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Bioactive ions (Mg, Sr, Zn) doped carbonated hydroxyapatite powders (dHAp) and pure carbonated hydroxyapatite (HAp) powders were prepared by wet chemical precipitation method. The bioactive ions were incorporated into the HAp matrix by co-precipitation from solution containing the appropriate amount of chloride salt of different ions. The morphology of pure HAp was mainly needle-like in nanometre size and the particles were disordered showing quasi-amorphous structure. The ion doping changed the morphology of particles, the dHAp particles had distorted spheroid shapes. Owing to the ion addition, the crystallinity of particles decreased. Particle aggregations can also be observed in both types of samples. HAp and dHAp loaded biopolymer polyvinylpyrrolidone (PVP) composite materials have also been developed by novel electrospinning technique. It has been shown that both the HAp and dHAp particles can be successfully incorporated into the PVP fibre web matrix and simultaneously the bioceramic powders were attached to the surface of polymer fibres. The surface of fibres was not fully covered with the particles. The ceramic powder addition to the polymer solution caused the polymer fibres to become more entangled and the diameters of fibres varied over a wider range compared to the base polymer fibres without bioceramic powder addition.

Utilizing solar radiation for driving chemical reactions has been of great interest in the last decade. Although Cu2O nanocrystals as a low-cost, abundant, and tailorable photocatalyst are promising candidates to provide a platform for solar-driven applications, their photophysical properties are affected by the limited charge carrier mobility. This paper focuses on the more efficient utilization of the UV light-excited charge carriers in cuprous oxide by preparing different heterostructures with gold. While keeping the size, shape as well as overall composition of the heterostructures identical, the realization of the gold component is varied: either nanograins are created at the surface of the Cu2O nanooctahedra or nanorods are embedded in their interior. The effect of the morphology and the semiconductor-metal contact on the optical and photocatalytic properties is investigated in-detail by spectroscopy, spectrofluorometry, imaging techniques, X-ray diffractometry, and photoelectron spectroscopy extended with optical simulations and single-particle spectroscopy measurements. In terms of particle stability and photocatalytic activity, gold-decorated Cu2O nanooctahedra show superior properties. The comprehensive comparison of the multicomponent nanoparticles underlines the importance of the nanoscale design (including composition, morphology, and surface chemistry), which utilizes the photoexcited carriers in the semiconductor without injecting hot electrons from the metal.

Herein, we compare the electrochemical and electrocatalytic properties of two selected, water-insoluble Fe(II) coordination complexes made with the non-symmetric, bidentate ligands, 2-(2′-pyridyl)benzimidazole (PBI) in [Fe(PBI)3](OTf)2 (1, OTf− = trifluoromethyl sulfonate anion) and 2-(2′-pyridyl)benzoxazole (PBO) in [Fe(PBO)2(OTf)2] (2) . Cyclic voltammetry in water/acetonitrile mixture indicates considerable activity for both compounds. However, only 1 acts as homogeneous catalyst. The complexes have been successfully immobilized on indium-tin-oxide (ITO) electrode surface. The hydrophobic ligands allowed for a simple dip-coating and drop-casting of 1 and 2 onto ITO. Both 1/ITO and 2/ITO showed increased activity in electrocatalytic O2 evolution in borate buffer at pH 8.3. According to scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), moreover, re-dissolution tests, the Fe remains in complex with PBI during electrolysis in the drop-casted, nano-porous films of 1/ITO. In contrast, the PBO complex in 2/ITO undergoes a rapid in situ decomposition yielding a mineralized form that is responsible for catalysis.

Nanostructured photoactive systems are promising for applications such as air and water purification, including self-cleaning coatings. In this study, mesoporous TiO2 sol-gel coatings with different pore structures were prepared and modified with silver by two methods: the “mixing” method by adding AgNO3 to the precursor sol, and the “impregnation” method by immersing the samples in AgNO3 solution (0.03 and 1 M) followed by heat treatment. Our aim was to investigate the effects that silver modification has on the functional properties (e.g., those that are important for self-cleaning coatings). Transmittance, band gap energy, refractive index, porosity and thickness values were determined from UV-Vis spectroscopy measurements. Silver content and structure of the silver modified samples were characterized by X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, High-resolution transmission electron microscopy and Energy Dispersive X-ray Spectrometry elemental mapping measurements. Wettability properties, including photoinduced wettability conversion behavior were investigated by water contact angle measurements. Photoactivity was studied under both UV and visible light with rhodamine 6G and methylene blue dye molecules, at the liquid–solid and air–solid interfaces modeling the operating conditions of self-cleaning coatings. Samples made with “impregnation” method showed better functional properties, in spite of their significantly lower silver content. The pore structure influenced the Ag content achieved by the “impregnation” method, and consequently affected their photoactivity.

