An atmospheric pressure microwave plasma tubular furnace apparatus (MPTF) for the rapid synthesis of carbon nanotubes (CNTs) has been developed. CNTs have been synthesized by an Argon-Hydrogen microwave plasma using ethanol vapor as carbon source with the furnace temperature of 800 °C at the atmospheric pressure. The synthesized CNTs have been analyzed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and are shown to be multi-walled and tangled and chemically connected to form a high-density network with the diameter at the range of 25-70 nm. The measurement of X-ray photoelectron spectroscopy (XPS) indicates that a large number of oxygenated functional groups grown on the surface of CNTs. These properties proved that the CNTs could be utilized as nanoscale templates for various applications.

A novel high-power impulse plasma source (HiPIPS) technology that combines atmospheric pressure plasma jets with high-power pulsed direct current generators is described. Pulsed power is applied in microsecond pulses (20 µs) at low duty cycle (10%) and low frequency (0.5 kHz) leading to high peak power densities (10–75 kW) and high peak currents (100–250 A) while maintaining low average power (<40 W) and low processing temperatures (<50 °C). These conditions result in the generation of a highly dense plasma discharge (ne = 6.23 × 1016 cm−3) for surface modification and deposition of coatings. Using HiPIPS, Ar-initiated metallic Ti, CoCr, or Ti–6Al–4V plasma was generated, and the plasma properties were characterized by measuring current–voltage characteristics, electron densities (Langmuir probe), and optical emission spectra. HiPIPS CoCr and Ti–6Al–4V coatings were deposited for proof of concept of the technique. The resulting coatings were examined with scanning electron microscopy, energy-dispersive X-ray spectroscopy, and nanoindentation.

Polypyrrole (PPy) thin films were synthetized by plasma and simultaneously doped with Iodine to enhance electromagnetic absorption and charge transfer capability in a resistive coupling cylindrical reactor. Pyrrole monomer and Iodine were the principal reagents used and the chemical reactions were created by high frequency plasma. Micrographs show an irregular surface formed by semi-spherical protrusions with tiny particles in the PPy/I samples and a rather smooth surface with wrinkles and less participation of tiny particles to PPy ones. Infrared spectroscopy analysis reveals important absorption peaks at 3253, 2932, 1668 and 635 cm-1 corresponding to the chemical bonds N-H and C-H, C-H aliphatic, C=C and C-I, respectively, belonging to the chemical structure of Pyrrole. Electrical conductivity of PPy increased from 10-10 to 10-8 S/cm due to Iodine doping. Electromagnetic absorption showed a higher response between 340 and 800 nm in the visible region. Activation energy was calculated in the range from -0.09 to 0.49 eV.

The objective of the study was to modify the external surface of commercially produced polyethylene (PE) tubes made by Balton, Poland, to improve their hydrophilic properties. The process was conducted in a new dielectric barrier discharge reactor. The carrier gases were argon and air, whereas carbon dioxide and hydrogen were the doping gases. The influence of the gas composition in the plasma chamber on the surface free energy (SFE) of PE tubes was investigated. For the gas composition 50 vol% of Ar + 50 vol% of CO2, the highest value of the SFE (53.4 mJ/m2) was obtained. It means an increase in SFE approx. 17% as compared to the unmodified sample (46.0 mJ/m2). Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) results indicates that on the surface of the tubes, carboxyl, carbonyl, and hydroxyl groups were formed. Those oxygen-containing groups could be responsible for the increase of the hydrophilic effect. The O/C ratio on the surface, measured by the X-ray photoelectron spectroscopy method, was three times higher in the case of the modified samples than in those which were not subjected to plasma treatment.

Indium oxide (InOx) and indium tin oxide (ITO) thin films were deposited on glass substrates by plasma enhanced reactive thermal evaporation (PERTE) at different substrate temperatures. The films were then submitted to two etching solutions with different chemical reactivity: i) HNO3 (6%), at room temperature; ii) HCl (35%): (40 °Bé) FeCl3 (1:1), at 40 °C. The dependence of the etchability of the films on the structural and deposition conditions is discussed. Previously to etching, structural characterization was made. X-ray diffraction showed the appearance of a peak around 2θ=31° as the deposition temperature increases from room temperature to 190 °C, both for ITO and InOx. AFM surface topography and SEM micrographs of the deposited films are consistent with the structural properties suggested by X-ray spectra: as the deposition temperature increases, the surface changes from a finely grained structure to a material with a larger-sized grain or/and agglomerate structure of the order of 250-300 nm. The roughness Rq varies from 0.74 nm for the amorphous tissue to a maximum of 10.83 nm for the sample with the biggest crystalline grains. Raman spectra are also presented.

