Surface Kinetic Processes Research Articles

Dual Electric Field Coupling with Tunable Schottky Barrier Synergistically Regulating Electronic Configuration in CoP@Ni‐CdS Heterojunction for Efficient Photocatalytic H2 Evolution

AbstractDesigning and exploiting visible‐light‐responsive materials that converts solar into chemical energy is promising in achieving green energy sustainability, but addressing low electron–hole separation efficiency and sluggish surface kinetic process remains formidable challenges. Herein, a novel CoP@Ni‐CdS Schottky junction composed of Ni‐doped CdS nanorods and quasi‐metallic CoP nanoparticles is constructed via a simple hydrothermal–calcination method. Experiments and theoretical calculations demonstrate that magnetic Ni‐doping not only induces a spin‐polarized electric field and enhances the built‐in interfacial electric field strength, but also rises the Schottky barrier height at the heterointerface, which synergistically accelerates the separation efficiency of photoinduced charges and modulates the electronic configuration of the active site to optimize the adsorption–desorption behaviors for H2O molecules and H* intermediates. Therefore, the designed CoP@Ni‐CdS catalyst exhibits an exceptional photocatalytic performance with H2 evolution rate of 42.14 mmol g−1 h−1 with the apparent quantum efficiencies of 16.8% at 420 nm, which is 14.14 and 2.21 times higher than that of pristine CdS and Ni‐CdS, respectively. This work provides in‐depth insights into fabricating dual electric fields, tuning the Schottky barrier and modulating the electronic configuration of active sites in Schottky heterojunction for ameliorative photocatalytic activity.

Molecular Interactions in Copper Chemical Mechanical Planarization: A Phenomenological Study

In this study, the molecular interactions occurring during Chemical Mechanical planarization of Copper in Ferric nitrate–Alumina–Benzotriazole system is investigated. This system is characterized by sudden and dramatic transitions in removal rates when experimental parameters such as downforce and concentrations of the slurry components (Benzotriazole, abrasive, oxidizer) are varied. This behavior is interpreted in terms of the three surface kinetic processes viz. Cu dissolution, film formation and film removal by abrasion, that determine the overall removal rate. A phenomenological model incorporating Frumkin isotherm for the adsorption of Benzotriazole molecules and Langmuir isotherm for the adsorption of surfactants/ions is proposed. Mathematical equations relating the rates of film formation, film removal and metal dissolution to the overall removal rates are derived. The model is validated by comparing the model predictions with experimental data. The non-linear equations describing the sudden transitions are shown to exhibit a cusp catastrophe when the interaction parameter exceeds a certain value.

Surface states modulation of topological insulator Bi2Se3 by noble metal decoration for gas sensing kinetic engineering

The chemical reaction of gas adsorption/desorption is strongly correlated with the surface state of sensitive films. Thus, understanding the surface state and kinetic process of gas-sensing reactions is crucial to design highly active sensing films. In this study, bismuth selenide (Bi2Se3) was selected as the platform to clarify those matters. The noble metal nanocrystals (Au, Ag and Pt) were decorated on the (001) surface of layered Bi2Se3 to tune the surface state and improve the dynamical gas sensing parameter. The response and response rate toward 10 ppm of NO2 were respectively improved by 2.5 and 3.8 times by the Au decoration, and 2.3 and 3.2 times by the Ag decoration, and 1.3 and 2.7 times by the Pt decoration. The gas adsorption/desorption isotherm was established to analyze the reaction kinetic parameters of the response (S), kinetic reaction rate (kr and k-r) and beta value (β). These results demonstrate that noble metals can greatly promote the reaction kinetic parameters by modulation the surface state. Especially, the Au10 sample acquired maximum kr values of 633.963, which is 9.3 times higher than pure Bi2Se3. This work provides an important strategy for designing gas sensing performance between topological insulators and noble metal particles.

