Coatings based on CoCrMo cobalt alloy have been designed to increase corrosion resistance of AISI 316L austenitic steel in body fluids. The CoCrMo-C coatings, with different carbon content (from 0 to 65 at.%), were synthesised by reactive magnetron sputtering of the medical CoCrMo (ISO 5832-12) alloy in the argon -acetylene atmosphere. Evolution of their structure, crystalline phase and chemical composition with increasing carbon fraction were investigated by X-ray diffractometry and X-ray photoelectron spectroscopy. Evaluation of corrosion resistance of CoCrMo-C films on 316L steel substrates was performed in Hanks Balanced Salt Solution (HBSS) by means of electrochemical impedance spectroscopy and potentiodynamic polarisation tests. The studies have revealed high chemical inertness of all coatings. Passive/blocking layers formed on their surfaces exhibit a capacitive character, while their resistivity is nearly two orders of magnitude higher compared to the corresponding values obtained for the CoCrMo and 316L alloys tested under similar conditions. The CoCrMo-C coatings provide pitting corrosion protection for 316L austenitic steel. This is expected to extend the residence time of stainless steel in the tissue environment. The 316L/CoCrMo-C systems were also subjected to tribocorrosion tests in HBSS at three electrochemical potentials, i.e. at open circuit, cathodic, and anodic potential. A model was developed to relate the electrical values recorded during tribocorrosion experiments with the phenomena that characterize the coating wear process. It was found that the friction coefficient systematically decreased from 0.7 to 0.1 with increasing the carbon content under all potentials applied. The wear rate observed for majority of the coatings was lower than that for CoCrMo and 316L alloys. For the samples with the highest carbon content, the wear rate under oxidative conditions became even lower than for the cathodic potential.

The operation of graphite targets with an increased temperature (HT - hot target) is studied for the case of gas injection magnetron sputtering (GIMS) of: 1) diamond-like carbon (DLC), and 2) carbon-silicon carbide (C-SiC) films. A purposely-thinned graphite target with a reduced thermal conductivity is applied for DLC deposition, extending its high temperature sputtering range up to 1636 degrees C. For the purpose of C-SiC synthesis four sockets with a silicon carbide powder are designed within graphite target. In this approach, the C-SiC target surface can be heated up to 1443 degrees C due to a greater energy input from impulse plasma, in the range 322-932 J. The HT sputtering is energy-controlled by a pulsed injection of a neon-helium gas mixture. High-energy Ne+ and He+ ions extend the length of pulsed GIMS discharge due to the self-sputtering effect observed during the deposition of DLC and C-SiC films. These conditions result in an almost 5-fold increase in the film growth rate (up to 185 nm/min) with respect to the operation with a cold target, which is due to the assisting vapour sublimation from custom-designed graphite-based targets. The temperature boosted HT GIMS discharge, proves to be an efficient tool for reaching relatively high (similar to 35 %) sp(3)-hybridized C content in both carbon-based materials. It also allows for tailoring the energy bandgap of DLC-based optical structure, in the range from 1.7 to 2.75 eV, due to the formation of the (C-C) and (C-O) bonds. Higher content of silicon oxide (SiO2-x) and silicon carbide (SiC) phases (15 - 23 %) in the case of C-SiC films results in hardness increase from 21.8 to 30.1 GPa.

We arc deposit Cr-rich Cr-N coatings and show that these coatings are a promising alternative to electrodeposited hard chrome. We find that the substrate bias is of importance for controlling the N content in the grown coatings as it determines the degree of preferential resputtering of N. The substrate bias also affects the substrate temperature and film growth rate. Higher bias results in higher temperatures due to higher energy transfer to the substrate, while the growth rate decreases due to an increased re-sputtering. The N content affects the morphology, microstructure, hardness, and resistivity of the coatings. The hardness increases from 10 GPa with 0.5 at. % N to 17 GPa with 7.5 at. % N, after which no further increase in hardness is seen. At the same time, the grain structure changes from columnar to more featureless and the resistivity rises from 15 to 45 mu omega cm.

Correct binding energy (BE) spectra referencing of insulating samples remains the major challenge in modern XPS analyses. Ar 2p signal of implanted Ar is sometimes used for this purpose. The method relies upon the assumption that chemically inert species such as noble gas atoms would be ideally suited as other factors affecting core level peak positions (such as chemical bonding) can be excluded. Here, we present a systematic study on the Ar 2p referencing method applied to a wide range of thin film sample materials of metals, nitrides, carbides, and borides. All specimens exhibit a well-defined Fermi edge, which serves as an independent internal reference for Ar 2p spectra of in-situ implanted Ar. Ar 2p3/2 binding energy is shown to vary by as much as 5.1 eV between samples. This is more than typical chemical shifts of interest, which obviously disqualifies Ar 2p referencing. The BE of the Ar 2p peaks shows a strong correlation to the number of valence electrons available for screening, implying that the polarization energy has a major role for the observed large spread of Ar 2p3/2 BE values. In several cases of single-phase films, an additional Ar 2p doublet is observed with the Ar 2p3/2 BE referenced to the vacuum level higher than the gas phase value of 248.6 eV, which is tentatively assigned to the formation of Ar-N and Ar-C complexes stabilized by Van der Waals forces. Ar implantation into two-phase samples, exemplified here by phase-segregated NiCrC/a-C:H and nanocomposite c-TiN/SiNx thin films, leads to complex Ar 2p spectra, which further demonstrates unreliability of the referencing method. The firm conclusion of the study is that the Ar 2p3/2 peak from implanted Ar is not a remedy for the charge referencing problem.

Titanium tungsten carbide (TiWC) coatings are deposited by a combined high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) technique. No external heating is applied during deposition phase, instead, the thermally driven adatom mobility is substituted by heavy ion irradiation. DCMS sources equipped with titanium carbide targets provide constant neutral fluxes to establish the predominant coating structures, whereas tungsten carbide target in HiPIMS mode serves as the source of heavy metal-ions. Substrate bias of −60 V is synchronized to W+ ion-rich time domains of HiPIMS pulses to minimize the contribution from working gas ions. The influence of W+ ion flux intensity, controlled by varying peak target current density (JT), on film properties is investigated. X-ray photoelectron spectroscopy reveals the presence of over stoichiometric carbon forming an amorphous phase, the amount of which can be fine-tuned by varying JT. Changes in film composition as a function of JT are explained based on the in-situ ion mass spectroscopy analyses. Dense TiWC coatings by hybrid process exhibit hardness higher than 30 GPa, which are comparable to TiWC films deposited by DCMS with dc substrate bias and external heating. The relative energy consumption in the hybrid process is reduced by 77 % as compared to high-temperature DCMS processing.

Hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) with substrate bias synchronized to the high mass metal-ion fluxes was previously proposed as a solution to reduce energy consumption during physical vapor deposition processing and enable coatings on temperature-sensitive substrates. In this approach, no substrate heating is used (substrate temperature is lower than 150 C-o) and the thermally activated adatom mobility, necessary to grow dense films, is substituted by overlapping collision cascades induced by heavy ion bombardment and consisting predominantly of low-energy recoils. Here, we present direct evidence for the crucial role of W+ ion irradiation in the densification of Ti0.31Al0.60W0.09N films grown by the hybrid W-HiPIMS/TiAl-DCMS co-sputtering. The peak target current density J(max) on the W target is varied from 0.06 to 0.78 A/cm(2) resulting in more than fivefold increase in the number of W+ ions per deposited metal atom, eta = W+/(W + Al + Ti) determined by time-resolved ion mass spectrometry analyses performed at the substrate plane under conditions identical to those during film growth. The DCMS is adjusted appropriately to maintain the W content in the films constant at Ti0.31Al0.60W0.09N. The degree of porosity, assessed qualitatively from cross-sectional SEM images and quantitatively from oxygen concentration profiles as well as nanoindentation hardness, is a strong function of eta ( J m a x ). Layers grown with low eta values are porous and soft, while those deposited under conditions of high eta are dense and hard. Nanoindentation hardness of Ti0.31Al0.60W0.09N films with the highest density is & SIM;33 GPa, which is very similar to values reported for layers deposited at much higher temperatures (420-500 C-o) by conventional metal-ion-based techniques. These results prove that the hybrid HiPIMS/DCMS co-sputtering with bias pulses synchronized to high mass metal ion irradiation can be successfully used to replace conventional solutions. The large energy losses associated with heating of the entire vacuum chamber are avoided, by focusing the energy input to where it is in fact needed, i.e., the workpiece to be coated.