An investigation of the effect of experimental parameters on the temperature and uniformity of material deposition by atmospheric pressure dielectric barrier discharge (DBD) planar plasma reactors was conducted. The apparatus consisted of a pulsed AC high voltage power source with various electrode materials (aluminum, copper wire mesh, and aluminum/copper wire mesh) operating under a range of load resistances. Possible effects of non-ideal interfacial conditions for the contact surface between the electrode and the substrate were also studied with various modified surface thermal conditions. It was found that a hybrid electrode design with a fine copper (Cu) wire mesh attached to an aluminum plate of approximately 3 mm thickness produced the most visually uniform deposit, presumably as a result of both the superior conductivity provided by the Al metal plate and the stable plasma resulting from the relatively low breakdown voltage by using helium (He) as the dilution gas. Although the experimental conditions of plasma-enhanced chemical vapor deposition (PECVD) are often specific to particular systems and applications, this work provides insights on technical details which can be applied to various plasma DBD reactors.

Mechanical integrity of the interfacial region between ceramic coatings and substrates is critical to high performance coated mechanical components and manufacturing tools. Mechanical failure of the coating/substrate interfacial region often leads to catastrophic failure of the coated system as a whole. Despite extensive research over the past two decades, quantitative assessment of the mechanical response of coating/substrate interfacial regions remains a challenge. The lack of reliable protocols for measuring the mechanical response of coating/substrate interfacial regions quantitatively hampers the understanding of key factors controlling the mechanical integrity of coating/substrate interfaces. In this paper, we describe a new micro-pillar testing protocol for quantitative measurement of critical stresses for inducing shear failure of interfacial regions in ceramic-coating/metal-adhesion-layer/substrate systems. We observe significant differences in the critical stress for shear failure of interfacial regions in CrN/Cu/Si, CrN/Cr/Si, and CrN/Ti/Si systems. The present testing protocol has general applicability to a wide range of coating/interlayer/substrate systems.

Pulsed electron beam ablation (PEBA) has proven to be a promising and powerful technique for the growth of high quality thin films. Pulsed electron beam film deposition consists of many physical processes including target material heating, target ablation, plasma plume expansion, and film growth on a substrate. Plasma plume expansion into a vacuum or an ambient gas is a fundamental issue in PEBA as the quality of thin films deposited onto the substrate depends on the composition, energy and density of particles ejected from the target. In the present study, gas-dynamics equations are solved to investigate plasma expansion induced by interaction of a nanosecond electron beam pulse (∼100 ns) with a graphite target in an argon atmosphere at reduced pressure. The spatio-temporal profiles of the temperature, pressure, velocity, and density of the plasma plume are numerically simulated for a beam efficiency of 0.6 and accelerating voltage of 15 kV. The preliminary results show a rich variety of behaviors. The model is validated by comparing some of the obtained simulation results with experimental data available in the literature.

Thick coatings of tetrahedral amorphous carbon (ta-C) have great existing and potential commercial importance for components such as automobile accessories. We confirmed the feasibility of depositing thick ta-C coating on Si wafer, WC, stainless steel (STS), and Al alloy substrates by a home-made filtered cathode vacuum arc. A ta-C coating of 800 nm thickness was successfully deposited over 20 min continuous coating. Interestingly, coatings with thicknesses exceeding 1 μm were easily delaminated by thermal and internal stress effects when the coating time exceeded 20 min. Varying the bias (0 V ↔ 500 V) was highly effective in controlling the internal stress relaxation of the ta-C. This method showed significant improvements in the stress relaxation of the ta-C coatings. By applying multicycle coating, the thickness and hardness of the ta-C coating could reach 9.3 μm and 45 GPa, respectively, at a coating speed of 3.0 μm/h on a fixed substrate.

A scalable approach for synthesis of ultra-thin (<10 nm) transition metal dichalcogenides (TMD) films on stretchable polymeric materials is presented. Specifically, magnetron sputtering from pure TMD targets, such as MoS2 and WS2, was used for growth of amorphous precursor films at room temperature on polydimethylsiloxane substrates. Stacks of different TMD films were grown upon each other and integrated with optically transparent insulating layers such as boron nitride. These precursor films were subsequently laser annealed to form high quality, few-layer crystalline TMDs. This combination of sputtering and laser annealing is commercially scalable and lends itself well to patterning. Analysis by Raman spectroscopy, scanning probe, optical, and transmission electron microscopy, and x-ray photoelectron spectroscopy confirm our assertions and illustrate annealing mechanisms. Electrical properties of simple devices built on flexible substrates are correlated to annealing processes. This new approach is a significant step toward commercial-scale stretchable 2D heterostructured nanoelectronic devices.

