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Abstract: We present a study of the nitrogen-implanted SiC, with the focus being to understand the structure and composition of the implanted region and its evolution with annealing. The implantation region was probed as a function of implant and annealing conditions using a combination of transmission electron microscopy (TEM) based imaging and spectroscopy techniques as well as Raman spectroscopy. Raman spectroscopy revealed carbon bands at ∼1600cm−1 and 1370cm−1 and silicon nitride bands at ∼460cm−1 and 790cm−1 for the samples processed at high temperatures. TEM showed that nitrogen ion implantation of the silicon carbide followed by thermal annealing creates complicated nanocomposite structure. Elemental maps obtained using energy-filtered TEM revealed concentration variation across the implanted layer with carbon accumulation observed at the interfaces and the center of the implanted layer. The nitrogen atoms substitution of carbon in SiC and the segregation of implantation-induced carbon atoms are believed to be the reason for the observed structure. [Copyright &y& Elsevier]

Abstract: Focused ion beam (FIB) technique is a well established technique for processing and modifying materials at micro- and nanoscale. FIB implantation with 30keV Ga+ ions into a single crystal diamond has been studied via a combination of transmission electron microscopy (TEM) imaging and spectroscopy in the attempt to understand the damage formation in diamond. The damage formation has been studied as a function of implantation dose with eight different doses ranging from 6×1014 to 1×1016 ions/cm2. The TEM studies have revealed different structure of low-dose and high-dose implanted regions. 3.5nm diamond cap layer was observed in the low-dose implanted layer. TEM analysis has shown volume extension of around 50% in the amorphous region and up to 7% in diamond at the crystal–amorphous interface. The density of amorphous damage layer was measured to be 2.51g/cm3 and 2.24g/cm3 in the low-dose and high-dose implanted regions, respectively. The amorphisation threshold for ion implantation in diamond at room temperature was determined to be 5.2×1022 vacancies/cm3. [Copyright &y& Elsevier]

A hydrogen-terminated diamond (H-terminated diamond) surface supports a two-dimensional (2D) p-type surface conductivity when exposed to the atmosphere, as a result of the surface transfer doping process. The formation of reliable Ohmic contacts that persist to cryogenic temperature is essential for the exploration of quantum transport in the diamond 2D conducting channel. Herein, the contact properties of Pd on H-terminated diamond have been fully investigated down to 4 K using transmission line method measurements. Pd is shown to form an Ohmic contact on H-terminated diamond with linear I–V characteristics and low specific contact resistance in the range of (8.4 ± 1) ×10−4 Ω·cm2 to (1.3 ± 0.2) ×10−3 Ω·cm2 for the temperature range of 300 K–4 K. This is in stark contrast to reference devices with Au/Pt/Ti contacts, which exhibit a significant temperature dependence and non-Ohmic behavior at low temperature. Using 2D thermionic emission theory, a negative Schottky barrier height (SBH), − 23 ± 1 meV, between Pd and H-terminated diamond has been determined, in comparison to a positive SBH of 42 ± 1 meV for the Au/Pt/Ti/H-terminated diamond interface. These results show that Pd serves as an excellent candidate for forming reliable Ohmic contacts on H-terminated diamond for enabling precise electrical transport measurements at cryogenic temperature. [ABSTRACT FROM AUTHOR]

A device fabrication method is reported to efficiently produce CH 3 NH 3 PbI 3 -based planar perovskite solar cells on polymer substrates with the entire process conducted at 150 °C or below. The hole blocking layer employed is a solution processed 100 nm thick mesoporous TiO 2 layer. A gas-assisted perovskite deposition method is used to produce excellent coverage of the hole blocking layer by a ∼350 nm thick CH 3 NH 3 PbI 3 film, resulting in high device performance reproducibility. We show that an average efficiency of 10.6 ± 1.2%, and a maximum efficiency of 12.3% are obtained for flexible perovskite solar cells, offering great promise for further improvement of this low-temperature, low-cost processing solar technology. [ABSTRACT FROM AUTHOR]