Traditional age hardening mechanisms in refractory ceramics consist of precipitation of fine particles. These processes are vital for widespread wear-resistant coating applications. Here, we report novel Guinier-Preston zone hardening, previously only known to operate in soft light-metal alloys, taking place in refractory ceramics like multicomponent nitrides. The added superhardening, discovered in thin films of Ti-Al-W-N upon high temperature annealing, comes from the formation of atomic-plane-thick W disks populating {111} planes of the cubic matrix, as observed by atomically resolved high resolution scanning transmission electron microscopy and corroborated by ab initio calculations and molecular dynamics simulations. Guinier-Preston zone hardening concurrent with spinodal decomposition is projected to exist in a range of other ceramic solid solutions and thus provides a new approach for the development of advanced materials with outstanding mechanical properties and higher operational temperature range for the future demanding applications.

On-site electrosynthesis of hydrogen peroxide (H2O2) is a promising alternative technology to the conversional centralized anthraquinone oxidation process. Here, we report a platinum group metal (PGM)-free H2O2 electrogenerator with mesoporous Cr2O3 and NiCo2O4 used as electrocatalysts for oxygen reduction and evolution reactions (ORR and OER), respectively. The catalysts were synthesized via a hydrothermal synthesis route and had pore sizes of 3 and 7 nm and specific surface areas of 112 and 62 m(2) g(-1), respectively. Mesoporous Cr2O3 was evaluated in a half cell with 0.1 M KOH for electrocatalytic oxygen reduction, which shows 2.2 transferred electrons per oxygen and an in situ H2O2 yield of 70%. This enables the electrosynthesis of hydrogen peroxide in alkaline medium using Cr2O3 as a 2e-ORR-H2O2 electrocatalyst, with oxygen evolution as an auxiliary reaction on NiCo2O4. The effect of electrolyte flow on the H2O2 electrogenerator was investigated. It is observed that one-way feeding of the catholyte suppresses deterioration of the electrocatalyst and allows a faradic conversion up to similar to 90% with a production rate of similar to 0.36 [g (h<middle dot>g(cat))(-1)], operating within the cell voltage of 1.2 V. This work demonstrates both a viable method for electrosynthesis of H2O2 production using PGM-free electrocatalysts and the possibility to obtain a high faradic efficiency by mitigating the effect from catalyst degradation.

A common design of sputtering systems is to integrate many magnetron sources in a tilted closed-field configuration, which can drastically affect the magnetic field in the chamber and thus plasma characteristics. To study this effect explicitly, multicomponent TiZrNbTaN coatings were deposited at room temperature using direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS) with different substrate biases. The coatings were characterized by x-ray diffraction, scanning electron microscopy, nano-indentation, and energy dispersive x-ray spectroscopy. Magnetic field simulations revealed ten times higher magnetic field strengths at the substrate in single-magnetron configuration when compared to the closed-field. As a result, the substrate ion current increased similar to 3 and 1.8 times for DCMS and HiPIMS, respectively. The film microstructure changed with the discharge type, in that DCMS coatings showed large sized columnar structures and HiPIMS coatings show globular nanosized structures with (111) orientation with a closed-field design. Coatings deposited from a single source showed dense columnar structures irrespective of the discharge type and developed (200) orientation only with HiPIMS. Coatings deposited with closed-field design by DCMS had low stress (0.8 to -1 GPa) and hardness in the range from 13 to 18 GPa. Use of HiPIMS resulted in higher stress (-3.6 to -4.3 GPa) and hardness (26-29 GPa). For coatings deposited with single source by DCMS, the stress (-0.15 to -3.7 GPa) and hardness were higher (18-26 GPa) than for coatings grown in the closed-field design. With HiPIMS and single source, the stress was in the range of -2.3 to -4.2 GPa with a similar to 6% drop in the hardness (24-27 GPa).

A combined high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) technique is used to deposit Ti0.6Al0.32Si0.08N films with 1-fold substrate table rotation. Layers are grown at two different substrate-target separations, two different rotational speeds, and with different values of substrate bias. The aim is to study the role of (1) overlap between ion and neutral fluxes generated from HiPIMS and DCMS sources, respectively, and (2) the subplantation range of low-mass ions. Results from X-ray diffractometry highlight the necessity of flux intermixing in the formation of the metastable B1-structured TiAlSiN solid solutions. All films grown at short target-to-substrate distance contain the hexagonal AlN phase, as there is essentially no overlap between HiPIMS and DCMS fluxes, thus the Al+ and Si+ subplantation is very limited. Under conditions of high flux intermixing corresponding to larger target-to-substrate distance, no w-AlN forms irrespective of rotational speed (1 or 3 rpm) and bias amplitude (120 or 480 V), indicating that the role of Al+/Si+ and Ti flux overlap is crucial for the phase formation during film growth by HiPIMS/DCMS with substrate rotation. This conclusion is further supported by the fact that the reduction of the bilayer thickness with increasing the target-to-substrate distance (hence increasing flux overlap) is larger for films grown with higher amplitude of the substrate bias, indicative of more efficient Al+/Si+ subplantation into the c-TiN phase. Single-phase films with the hardness close to that of layers grown with stationary substrate table can be achieved, however, at the expense of higher compressive stress.

Decreasing the growth temperature to lower energy consumption and enable deposition on temperature-sensitive substrates during thin film growth by magnetron sputtering is crucial for sustainable develop-ment. High-mass metal ion irradiation of the growing film surface with ion energy controlled by metal-ion-synchronized biasing, allows to replace conventionally-used resistive heating, as was recently demonstrated in experiments involving a hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) setup and stationary substrates. Here, we report the extension of the method to indus-trial scale conditions. As a model-case towards understanding the role of one-fold substrate rotation on Ti0.50Al0.50N film growth employing W irradiation, we investigate the effect of two parameters: W ion energy (controlled in the range 45 <= EW <= 630 eV by the amplitude of synchronized substrate bias voltage) and W ion dose per deposited metal atom (determined by the target power). We show that the efficient densification of coatings grown without external heating can be achieved by minimizing the thickness of DCMS-deposited Ti0.50Al0.50N layer that is exposed to an W ion flux, or by increasing EW, at a given Ti0.50Al0.50N thickness.(c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Synthesis of high-entropy sublattice nitride (HESN) coatings by magnetron sputtering is typically done using custom-made alloyed targets with specific elemental compositions. This approach is expensive, requires long delivery times, and offers very limited flexibility to adjust the film composition. Here, we demonstrate a new method to grow HESN films, which relies on elemental targets arranged in the multicathode configuration with substrates rotating during deposition. TiVNbMoWN films are grown at a temperature of similar to 520(degrees)C using Ti, V, Nb, and Mo targets operating in the direct current magnetron sputtering mode, while the W target, operated by high power impulse magnetron sputtering (HiPIMS), provides a source of heavy ions. The energy of the metal ions EW+ is controlled in the range from 80 to 620 eV by varying the amplitude of the substrate bias pulses V-s, synchronized with the metal-ion-rich phase of HiPIMS pulses. We demonstrate that W(+ )irradiation provides dynamic recoil mixing of the film-forming components in the near-surface atomic layers. For EW+ >= 320 eV the multilayer formation phenomena, inherent for this deposition geometry, are suppressed and, hence, compositionally uniform HESN films are obtained, as confirmed by the microstructural and elemental analysis.(c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(http://creativecommons.org/licenses/by/4.0/)

The optical contrast and minimum layer thickness of Ni/Ti broadband neutron multilayer supermirrors is usually hampered by an interface width, typically 0.7 nm, caused by nanocrystallites, interdiffusion, and/or intermixing. We explore the elimination of nanocrystallites in combination with interface smoothening by modulation of ion assistance during magnetron sputter deposition of 0.8 to 6.4 nm thick Ni and Ti layers. The amorphization is achieved through incorporation of natural B₄C where B and C preferably bond to Ti. A two-stage substrate bias was applied to each layer; -30 V for the initial 1 nm followed by -100 V for the remaining part, generating multilayer mirrors with interface widths of 0.40-0.45 nm. The results predict that high performance supermirrors with m-values as high as 10 are feasible by using ¹¹B isotope-enriched B₄C combined with temporal control of the ion assistance.