Ca- and P-based bioactive glasses are excellent candidates for design and manufacture of biomaterials. Understanding the structure and physico-chemical–thermal behaviour of bioactive glasses is a fundamental step towards the design of a new generation of biocompatible materials. In this study, the structure of SiO2–CaO–Na2O glasses and its derivatives, obtained by substituting Na2O with P2O5 and prepared by melt–quench technique, was studied with neutron and electron diffraction techniques combined with thermal analysis, high-resolution electron microscopy and X-ray photoelectron spectroscopy. Neutron and electron diffraction data were analysed with reverse Monte Carlo simulation and pair distribution function analysis, respectively. Bioactivity of P2O5 substituted glasses was also investigated and proven in vitro using simulated body fluid. Based on the structural analysis, it was found that Si and P atoms are in well-defined tetrahedral units with a bond distance of 1.60 Å for both Si–O and P–O bonds, although P exhibits a higher average coordination number than Si. With increasing phosphate content, tendentious changes in the glass behaviour were observed. Linear increase in Tg, supported by the changes in the average coordination numbers of Si and P, indicates strengthening of network structure with increasing P content and formation of P–O–Ca atomic linkages, which lead to Ca–P-rich atomic environments in the silicate network. These Ca–P-rich environments trap volatile elements and thus decrease the total weight loss during heating at higher P concentrations. In the case of the highest investigated P2O5 content (5 mol%), nanoscale structural inhomogeneity and the formation of Ca–P-rich clusters were also revealed by electron diffraction and atomic resolution imaging. This type of Ca–(Na)–P clustering has a key role in the behaviour of phosphate-substituted silicate glasses under physiological conditions.

Micropatterning of living single cells and cell clusters over millimeter-centimeter scale areas is of high demand in the development of cell-based biosensors. Micropatterning methodologies require both a suitable biomimetic support and a printing technology. In this work, we present the micropatterning of living mammalian cells on carboxymethyl dextran (CMD) hydrogel layers using the FluidFM BOT technology. In contrast to the ultrathin (few nanometers thick in the dry state) CMD films generally used in label-free biosensor applications, we developed CMD layers with thicknesses of several tens of nanometers in order to provide support for the controlled adhesion of living cells. The fabrication method and detailed characterization of the CMD layers are also described. The antifouling ability of the CMD surfaces is demonstrated by in situ optical waveguide lightmode spectroscopy measurements using serum modeling proteins with different electrostatic properties and molecular weights. Cell micropatterning on the CMD surface was obtained by printing cell adhesion mediating cRGDfK peptide molecules (cyclo(Arg-Gly-Asp-d-Phe-Lys)) directly from aqueous solution using microchanneled cantilevers with subsequent incubation of the printed surfaces in the living cell culture. Uniquely, we present cell patterns with different geometries (spot, line, and grid arrays) covering both micrometer and millimeter-centimeter scale areas. The adhered patterns were analyzed by phase contrast microscopy and the adhesion process on the patterns was real-time monitored by digital holographic microscopy, enabling to quantify the survival and migration of cells on the printed cRGDfK arrays.

Interface induced diffusion had been identified in a thin film system damaged by electron bombardment. This new phenomenon was observed in Al2O3 (some nm thick)/Si substrate system, which was subjected to low energy (5 keV) electron bombardment producing defects in the Al2O3 layer. The defects produced partially relaxed. The rate of relaxation is, however, was different in the vicinity of the interface and in the "bulk" parts of the Al2O3 layer. This difference creates an oxygen concentration gradient and consequently oxygen diffusion, resulting in an altered layer which grows from the Al2O3/Si substrate interface. The relative rate of the diffusion and relaxation is strongly temperature dependent, resulting in various altered layer compositions, SiO2 (at room temperature), Al2O3 + AlOx + Si (at 500 °C), Al2O3 + Si (at 700 °C), as the temperature during irradiation varies. Utilizing this finding it is possible to produce area selective interface patterning.

Interface induced diffusion had been identified in thin film system damaged by electron bombardment. This new phenomenon was observed in Al2O3 (some nm thick) / Si substrate system, which was subjected to low energy (5 keV) electron bombardment producing defects in the Al2O3 layer. The defects produced partially relaxed. The rate of relaxation is, however, different in the surrounding of the interface and in the "bulk" parts of the Al2O3 layer. This difference generates an oxygen concentration gradient and consequently oxygen diffusion, resulting in an altered layer which grows from the Al2O3 / Si substrate interface. The relative rate of the diffusion and relaxation is strongly temperature dependent, resulting in various altered layer compositions, SiO2 (at room temperature), Al2O3 + AlOx+Si (at 500o C), Si(at 700o C), as the temperature during irradiation varies. Utilizing this finding it is possible to make area selective interface patterning.

Cross-sectional study of sound primary dental enamel revealed hardness zonation and, in parallel, significant change in the Mg content below the prismless layer. Mg content is known to play an important role in enamel apatite biomineralization, therefore, Mg ion exchange experiments were carried out on the outer surface of sound primary molars and on reference abiogenic Ca-phosphates using MgCl2 solution. Effects of Mg incorporation on crystal/particle size, ionic ratio and morphology were compared and the observed changes were explained by parallel diffusion and dissolution/reprecipitation processes. Based on depth profile analysis and high resolution electron microscopy of the Mg-exchanged dental enamel, a poorly ordered surface layer of approximately 10-15 nanometer thickness was identified. This thin layer is strongly enriched in Mg and has non-apatitic structure. Below the surface layer, the Mg content increased only moderately (up to ∼3 at%) and the apatite crystal structure of enamel was preserved. As a common effect of the Mg exchanged volume, primary dental enamel exhibited about 20% increase of nanohardness, which is intrepreted by strengthening of both the thin surface layer and the region below due to the decreased crystallite size and the effect of incorporated Mg, respectively.