Growth of GaN on Si(111) and Ge coated Si(111) using pulsed electron beam deposition (PED) process is reported. GaN was deposited on Si(111) and Ge/Si(111) at 600°C in an N2 environment without any surface pre-treatment such as pre-nitridation. X-ray diffraction confirmed that c-plane oriented GaN was grown. Photoluminescence showed near-band-edge emission, the intensity of which was improved with hydrogen passivation. Electrical characterization showed n-type conductivity with room temperature electron mobilities in the range of 300 cm2/V-sec.

We succeeded in photovoltaic power generation of p-i-n solar cells utilizing epitaxial ZnInON film with a wide band gap of 3.1 eV as the intrinsic layer, suitable for a top cell of tandem solar cells. The solar cell shows a high open circuit voltage (Voc) of 1.68 V under solar simulator light irradiation of 3.2 mW/cm2. The solar cell performance becomes worse under 100 mW/cm2, which is mainly attributed to the leakage current caused by crystal defects and grain boundaries. X-ray diffraction analysis reveals that the ZnInON film has rather large tilt and twist angles and a high dislocation density of 7.62×1010 cm-2. Such low crystallinity is a bottleneck for high performance of the solar cells. Our results demonstrate a potential of epitaxial ZnInON films as an intrinsic layer of wide band gap p-i-n solar cells with a high Voc.

Biomolecules have been traditionally immobilised onto surfaces using wet chemical techniques for various medical applications. Recent decades have seen plasma methods being used to prepare these surfaces through various forms of surface modification, but the direct exposure of biomolecules to plasma has been avoided due to fears that the molecules would be denatured by the energetic plasma species. Recent results are now demonstrating that direct plasma deposition of biomolecule coatings can be achieved. This creates the possibility to directly modify the surface of implants without any form of surface pre-treatment and this opens up the possibility to alter the healing processes. Materials such as collagen, chitosan, catalase and heparin can be effectively deposited onto surfaces with minimal impact on biological performance and without any chemical binders, linkers or impurities. The performance of these materials has been characterised using both in vitro and in vivo methodologies. In a further step, the results of a preclinical trial are presented which reveal that direct deposition of biomolecules onto open wounds can also be achieved and the impact of this on wound healing is measured in an immunocompromised animal model. A non-thermal plasma device was used to deliver collagen on to chronic wounds and the treatment was shown to promote wound closure in a rabbit wound healing model.

SnZn(OH)6 (ZHS) hollow cubes were synthesized by a facile self-templated method at room temperature, and Ag/AgCl/ZHS particles were prepared by a photodepositing method. The crystalline structure and morphology of the prepared particles were characterized by x-ray diffraction, UV-vis diffuse reflectance spectroscopy, scanning electron microscopy, and N2 adsorption. The results indicated that the particles had almost uniform monoclinic geometry and size. The photocatalytic oxidation of Rhodamine B was used to evaluate the photocatalytic activity of the synthesized photocatalysts. It is found that the hollow Ag/AgCl/ZHS showed the highest catalytic performance under visible or UV light, which can be attributed to the synergetic effect of Ag, AgCl, and ZHS.

One of the major barriers to the adoption of solid oxide fuel cells (SOFCs) is the short lifetime of the fuel cell stacks. A stack consists of a number of cells in series separated by an interconnect. Due to the high temperatures necessary for SOFCs, typical commercial interconnects are ceramic. Great attention has been paid to decreasing the operating temperature of SOFCs in order to extend the life and decrease the cost of the stack. As operating temperatures decrease below 1000°C, alternative interconnect materials become viable. Stainless steel interconnects are more cost effective than ceramic interconnects but the high temperatures and the oxidizing environment of the cathode leads to the formation of a chromium oxide scale that increases the stack resistance. Chromium from the stainless steel can also enter the vapor phase and redeposit on the cathode thereby blocking the electrochemically active sites. One method to neutralize these effects is to coat the metallic interconnect in a ceramic such as La.8Sr.2MnO3 (LSM). The coating acts as a diffusion barrier both against chromium diffusing into the cathode and oxygen diffusing into the interconnect. In this study LSM has been deposited using plasma spray and tested in a dual atmosphere setup using impedance spectroscopy to analyze the performance of the coatings at various temperatures. The area specific resistance and chemical composition of the scale was examined in order to determine the affect of the LSM coating.