Metastable super-saturated Zr1_xAlxN alloys tend to phase separate into the equilibrium cubic (c) ZrN and wurtzite (w) AlN due to a deep miscibility gap. Transformation is shown here to follow distinctly different paths depending on if Zr1_xAlxN (x = 0.3 and 0.6) is sputter deposited as a single layer or multi-layered with TiN, and further varied by post-deposition annealing. Using in situ high-energy synchrotron wide-angle X-ray scattering and analytical transmission electron microscopy, surface segregation effects are compared to secondary phase transformations occurring in as-deposited layers during thermal annealing up to 1000 degrees C. For the primary phase transformation from the vapor phase, w-AlN nucleates and an AlN-ZrN labyrinthine structure evolves at elevated deposition temperature with semi-coherent interfaces over several nanometers, where the higher Al content narrows the structure in both single and multilayers. Transformation in thinner alloy layers is governed by epitaxial forces which stabilize single-phase c-Zr0.4Al0.6N, which enables c-Zr0.4Al0.6N/TiN superlattice growth at temperatures as low as 350 degrees C. Regardless of the decomposition route, the formation of c-AlN is impeded and w-AlN instantaneously forms during transformation. In contrast, isostructural decomposition into w-AlN and w-Zr (Al)N occurs in w-Zr0.4Al0.6N alloys during annealing.

Direct electrification of oxygen-associated reactionscontributesto large-scale electrical storage and the launch of the green hydrogeneconomy. The design of the involved catalysts can mitigate the electricalenergy losses and improve the control of the reaction products. Weevaluate the effect of the interface composition of electrocatalystson the efficiency and productivity of the oxygen reduction reaction(ORR) and oxygen evolution reaction (OER), both mechanistically andat device levels. The ORR and OER were benchmarked on mesoporous nickel-(II)oxide and nickel cobaltite (NiO and NiCo2O4,respectively) obtained by a facile template-free hydrothermal synthesis.Physicochemical characterization showed that both NiO and NiCo2O4 are mesoporous and have a cubic crystal structurewith abundant surface hydroxyl species. NiCo2O4 showed higher electrocatalytic activity in OER and selectivity towater as the terminal product of ORR. On the contrary, ORR over NiOyielded hydroxyl radicals as products of a Fenton-like reaction ofH(2)O(2). The product selectivity in ORR was usedto construct two electrolyzers for electrified purification of oxygenand generation of hydroxyl radicals.

Chromium-based nitrides are used in hard, resilient coatings and show promise for thermoelectric applications due to their combination of structural, thermal, and electronic properties. Here, we investigate the electronic structures and chemical bonding correlated to the thermoelectric properties of epitaxially grown chromium-based multicomponent nitride Cr(Mo,V)Nx thin films. The small amount of N vacancies causes Cr 3d and N 2p states to appear at the Fermi level and reduces the band gap in Cr0.51N0.49. Incorporating holes by alloying of V in N-deficient CrN results in an enhanced thermoelectric power factor with marginal change in the charge transfer of Cr to N compared with Cr0.51N0.49. Further alloying of Mo, isoelectronic to Cr, increases the density of states at the Fermi level due to hybridization of the (Cr, V) 3d and Mo 4d-N 2p states in Cr(Mo,V)Nx. This hybridization and N off-stoichiometry result in more metal-like electrical resistivity and reduction in Seebeck coefficient. The N deficiency in Cr(Mo,V)Nx also depicts a critical role in reduction of the charge transfer from metal to N site compared with Cr0.51N0.49 and Cr0.50V0.03N0.47. In this paper, we envisage ways for enhancing thermoelectric properties through electronic band engineering by alloying and competing effects of N vacancies.

X-ray photoelectron spectroscopy (XPS) spectra from solid samples are conventionally referenced to the spectrometer Fermi level (FL). While, in the case of metallic samples, alignment of the sample and the spectrometer FLs can be directly verified from the measured Fermi edge position, thus allowing to assess the surface electrical potential, this is not a workable option for insulators. When applied, it generates a large spread in reported binding energy values that often exceed involved chemical shifts. By depositing insulating amorphous alumina thin films on a variety of conducting substrates with different work functions, we show not only that FL referencing fails but also that the Al2O3 energy levels align instead to the vacuum level, as postulated in the early days of XPS. Based on these model experiments that can be repeated for all sorts of thin-film insulators, a solution to the binding energy reference problem is proposed for reliable assessment of chemical bonding.

The quest for lowering energy consumption during thin film growth by magnetron sputtering techniques becomes of particular importance in view of sustainable development goals. As large fraction of the process energy is consumed in substrate heating for the purpose of providing high adatom mobility necessary to grow dense films, the most straightforward strategy toward more environment-friendly processing is to find alternatives to thermally activated surface diffusion. One possibility is offered by high mass metal ion irradiation of the growing film surface, which has been recently shown to be very effective in densification of transition metal nitride layers grown with no external heating, such that Zone 2 microstructures of the structure-zone model are obtained in the substrate temperature T-s range otherwise typical for Zone 1 growth. The large mass difference between the incident ion and the atoms constituting the film results in effective creation of low energy recoils, which leads to film densification at low T-s. Due to their high mass, metal ions become incorporated at lattice sites beyond the near-surface region of intense recoil generation leading to further densification, while preventing the buildup of residual stress. The practical implementation of this technique discussed in this Perspective employs heavy metal targets operating in the high-power impulse magnetron sputtering (HiPIMS) mode to provide periodic metal-ion fluxes that are accelerated in the electric field of the substrate to irradiate layers deposited from direct current magnetron sputtering (DCMS) sources. A key feature of this hybrid HiPIMS/DCMS configuration is the substrate bias that is synchronized with heavy metal ion fluxes for selective control of their energy and momentum. As a consequence, the major fraction of process energy is used at sputtering sources and for film densification, rather than for heating of the entire vacuum vessel. Model material systems include TiN and metastable NaCl-structure Ti1-yAlyN films, which are well-known for challenges in stoichiometry and phase stability control, respectively, and are of high relevance for industrial applications. This Perspective provides a comprehensive overview of the novel film growth method. After presenting basic concepts, time-resolved measurements of ion fluxes at the substrate plane, essential for selective control of metal ion energy and momentum, are discussed. The role of metal ion mass, energy, momentum, and concentration is described in more detail. As some applications require substrate rotation for conformal coating, a section is devoted to the related complexity in the implementation of metal-ion-synchronized growth under industrial conditions.

X-ray photoelectron spectroscopy (XPS) is a popular analytical technique in materials science as it can assess the surface chemistry of a broad range of samples. This Primer concerns best practice in XPS analysis, aimed at both entry-level and advanced users, with a focus on thin film samples synthesized under vacuum conditions. The high surface to volume ratio of thin films means that factors such as substrate choice and air exposure time are important for the final result. Essential concepts are introduced, such as binding energy, photoelectric effect, spectral referencing and chemical shift, as well as practical aspects including surface sensitivity, probing depth, energy resolution, sample handling and sputter etching. Correct procedures for experimental planning, instrument set-up, sample preparation, data acquisition, results analysis and presentation are reviewed in connection with physical principles and common applications. Typical problems, including charging, spectral overlap, sputter damage and binding energy referencing, are discussed along with possible solutions or workarounds. Finally, a workflow is presented for arriving at high-quality results. X-ray photoelectron spectroscopy (XPS) can be used to investigate chemical bonding and elemental composition. This Primer discusses how XPS can be used to characterize thin films, including key considerations for sample preparation, experimental set-up and data analysis.