Copper oxide composites were successfully synthesized by a catalyst-free method, plasma arc technology. The as-synthesized composites were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. The analysis revealed a mixture of crystalline copper oxide (CuO), cuprous oxide (Cu2O) and copper (Cu) phases of the copper oxide composites constitute of irregularly spheroidal particlesµ with nanoparticles aggregate on the surface. Gas pressure during plasma arc process noticeably influences the composition and solar radiative properties of the composite materials. Among the samples studied, the composites synthesized with an arc current of 80 A and a pressure of 300 Torr exhibited the highest near infrared diffuse reflectance, providing a total solar reflectance of 22.96%. The mixed phase composition together with the nanostructures among the composites are considered to contribute to the excellent near infrared reflectance of copper oxide composites. Low reflectance in the visible region combined with high reflectance in the near infrared region make this composite material a good candidate for solar reflective coating which will demonstrate black appearance but keep a cool surface under solar irradiation. [ABSTRACT FROM AUTHOR]

The mechano-bactericidal activity of nanostructured surfaces has become the focus of intensive research toward the development of a new generation of antibacterial surfaces, particularly in the current era of emerging antibiotic resistance. This work demonstrates the effects of an incremental increase of nanopillar height on nanostructure-induced bacterial cell death. We propose that the mechanical lysis of bacterial cells can be influenced by the degree of elasticity and clustering of highly ordered silicon nanopillar arrays. Herein, silicon nanopillar arrays with diameter 35 nm, periodicity 90 nm and increasing heights of 220, 360, and 420 nm were fabricated using deep UV immersion lithography. Nanoarrays of 360-nm-height pillars exhibited the highest degree of bactericidal activity toward both Gram stain-negative Pseudomonas aeruginosa and Gram stain-positive Staphylococcus aureus bacteria, inducing 95 ± 5% and 83 ± 12% cell death, respectively. At heights of 360 nm, increased nanopillar elasticity contributes to the onset of pillar deformation in response to bacterial adhesion to the surface. Theoretical analyses of pillar elasticity confirm that deflection, deformation force, and mechanical energies are more significant for the substrata possessing more flexible pillars. Increased storage and release of mechanical energy may explain the enhanced bactericidal action of these nanopillar arrays toward bacterial cells contacting the surface; however, with further increase of nanopillar height (420 nm), the forces (and tensions) can be partially compensated by irreversible interpillar adhesion that reduces their bactericidal effect. These findings can be used to inform the design of next-generation mechano-responsive surfaces with tuneable bactericidal characteristics for antimicrobial surface technologies. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Near-surface superparamagnetic Ni 1−x Fe x nanoparticles in SiO 2 with x = 0.47 and 0.20 but the same Ni fluence. • Higher fraction of ordered moment in the cores for x = 0.47. • Spin-stiffness highest for x = 0.20. • Negligible demagnetization and magnetic dipole interactions between nanoparticles. • Enhanced superparamagnetic dM/dH for x = 0.47 due to larger nanoparticle sizes. Abstract Structural and magnetic measurements were performed on SiO 2 films containing near-surface Ni 1− x Fe x superparamagnetic nanoparticles made by low energy ion implantation into SiO 2 with the same Ni fluences of 2 × 1016 at./cm2 and two different Fe fluences so that x = 0.47 and x = 0.20. The x = 0.47 films had larger nanoparticles, a higher fraction of ordered moments in the nanoparticle cores, and thinner spin-disordered shells. The nanoparticle core spin-stiffnesses were slightly higher for x = 0.20 and smaller than that expected for bulk Ni 1− x Fe x for both Fe concentrations. There was no evidence for magnetic dipole interactions between the nanoparticles that have been reported in compressed superparamagnetic ferromagnetic nanoparticles. d M /d H was estimated and found to be highest for x = 0.47 where it reached 15 at 300 K and 56 at 100 K. The measured d M /d H is consistent with that expected from a derivative of the Langevin function with negligible demagnetization where larger nanoparticles are expected to have a higher d M /d H. [ABSTRACT FROM AUTHOR]