Bioregulation of FeNi LDH morphology and electronic structure to highly promote electrocatalytic oxygen evolution

NiFe-based layered double hydroxides (LDHs) are currently the most efficient oxygen evolution reaction (OER) catalysts in alkaline medium. However, their shortcomings such as insufficient electron transport ability, few exposed active sites and susceptibility to aggregation hindered their further development. In this paper, soluble extracellular polymer substances (s-EPS) modified by urea was used as biosurfactant and pH regulator, micro-morphology and electronic structure of FeNi LDH were accurately regulated to upgrade its stability, electrical conductivity, electrochemical active surface area and kinetic process. Tryptophan residue protein in EPS is mainly responsible for the interaction between s-EPS and FeNi LDH. Experimental and theoretical calculation results demonstrate that the introduction of s-EPS can coordinate the morphology and electron distribution of active centers, consequently optimizing the adsorption energy of reaction intermediates and enhancing the inherent catalytic activity for OER. As expected, s-EPS@FeNi LDH exhibited excellent OER performance under alkaline conditions, and only had an overpotential of 220 mV at a current density of 10 mA cm−2, which is superior to other promising FeNi-based catalysts. This work sheds light on realizing the efficient assembly of LDH and s-EPS, and provides a reliable method for the morphology and electronic structure modification of LDH for more efficient OER.

Preparation of ZrC-SiC composite coatings by chemical vapor deposition and study of co-deposition mechanism

In this work, the ZrC-SiC composite coatings were co-deposited by chemical vapor deposition (CVD) using ZrCl4, MTS, CH4 and H2 as raw materials. The morphologies, compositions and phases of the composite coatings were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results indicated that the morphologies, compositions and phases of the composite coatings were related to the deposition temperature, the flow rate of the carrier H2 gas, and the ratio of C/Zr. Moreover, the co-deposition mechanism of the composite coatings was also studied. It was found that different deposition temperatures resulted in different deposition mechanisms. At temperatures in the range of 1150–1250 °C, the ZrC-SiC co-deposition was controlled by the surface kinetic process. At temperatures in the range of 1250–1400 °C, the ZrC-SiC co-deposition was controlled by the mass transport process.

Controlling defects and secondary phases of CZTS by surfactant potassium

Cu2ZnSnS4 (CZTS) is a promising photovoltaic absorber material with earth abundant and nontoxic elements. However, the detrimental native defects and secondary phases of CSTS will largely reduce the energy conversion efficiencies. To understand the origin of these problems during the growth of CZTS, we investigated the kinetic processes on CZTS (-1-1-2) surface, using first principles calculations. A surface Zn atom was found to occupy the subsurface Cu site easily due to a low reaction barrier, which may lead to a high ZnCu concentration and a secondary phase of ZnS. These n-type defects may create deep electron traps near the interface and become detrimental to device performance. To reduce the population of ZnCu and the secondary phase, we propose to use K as a surfactant to alter surface kinetic processes. Improvements on crystal quality and device performance based on this surfactant are consistent with early experimental observations.

A model for arsenic anti-site incorporation in GaAs grown by hydride vapor phase epitaxy

GaAs growth by hydride vapor phase epitaxy (HVPE) has regained interest as a potential route to low cost, high efficiency thin film photovoltaics. In order to attain the highest efficiencies, deep level defect incorporation in these materials must be understood and controlled. The arsenic anti-site defect, AsGa or EL2, is the predominant deep level defect in HVPE-grown GaAs. In the present study, the relationships between HVPE growth conditions and incorporation of EL2 in GaAs epilayers were determined. Epitaxial n-GaAs layers were grown under a wide range of deposition temperatures (TD) and gallium chloride partial pressures (PGaCl), and the EL2 concentration, [EL2], was determined by deep level transient spectroscopy. [EL2] agreed with equilibrium thermodynamic predictions in layers grown under conditions in which the growth rate, RG, was controlled by conditions near thermodynamic equilibrium. [EL2] fell below equilibrium levels when RG was controlled by surface kinetic processes, with the disparity increasing as RG decreased. The surface chemical composition during growth was determined to have a strong influence on EL2 incorporation. Under thermodynamically limited growth conditions, e.g., high TD and/or low PGaCl, the surface vacancy concentration was high and the bulk crystal was close to equilibrium with the vapor phase. Under kinetically limited growth conditions, e.g., low TD and/or high PGaCl, the surface attained a high GaCl coverage, blocking As adsorption. This competitive adsorption process reduced the growth rate and also limited the amount of arsenic that incorporated as AsGa. A defect incorporation model which accounted for the surface concentration of arsenic as a function of the growth conditions, was developed. This model was used to identify optimal growth parameters for the growth of thin films for photovoltaics, conditions in which a high growth rate and low [EL2] could be attained.