There is a growing concern within the surface science community that the massive increase in the number of XPS articles over the last few decades is accompanied by a decrease in work quality including in many cases meaningless chemical bond assignment. Should this trend continue, it would have disastrous consequences for scientific research. While there are many factors responsible for this situation, the lack of insight of physical principles combined with seeming ease of XPS operation and insufficient training are certainly the major ones. To counter that, we offer a comprehensive tutorial written in the form of a step-by-step guide starting from experimental planning, through sample selection and handling, instrument setup, data acquisition, spectra analysis, and results presentation. Six application examples highlight the broad range of research questions that can be answered by XPS. The topic selection and the discussion level are intended to be accessible for novices yet challenging possible preconceptions of experienced practitioners. The analyses of thin film samples are chosen for model cases as this is from where the bulk of XPS reports presently emanate and also where the authors key expertise lies. At the same time, the majority of discussed topics is applicable to surface science in general and is, thus, of relevance for the analyses of any type of sample and material class. The tutorial contains ca. 160 original spectra and over 290 references for further reading. Particular attention is paid to the correct workflow, development of good research practices, and solid knowledge of factors that impact the quality and reliability of the obtained information. What matters in the end is that the conclusions from the analysis can be trusted. Our aspiration is that after reading this tutorial each practitioner will be able to perform error-free data analysis and draw meaningful insights from the rich well of XPS. Published under an exclusive license by AIP Publishing.

Bifunctional electrocatalysts with both accelerated oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) enable high-power density electricity storage and decentralized extraction of pure oxygen from air for usage in health care. Herein, a hydrothermal synthesis employing the anionic surfactant sodium dodecyl sulfate as structure-directing agent is developed to fabricate a family of crystalline mesoporous metal oxides (meso-MO X , M = Cr, Fe, Co, Ni, Ce). The pore size and specific surface area depend on the metal used and they range from 3 to 6 nm and 60 to 200 m(2) g(-1), respectively. NiO and Co3O4 show a higher catalytic efficiency in alkaline media in comparison with the other oxides studied, and their activities are comparable with the values reported for platinum group metal (PGM)-based electrocatalysts. This stems from lower voltage losses and by the presence of specific hydroxide adsorbates on the surface. Both ORR and OER driven on Co3O4 show the unified rate-determining chemical step (|OO-|(center dot) (ads) + H2O <-> |OOH|(center dot) (ads) + OH-, where | X | ads are the species adsorbed on active sites). The bifunctional ORR/OER electrocatalysis obtained on mesoporous NiO is utilized for the first symmetrical PGM-free oxygen pump fed by air and water only.

The quest for lowering energy consumption during thin film growth, as by magnetron sputtering, becomes of particular importance in view of sustainable development goals. A recently proposed solution combining high power impulse and direct current magnetron sputtering (HiPIMS/DCMS) relies on the use of heavy metal-ion irradiation, instead of conventionally employed resistive heating, to provide sufficient adatom mobility, in order to obtain high-quality dense films. The major fraction of process energy is used at the sputtering sources rather than for heating the entire vacuum vessel. The present study aims to investigate the W+ densification effects as a function of increasing Al content in (Ti1-yAly)(1-x)WxN films covering the entire range up to the practical solubility limits (y similar to 0.67). Layers with high Al content are attractive to industrial applications as the high temperature oxidation resistance increases with increasing Al concentration. The challenge is, however, to avoid precipitation of the hexagonal wurtzite AIN phase, which is softer. We report here that (T1-yAly)(1-x)WxN layers with y= 0.66 and x= 0.05 grown by a combination ofW-HiPIMS and TiAI-DCMS with the substrate bias V-s synchronized to the W+-rich fluxes (to provide mobility in the absence of substrate heating) possess single-phase NaCl-structure, as confirmed by XRD and SAED patterns. The evidence provided by XTEM images and the residual oxygen content obtained from ERDA analyses reveals that the alloy films are dense without discernable porosity. The nanoindentation hardness is comparable to that of TiAlN films grown at 400-500 degrees C, while the residual stresses are very low. We established that the adatom mobility due to the heavy ion W+ irradiation (in place of resistive heating) enables the growth of high-quality coatings at substrate temperatures not exceeding 130 degrees C provided that the W+ momentum transfer per deposited metal atom is sufficiently high. The benefit of this novel film growth approach is not only the reduction of the process energy consumption by 83%, but also the possibility to coat temperature-sensitive substrates.

Tritantalum pentanitride (Ta₃N₅) semiconductor is a promising material for photoelectrolysis of water with high efficiency. Ta₃N₅ is a metastable phase in the complex system of TaN binary compounds. Growing stabilized single-crystal Ta₃N₅ films is correspondingly challenging. Here, we demonstrate the growth of a nearly single-crystal Ta₃N₅ film with epitaxial domains on c-plane sapphire substrate, Al₂O₃(0001), by magnetron sputter epitaxy. Introduction of a small amount ~2% of O₂ into the reactive sputtering gas mixed with N₂ and Ar facilitates the formation of a Ta₃N₅ phase in the film dominated by metallic TaN. In addition, we indicate that a single-phase polycrystalline Ta₃N₅ film can be obtained with the assistance of a Ta₂O₅ seed layer. With controlling thickness of the seed layer smaller than 10 nm and annealing at 1000 °C, a crystalline β phase Ta₂O₅ was formed, which promotes the domain epitaxial growth of Ta₃N₅ films on Al₂O₃(0001). The mechanism behind the stabilization of the orthorhombic Ta₃N₅ structure resides in its stacking with the ultrathin seed layer of orthorhombic β-Ta₂O₅, which is energetically beneficial and reduces the lattice mismatch with the substrate.

Deviation from equimolar composition in high-entropy multielement ceramics offers a possibility of fine-tuning the materials properties for targeted application. Here, we present a systematic experimental and theoretical study on the effects of alloying equimolar pentanary (TiHfNbVZr)N and hexanary (TiHfNbVZrTa)N high-entropy nitrides with Al. Although being predicted to be metastable by ab initio density-functional theory calculations, single-phase fcc NaCl-structured solid solution thin films with Al solubility limits as high as x similar to 0.51-0.61 in (TiHfNbVZr)(1-x)AlxN and x similar to 0.45-0.64 in (TiHfNbVZrTa)(1-x)AlxN are synthesised utilizing a hybrid deposition technique that offers dynamic mixing of film atoms from Al+ subplantation and non-equilibrium growth conditions leading to quenching of the desired film structure. In experimental studies supplemented with density-functional theory calculations, it is demonstrated that Al concentration in alloys with the multielement compositions of high-entropy nitride thin films determine hardness, yield strength, toughness, and ability to deform plastically up to fracture due to different deformation mechanisms arising from the electronic structure and phase compositions. (C) 2022 The Author(s). Published by Elsevier Ltd.

The type and degree of contamination on surfaces intended for X-ray photoelectron spectroscopy (XPS) studies is considered decisive for meaningful and reliable analysis as in many cases in-situ cleaning methods are not applicable or otherwise undesired. We report on the effects of sample storage environment on predominantly carbon-and oxygen-containing species accumulating on the surfaces of fourteen types of thin film samples spanning group IVB-VIB transition metals (TMs), TM nitrides, and TM diborides. All specimens were deposited by magnetron sputtering and stored for six months in different common sample storage environments such as openly on a shelf in the office or XPS lab, or within a polypropylene wafer carrier, polystyrene box, cellulose/polyester wipers or sealed polyethylene bag. Self-consistent modelling of C 1s, O 1s, B 1s, N 1s, and metal core level spectra allowed to identify the types and quantities of surface contaminants, metal oxidation states, and thicknesses of native oxides, as well as to address influence from storage ambient type and volume, direct sample contact to other surfaces, or material release from containers. The results reveal significant differences between the various storage types and, hence, provide guidance for all sorts of studies including even those that employ Ar+ ion etch prior to analyses, as also in such cases the amount and type of surface contaminants may impact the outcome.