Biofunctional coatings are key elements of biosensors regulating interactions between the sensing surface and analytes as well as matrix components of the sample. These coatings can improve sensing capabilities both by amplifying the target signal and attenuating interfering signals originating from surface fouling (non-specific binding). Considering the tested materials so far, hydrogel-based layers have been verified to be among the most effective layers in improving biochip performance. The polysaccharide dextran can be efficiently used to form hydrogel layers displaying extended three-dimensional structure on biosensor surfaces. Owing to their high water content and flexible structure, dextran coatings present advanced antifouling abilities, which can be exploited in classic bioanalytical measurements as well as in the development of cell-on-a-chip type biosensors. However, in spite of the numerous applications, the deep characterization of dextran layers has been missing from the literature. This phenomenon can be attributed to the challenging analysis of few nanometer-thick layers with high water content. The lack of available data is more pronounced regarding the layer behaviors under aqueous conditions. In this chapter we present various surface analytical methods (including biosensor-type techniques) suitable for the complex characterization of hydrogel coatings whose thickness ranges from few to several ten nanometers. As a case study, we focus on the analysis of carboxymethyl dextran (CMD) layers developed for waveguide-based label-free optical biosensor applications. Examination methodologies both under dry and aqueous conditions as well as testing of antifouling abilities are also presented.

The formation of TiC and Ti phases and their influence on their mechanical properties was studied in this work. Thin layers were deposited by DC magnetron sputtering at room temperature in ultrahigh vacuum from Ti and C targets. Cubic TiC phase (c-TiC) was formed from 58 to 86 at.% Ti content. First formation of hexagonal Ti (h-Ti) occurred from 86 at.% Ti content. The c-TiC disappears from 90 at.% Ti content. Films with 86 at.% Ti content the c-TiC structure can transform to h-Ti by sequential stacking faults. Dominance of c-TiC(111) texture with increasing Ti content was observed. The hardness of thin films agree with structural observations. The highest hardness value (∼26 GPa) showed the c-TiC thin film with 67 at% Ti content. The nanohardness values showed decreasing character with increasing Ti content over 70 at.%. The lowest values of nanohardness (∼10 GPa) was observed for thin films with only h-Ti phase.

CoCrFeMnNi multi-principal element alloy films were grown by direct current magnetron sputtering in a mixture of argon and air. The air fraction was varied from 4 to 50%, which resulted in a change of the phase state of the growing film. A 〈100〉 preferred orientation face centered cubic metal (doped with O and N) structure develops below 12% of air. Between 12 and 30% air, a two phase 〈100〉 preferred orientation face centered cubic metal + oxynitride (B1) structure forms. Above 30% of air a single phase B1 oxynitride structure is observed. Compared to nitrogen, oxygen is preferentially incorporated into the growing structures. The 〈100〉 preferential orientation is the result of selective nucleation (below 30% of air) or competing growth (above 30% of air) of the forming crystals. Detailed microscopic analysis shows a complex structure for both the metal and the oxynitride phase in the films deposited at low and high air fraction. In both cases, the films are characterized by local structures ordered on a few nanometer scale and their formation is explained as a result of spinodal decomposition of the as-formed homogenous structure which occurs during film growth.

Ion beam mixing has been used to produce a silicon carbide (SiC)-rich nanolayer for protective coating. Different C/Si/C/Si/C/Si(substrate) multilayer structures (with individual layer thicknesses falling in the range of 10–20 nm) have been irradiated by Ar+ and Xe+ ions at room temperature in the energy and fluence ranges of 40–120 keV and 1–6 × 1016 ion/cm2, respectively. The effects of ion irradiation, including the in-depth distribution of the SiC produced, was determined by Auger electron spectroscopy depth profiling. The thickness of the SiC-rich region was only some nanometers, and it could be tailored by changing the layer structure and the ion irradiation conditions. The corrosion resistance of the layers was investigated by potentiodynamic electrochemical test in 4 M KOH solution. The measured corrosion resistance of the SiC-rich layers was orders of magnitude better than that of pure silicon, and a correlation was found between the corrosion current density and the effective areal density of th...

Optical properties of Zr and its oxide have been measured on the surface of nuclear fuel cladding tubes. It has been shown that ellipsometry with focusing can routinely be used to measure thin layers and surface properties on Zr tubes with a diameter as small as 9.1 mm. Multi-sample and depth profiling models have been used to determine reference dielectric function spectra for both the Zr substrate and its oxide. Temporal behavior of the oxide thickness has been measured for oxidation temperatures of 600 °C and 800 °C. A vertical inhomogeneity of the oxide properties has been found by the optical measurements as well as by depth-profiling X-ray photoelectron spectroscopy investigations that revealed the formation of sub-oxides at the interface region of Zr and its surface oxide.