Metalorganic chemical vapor deposition of Al2O3 using trimethylaluminum and O2 precursors: Growth mechanism and crystallinity

Metalorganic chemical vapor deposition (MOCVD) of Al2O3 was studied by using trimethylaluminum and O2 precursors over a variety of temperature, flow, and pressure conditions. Growth within the low temperature region from 600 to 800°C was found to be limited by a surface kinetic process that follows the Langmuir-Hinshelwood mechanism. In the high temperature region from 900 to 1050°C, the growth process was influenced by prereactions in the gas phase. The crystallinity of MOCVD Al2O3 films grown in situ on GaN substrates was characterized by grazing incidence x-ray diffraction (GIXRD) and high-resolution transmission electron microscopy (HRTEM). GIXRD suggested that the Al2O3 films grown at 600 and 700°C were amorphous, while those grown at 800, 900, 1000, and 1050°C were crystalline with primarily γ-phase. HRTEM further showed that the γ-Al2O3 films grown at 900 and 1050°C were poly and single crystalline, respectively. The crystal orientation relationships during the epitaxial growth of γ-Al2O3 on GaN at 1050°C were also determined.

Incipient hydration of mantle lithosphere at ridges: A reactive-percolation experiment

A reactive percolation experiment was conducted by injecting seawater into a permeable olivine aggregate at 190°C and 19MPa to explore the relationships between hydration reactions and hydrodynamic properties during the onset of serpentinization in the ultramafic lithosphere exposed at mid-ocean ridges. The experiment was stopped after 23 days when the sample became impermeable. The initial flow rate was 0.2mL/h and then was decreased down to 0.06mL/h after 8 days. Permeability decreased continuously throughout the experiment. The analyses of fluid chemistry time series and of the mineralogy and structure of the reacted sample showed olivine dissolution and precipitation of proto-serpentine, brucite and Fe-oxides. These reactions are controlled by coupled hydrodynamic and chemical processes interacting at different time and spatial scales. Their first characteristic is the production of silica rich outlet fluids in disequilibrium with the observed reacted mineral assemblages. These compositions are interpreted as resulting from a suite of coupled dissolution–precipitation reactions, controlled at the pore scale by surface kinetic processes, that rapidly reaches steady-state (constant fluid composition independent of fluid flux). Hence, the effective rate of serpentinization was controlled, to the first order, by the transport of reactants during the experiment. Mass balance calculations show that the rate of olivine conversion was fast (0.2–0.5wt%/day), yet only ∼8wt% of the olivine sample reacted, because the permeability drop limited fluid circulation. Porosity varied little during the experiment compared to permeability changes: the decrease of permeability was explained by the structure of the newly formed serpentine favouring the clogging of fluid paths. The rate at which permeability decreased was the fastest at low flux conditions. This suggests that permeability changes were not controlled simply by the kinetics of the serpentinization reactions, but mainly reflected the development of low Peclet pore scale zones forming micro-environments that control the serpentinization reaction-paths. These results outline the need to take into account the coupling of hydrodynamic and chemical processes when modelling the effects of reactive transport within the hydrating oceanic lithosphere.

Heteroepitaxy of GaAs on (001) ⇒ 6° Ge substrates at high growth rates by hydride vapor phase epitaxy

The growth of GaAs on (001) ⇒ 6° Ge substrates by hydride vapor phase epitaxy has been investigated. The effects of varying deposition temperature and gas phase supersaturation on growth rate and material quality as determined by atomic force microscopy measured surface roughness and x-ray diffraction were established. GaAs growth rates up to 44 μm/hr were achieved. The deposition temperature has a strong effect on growth rate under the investigated range of growth conditions indicating that growth is typically limited by surface kinetic processes. An apparent activation energy of 35.1 ± 2.0 kcal/mol was determined for growth on these Ge substrates, agreeing well with past kinetic data for GaAs growth on GaAs substrates. The deposition temperature also had a significant effect on both root mean square surface roughness and x-ray full width at half maximum, with minima of 0.92 nm and 26 arcsec occurring for samples grown at temperatures of 725 °C and 750 °C, respectively. These values are comparable to or better than values measured for GaAs on Ge layers grown by metalorganic vapor phase epitaxy. The use of a thin Si3N4 coating on the Ge substrate backside mitigated the observed Ge gas phase autodoping effect. With back surface passivation, GaAs background doping levels within the GaAs epilayer of n = 1.2 × 1016 cm−3 were achieved 2.3 μm from the heterointerface. The heterointerfaces of the samples grown at 725 °C and 775 °C were imaged by transmission electron microscopy. Anti-phase domain boundaries (APBs) were observed near the heterointerface of the 775 °C sample. These APBs self-annihilated after roughly 100 nm of epilayer thickness. The 725 °C sample exhibited no APBs in the vicinity of the interface or elsewhere in the film, indicating a more optimal growth temperature. Ge diffusion through the GaAs/Ge interface was profiled by secondary ion mass spectrometry and multiple regions of diffusion behavior were observed. In the region of high Ge concentration ([Ge] > 5 × 1019 cm−3) closest to the heterointerface, the concentration vs. position data fit a vacancy-assisted diffusion mechanism. The data between 0.05 and 0.20 μm from the heterointerface were fit to a concentration independent, semi-infinite diffusion model with a constant diffusion coefficient. These models indicate that complex mechanisms control diffusion during growth at these temperatures.

