameworks functions as a homogeneous interfacial diffusion-resistant layer between Al and NiO nanoparticles. Under the guidance of experimental time-resolved oxidation curves and theoretical simulation results, the carbon content can be easily controlled, thereby achieving the goal of tuning energetic performances. It is found that the chemical nature of the carbon barrier layer rather than its content provides the resistance against interdiffusion of Al and O atoms in the solid-state reaction, thus leading to a higher reaction onset temperature. The importance of the interfacial layer on the thermal properties of nEMs is also emphasized when compared with physically mixed ones. Combustion tests reveal that both interfacial resistance and gas generation play roles in tuning the combustion propagation, flame temperature, ignition delay time, and pressurization rate. These results indicate the promising potential of pre-engineered interfacial structure for targeted reactivity of carbon-based nEMs.

Interface studies of Mo/Si multilayers with carbon diffusion barrier by grazing incidence extended X-ray absorption fine structure

Single layer Mo and Si thin films deposited for different deposition times on c-Si substrates by Ion beam sputtering technique have been characterized by Grazing Incidence X-ray Reflectivity (GIXRR) measurements. Subsequently, few Mo/Si multilayers having 5 bi-layers with different Mo to bi-layer thickness ratio (Γ) at a fixed bi-layer thickness have been deposited and characterized by GIXRR measurements. Investigation has been carried out on the different behaviors of the interfaces and also variation of the interface width with Γ has been studied. Finally, 25 bi-layer Mo/Si multilayer samples having the lowest Γ value and with and without carbon diffusion barrier layer at both the Mo/Si interfaces are deposited and the interfaces have been characterized by hard X-ray and soft X-ray reflectivity measurements. The study shows improvement in reflectivities of the multilayer with carbon diffusion barrier layer from 38% to 54% at 130 Å wavelength. To have further insight into the modification of the interface due to introduction of the carbon barrier layer, depth selective study of both the multilayers have been carried out by Grazing Incidence Extended X-ray Absorption Fine Structure measurements using synchrotron radiation and thereby investigating the local structures around Mo atoms in Si bulk region and Si-on-Mo interface. This study confirms the reduction of diffusion of Mo and Si layer into each other when the carbon buffer layers are present at the interfaces, thus reducing the chance of formation of MoSi2.

The role of ultra-thin carbon barrier layers for fabrication of La/B4C interferential mirrors: Study by time-of-flight secondary ion mass spectrometry and high-resolution transmission electron microscopy

Time-of-flight secondary ion mass spectrometry and high-resolution transmission electron microscopy study is reported on depth profiling of 375nm-thick multilayer La/B4C interferential mirrors produced by magnetron sputtering for X-ray radiation at the wavelength of 6.7nm. The introduction of ultra-thin (0.5nm) carbon barrier layer inside each period of ca. 7.5nm suppressed the broadening of interface regions, decreased the width of La and B profiles and as a result improved the reflectance of mirrors. Depending on the layers' sequence (La/C/B4C or La/B4C/C upward the Si substrate), two different mechanisms–chemical interaction and reaction diffusion, were employed for qualitative explanation of the obtained results.

Silver surface segregation in Ag-DLC nanocomposite coatings

AgDLC coatings were deposited by magnetron sputtering in order to evaluate: i) the Ag nanoparticle size distribution along the coatings thickness and ii) the silver stability in DLC coatings. Four different coatings were deposited, two AgDLC nanocomposite coatings containing 20at.% of Ag, with thicknesses of 250nm and 1000nm, a 250nm AgDLC nanocomposite coating with carbon barrier layer of 75nm and a multilayer coating, consisting of a pure Ag layer with a carbon barrier layer of 75nm. The coatings were characterized with respect to their structure (by means of X-ray diffraction (XRD)), morphology (by scanning electron microscopy (SEM)) and Ag distribution in depth (by glow discharge optical emission spectroscopy (GDOES)). The AgDLC nanocomposite coatings are composed of Ag nanograins (with a size of about 3nm) dispersed in an amorphous carbon matrix. The SEM results suggest a bimodal size distribution along the coatings thickness, it was found that Ag forms nanoparticles and aggregates with sizes ranging from 14nm up to 52nm on the coating's surface, whereas in bulk, no Ag nanoparticles were visible by SEM. The monitoring of the Ag stability at room temperature conditions during a period of 6months showed that Ag segregates to the coatings surface, in the AgDLC nanocomposite coating with 1000nm forming Ag nanofibers, while the thinner AgDLC (250nm) as well as the multilayer (Ag+DLC and AgDLC+DLC) coatings were stable over time.