Alternating TiB2-DCMS and Cr-HiPIMS layers are used to fabricate TiB2/Cr multilayer films with varying the Cr-interlayer thickness, 2 and 5 nm, and the substrate bias during growth of Cr interlayers from floating, to -60 V and -200 V. The effects of multilayer structure on mechanical properties, static oxidation, and tribological behavior of the TiB2/Cr multilayers are investigated. The results reveal that TiB2 nanocolumns renucleate at each Cr interface maintaining smooth film surface and film density. Interlaying with Cr with thicknesses of 2-5 nm improves the resistance to oxidation at 500-600 ?& nbsp;as compared to TiB2 monolayer. The increase of the thickness of the Cr interlayers from 2 to 5 nm decreases the hardness of the multilayer slightly but deteriorates the wear rate significantly. The friction coefficients at 500 ?& nbsp;are lower than those at RT due to boric acid liquid lubrication induced by surface oxidation. The TiB2/Cr multilayer films show higher wear resistance than TiB2 monolayer. The multilayer films with 2 nm-thick Cr deposited at -60 V have the lowest recorded wear rates. Irradiation with 200 eV Cr+ leads to interface mixing, resulting in the formation of B-deficient TiBx phase (x < 2) and higher wear rates compared to multilayers grown at -60 V.

We study microstructure, mechanical, and corrosion properties of Zr1-xCrxBy coatings deposited by hybrid high power impulse/DC magnetron co-sputtering (CrB2-HiPIMS/ZrB2-DCMS). Cr/(Zr + Cr) ratio, x, increases from 0.13 to 0.9, while B/(Zr + Cr) ratio, y, decreases from 2.92 to 1.81. As reference, ZrB2.18 and CrB1.81 layers are grown at 4000 W DCMS. ZrB2.18 and CrB1.81 columns are continual from near substrate toward the surface with open column boundaries. We find that the critical growth parameter to achieve dense films is the ratio of Cr+- dominated ion flux and the (Zr + B) neutral flux from the ZrB2 target. Thus, the alloys are categorized in two groups: films with x < 0.32 (low Cr+/(Zr + B) ratios) that have continuous columnar growth, rough surfaces, and open column boundaries, and films with x >= 0.32 (high Cr+/(Zr + B) ratios) that Cr+-dominated ion fluxes are sufficient to interrupt continuous columns, resulting in smooth surface and dense fine-grain microstructure. The pulsed metal-ion irradiation is more effective in film densification than continuous Ar+ bombardment. Dense Zr0.46Cr0.54B2.40 and Zr0.10Cr0.90B1.81 alloys are hard (> 30 GPa) and almost stress-free with relative nano indentation toughness of 1.3 MPa root m and 2.3 MPa root m, respectively, and remarkedly low corrosion rates (~& nbsp;1.0 x 10(-6) mA/cm(2) for Zr0.46Cr0.54B2.40 and~& nbsp; 2.1 x 10(-6) mA/cm(2) for Zr0.10Cr0.90B1.81).

Oxygen evolution reaction (OER) is critical for producing high purity hydrogen and oxygen via electrocatalytic water splitting. In this work, single crystalline, nanoporous nickel oxide (NiO) was prepared using a hydro thermal, soft-templated synthesis route followed by calcination at different temperatures. It is shown that the NiO crystals have a cubic lattice, and the pore size can be tuned from similar to 1 to similar to 70 nm by varying the calcination temperature, i.e. variation from micro to macroporosity. The NiOs catalytic performance as electrocatalysts was evaluated in OER, both thermodynamically and kinetically. Mesoporous NiO with calcination temperature of 400 degrees C had the lowest overpotential (335 mV) required @ 10 mA/cm(2) accompanied with the highest turnover frequency value and mass activity among of the obtained NiO electrocatalysts. The study shows that the electrocatalytic activity of nanoporous NiO outperforms that of commercial catalyst Ir/C (similar to 360 mV @ 10 mA/cm(2)). Microporous NiO possess the highest specific surface area and electrical double layer capacitance, while the nonporous NiO particles have the highest specific activity and BET activity of the catalysts. It is concluded that the minimization of voltage losses by the nanoscale enlargement of the electrocatalyst surface area shows the coherence between gas adsorption and electrocapacitive measurements. Conversely, the OER kinetics showed deterioration with surface area maximization due to the impediment of ionic transport inside the micropores. This work demonstrates the importance of morphology optimization to obtain an efficient OER electrocatalyst with low required overpotential and kinetic loss.

We systematically study the oxidation properties of sputter-deposited TiB2.5 coatings up to 700 °C. Oxide-scale thickness dox increases linearly with time ta for 300, 400, 500, and 700 °C, while an oxidation-protective behavior occurs with dox=250∙ta0.2 at 600 °C. Oxide-layer’s structure changes from amorphous to rutile/anatase-TiO2 at temperatures ≥ 500 °C. Abnormally low oxidation rate at 600 °C is attributed to a highly dense columnar TiO2-sublayer growing near oxide/film interface with a top-amorphous thin layer, suppressing oxygen diffusion. A model is proposed to explain the oxide-scale evolution at 600 °C. Decreasing heating rate to 1.0 °C/min plays a noticeable role in the TiB2.5 oxidation.

C 1s peak of adventitious carbon (AdC), often used for charge referencing XPS spectra, shows markedly large shifts from the "recommended" value of 284.8 eV that basically disqualifies its reliability. In some earlier papers we attributed this spreading effect to the vacuum level (VL) alignment at the AdC/sample interface, which makes the measured position of C 1s peak highly sensitive to the sample work function . Recently, it was suggested [M.C. Biesinger, Appl. Surf. Sci. 597 (2022) 153681] that it is instead the differential charging in the native oxide layers that sometimes accounts for C 1s shifts and that electrically isolating samples from the spectrometer would solve the problem. To evaluate this hypothesis, we performed a series of experiments with Au and Al foils electrically isolated from the spectrometer, while varying the surface potential in a relatively wide range by adjusting the charge neutralizer settings. Markedly, the C 1s peak positions recorded from Au and Al foils are distinctly different when referred to their Fermi levels, at respectively 284.80 +/- 0.05 eV and 286.31 +/- 0.06 eV, independent of the surface potential. This confirms the interpretation presented in our previous papers (experiments performed in a conventional way with samples connected to spectrometer), that the binding energy of C 1s peaks from Au and Al foils differs significantly due to the corresponding difference in their work function values, such that the sum is constant at similar to 289.6 eV, as imposed by the VL alignment. In addition, the energy separation between metal and oxide peaks in Al 2p spectra from Al foil is independent of the surface potential (controlled by the charge neutralizer settings), the photoelectron current (varied by adjusting x-ray power) and the Al oxide thickness (in the range from 0.7 to 4.7 nm). These observations disprove differential charging as the general cause of C 1s peak shifts at least for the case of Al foils with thinner oxide layers. As many thicker oxides are well-known to develop charging, a similar type of analysis can be performed on the case-tocase bases to determine the reasons for C 1s peak shifts.

Alternating TiB2-DCMS and Cr-HiPIMS layers are used to fabricate TiB2/Cr multilayer films with varying the Cr interlayer thickness, 2 and 5 nm, and the substrate bias during growth of Cr interlayers from floating, to -60 V and -200 V. The effects of multilayer structure on mechanical properties, static oxidation, and tribological behavior of the TiB2/Cr multilayers are investigated. The results reveal that TiB2 nanocolumns renucleate at each Cr interface maintaining smooth film surface and film density. Interlaying with Cr with thicknesses of 2-5 nm improves the resistance to oxidation at 500-600 degrees C as compared to TiB2 monolayer. The increase of the thickness of the Cr interlayers from 2 to 5 nm decreases the hardness of the multilayer slightly but deteriorates the wear rate significantly. The friction coefficients at 500 degrees C are lower than those at RT due to boric acid liquid lubrication induced by surface oxidation. The TiB2/Cr multilayer films show higher wear resistance than TiB2 monolayer. The multilayer films with 2 nm-thick Cr deposited at -60 V have the lowest recorded wear rates. Irradiation with 200 eV Cr+ leads to interface mixing, resulting in the formation of B-deficient TiBx phase (x < 2) and higher wear rates compared to multilayers grown at -60 V.