The aim of this article is to study the influence of TiC/a:C protective thin film on the corrosion and mechanical properties of sandblasted/polished Ti and TiAl6V4 substrates. The electrochemical corrosion behaviors of the samples were investigated in simulated body fluid (SBF) by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques at 7.4 pH and 37 °C. The metal ion release has been quantified by inductively coupled plasma optical emission spectroscopy (ICP-OES). The experimental results obtained from different electrochemical methods, ICP-OES, and scanning electron microscopy (SEM) showed that the TiC/a:C protective coating on sandblasted implant device improves the corrosion properties of the implant material and it is able to control the metal ion release. It was also shown that the hardness of the bare implant materials is improving by four orders of magnitude with the TiC/a:C nanocomposite coating beside a moderate elastic modulus value. The highest hardness (H) o...

We use argon ion-bombardment during Fe layer deposition as a way to tailor the structural and magnetic properties of bilayer and multilayer systems containing Fe/FeV components. We present structural and magnetic results on Fe/FeV bilayer and Fe/Fe-oxide/Fe/FeV multilayer systems. Magnetization measurements were taken over a range of temperatures and show the expected ferromagnetic behavior for the Fe/FeV bilayer. The Fe/Fe-oxide/Fe/FeV multilayer demonstrates an enhanced coercivity and exchange bias at low temperatures, both due to the presence of the antiferromagnetic Fe-oxide layer. Polarized neutron reflectometry results (scattering length density depth profile and neutron spin asymmetry) were used to identify mixed interfacial layers resulting from ion-bombardment. These demonstrated a lower magnetic moment than bulk Fe layers and may undergo a reversal process that differs from non-mixed layers within the sample.

Surface coatings of the polysaccharide dextran and its derivatives are key ingredients especially in label-free biosensors for the suppression of non-specific binding and for receptor immobilization. Nevertheless, the nanostructure of these ultrathin coatings and its tailoring by the variation of the preparation conditions have not been profoundly characterized and understood. In this work carboxymethylated dextran (CMD) was prepared and used for fabricating ultrathin surface coatings. A grafting method based on covalent coupling to aminosilane- and epoxysilane-functionalized surfaces was applied to obtain thin CMD layers. The carboxyl moiety of the CMD was coupled to the aminated surface by EDC-NHS reagents, while CMD coupling through epoxysilane molecules was performed without any additional reagents. The surface analysis following the grafting procedures consisted of X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared spectroscopy (ATR-IR), spectroscopic ellipsometry, atomic force microscopy (AFM) and optical waveguide lightmode spectroscopy (OWLS). The XPS and AFM measurements showed that the grafting resulted in a very thin dextran layer of a few nanometers. The OWLS method allowed devising the structure of the interfacial dextran layers by the evaluation of the optogeometrical parameters. The alteration in the nanostructure of the CMD layer with the chemical composition of the silane coverage and the pH of the grafting solution was revealed by in situ OWLS, specifically, lain down chains were found to be prevalent on the surface under neutral and basic conditions on epoxysilylated surfaces. The developed methodologies allowed to design and fabricate nanometer scale CMD layers with well-controlled surface structure, which are very difficult to characterize in aqueous environments using present instrumentations and highly hydrated surface layers.

TiC/amorphous carbon (TiC/a:C) nanocomposite thin films were deposited from two targets by direct current (DC) magnetron sputtering system at room temperature. The film's composition and morphology were studied in detail by High Resolution Transmission Electron Microscopy (HRTEM), Selected Area Electron Diffraction (SAED), X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy. The sputtering power of carbon target (P C ) was kept at the constant 150 W, while the sputtering power of titanium target (P Ti ) was changed between 5 W and 150 W. Additionally, a C/Ti multilayer was deposited and characterized for comparison. The growth mechanism was derived from the XPS, Raman and HRTEM observations on the grown layer structures and it was completed by a semi-empirical equation for the dependence on the average atomic fraction of Ti. The HRTEM investigations confirmed that the first nucleating phase is amorphous carbon due to its lowest surface energy among the possible phases. The second nucleating phase within the amorphous carbon matrix is TiC; its growth is kinetically not limited. The increase of Ti content resulted in larger TiC nanocrystallites and thinner amorphous carbon spacing between the TiC phases shown by HRTEM analysis. The characteristic texture of the crystallite structure was observed in the case of 120 W and 150 W of P Ti . All observation confirmed the two main phases; amorphous carbon + carbide phase. The hcp titanium phase was not formed due to nucleation barrier. The average sputtered composition differs from the average deposited composition due to different nucleation barriers of different phases.

Ion irradiation of interfaces causes intermixing of the adjacent regions, which leads to compound formation in certain cases. With the aim of building, some nm thick protective coating at ambient temperature, C/Si/C/Si/C/Si substrate samples were irradiated with Ar + , Xe + , and Ga + ions in the energy and fluence ranges of 20–200 keV and 1–3 × 10 16 ion cm − 2 , respectively. The effect of ion irradiation was studied by Auger electron spectroscopy depth profiling and cross sectional transmission electron microscopy. All ion irradiations produced SiC rich regions the thickness of which, being some nm, could be tailored by changing the ion irradiation conditions. The chemical resistance of the SiC rich layer has been tested by polysilicon etchant. Rutherford Backscattering Spectrometry (RBS) analysis showed that etching rate of the SiC rich region was orders of magnitude lower than that of polysilicon on the whole irradiated area. It was also shown that Transport of Ions in Dynamic (TRIDYN) simulation combined with a simple compound formation rule provides a fair description of the resultant SiC distributions. Thus, it is possible to design and fabricate wafer-scale SiC for a given sample architecture by “TRIDYN simulation assisted” ion irradiation.