High performance multilayer La/B4C mirrors with carbon barrier layers

Recent results from manufacturing multilayer La/B4C mirrors at wavelengths above 6.7 nm with carbon barrier layers are presented. It is shown that maximum reflection R = 58.6% is attained at λ = 6.661 nm.

Mo/Si Multilayers with Different Barrier Layers for Applications as Extreme Ultraviolet Mirrors

Pulsed laser deposition (PLD) and magnetron sputter deposition (MSD) have been used to prepare different types of Mo/Si multilayers for the extreme ultraviolet (EUV) spectral range. In the case of PLD prepared Mo/Si multilayers the deposition of 0.3–0.5 nm thick carbon barrier layers at the interfaces leads to a substantial improvement of the interface quality. This can be deduced from Cu-Kα reflectivity measurements and HRTEM observations. Consequently the EUV reflectivity has been substantially increased. For pure Mo/Si-multilayers prepared by MSD the deposition parameters have been optimized so that a normal incidence reflectivity of REUV=68.7% could be realized. Although this is one of the best experimental results achieved so far, there is still a gap between this experimental value and the theoretical limit (REUV=75.5%). One of the main reasons for this discrepancy is the formation of intermixing zones at the interfaces. With B4C and C barrier layers at the interfaces interdiffusion can be reduced. The resulting EUV reflectivity of this new type of EUV multilayers is 69.8% (λ=13.42 nm, α=1.5°) and 71.4% (λ=12.52 nm, α=22.5°).

Recovery of multilayer-coated Zerodur and ULE optics for extreme-ultraviolet lithography by recoating, reactive-ion etching, and wet-chemical processes

Extreme-ultraviolet lithography requires expensive multilayer-coated Zerodur or ULE optics with extremely tight figure and finish specifications. Therefore it is desirable to develop methods to recover these optics if they are coated with a nonoptimum multilayer films or in the event that the coating deteriorates over time owing to long-term exposure to radiation, corrosion, or surface contamination. We evaluate recoating, reactive-ion etching, and wet-chemical techniques for the recovery of Mo/Si and Mo/Be multilayer films upon Zerodur and ULE test optics. The recoating technique was successfully employed in the recovery of Mo/Si-coated optics but has the drawback of limited applicability. A chlorine-based reactive-ion etch process was successfully used to recover Mo/Si-coated optics, and a particularly large process window was observed when ULE optics were employed; this is an advantageous for large, curved optics. Dilute HCl wet-chemical techniques were developed and successfully demonstrated for the recovery of Mo/Be-coated optics as well as for Mo/Si-coated optics when Mo/Be release layers were employed; however, there are questions about the extendability of the HCl process to large optics and multiple coat and strip cycles. The technique of using carbon barrier layers to protect the optic during removal of Mo/Si in HF:HNO(3) also showed promise.

Design and fabrication of highly heat-resistant Mo/Si multilayer soft X-ray mirrors with interleaved barrier layers.

Introducing interleaved carbon barrier layers improves the heat-resistance of Mo/Si multilayers. The soft X-ray reflectivities of the multilayers were calculated, and the effects of heating on both the reflectivities and layer structures of Mo/Si multilayers with and without barrier layers were investigated using X-ray diffraction and transmission electron microscopy. The results show that, for applications using intense soft X-ray beams, Mo/Si multilayers with interleaved carbon barrier layers are better mirrors than Mo/Si multilayers because they have much better heat resistance and almost the same soft X-ray reflectivity as the Mo/Si multilayers.