Multicomponent as well as high-entropy-based nitrides have received increasing interest in the field of materials science and engineering. The structural characteristics of these compounds result in a mix of covalent, metallic, and ionic bonds that give rise to a number of attractive properties including high hardness, electrical and thermal conductivities as well as chemical stability. These properties render these materials promising candidates for various industrial applications involving harsh operating conditions. Herein, the corrosion resistances of dc magnetron sputtered nitrogen-containing TiZrTaNby thin films with Nb content ranging from 8.0 to 24.5 at% have been investigated to provide insights regarding the corrosion resistances of multicomponent systems containing more than one passive element. The corrosion resistances and anodic behavior of the films were examined by electrochemical means in 0.1 M H2SO4 and 0.1 M HCl solutions. The results demonstrate that despite the significant differences in the concentration of one of the two main passive elements in the films i.e., Nb, the corrosion resistance did not differ significantly between the films. To provide insights into this phenomenon, the surface chemical state and composition of the prepared films were probed using X-ray photoelectron spectroscopy. It was shown that all samples exhibited Ta-rich surfaces after positive polarization up to 3.0 V vs. Ag/AgCl (3 M NaCl) as a result of the anodic dissolution of Zr and Ti. The thickness of the oxide layer formed upon different anodic polarization was studied using transmission electron microscopy, while complementary electrochemical impedance studies were performed. The extent of Nb dissolution from the surface of the films was, on the other hand, found to be small. These findings highlight the dominant role of Ta in the passivation of the films and demonstrate the minor effect of Nb concentration on the corrosion resistances of the films. However, it was demonstrated that the presence of Nb was still important for the corrosion resistance of the films above 1.4 V vs. Ag/AgCl (3 M NaCl), when replacing Nb with Cr, due to transpassive dissolution of Cr. These results facilitate the design of highly corrosion resistant multicomponent nitrides containing more than one passive element.(c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Cr-N based materials, including stoichiometric CrN and Cr:N with a wide range of nitrogen contents, are commonly used as hard and corrosion-resistant coatings. Cr-rich films in this materials system can retain the bcc structure of metallic Cr with few percent of dissolved nitrogen, which can be used for tailoring the mechanical, thermal, and electrical properties. Here, we investigated low nitrogen containing Cr thin films deposited by high ion assisted magnetron sputtering with a substrate temperature of 200 degrees C. With the gas flow ratio maintained at f(N2/Ar) = 0.02, the substrate bias and the target power allows for control of the film composition (0.03 < N/Cr < 0.34). The films comprise a mixture of bcc-Cr and hexagonal Cr2N1-delta phases. The mechanical properties studied by nanoindentation and Brillouin inelastic light scattering revealed a hardening effect due to the multiphase nanostructure. The mechanical properties of the Cr:N films depend on the residual stress, on the amount of h-Cr2N1-delta phase and on the nanostructuring nature of the coatings. A maximum hardness of 37 GPa was achieved for a dense film with a Youngs modulus of 340 GPa, a shear modulus of 118 GPa, and a relatively low thermal conductivity of 7 W/mK.

We recently showed that sputter-deposited Zr_1-xTa_xB_y thin films have hexagonal AlB₂-type columnar nanostructure in which column boundaries are B-rich for x < 0.2, while Ta-rich for x ≥ 0.2. As-deposited layers with x ≥ 0.2 exhibit higher hardness and, simultaneously, enhanced toughness. Here, we study the mechanical properties of ZrB_2.4, Zr_0.8Ta_0.2B_1.8, and Zr_0.7Ta_0.3B_1.5 films annealed in Ar atmosphere as a function of annealing temperature T_a up to 1200 °C. In-situ and ex-situ nanoindentation analyses reveal that all films undergo age hardening up to T_a = 800 °C, with the highest hardness achieved for Zr_0.8Ta_0.2B_1.8 (45.5±1.0 GPa). The age hardening, which occurs without any phase separation or decomposition, can be explained by point-defect recovery that enhances chemical bond density. Although hardness decreases at T_a > 800 °C due mainly to recrystallization, column coarsening, and planar defect annihilation, all layers show hardness values above 34 GPa over the entire T_a range.

There is a need for developing synthesis techniques that allow the growth of high-quality functional films at low substrate temperatures to minimize energy consumption and enable coating temperature-sensitive substrates. A typical shortcoming of conventional low-temperature growth strategies is insufficient atomic mobility, which leads to porous microstructures with impurity incorporation due to atmosphere exposure, and, in turn, poor mechanical properties. Here, we report the synthesis of dense Ti_0.67Hf_0.33B_1.7 thin films with a hardness of ∼41.0 GPa grown without external heating (substrate temperature below ∼100 °C) by hybrid high-power impulse and dc magnetron co-sputtering (HfB₂-HiPIMS/TiB₂-DCMS) in pure Ar on Al₂O₃(0001) substrates. A substrate bias potential of −300 V is synchronized to the target-ion-rich portion of each HiPIMS pulse. The limited atomic mobility inherent to such desired low-temperature deposition is compensated for by heavy-mass ion (Hf⁺) irradiation promoting the growth of dense Ti_0.67Hf_0.33B_1.7.

Transition-metal diboride thin films, which have high melting points, excellent hardness, and good chemical and thermal conductivity, severely suffer from rapid oxidation in air. Here, we explore the influence of varying B content and resulting nanostructure change on the oxidation properties of TiBx thin films, with x = 1.43, 2.20, and 2.70. Results show that all as-deposited layers have columnar structure. The column boundaries of asdeposited TiB2.20 and TiB2.20 films grown by direct current magnetron sputtering (DCMS) are B-rich, while the as-deposited TiB1.43 films grown by high-power impulse magnetron sputtering (HiPIMS) show no apparent grain boundary phases and contain Ti-rich planar defects. The oxidation rate of TiBL43 air-annealed at 400 degrees C up to 48 h is significantly lower than that of TiB2.20 and TiB2.20 films. The oxidation rate of TiB1.43, TiB2.20, and TiB2.20 films was measured at 2.9 +/- 1.5, 7.1 +/- 1.0, and 20.0 +/- 5.0 nm/h, respectively, with no spallation of even as thick oxide scales as 0.5 mu m in any of the films. The improved oxidation resistance can be explained by the absence of B-rich tissue phase at the column boundaries of understoichiometric TiBx films, a phase that interlaces the nanocolumnar TiB2 structures in the corresponding overstoichiometric films. An easy oxidation pathway is thus eliminated.

Ti1-x(AlySi1-y)xN coatings covering a wide compositional range, 0.38 < x < 0.76 and 0.68 ≤ y ≤ 1.00, are deposited to investigate the influence of Al+/Si+ ion irradiation on microstructural and mechanical properties. The samples are grown in Ar/N2 atmosphere by the hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) method with substrate bias synchronized to the Al+/Si+-rich portion of the HiPIMS pulses. Two Ti targets are operated in DCMS mode, while one AlSi target is operated in HiPIMS mode. Four different AlSi target compositions are used: Al1.0Si0.0, Al0.9Si0.1, Al0.8Si0.2, and Al0.6Si0.4. X-ray diffractometry reveals that films without Si (i.e., y = 1.0) have high Al solubility in NaCl-structure, c-TiAlN, up to x ≤ 0.67 no w-AlN is detected. Once Si (y < 1.0) is introduced the Al solubility limit decreases, but remains higher than other PVD techniques, along with grain refinement and the formation of a SiNz rich tissues phase, as shown by transmission electron microscopy. The nanoindentation hardness is high (~ 30 GPa) for all films that do not contain the w-AlN phase. All the coatings have compressive stresses lower than -3 GPa. Interestingly, a range of films with different compositions displayed both high hardness (~ 30 GPa) and low residual stress (σ < 0.5 GPa). Such an unique combination of properties highlights the benefits of using HiPIMS/DCMS configuration with metal-ion-synchronized substrate bias, which utilizes the Al+/Si+ supplantation effect and minimizes the Ar+ incorporation.