Structure/Processing/Properties Relationships in Nanoporous Nanoparticles As Applied to Catalysis of the Cathodic Oxygen Reduction Reaction

We present a comprehensive experimental study of the formation and activity of dealloyed nanoporous Ni/Pt alloy nanoparticles for the cathodic oxygen reduction reaction. By addressing the kinetics of nucleation during solvothermal synthesis we developed a method to control the size and composition of Ni/Pt alloy nanoparticles over a broad range while maintaining an adequate size distribution. Electrochemical dealloying of these size-controlled nanoparticles was used to explore conditions in which hierarchical nanoporosity within nanoparticles can evolve. Our results show that in order to evolve fully formed porosity, particles must have a minimum diameter of ∼15 nm, a result consistent with the surface kinetic processes occurring during dealloying. Nanoporous nanoparticles possess ligaments and voids with diameters of approximately 2 nm, high surface area/mass ratios usually associated with much smaller particles, and a composition consistent with a Pt-skeleton covering a Ni/Pt alloy core. Electrochemical measurements show that the mass activity for the oxygen reduction reaction using carbon-supported nanoporous Ni/Pt nanoparticles is nearly four times that of commercial Pt/C catalyst and even exceeds that of comparable nonporous Pt-skeleton Ni/Pt alloy nanoparticles.

Study on the influence of reaction temperature on the preparation of C-Core SiC filaments

SiC filaments were widely used as reinforcements in metal-matrix and ceramic-matrix composites. C-core SiC filaments were prepared by CVD process using DC electrically heating for the first time in domestic. The effects of reaction temperature on the morphologies, deposition rate, microstructure, grain size and composition for the C-core SiC filaments coating prepared by CVD process in CH3SiHCl2-H2-Ar system, were explored by means of SEM, XRD, Raman, and AES. The experimental results show that with increasing reaction temperature the deposition rate increases rapidly in an exponential manner, surface kinetic processes become stronger, and Si/C atomic ratio decreases. At low temperatures, Si phase co-deposites with SiC, inhibiting the grain growth, while at high temperatures, the grain growth results in rough surface, and the stress changed from tensile to compressive.

Influence of silica nanoparticles on dilational rheology of DPPC–palmitic acid Langmuir monolayers

The effect of silica nanoparticles on the dynamic behavior of monolayers composed by 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and a mixture of DPPC with Palmitic acid (PA), has been investigated by comparing the dilational rheological response of these lipid layers, spread on water and on a silica nanoparticle dispersion. To this aim, the dilational viscoelasticity has been measured against the frequency of the surface area perturbation of the monolayer, according to the Oscillatory Barrier method in a Langmuir trough. These measurements were performed at different values of the surface pressure, corresponding to different degrees of compression of the monolayer. The results show that the incorporation of particles in the layer induces additional surface kinetic processes and, depending on the surface pressure, modifies both the quasi-equilibrium dilational elasticity and the high frequency limit of the viscoelastic modulus. Another important effect concerns the linearity of the dilational rheological response which is appreciably worsened by the presence of nanoparticles. With DPPC being the major component of pulmonary surfactant and PA used as a component in synthetic substitutes of it, the results here obtained are relevant in the framework of wider studies on the effect of nanoparticles on the pulmonary surfactant interfacial properties.