Fe 3 O 4 nanoparticles have been made by a co-precipitation method with an average size of 13 nm. Raman measurements show that there is also a small fraction of maghemite that is not seen in the XRD data. The saturation magnetization is high for this preparation method and the coercive field is low at 300 K. The high field magnetic moment cannot be fitted to a Bloch temperature dependence over the full temperature range, which is likely due to the effect of the Verwey transition at 120 K. Pressed powders shows a magnetoresistance of up to −6.5% at 8 T and 300 K. The magnetoresistance can be fitted to a model where there is a spin-dependent tunnelling between nanoparticles with a spin-disordered shell. The temperature dependence of the resistivity can be attributed to nanoparticle electrostatic charging effects. [ABSTRACT FROM AUTHOR]

The growth of oriented buffer layers by chemical solution deposition (CSD) on cube-textured Ni-based substrate is a key point for the development of low-cost YBa2Cu3O7-x (YBCO) coated conductor. Among the suitable compounds, La2Zr2O7 (LZO) and CeO2 are of particular interest as they enabled an all-chemical route for the fabrication of YBCO coated conductor. It has been recently shown that CSD films can be grown by direct precurson solution deposition on as-rolled, i.e., without cube orientation, metallic substrate. In particular, LZO film with biaxially {001}<110> texture has been successfully grown on either pure copper or Ni-W alloy substrate. In the present contribution, the deposition either LZO or Zr-doped CeO2 (CZO) on as-rolled Ni 3.5 at% W (Ni-W) substrate is reported. It is shown that film orientation enhances using low-roughness substrates, with an area fraction of {001}<110> oriented film as high as 96.4% for LZO and 95.4% for CZO. In both cases, the films are well adherent, without blister formation or delamination. Moreover, the film acts as a planarization layer, by smoothing Ni-W intrinsic roughness, also in correspondence of Ni-W grain boundary, where no grooving seems to appear on film surface. [ABSTRACT FROM AUTHOR]

High temperature superconducting tapes based on cuprate compounds are nowadays available on long lengths by several companies. Because high superconducting properties are strongly influenced by the crystallographic orientation of the superconducting film, and because the appropriate crystallographic orientation is obtained through epitaxial film growth, the development of an oriented template is of crucial technological importance. In the rolling assisted biaxially textured substrate (RABiTS) technique, a strong cube texture is obtained by cold rolling fcc metal tape and high temperature annealing, followed by the deposition of one or more buffer layer by either physical vapor deposition (PVD) or chemical solution deposition (CSD). Using the latter approach, it has been recently shown that it is possible to combine substrate recrystallization and buffer layer growth in a single step if the onset of recrystallization occurs at a temperature lower than buffer layer nucleation. In the present contribution, a detailed investigation of biaxially-oriented La 2 Zr 2 O 7 (LZO) buffer layer grown on cold-rolled Ni-W substrate by combined EBSD, AFM and TEM analyses is reported. It is shown that it is possible to obtain highly {001}〈110〉-textured LZO film directly on cold-rolled Ni-W substrate. Although some small polycrystalline regions appear, this approach leads to a strong suppression of grain boundary grooving typically occurring in RABiT-type substrates. Further, it is shown that, notwithstanding the microstructure of the metal substrate continues to evolve during the conversion heat treatment, the obtained LZO film is well adherent, without cracks or delamination. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles have been made by Ni and Fe implantation into a SiO 2 film with a Ni:Fe ratio of 82:18 both before and after electron beam annealing (EBA). Superparamagnetic nanoparticles with diameters ∼4 nm were observed after implantation. The moment per implanted ion at high magnetic fields was significantly lower than that reported for bulk Ni 1− x Fe x with a similar x , which may be due to some implanted ions not magnetically ordering and the appearance of antiferromagnetic phases. The high field moment did not follow Bloch's T 3/2 law where T is the temperature. This behaviour is likely to be due to spin-waves propagating in the nanoparticle/Ni y Fe 1− y Si z O n matrix as well as the effect of disordered spins on the surfaces of the nanoparticles. After EBA, a bimodal size distribution was observed with large isolated particles closer to the surface and smaller nanoparticles further into the film. Such a distribution has not been previously reported for similar Fe or Ni implantation. All of the Ni and Fe moments have magnetically ordered and the high field moment can be modelled using Bloch's law and a small contribution from disordered moments in the shell with an average thickness of ∼0.3 nm. [ABSTRACT FROM AUTHOR]