The relationship between the structure, elemental composition, mechanical and tribological properties of TiC/amorphous carbon (TiC/a:C) nanocomposite thin films was investigated. TiC/a:C thin film of different compositions were sputtered by DC magnetron sputtering at room temperature. In order to prepare the thin films with various morphology only the sputtering power of Ti source was modified besides constant power of C source. The elemental composition of the deposited films and structural investigations confirmed the inverse changes of the a:C and titanium carbide (TiC) phases. The thickness of the amorphous carbon matrix decreased from 10 nm to 1–2 nm simultaneously with the increasing Ti content from 6 at% to 47 at%. The highest hardness (H) of ~26 GPa and modulus of elasticity (E) of ~220 GPa with friction coefficient of 0.268 was observed in case of the film prepared at ~38 at% Ti content which consisted of 4–10 nm width TiC columns separated by 2–3 nm thin a:C layers. The H3/E2 ratio was ~0.4 GPa that predicts high resistance to plastic deformation of the TiC based nanocomposites beside excellent wear-resistant properties (H/E=0.12).

Unstructured-mesh based numerical algorithms such as finite volume and finite element algorithms form an important class of applications for many scientific and engineering domains. The key difficulty in achieving higher performance from these applications is the indirect accesses that lead to data-races when parallelized. Current methods for handling such data-races lead to reduced parallelism and suboptimal performance. Particularly on modern many-core architectures, such as GPUs, that has increasing core/thread counts, reducing data movement and exploiting memory locality is vital for gaining good performance. In this work we present novel locality-exploiting optimizations for the efficient execution of unstructured-mesh algorithms on GPUs. Building on a two-layered coloring strategy for handling data races, we introduce novel reordering and partitioning techniques to further improve efficient execution. The new optimizations are then applied to several well established unstructured-mesh applications, investigating their performance on NVIDIA's latest P100 and V100 GPUs. We demonstrate significant speedups ($1.1\text{--}1.75\times$) compared to the state-of-the-art. A range of performance metrics are benchmarked including runtime, memory transactions, achieved bandwidth performance, GPU occupancy and data reuse factors and are used to understand and explain the key factors impacting performance. The optimized algorithms are implemented as an open-source software library and we illustrate its use for improving performance of existing or new unstructured-mesh applications., Comment: Number of pages: 36 Number of figures: 21 Submitted to JPDC

30 keV Ga + implantation was applied to a nominally C(20 nm)/Si(20 nm)/C(20 nm)/Si(20 nm)/C(20 nm)/Si substrate multilayer system. Due to the irradiation intermixing occurred and a layer containing C, Si, Ga and (amorphous) SiC was obtained. The thickness (7–30 nm) and composition of the layer depended on the fluence of irradiation. The chemical resistance of the layer was tested by applying microwave oxidation and various polysilicon etchants and was found to be excellent if the SiC concentration was above 20%. Using an etchant with an etching rate of about 100 nm/s for poly-Si during 10 s had not affected the integrity of the intermixed region with a thickness of 10 nm; only some defects appeared. With a further increase of the etching time the size of defects increased resulting in inhomogeneous layer removal. The in-depth composition of non-defective region that remained on the surface was determined by AES depth profiling, which revealed that the intermixed layer did not change during the harsh etching except the removal of its thin surface layer containing less than 20% SiC. The etching rate of the intermixed layer is orders of magnitude lower than that for poly-Si.

The relationship between structural, chemical and mechanical properties of nanocrystalline TiC/amorphous C (TiC/a:C) thin films was studied. Thin films were deposited by DC magnetron sputtering on oxidized silicon (Si/SiO2) substrates in argon at 25 °C and 0.25 Pa. The input power of the carbon target was kept at constant value of 150 W while the input power of the titanium target was varied between 15 and 50 W. It was found that all thin films consist of a few nanosized columnar TiC crystallites embedded in carbon matrix. The average size of TiC crystallites and the thickness of the carbon matrix have been found to correlate with Ti content in the films. The mechanical properties of the films have been strictly dependent on their structure. The highest values of the nanohardness (∼66 GPa) and Young's modulus (∼401 GPa) were observed for the film with the highest TiC content which was prepared at the largest input power of Ti target.