An overview of current issues in the uptake of atmospheric trace gases by aerosols and clouds

Abstract. A workshop was held in the framework of the ACCENT (Atmospheric Composition Change – a European Network) Joint Research Programme on "Aerosols" and the Programme on "Access to Laboratory Data". The aim of the workshop was to hold "Gordon Conference" type discussion covering accommodation and reactive uptake of water vapour and trace pollutant gases on condensed phase atmospheric materials. The scope was to review and define the current state of knowledge of accommodation coefficients for water vapour on water droplet and ice surfaces, and uptake of trace gas species on a variety of different surfaces characteristic of the atmospheric condensed phase particulate matter and cloud droplets. Twenty-six scientists participated in this meeting through presentations, discussions and the development of a consensus review. In this review we present an analysis of the state of knowledge on the thermal and mass accommodation coefficient for water vapour on aqueous droplets and ice and a survey of current state-of the-art of reactive uptake of trace gases on a range of liquid and solid atmospheric droplets and particles. The review recommends consistent definitions of the various parameters that are needed for quantitative representation of the range of gas/condensed surface kinetic processes important for the atmosphere and identifies topics that require additional research.

Cubic boron nitride based metastable coatings and nanocomposites

Various PVD and plasma-assisted CVD methods presently used for the deposition of cubic boron nitride (c-BN) thin films demand adequate conditions relating to ion bombardment of growing films, growth temperature, film stoichiometry, etc. The deposition conditions, often appearing rather apparatus-dependent, can be well categorized according to the fundamental parameters of bombarding ions as well as condensing neutral particles, including their energy and flux ratio, and a few of others like ion mass and incident angle. According to these parameters, various surface kinetic processes and their consequences are discussed particularly in connection with the resulting film phases and stress. Typical c-BN films are known for their extremely high compressive stress and poor adhesion as a result of intensive ion bombardment during deposition. Individual measures attempting to relieve this detrimental stress are briefly summarized. The present paper focuses on magnetron-sputtered, c-BN-based metastable films and nanocomposite films with considerably reduced internal stress in comparison to the usual “pure” c-BN films. Two examples will be shown, namely c-BN/a-C nanocomposite and c-BN:O metastable films, including their deposition details, structure and composition characterization, and mechanical properties. Also illustrated is a growth scheme tailored for the deposition of thick, adhered, cubic-phase dominated, superhard c-BN:O films above 2µm on silicon substrates.

Low pressure chemical vapor deposition of niobium coating on silicon carbide

Nb coatings were prepared on a SiC substrate by low pressure chemical vapor deposition using NbCl 5. Thermodynamic calculations were performed to study the effect of temperature and partial pressure of NbCl 5 on the final products. The as-deposited coatings were characterized by scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy. The Nb coatings are oriented and grow in the preferred (2 0 0) plane and (2 1 1) plane, at 1173 K and 1223–1423 K, respectively. At 1123–1273 K, the deposition is controlled by the surface kinetic processes. The activation energy is found to be 133 kJ/mol. At 1273–1373 K, the deposition is controlled by the mass transport processes. The activation energy is found to be 46 kJ/mol. The growth mechanism of the chemical vapor deposited Nb is also discussed based on the morphologies and the deposition rates.

Fractal crystal growth of poly(ethylene oxide) crystals from its amorphous monolayers

The fractal crystal growth process of the PEO monolayer with a molecular weight (M¯w≈2.0×106g/mol) and a distribution (M¯w/M¯n=4.24) has been followed on the substrate of the silicon wafer using AFM equipped with a hot stage. A depletion zone between the ramified crystals and the viscous amorphous layer was found in the AFM height images. The formation of the depletion zone shows that the molecules have to “break up” with the amorphous layer and then diffuse through the depletion zone to join the crystals. The diffusion process further means the diffusion-controlled mechanism resulting in the fractal crystal pattern with a fractal dimension Df≈1.63. The linear feature of the crystal pattern radius growth with time means that the surface kinetic process plays a key role in the crystal growth.

Making waves: Kinetic processes controlling surface evolution during low energy ion sputtering

When collimated beams of low energy ions are used to bombard materials, the surface often develops a periodic pattern or “ripple” structure. Different types of patterns are observed to develop under different conditions, with characteristic features that depend on the substrate material, the ion beam parameters, and the processing conditions. Because the patterns develop spontaneously, without applying any external mask or template, their formation is the expression of a dynamic balance among fundamental surface kinetic processes, e.g., erosion of material from the surface, ion-induced defect creation, and defect-mediated evolution of the surface morphology. In recent years, a comprehensive picture of the different kinetic mechanisms that control the different types of patterns that form has begun to emerge. In this article, we provide a review of different mechanisms that have been proposed and how they fit together in terms of the kinetic regimes in which they dominate. These are grouped into regions of behavior dominated by the directionality of the ion beam, the crystallinity of the surface, the barriers to surface roughening, and nonlinear effects. In sections devoted to each type of behavior, we relate experimental observations of patterning in these regimes to predictions of continuum models and to computer simulations. A comparison between theory and experiment is used to highlight strengths and weaknesses in our understanding. We also discuss the patterning behavior that falls outside the scope of the current understanding and opportunities for advancement.