Hypervelocity dust has a speed of greater than 5 km/s and is a significant problem for equipment deployed in space such as satellites because of impacts that damage vulnerable components. Photovoltaic (PV) arrays are especially vulnerable because of their large surface area and the performance can be degraded owing to the disruption of the structure of the junction in the cells making up the array. Satellite PV arrays returned to Earth after service in orbit reveal a large number of craters larger than 5 μm in diameter arising from hypervelocity dust impacts. Extensive prior work has been done on the analysis of the morphology of craters in PV cells to understand the origin of the micrometeoroid that caused the crater and to study the corresponding mechanical damage to the structure of the cell. Generally, about half the craters arise from natural micrometeoroids, about one third from artificial Al-rich debris, probably from solid rocket exhausts, and the remainder from miscellaneous sources both known and unknown. However to date there has not been a microscopic study of the degradation of the electrical characteristics of PV cells exposed to hypervelocity dust impacts. Here we present an ion beam induced charge (IBIC) pilot study by a 2 MeV He microbeam of craters induced on a Hamamatsu PIN diode exposed to artificial hypervelocity Al dust from a dust accelerator. Numerous 5–30 μm diameter craters were identified and the charge collection efficiency of the crater and surrounds mapped with IBIC with bias voltages between 0 and 20 V. At highest bias, it was found the efficiency of the crater had been degraded by about 20% compared to the surrounding material. The speed distribution achieved in the Al dust accelerator was peaked at about 4 km/s compared to 11–68 km/s for dust encountered in low Earth orbit. We are able to extrapolate the charge collection efficiency degradation rate of unbiased cells in space based on our current measurements and the differences in the structure of the targets. [ABSTRACT FROM AUTHOR]

Highlights: [•] New method of arc discharge used to synthesise permalloy containing nanoparticles. [•] The highest quality powders were made using a 78% Ni permalloy rod in N2. [•] The Saturation moment was slightly less and the coercive field was low (3mT). [•] MR contributions from the spin-dependent tunneling between the particles. [Copyright &y& Elsevier]

Highlights: [•] TiO2 spherical nanopowders were successfully synthesized by arc discharge method. [•] Anatase to rutile phase transformation occurred before arc current reached to 50A. [•] TiO2 crystallite size was significant effected by the arc discharge current. [•] Up to 50% of near infrared reflection of TiO2 nanopowders was shown in this paper. [ABSTRACT FROM AUTHOR]

We report the catalyst-free synthesis of the arrays ofcore–shell,ultrathin, size-uniform SiC/AlSiC nanowires on the top of a periodicanodic aluminum oxide template. The nanowires were grown using anenvironmentally friendly, silane-free process by exposing the siliconsupported porous alumina template to CH4 H2plasmas. High-resolution scanning and transmission electron microscopystudies revealed that the nanowires have a single-crystalline corewith a diameter of about 10 nm and a thin (1–2 nm) amorphousAlSiC shell. Because of their remarkable length, high aspect ratio,and very high surface area-to-volume ratio, these unique structuresare promising for nanoelectronic and nanophotonic applications thatrequire efficient electron emission, light scattering, etc. A mechanismfor nanowire growth is proposed based upon the reduction of the aluminatemplate to nanosized metallic aluminum droplets forming between nanopores.The subsequent incorporation of silicon and carbon atoms from theplasma leads to nucleation and growth from the top of the aluminatemplate. [ABSTRACT FROM AUTHOR]

A detailed study on YBa2Cu3O7-δ (YBCO) films with BaZrO3(BZO) inclusions (YBCO-BZO) deposited on SrTiO3 substrate with different BZO contents is presented. X ray diffraction, SEM imaging and superconductive critical temperature (Ta) measurements were performed to evaluate film growth quality. Independently from the BZO content, all YBCO-BZO films showed Tc values close to that of pure YBCO indicating that the Tc reduction which is usually observed on YBCO-BZO films can be successfully recovered by changing the deposition conditions. All YBCO-BZO films showed an improved critical current density (Jc) dependence on magnetic field if compared to the typical Jc(H) of YBCO, resulting in higher irreversibility fields up to 9 T at 77 K. SEM observation on etched samples suggests a direct link between the defect density measured in YBCO-BZO samples and that calculated from the observed in field performances. The analysis of Jc(B) as a function of applied magnetic field direction revealed that the pinning due to isotropic pinning centers typical for YBCO is coupled with a c-axis correlated pinning in YBCO-BZO which can be ascribed to BZO induced columnar defects. Jc(B) recorded at several temperatures down to 10 K revealed matching effect features. [ABSTRACT FROM AUTHOR]