Refractory transition-metal (TM) diborides have high melting points, excellent hardness, and good  chemical  stability.  However, these properties are not sufficient for applications involving extreme  environments that require high mechanical strength as well as oxidation and corrosion resistance. Here, we study the effect of Cr addition on the properties of ZrB₂-rich Zr₁-_xCr_xB_y thin films grown by hybrid high-power impulse and dc magnetron co-sputtering (Cr-HiPIMS/ZrB₂-DCMS) with a 100-V Cr-metal-ion synchronized potential. Cr metal fraction, x = Cr/(Zr+Cr), is increased from 0.23 to 0.44 by decreasing the power P_zrb2 applied to the DCMS ZrB₂ target from 4000 to 2000 W, while the average power, pulse width, and frequency applied to the HiPIMS Cr target are maintained constant. In addition, y decreases from 2.18 to 1.11 as a function of P_zrb2, as a result of supplying Cr to the growing film and preferential B resputtering caused by the pulsed Cr-ion flux. ZrB_2.18, Zr_0.77Cr_0.23B_1.52, Zr_0.71Cr_0.29B_1.42, and Zr_0.68Cr_0.32B_1.38 2 films have hexagonal AlB₂ crystal structure with a columnar nanostructure, while Zr_0.64Cr_0.36B_1.30 and Zr_0.56Cr_0.44B_1.11 are  amorphous. All films show hardness above 30 GPa. Zr_0.56Cr_0.44B_1.11 alloys exhibit much better toughness, wear, oxidation, and corrosion resistance than ZrB_2.18. This combination of properties   makes Zr_0.56Cr_0.44B_1.11 ideal candidates for numerous strategic applications.

Direct growth of orthorhombic Ta3N5-type Ta-O-N compound thin films, specifically Ta3-xN5-yOy, on Si and sapphire substrates with various atomic fractions is realized by unbalanced magnetron sputtering. Low-degree fiber-textural Ta3-xN5-yOy films were grown through reactive sputtering of Ta in a gas mixture of N-2, Ar, and O-2 with keeping a partial pressure ratio of 3:2:0.1 in a total working pressure range of 5-30 mTorr. With increasing total pressure from 5 to 30 mTorr, the atomic fraction of O in the as-grown Ta3-xN5-yOy films was found to increase from 0.02 to 0.15 while that of N and Ta decrease from 0.66 to 0.54 and 0.33 to 0.31, respectively, leading to a decrease in b lattice constant up to around 1.3%. Metallic TaNx phases were formed without oxygen. For a working pressure of 40 mTorr, an amorphous, O-rich Ta-N-O compound film with a high O fraction of similar to 0.48, was formed, mixed with non-stoichiometric TaON and Ta2O5. By analyzing the plasma discharge, the increasing O incorporation is associated with oxide formation on top of the Ta target due to a higher reactivity of Ta with O than with N. The increase of O incorporation in the films also leads to a optical bandgap widening from similar to 2.22 to similar to 2.96 eV, which is in agreement with the compositional and structural changes from a crystalline Ta3-xN5-yOy to an amorphous O-rich Ta-O-N compound.

The Cantor alloy (CoCrFeMnNi) and its variants, in bulk as well as thin films, have been extensively studied. They are known to exhibit cubic crystal structures and thermodynamic stability regardless of their complex chemical composition. Therefore, they may find use as hard, wear-resistant, corrosion and oxidation-resistant coatings. The addition of light elements, such as nitrogen, is known to help improve these properties further through processes such as amorphization and nitride compound formation. Here, we investigate the ternary CrFeCo system to study the effects of nitrogen addition. (CrFeCo)N_y multicomponent thin films are grown on silicon substrates by DC magnetron sputtering. Changes in crystal structure, morphology, mechanical and electrical properties with gradual increases of nitrogen in the film are described and discussed. Increased addition of nitrogen from 14 at.% to 28 at.% in the film leads to a transformation from an fcc to a bcc crystal structure, affects both the mechanical and electrical properties. XPS analysis shows the tendency of nitrogen to bond with Cr over other metals. The films display hardness values between 7 and 11 GPa with resistivities values ranging between 28 and 165 μΩ cm.

(Ti-0.5, Mg-0.5)N thin films were synthesized by reactive dc magnetron sputtering from elemental targets onto c-cut sapphire substrates. Characterization by theta-2 theta X-ray diffraction and pole figure measurements shows a rock-salt cubic structure with (111)-oriented growth and a twin-domain structure. The films exhibit an electrical resistivity of 150 m omega center dot cm, as measured by four-point-probe, and a Seebeck coefficient of -25 mu V/K. It is shown that high temperature (similar to 800 degrees C) annealing in a nitrogen atmosphere leads to the formation of a cubic LiTiO2-type superstructure as seen by high-resolution scanning transmission electron microscopy. The corresponding phase formation is possibly influenced by oxygen contamination present in the as-deposited films resulting in a cubic superstructure. Density functional theory calculations utilizing the generalized gradient approximation (GGA) functionals show that the LiTiO2-type TiMgN2 structure has a 0.07 eV direct bandgap.

Thin films in the aluminosilicate (AlSiO) system containing up to 31 at. % Al and 23 at. % Si were prepared by reactive RF magnetron co-sputtering in order to investigate the dependence of film formation and optical properties on substrate temperature and Si and Al contents. The obtained films were amorphous with smooth microstructure. The growth rate at different substrate temperatures ranged from 1.2 to 3.3 nm/min and increase with increasing the Si target power. The roughness decreases and thickness increases with increasing Si content. The thickness of the films grown at a deposition temperature of 100 °C is found to be higher than the films deposited at 300 and 500 °C. The AlSiO-coated glasses have a higher transmission in the visible region than the uncoated glass. The spectroscopic ellipsometry analysis reveals that the refractive index value decreased with decreasing the Al content, having extinction coefficient values of zero in the measured spectral region and band gap values ≥ 3.4 eV. The obtained thin films have over 90% transmittance in the visible range and no systematic variation of transmittance was observed with substrate temperature. The results suggest that glass substrate coated with AlSiO thin films have improved optical properties.

Present study aimed to develop nanocoating of cucurbit[7]uril (CB[7]) on surfaces of silicon and epitaxial graphene using drop casting and spin coating techniques. Here, we report a systematic study for the influence of sonication, probe sonication, and centrifugation time on the dispersion of CB[7] in aqueous solutions for the preparation of high-quality CB[7] nanocoating. Spin speed, spin time, and spin acceleration have been optimised to attain uniform films with minimum rms. Atomic force microscopy is used to study morphology, rms, and height of CB[7] nanocoating under different parameters. The presence of CB[7] on the nanocoating and its binding nature was determined by Infrared absorption and X-ray photoelectron spectroscopy. The present method of CB[7] nanocoating preparation is easy, versatile, scalable, and does not need the addition of electrolyte additives. Prepared CB[7] films are high-quality, uniform, and could be used as a novel sensing platform to tether required functional groups.

Boron-containing materials exhibit a unique combination of ceramic and metallic properties that are sensitively dependent on their given chemical bonding and elemental compositions. However, determining the composition, let alone bonding, with sufficient accuracy is cumbersome with respect to boron, being a light element that bonds in various coordinations. Here, we report on the comprehensive compositional analysis of transition-metal diboride (TMBx) thin films (TM = Ti, Zr, and Hf) by energy-dispersive x-ray spectroscopy (EDX), x-ray photoelectron spectroscopy (XPS), time-of-flight elastic recoil detection analysis (ToF-ERDA), Rutherford backscattering spectrometry (RBS), and nuclear reaction analysis (NRA). The films are grown on Si and C substrates by dc magnetron sputtering from stoichiometric TMB2 targets and have hexagonal AlB2-type columnar structures. EDX considerably overestimates B/TM ratios, x, compared to the other techniques, particularly for ZrBx. The B concentrations obtained by XPS strongly depend on the energy of Ar+ ions used for removing surface oxides and contaminants prior to analyses and are more reliable for 0.5 keV Ar+. ToF-ERDA, RBS, and NRA yield consistent compositions in TiBx. They also prove TiBx and ZrBx films to be homogeneous with comparable B/TM ratios for each film. However, ToF-ERDA, employing a 36-MeV 127I8+ beam, exhibits challenges in depth resolution and quantification of HfBx due to plural and multiple scattering and associated energy loss straggling effects. Compared to ToF-ERDA, RBS (for the film grown on C substrates) and NRA provide more reliable B/Hf ratios. Overall, a combination of methods is recommended for accurately pinpointing the compositions of borides that contain heavy transition metals.