Nitrogen dissociation in low-pressure microwave plasmas

This work reviews a number of important aspects of the kinetic processes occurring in microwave discharge plasmas in nitrogen containing mixtures. The fundamental problems which are addressed include: (1) the determination of the non-equilibrium electron energy distribution function and its coupling to the vibrational kinetics; (2) the processes determining the vibrational distribution function in N2, N2-H2, and N2-Ar plasmas; and (3) the influence of surface kinetic processes on the whole discharge physics. The mechanisms of dissociation and ionization in N2, N2-Ar and N2-H2 are discussed in detail. The important role of plasma-wall interactions is stressed. It is shown that in N2-Ar mixtures there is an increase in the dissociation degree of N2 molecules at high Ar fractional concentrations, which can be ascribed to the contribution of fast Ar++ N2→ N+2+ Ar exchanges followed by N+2 dissociative recombination. It is further demonstrated that surface electron-ion recombination processes involving NH+2and N+2 ions are the most important sources of N(4S) gas phase atoms in N2-H2 mixtures. As the amount of H2 in the discharge increases, the channel associated with HN+2 ions becomes dominant. At nearly constant electron density there is a smooth decrease in the dissociation degree of hydrogen in N2-H2 when the H2 percentage increases up to 50%, which is due both to electron impact dissociation and H2 dissociation upon quenching of nitrogen N2(A3∑+u) and N2(a' 1∑−u) metastables.

Phase separation and formation of the self-organised layered nanostructure in C/Cr coatings in conditions of high ion irradiation

The paper discusses the effect of ion irradiation on a new type of nanoscale multilayer structure in C/Cr PVD coatings formed by a self-organisation mechanism. C/Cr coatings were deposited by the combined steered cathodic arc/unbalanced magnetron sputtering technique, at wide range of bias voltages, U b from − 65 to − 550 V. Plasma diagnostics carried out by electrostatic probe measurements revealed that C/Cr films grow under conditions of intensive ion bombardment with ion-to-neutral ratio exceeding J i/ J n = 6. Under these conditions the high diffusion mobility and the reactivity of the C leads to distinct changes in the coatings microstructure and phase composition. Raman spectroscopy and XPS (X-ray photoelectron spectrometer) analysis of the chemical bonding in the films showed that the phase composition of the films gradually transforms from more graphite like (sp 2 C–C bonded) to more Me-carbon (Cr–C bonded), where the content of the carbide phase increases with increase of the bias voltage to U b = − 350 V and higher. In parallel HRTEM (high-resolution transmission electron microscopy) employing HAADF (high-angle annular dark field) imaging revealed that the microstructure evolved from columnar with carbon accumulated at the column boundaries ( U b = − 65 V, − 95 V) to a structure dominated by onion like C–Cr clusters ( U b = − 120 V), which than converts to a distinct nanoscale layered structure ( U b = − 350 V, − 450 V), finally transforming to a uniform fine grain structure at U b = − 550 V. The new nanoscale layered structure forms via ion irradiation induced self-organisation mechanism. It is characterized by an abnormally large values for the bi-layer thickness of 20 nm and 25 nm, which are not related to substrate rotation, for films grown at U b = − 350 V and U b = − 450 V, respectively. ADF (annular dark field) STEM (scanning TEM) imaging and quantitative EELS (electron-energy loss spectroscopy) analysis showed that the nanoscale multilayer structure comprises of alternating layers of Me-carbide phase (48%C, 52%Cr) and almost pure C (91.34%C), where the bias voltage defines the bi-layer thickness. A coating growth model is proposed accounting for the irradiation-induced ion mixing, re-sputtering, condensation surface temperature effects, nucleation and kinetic segregation process, as well as the diffusivity of the coating elements to explain the phase separation and formation of the self-organised layered nanostructure observed in C/Cr coatings.