Published results of the multitudinous experiments studying the relationships between the properties and process parameters of sputter deposited TiN films indicate a very complex problem. The complexity manifests itself preferentially in the sporadic formation of the and preferred orientation (PO) and in the sequential formation (crossover) of the and PO in thicker films, even when the deposition parameters are maintained constant during the deposition. The first problem has been clarified by dedicated experiments as well as theoretical works. These revealed that the selection between the development of the and PO is related to the condition of the impinging species, i.e. whether they are neutral or ionized, molecular or atomic Ti and N species, to the degree of ionization, to the ratio of the impinging rates of these species and to their energy as well. Understanding the cross-over formation between the and PO remained, however, an open question so far. As the driving force for this process, the operation of the proposed overall energy minimisation effect, the interplay of the surface and interface and the inner stress energy during thickness growth of the film has been queried. In the present work authors point out that the complex structural and micro-chemical analysis of the cross-sectional specimens of TiN thin films with PO crossover could provide the fundamental information required to discover the possible phenomena governing the evolution of this particular structure and to reconstruct its pathway. That is demonstrated for the situation when the origin of the to PO crossover could be related to the contamination effect, caused by gas desorption at starting the deposition. In the discussed experiment the TiN film is doped by oxygen and the oxygen concentration changing from 18 to 11 at.% during the deposition.

Biomimetic coatings with cell-adhesion-regulating functionalities are intensively researched today. For example, cell-based biosensing for drug development, biomedical implants, and tissue engineering require that the surface adhesion of living cells is well controlled. Recently, we have shown that the bacterial flagellar protein, flagellin, adsorbs through its terminal segments to hydrophobic surfaces, forming an oriented monolayer and exposing its variable D3 domain to the solution. Here, we hypothesized that this nanostructured layer is highly cell-repellent since it mimics the surface of the flagellar filaments. Moreover, we proposed flagellin as a carrier molecule to display the cell-adhesive RGD (Arg-Gly-Asp) peptide sequence and induce cell adhesion on the coated surface. The D3 domain of flagellin was replaced with one or more RGD motifs linked by various oligopeptides modulating flexibility and accessibility of the inserted segment. The obtained flagellin variants were applied to create surface coatings inducing cell adhesion and spreading to different levels, while wild-type flagellin was shown to form a surface layer with strong anti-adhesive properties. As reference surfaces synthetic polymers were applied which have anti-adhesive (PLL-g-PEG poly( l -lysine)-graft-poly(ethylene glycol)) or adhesion inducing properties (RGD-functionalized PLL-g-PEG). Quantitative adhesion data was obtained by employing optical biochips and microscopy. Cell-adhesion-regulating coatings can be simply formed on hydrophobic surfaces by using the developed flagellin-based constructs. The developed novel RGD-displaying flagellin variants can be easily obtained by bacterial production and can serve as alternatives to create cell-adhesion-regulating biomimetic coatings. Statement of Significance In the present work, we show for the first time that - an oriented and dense monolayer of flagellin molecules mimics the surface of the bacterial flagellar filament. Consequently, the fabricated layer is completely cell repellent. - By genetically modifying flagellin, we incorporate cell adhesion regulating functionalities into this anti-adhesive coating. - We can easily tune the adhesion of living cells from completely cell repellent to highly adhesive.

Focused ion beam (FIB)-induced ion mixing was studied in a C/Si/C/Si/C/Si substrate multilayer structure sample by means of Auger electron spectroscopy (AES) depth profiling, and transmission electron microscopy (TEM). The multilayer sample was irradiated with Ga+ ions using focused ion beam (FIB) at room temperature. The ion energy and fluence of the ion irradiation varied in the range of 10–30 keV and 10–120 × 1015 ions/cm2, respectively. The ion irradiation induced a slightly asymmetric intermixing of the top C and Si layers, which could be modeled by the TRIDYN code. During ion mixing, part of the intermixed C and Si atoms reacted, forming amorphous SiC. The amount of SiC depends on the square root of the Ga+ fluence. Thus, amorphous SiC thin film (with Ga contamination) with thickness in the nanometer range can be produced by means of FIB.

Ion-beam mixing in C/Ta layered systems was investigated. C 8 nm/Ta 12 nm and C 20 nm/Ta 19 nm/C 20 nm layer systems were irradiated by Ga + ions of energy in the range of 2–30 keV. In case of the 8 nm and 20 nm thick C cover layers applying 5–8 keV and 20–30 keV Ga + ion energy, respectively resulted in strongly asymmetric ion mixing; the carbon was readily transported to the Ta layer, while the reverse process was much weaker. Because of the asymmetrical transport the C/TaC interface remained sharp independently from the applied fluence. The carbon transported to the Ta layer formed TaC x . The stoichiometry of the carbide produced varied along the depth. The TaC x layer contained implanted Ga, the concentration of which decreased with increasing depth. The thickness of the TaC x layer could be tailored by the ion fluence and energy making possible to produce coating layer of desired thickness.

In this paper we report on the ion beam bombardment-induced alteration of SiC measured at different ion energies (300–1700 eV) and at wide range of incident angle (43°–87°). Surface roughening was reduced by sample rotation during sputtering. The change of the concentration was characterized by Auger electron spectroscopy. Both low and high energy Auger peaks of Si were detected, which allowed us to estimate the depth distribution of the components. The observed alteration of Auger peak heights will be explained by simple model of the changed in-depth distribution. The model gives an estimate for the composition of top layer (the real surface) of SiC in different sputtering conditions, as well as the in-depth distribution of Si and C.