Pr0.5Ca0.5MnO3 (PCMO) films were deposited on LaAlO3 (100) substrates under pressure from 1.33 to 5.33 Pa by RF magnetron sputtering. Resistance switching and dielectric functions of PCMO films were studied by DC current-voltage characteristic measurements and spectroscopic ellipsometry (SE) measurements. Resistance switching was observed in the devices composed of PCMO films deposited under low pressures of 1.33 and 2.67 Pa. SE measurements revealed that dielectric functions also depended on deposition pressure. PCMO films deposited under lower pressure had larger high-frequency dielectric constant, larger oscillator strength of the electric dipole charge transitions in MnO6 octahedral complexes, and lower oscillator strength of d-d transitions in Mn3+ and Mn4+ ions. SE measurements suggested that oxygen vacancies and MnO6 octahedral complexes play an important role in resistance switching in PCMO films.

Gas-turbine engines used in transportation, energy, and defense sectors rely on high-temperature thermal-barrier coatings (TBCs) for improved efficiencies and power. The promise of still higher efficiencies and other benefits is driving TBCs research and development worldwide. An introduction to TBCs—complex, multi-layer evolving systems—is presented, where these fascinating systems touch on several known phenomena in materials science and engineering. Critical elements identified as being important to the development of future TBCs form the basis for the five articles in this issue of MRS Bulletin. These articles are introduced, together with a discussion of the major challenges to improved coating development and the rich opportunities for materials research they provide.

Transparent conductive oxides (TCOs) are degenerately doped compound semiconductors with wide band gaps (Eg > 3 eV), which are used as transparent electrodes in optoelectronic devices. Reports on the influence of negative ions on the electrical properties of TCO films are reviewed and compared with our results. It was reported that the radial resistivity distributions depend (i) on the excitation mode of the magnetron (direct current or radio frequency), (ii) on the erosion state of the sputtering target, and (iii) on the density of the ceramic targets. This can be explained by the fact that the negative ions in magnetron discharges (in our case O−) are generated at the target surface and accelerated toward the growing films. Their energy and their radial distribution depend on the discharge voltage and the shape of the emitting surface, i.e., of the erosion groove. Ways for reducing the effect of negative ion bombardment are discussed.

High-power impulse magnetron sputtering (HiPIMS) is a promising sputtering-based ionized physical vapor deposition technique and is already making its way to industrial applications. The major difference between HiPIMS and conventional magnetron sputtering processes is the mode of operation. In HiPIMS the power is applied to the magnetron (target) in unipolar pulses at a low duty factor (<10%) and low frequency (<10 kHz) leading to peak target power densities of the order of several kilowatts per square centimeter while keeping the average target power density low enough to avoid magnetron overheating and target melting. These conditions result in the generation of a highly dense plasma discharge, where a large fraction of the sputtered material is ionized and thereby providing new and added means for the synthesis of tailor-made thin films. In this review, the features distinguishing HiPIMS from other deposition methods will be addressed in detail along with how they influence the deposition conditions, such as the plasma parameters and the sputtered material, as well as the resulting thin film properties, such as microstructure, phase formation, and chemical composition. General trends will be established in conjunction to industrially relevant material systems to present this emerging technology to the interested reader.

The gold nanoparticles (AuNPs) conjugated with carbon nanotubes (CNTs) and/or biomolecules such as DNA are synthesized using a novel plasma technique combined with introduction of ionic liquids or aqueous solution for application to life sciences.

First, we successfully generate the gas-liquid interfacial discharge plasma (GLIDP) using an ionic liquid, in which the large sheath electric field is formed on the ionic liquid and the plasma ion irradiation to the ionic liquid with high energy is realized.

Second, it is found that the high energy ion irradiation to the ionic liquid is effective for the synthesis of the AuNPs. Furthermore, the controlled ion irradiation to the ionic liquid including a carboxyl group can realize the density-controlled synthesis of the AuNPs on the CNTs by dissociation of the ionic liquid and the controlled functionalization of the CNTs by the dissociated carboxyl group.

Third, the size- and morphology-controlled AuNPs covered with DNA are synthesized using the GLIDP with aqueous solution, where DNA prevents the AuNPs from further clustering, resulting in the small-sized AuNPs. The synthesized AuNPs conjugated with DNA can be encapsulated into the CNTs using the DC electric field. The CNTs work as vectors to deliver DNA into living cells because the CNTs have the unique ability to easily penetrate cell membranes with low cytotoxicity.