Fugitive Diffusion Barrier for Integration of Sol‐Gel‐Derived Lead Titanate with Oxidized Silicon Substrates

The crystalline phase development and microstructural changes with heating of sol‐gel‐derived lead titanate (PT) particles and films on silica with and without a fugitive (or removable) diffusion barrier layer were investigated. Amorphous gel‐derived PT particles were deposited on SiO2‐coated TEM grids with and without polyimide (PI) or carbon barrier layers between SiO2 and PT. TEM analysis showed that PI or carbon barriers prevented reaction between the gel‐derived PT particles and SiO2. PT particles crystallize and then the PI or carbon film decomposes. Sol‐gel‐derived PT films were deposited on oxidized Si substrates (Si/SiO2) with and without a PI barrier layer. Perovskite PT films were prepared on Si/SiO2 substrates with a PI barrier; however, some porosity remained in the films. Identically prepared films without the PI barrier formed a mixture of pyrochlore and perovskite. X‐ray photoelectron spectroscopy results indicate that the PI film pre‐ vents the diffusion of Si into the PT film.

Repair of soft-x-ray optical elements by stripping and redeposition of Mo/Si reflective coatings

Experiments aimed at recovering soft-x-ray projection lithography mirrors that have defective reflective coatings by stripping and redeposition of Mo/Si multilayers are being reported. Two wet etchants were found that would remove the multilayers from composite glass substrates. One etchant is a solution of potassium ferricyanide and sodium hydroxide in water; the other is nitric acid with a minute quantity of hydrofluoric acid. Although each of these solutions offers preferential etch selection of the multilayers over the substrate glass, the selectivities are insufficient. The result is a surface roughening that lowers the reflectance from subsequently deposited multilayer coatings to an unacceptable level. With the addition of a carbon barrier layer between the substrate and the multilayer coating, either etchant can be used to strip the multilayers without damage to the underlying substrate surface.

Reduced Al/PtSi reaction up to 600 °C using an amorphous carbon barrier layer

An amorphous carbon barrier layer is used to reduce the reaction between PtSi and Al for interconnect application. Using a carbon layer of 1000 Å and a structure of Al/C/PtSi (2000 Å/1000 Å/850 Å/Si substrate), the preformed PtSi is shown to remain stable after a 30-min anneal at 600 °C in a N2-H2 ambient, with no PtAl2, the reaction product between Al and PtSi, detected. The Al-PtSi reaction is nearly completed after an anneal of 30 min at 650 °C. Sheet resistance measurement confirms the low resistance of the top Al layer at these temperatures. The much reduced reaction between Al and PtSi using an amorphous carbon barrier layer, with similar results on the Al/Pd2Si reaction, makes carbon a promising barrier between Al and silicide contacts.

Formation of palladium silicide in the presence of Al with and without a carbon barrier layer

The formation of Pd silicides in the presence of an Al layer is studied using Al/Pd/Si structures with and without a carbon barrier layer between the Al and Pd layers. Both the reactions between Al and Pd and between Pd and Si start around 200 °C, forming Pd2Al3 and Pd2Si, respectively. At higher temperatures, the excess Al present reacts with the Pd2Si formed, converting the latter to Pd2Al3 which is completed at 400 °C. In the presence of a carbon barrier layer using an Al/C/Pd/Si structure, the Pd2Si formed stays little changed up to an anneal of 30 min at 500 °C. The Pd2Si formed reacts with the Al present at higher temperatures, about two-thirds reacted after an anneal at 550 °C, and nearly completely reacted after an anneal at 600 °C, both for 30 min. The effectiveness of the carbon barrier layer for the Al/Pd2Si reaction is compared with that for the Al/PtSi reaction, where little reaction is observed after an anneal of 30 min at 600 °C. Application of the carbon barrier layer to device contact metallurgies is also discussed.

Some observations on interactions between unstressed AISI 304L steel and zinc or zinc oxide

A laboratory study has been made of the interactions of unstressed AISI 304L stainless steel with zinc and zinc oxide in air, carbon monoxide or argon-hydrogen. Erosion or penetration ranging from 0.003 to 1.7 mm was produced by molten zinc in 1 h at 500 to 850° C in air and argon-hydrogen. The penetration at 700 to 850° C formed mechanically detrimental structures such as cracked intermetallic layers, distorted and fissured interdiffusion zones and liquid channels. No penetration occurred in carbon monoxide atmospheres because of the deposition of a carbon barrier layer onto the steel surfaces. Similarly, thick oxide films could delay penetration. Zinc vapour and zinc oxide produced pitting of the steel surfaces, the attack by zinc oxide being the more severe.