The relative sputtering yield of carbon with respect to tantalum was determined for 1 keV Ar + ion bombardment in the angular range of 70°―82° (measured from surface normal) by means of Auger electron spectroscopy depth profiling of C/Ta and Ta/C bilayers. The ion bombardment-induced interface broadening was strongly different for the C/Ta and Ta/C, whereas the C/Ta interface was found to be rather sharp, the Ta/C interface was unusually broad. Still the relative sputtering yields (Y C /Y Ta ) derived from the Auger electron spectroscopy depth profiles of the two specimens agreed well. The relative sputtering yields obtained were different from those determined earlier on thick layers, calculated by simulation of SRIM2006 and by the fitting equation of Eckstein. The difference increases with increase of angle of incidence.

To investigate the details of the ion beam induced mixing and validate the Auger electron spectroscopy depth profiling technique, sputter-deposited Si 40 nm/Cr 40 nm multilayer samples were irradiated with a 20 keV CF 4 + ion beam. Due to the ion bombardment the top Si layer was damaged and a crater was created. Elemental depth profiles and layer thicknesses together with surface topography were measured with Rutherford backscattering spectrometry by applying a focussed 2 MeV He+ beam. The thickness of the top Si layer was also determined from ellipsometry measurements. The results are compared to that of obtained from Auger electron spectroscopy depth profiling.

In elastic peak electron spectroscopy (EPES), the nearest vicinity of elastic peak in the low kinetic energy region reflects electron inelastic and quasielastic processes. Incident electrons produce surface excitations, inducing surface plasmons, with the corresponding loss peaks separated by 1–20 eV energy from the elastic peak. In this work, X-ray photoelectron spectroscopy (XPS) and helium pycnometry are applied for determining surface atomic composition and bulk density, whereas atomic force microscopy (AFM) is applied for determining surface morphology and roughness. The component due to electron recoil on hydrogen atoms can be observed in EPES spectra for selected primary electron energies. Simulations of EPES predict a larger contribution of the hydrogen component than observed experimentally, where hydrogen deficiency is observed. Elastic peak intensity is influenced more strongly by surface morphology (roughness and porosity) than by surface excitations and quasielastic scattering of electrons by hydrogen atoms. Copyright © 2007 John Wiley & Sons, Ltd.

The inelastic mean free path (IMFP) of electrons was determined experimentally for selected polyaniline and polyacetylene samples with Ag and Ni references using elastic peak electron spectroscopy (EPES). The surface composition was determined by XPS and density by helium pycnometry. The high resolution hemispherical ESA-31 and ADES-400 spectrometers were used for measurements in the energy range E = 0.5–3.0 keV and E =0.4 − 1.6 keV, respectively. The integrated elastic peak intensity ratios for sample and reference were calculated using the Monte Carlo (MC) algorithm based on the electron elastic scattering cross-sections database NIST SRD64 version 3.1 and applying TPP-2M IMFPs for polymers. Surface excitation parameters (SEP) and material parameters (ach) for polymers were determined, using the model of Chen, from comparison of measured and MC calculated elastic peak intensity ratios. These corrections proved to be efficient in decreasing the percentage deviations between the obtained IMFPs and the TPP-2M formula IMFPs. The elastic peak of hydrogen was observed in the EPES spectra of polymers. The experimental contribution of the hydrogen to the total elastic peak was 0.58%, while this value obtained from the MC simulations was 1.98%.

The steady-state surface compositions of the polar (O and Zn terminated) faces of ZnO{0 0 0 1} produced by low energy (0.3–2 keV) Ar + ion bombardment were studied by Auger electron spectroscopy and electron energy loss spectroscopy. The alterations produced by the ion bombardment using different ion energies were monitored by calculating the intensity ratios of the low and high energy Zn Auger peaks (59 eV and 994 eV, respectively); Zn and O Auger peaks (59 eV and 510 eV, respectively). Based on the dependence of these ratios on the ion energy and termination of the surface, we could conclude that the stability of the Zn face is higher against the low energy argon ion bombardment-induced compositional changes than that of the O face.

Inelastic mean free paths (IMFPs) determined by elastic peak electron spectroscopy (EPES) have been frequently evaluated neglecting surface excitations that affect the elastic peak intensity for a sample and a reference material. The surface excitation correction is defined by the surface excitation parameter, P s , denoted by SEP. SEPs for eight selected conducting polymers (polythiophenes, polyaniline and polyethylene) undoped and doped with Pd were determined by EPES using Ag , Ni and Si reference materials for electron energies between 0.2 and 2.0 keV. The mean percentage deviations between IMFPs uncorrected for surface excitations and those calculated with the predictive formulae of Gries and Tanuma et al. were 4.32 and 27.32%, respectively. Relevant deviations for IMFPs corrected for surface excitations were 2.97 and 22.90%, respectively.