Much denser YBa2Cu3O7 (YBCO) superconducting films at least 1 μm thick with smooth surfaces have been obtained after introducing (Y/Nd)BCO multilayered structures. A significant enhancement of current carrying abilities has been achieved in these pulsed laser deposited films. The critical current density (Jc) has been increased by a factor of up to three in the entire field range. The imitation of the (Y/Nd)BCO multilayered structure by using YBCO ‘interlayers’ has also exhibited a considerable improvement in the current carrying ability. Similarities and differences between these two ‘multilayering’ approaches, leading to the observed effects, are discussed. The presence of interfaces even without element variation is likely to be the key to the improvements observed. In order to further promote Jc enhancement, small ‘multilayered’ additions of silver (Ag) to the films and multilayers provide various results: (i) rather strong enhancement for rather thin films and low addition levels, (ii) considerable degradation for large addition levels, and (iii) much less pronounced effect for thicker films. The enhancement of Jc is observed in zero and low magnetic fields, but has almost no effect at higher fields. All these experimental observations are discussed in terms of pinning, transparency and structural modifications introduced during the deposition of the film structures. [ABSTRACT FROM AUTHOR]

We have investigated the nature of the residual damage in diamond crystals following the ion implantation/graphitization 'lift-off' process, using near-edge x-ray absorption fine structure spectroscopy and transmission electron microscopy. A defective but crystalline interface is found, which displays dense pre-edge unoccupied states and an almost complete loss of the core-level C 1s exciton signature. This residual crystalline damage is resistant to standard chemical etching, however a hydrogen plasma treatment is found to completely recover a pristine diamond surface. Analysis and removal of residual ion-induced damage is considered crucial to the performance of many diamond device architectures. [ABSTRACT FROM AUTHOR]

Abstract Bismuth telluride (Bi 2 Te 3) based alloys are preferred thermoelectric materials for room temperature thermoelectric applications. Electrical transport and thermopower properties of n-type nanostructured Bi x Sb 2-x Te 3 films were tuned by post-growth heat treatment. We report that annealing of sputter-deposited nanostructured Bi 0.7 Sb 1.3 Te 3 films lead to several-fold increases in thermoelectric power factor α2σ, where σ is electronic conductivity and α is Seebeck coefficient. Annealing at T anneal = 200 °C nearly quadruples the power factor to α2σ = 3.1 μW cm−1 K−2. Spectroscopy and microscopy analyses indicate that the power factor increase is attributable to ~50% decrease in the Bi/Sb ratio, and grain growth, which increase the charge carrier concentration and mobility. The observed Bi depletion is contrary to annealing-induced Te depletion reported in p-type films. For T anneal > 200 °C, although continued Bi depletion increases σ, a precipitous decrease in α sharply lowers the power factor, yielding tenfold lower α2σ for T anneal = 400 °C than the as-deposited films. Our findings indicate that post-deposition annealing is a potent way to tune the thermoelectric properties of n-type Bi 2 Te 3 -based alloy films to fabricate devices for high-efficiency solid-state refrigeration and power harvesting from waste heat. Graphical abstract Unlabelled Image Highlights • Compositional, microstructural and thermoelectric properties of nanostructured n-type bismuth antimony telluride (Bi x Sb 2-x Te 3) • Multifold enhancement in thermoelectric power factor (PF) in Bi x Sb 2-x Te 3 films • PF enhancement correlates with annealing-induced grain growth and Bi depletion. • Thermal annealing potent way to improve PF by tuning composition and microstructure [ABSTRACT FROM AUTHOR]