Chemical state analysis in X-ray photoelectron spectroscopy (XPS) relies on assigning well-defined binding energy values to core level electrons originating from atoms in particular bonding configurations. Here, we present direct evidence for the violation of this paradigm. It is shown that the C 1s peak due to C-C/C-H bonded atoms from adventitious carbon (AdC) layers accumulating on Al and Au foils splits into two distinctly different contributions, as a result of vacuum level alignment at the AdC/foil interface. The phenomenon is observed while simultaneously recording the spectrum from two metal foils in electric contact with each other. This finding exposes fundamental problems with the reliability of reported XPS data as C 1s peak of AdC is routinely used for binding energy scale referencing. The use of adventitious carbon in XPS should thus be discontinued as it leads to nonsense results. Consequently, ISO and ASTM charge referencing guides need to be rewritten.

Rocksalt-structure (B1) (V,Mo)N alloys are inherently hard and tough ceramics. However, the mechanical properties and thermal stability of (V,Mo)N solid solutions at temperatures greater than or similar to 700 degrees C of relevance for practical applications have not been previously investigated. In this work, we synthesize single-phase B1 polycrystalline V0.57Mo0.43N0.95 coatings to investigate the effects induced by temperature on the nanostructural evolution and hardness (H) of the material. Nanoindentation measurements show that the as-deposited film (H = 23 +/- 3 GPa) becomes approximate to 30% harder (up to 31 +/- 2 GPa) upon annealing at 730 C. Experimental characterization and analyses, based on dispersive X-ray spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM), reveal that the age-hardening effect originates from decomposition of the solid solution into coherent strained cubic VN-rich/MoN-rich domains. The experimental results are complemented by the composition/temperature (V,Mo)N phase diagram - constructed upon ab initio molecular dynamics free-energies - which indicates that the separation observed in the solid solutions is of spinodal nature. Films annealed at temperatures exceeding 850 degrees C undergo structural coarsening, with formation of hexagonal MoxNy and cubic VN phases, which cause a decrease in hardness to approximate to 22 GPa. Our present findings indicate that (V,Mo)N coatings may offer outstanding mechanical performances during operation at elevated temperatures.

In view of the increasing demand for achieving sustainable development, the quest for lowering energy consumption during thin film growth by magnetron sputtering becomes of particular importance. In addition, there is a demand for low-temperature growth of dense, hard coatings for protecting temperature-sensitive substrates. Here, we explore a method, in which thermally-driven adatom mobility, necessary to obtain high-quality fully-dense films, is replaced with that supplied by effective low-energy recoil creation resulting from high-mass metal ion irradiation of the growing film surface. This approach allows the growth of dense and hard films with no external heating at substrate temperatures T-s not exceeding 130 degrees C in a hybrid high-power impulse and de magnetron co-sputtering (HiPIMS/DCMS) setup involving a high mass (m &gt; 180 amu) HiPIMS target and metal- ion-synchronized bias pulses. We specifically investigate the effect of the metal ion mass on the extent of densification, phase content, nanostructure, and mechanical properties of metastable cubic Ti0.50Al0.50N based thin films, which present outstanding challenges for phase stability control. Ti0.50Al0.50N based thin films are irradiated by group VIB transition metal (TM) target ions generated by Me-HiPIMS discharge, in which Me = Cr (m(Cr)= 52.0 amu), Mo (m(Mo) = 96.0 amu), and W (m(W) = 183.8 amu). Three series of (Ti1-yAly)(1-x)MexN films are grown with x = Me/(Me+Al+Ti) varied intentionally by adjusting the DCMS powers, while y = Al/(Al+Ti) also varies as a result of Me+ ion irradiation. Results reveal a strong dependence of film properties on the mass of the HiPIMS-generated metal ions. All layers deposited with Cr+ irradiation exhibit porous nanostructure, high ox- ygen content, and poor mechanical properties. In contrast, (Ti1-yAly)(1-x)WxN films are fully-dense even with the lowest W concentration, x = 0.09, show no evidence of hexagonal AlN precipitation, and exhibit state-of the-art mechanical properties typical of Ti0.50Al0.50N grown at 500 degrees C. The process energy consumption is lowered by 64% with no negative impact on the coating quality. TRIM simulations provide an insight into the densification mechanisms.

Hybrid high power impulse/direct current magnetron sputtering (HiPIMS/DCMS) film growth technique with metal-ion-synchronized substrate bias allows for significant energy savings as compared to conventional PVD methods. For carefully selected type of metal ion irradiation, taking into account ion mass, ionization potential, and reactivity towards working gas, fully dense and hard films can be obtained with no intentional substrate heating. The thermally-driven adatom mobility, which is an essential densification mechanism in conventional film growth that takes place at elevated temperatures, is replaced with that supplied by effective low-energy recoil creation. In this contribution we explore effects of the high-mass W+ irradiation, which has proven to be the most efficient in densifying Ti0.50Al0.50N layers, serving here as a model system, grown with no substrate heating. We study the effects of two essential parameters: W+ energy EW+ and W concentration x, on film porosity, phase content, nanostructure, and mechanical properties. EW+ varies from similar to 90 to similar to 630 eV (controlled by substrate bias voltage amplitude V-s) and x from 0.02 to 0.12 (controlled by the HiPIMS pulse length), while the HiPIMS peak target current is kept constant. Results reveal that a strong coupling exists between the W+ incident energy and the minimum W concentration required to grow dense layers.

Ar+ sputter etching is often used prior to X-ray photoelectron spectroscopy (XPS) analyses with the intention to remove surface oxides and contaminants. Since the XPS probing depth is comparable to the thickness of the ionbeam modified layer the signal from the latter dominates the spectra. We check here the conditions for reliable XPS analysis by studying ion irradiation effects for single-phase Group IVB transition metal (IVB-TM) boride, carbide, nitride, and oxide thin film specimens. The extent of sputter damage, manifested by changes in the surface composition, binding energy shift, peak broadening, and the appearance of new spectral features, varies greatly between material systems: from subtle effects in the case of IVB-TM carbides to a complete change of spectral components for IVB-TM oxides. The determining factors are: (i) the nature of compounds that may form as a result of ion-induced mixing in the affected layer together with (ii) the final elemental composition after sputtering, and (iii) the thickness of the Ar+-affected layer with respect to the XPS probing depth. Our results reveal that the effects of Ar+ ion irradiation on XPS spectra cannot be a priori neglected and a great deal of scrutiny, if not restraint, is necessary during spectra interpretation.

We report on a comprehensive analysis of titanium boride thin films by x-ray photoelectron spectroscopy (XPS). Films were grown by both direct current magnetron sputtering and high- power impulse magnetron sputtering from a compound TiB2 target in Ar discharge. By varying the deposition parameters, the film composition could be tuned over the wide range 1:3 &B/Ti &3:0, as determined by elastic recoil detection analysis and Rutherford backscattering spectrometry. By comparing spectra over this wide range of compositions, we can draw original conclusions about how to interpret XPS spectra of TiBx. By careful spectra deconvolution, the signals from Ti-Ti and B-B bonds can be resolved from those corresponding to stoichiometric TiB2. The intensities of the off-stoichiometric signals can be directly related to the B/Ti ratio of the films. Furthermore, we demonstrate a way to obtain consistent and quantum-mechanically accurate peak deconvolution of the whole Ti 2p envelope, including the plasmons, for both oxidized and sputter-cleaned samples. Due to preferential sputtering of Ti over B, the film B/Ti ratio is best determined without sputter etching of the sample surface. This allows accurate compositional determination, assuming that extensive levels of oxygen are not present in the sample. Fully dense films can be accurately quantified for at least a year after deposition, while underdense samples do not give reliable data if the O/Ti ratio on the unsputtered surface is *3:5. Titanium suboxides detected after sputter etching is further indicative of oxygen penetrating the sample, and quantification by XPS should not be trusted.