In this work, the influence of recoil effect and surface excitations on the inelastic mean free paths for polythiophenes is investigated. The inelastic mean free paths of electrons in polythiophenes are measured with the elastic peak electron spectroscopy method using the Ag standard and the electron elastic scattering cross-sections from the database NIST 3.1 in the electron kinetic energy range 200–5000 eV. The Monte Carlo model is applied for evaluating the electron backscattering intensities from the polymers and the Ag standard, as well as for evaluating electrons quasi-elastically backscattered from atoms of different atomic numbers (the recoil effect). The surface excitation corrections are accounted for using the formalism of Chen, with the material parameters for polythiophenes evaluated from the elastic peak electron spectroscopy method. Deviations due to recoil effect and surface excitations to the inelastic mean free paths are compared and discussed. Correction to the inelastic mean free paths due to recoil effect is considerable but is smaller, however, than the correction due to surface excitations. Accounting for recoil effect and surface excitations leads to improvement of the inelastic mean free paths, as compared to the inelastic mean free paths resulting from the predictive formulae of Gries.

The steady state surfaces of ion bombarded 3C-, 4H- and 6H-SiC samples were studied by means of reflected electron energy loss spectroscopy (REELS). The REELS exhibit a well-defined loss peak in the region of about 20 eV. The position of the maximum of the loss peak depends on the bombarding ion energy (decreasing with increasing ion energy), and on the primary electron beam energy (increasing with increasing primary energy). This behavior can be explained if we suppose that the plasmon energy in the altered layer (produced by ion bombardment) is different from that of the unaltered bulk. In this case the measured loss peak is the sum of two overlapping plasmon peaks. With modeling the system as a homogeneous altered layer and a homogeneous unaltered substrate the plasmon energy in the altered layer was derived to be 19.8 eV. The large change of the plasmon energy with respect to the bulk value of 23 eV is explained by a thin low density overlayer on the surface of the sample produced by the ion bombardment.

Electrons impinging into a solid surface produce excitations in the surface layer. The elastic reflection coefficient of a solid (i.e. elastic peak) is reduced by surface losses. Selected conducting polymers were studied with elastic peak electron spectroscopy (EPES) and reflection electron energy loss spectroscopy (REELS). The electron inelastic mean free path (IMFP) was determined using EPES with Ag and Si references and corrected for surface excitations, characterized by the surface excitation parameter Pse(E). A new procedure was developed for experimental determination of the parameter Pse(E), a further development of Tanuma's work. It is based on comparison of experimental and calculated integrated elastic peak ratios of sample and reference. Another procedure was based on the REELS method. Pse(E) of selected polymers were determined for E = 0.2–2.0 keV using a HSA analyser. Experiments were evaluated by Monte Carlo simulation using NIST elastic scattering databases. The IMFP values for polymers were calculated by Gries, Cumpson and TPP-2M formulae. Material parameter data, ach, using Chen's approach for selected polymers, and IMFPs of polyethylene corrected for surface excitation are presented. Copyright © 2004 John Wiley & Sons, Ltd.

Elastic peak electron spectroscopy (EPES) provides inelastic mean free path (IMFP) values in the near-surface region. Such values, which will be called effective IMFPs, might be different from these derived from bulk parameters. In this work we derive effective IMFP values from EPES measurements in the range of 300–2000 eV for SiO2 and Si3N4 using a Si reference. Corrections for surface excitation are applied. Our effective IMFP values agree well with those calculated from optical data in the case of SiO2; that is, the ion sputtering does not alter the SiO2 surface significantly. On the other hand, systematic deviations between our data and those provided by a predictive formula were found in the case of sputtered Si3N4. These differences are attributed to alteration in the surface layer caused by sputtering.

Ion sputtering induced surface composition changes by applying various ions (He + , Ne + , Ar + , Xe + ) in the energy range of 0.2–1.5 keV, was measured by AES on the polar faces of 6H–SiC{0 0 0 1}. Carbon enrichment was observed on both faces, and it was different if Ne + , Ar + , Xe + ion sputtering was applied with ion energy lower than 0.4–0.8 keV (depending on projectile); no different enrichment was found for He + ion bombardment at any energy (in this range). Thus C/Si ratio measured by AES after low energy ion (e.g. Xe + ) bombardment can be used to identify polarity of the surface.

The surface excitation produced by impinging or escaping electrons is a competitive process to elastic backscattering. It affects the intensity of Auger and XPS peaks and is characterized by the surface excitation parameter Pse. This appears in the surface loss peak I(Epls), and possibly a surface plasmon. In our work Pse is defined as the ratio of the probability to create a surface plasmon/elastic scattering and is deduced from the integrated surface loss peak and elastic peak, respectively. Our procedure is based on reflection electron energy loss spectroscopy and elastic peak electron spectroscopy spectra and Kλi spectra (K is the inelastic scattering cross-section and λi is the inelastic mean free path), determined using Tougaard's method. The normalized Kλi curves are fitted to the spectrum at E = 5 keV (primary energy) and EL = Epl1 (volume plasmon), approximated with the Lorentzian type three-parameter formula of Tougaard. For E>Epl1, the normalized curves are overlapping and Pse is deduced from the integrated difference spectra fitted with the Tougaard cross-sections. The procedure was applied on materials exhibiting surface and volume plasmons: III–V semiconductors (GaAs, InSb) and In and Sb metals. The REELS experiments were carried out with an ESA 31 HSA spectrometer covering the E = 0.2–5 keV energy range. Copyright © 2002 John Wiley & Sons, Ltd.