Table of contents

Spatially resolved atomic densities of argon 1s levels in a capacitively coupled plasma are measured by using an OES branching fraction method with the mono-directional escape factor. Different spatial profiles of the densities of the metastable and resonance levels are observed. The resonance levels increase more drastically than the metastable levels with the distance from the power electrode in the sheath, while in the bulk plasma, both resonance and metastable levels are more uniform. The relationship between the distribution of the electron density and those of the metastable and the resonance levels is also discussed.

Electrical bistable behaviour was demonstrated in memory devices based on n-type FeS₂ nanocrystals (NCs) embedded in a p-type poly(3-hexylthiophene) (P3HT) matrix. An organic/inorganic hybrid non-volatile memory device with a type-II band alignment, fabricated by a spin-coating process, exhibited electrical bistable characteristics. The bistable behaviour of carrier transport can be well described through the space-charge-limited current model. The small amount of FeS₂ NCs in this device serve as an excellent charge trapping medium arising from the type-II band alignment between FeS₂ and P3HT. Our study suggests a new way to integrate non-volatile memory with other devices such as transistor or photovoltaic since the presented FeS₂/P3HT offers a type-II band alignment.

Planar anisotropy Y₂Fe₁₇ powders were fabricated by rapid quenching and ball-milling techniques. The frequency dependence of complex permeability and permittivity of paraffin composites with 35 vol% Y₂Fe₁₇ powders have been investigated in the frequency range 0.1–10 GHz. The oriented composite shows a dramatic increase in permeability and a remarkable decrease in the matching thickness. The minimum reflection losses of unoriented Y₂Fe₁₇ composite and oriented Y₂Fe₁₇ composite were −48 dB at 2.34 GHz and −59 dB at 3.4 GHz, and the corresponding thicknesses were only 3.9 mm and 2.3 mm, respectively. Otherwise, the product of the static permeability and the resonance frequency for the oriented Y₂Fe₁₇ compound is 91.6 GHz, which is much higher than the value of 15.3 GHz calculated by Snoek's limit equation. Hence, the Y₂Fe₁₇ composite, with the specific property of the planar anisotropy, has great potential applications in the field of high-frequency microwave absorption.

(Fe_66.9Co_33.1)_86.8Sm_13.2 (FeCoSm) thin films with thickness from 110 to 330 nm are fabricated on silicon (1 1 1) substrates by magnetron co-sputtering under ambient condition. The as-deposited FeCoSm thin film is amorphous when the thickness is less than 150 nm. When the thickness increases further, the film becomes partially crystallized. The maximum in-plane uniaxial anisotropy field is up to 1200 Oe. After the films are heat treated in vacuum with a magnetic field, the in-plane uniaxial anisotropy field decreases with an increase in annealing temperature and becomes zero after annealing at 500 °C. The dynamic magnetic properties of the FeCoSm films are also investigated in the range 0.1–9 GHz. Based on the one-terminal micro-strip transmission-line perturbation method and an analysis by the Landau–Lifshitz equation, the anisotropy field and the resonance frequency of the FeCoSm_films are in the range 50–1200 Oe and 1.8–12.1 GHz, respectively. The anisotropy field and resonance frequency of the film can be controlled by varying the film thickness or annealing temperature, this means that FeCoSm films have great potential in high-frequency applications.

L1₀ CoPt nanoparticles with face-centred tetragonal (FCT) structure are synthesized by the sol–gel method. Differential thermal analyses show the dehydration of various water molecules and decomposition/combustion of organic groups at a temperature below 600 °C and melting of Co and Pt at 700 °C. X-ray diffraction results show a transition from face-centred cubic to the FCT phase and an increase in particle size with increasing temperature. Transmission electron microscope (TEM) images show that highly monodisperse particles are obtained. High-resolution TEM (HRTEM) images reveal the appearance of L1₀ ordered phase at temperatures above 600 °C. The survey scans of x-ray photoelectron spectroscopy show that no magnetic impurity is detected within the detection limit. The maximum coercivity (353 344 A m⁻¹) is obtained for the samples heated at 800 °C. The relationship between the temperature and the structure is discussed and the possible growth mechanism is given in terms of atomic diffusion.

We propose a single panel liquid crystal (LC) device that is switchable between reflective and transmissive modes. Operation in the reflective mode can be achieved by applying a vertical field to a dye-doped LC device, whereas the device can be in-plane switched for operation in the transmissive mode. Image inversion that was inevitable in a single panel device using a reflective polarizer is effectively eliminated through the absorption of ambient light by the dye-doped LCs. We believe that the proposed device can be applied to various display systems for outdoor mobile use.

A photonic band-gap cavity (PBGC) gyrotron with a frequency of about 98 GHz is designed. Theoretical analyses and numerical calculations are made for the PBGC operating at fundamental and second cyclotron harmonic with a TE₃₄ waveguide mode to demonstrate the beam–wave interaction. The results show that mode competition is successfully eliminated in the PBGC using mode selectivity and choosing the appropriate operating parameters. As a result, the second harmonic PBGC gyrotron operating at TE₃₄ mode achieves a higher output efficiency than that of the fundamental. It is also demonstrated that, in the case of the chosen parameters for TE₃₄ waveguide mode, the use of PBG structure in the second harmonic gyrotron brings about not only a lower operating B-field but also a weaker mode competition. The results show that the high-order electromagnetic mode can be developed to interact with the high cyclotron harmonic using the selectivity of the PBGC, which gives an encouraging outlook for the development of high-harmonic gyrotrons.

In this paper we present a complete theoretical analysis of the oscillating photocarrier grating (OPG) method, starting from the generalized equations that describe charge transport and recombination under oscillating grating illumination conditions. The solution of these equations allows us to implement a calculation reproducing the experimental OPG curves. We study both experimentally and from our calculations the dependence of the OPG curves on different external parameters, such as the applied electric field, grating period and illumination intensity. We find that the response of the sample is linked to a characteristic time of the material, which could be the dielectric relaxation time or the small signal lifetime depending on the regime at which the experiment is performed. Therefore, the OPG technique provides a simple method to estimate these parameters. In addition, we demonstrate that the small signal lifetime provides information on the density of states of the material.

Cold atmospheric pressure plasmas can be used for treatment of living tissues or for inactivation of bacteria or biological macromolecules. The treatment is usually characterized by a combined effect of UV and VUV radiation, reactive species and ions. This combination is usually beneficial for the effectiveness of the treatment but it makes the study of fundamental interaction mechanisms very difficult. Here we report on an effective separation of VUV/UV photons and heavy reactive species in the effluent of a microscale atmospheric pressure plasma jet (μ-APPJ). The separation is realized by an additional flow of helium gas under well-defined flow conditions, which deflects heavy particles in the effluent without affecting the VUV and UV photons. Both components of the effluent, the photons and the reactive species, can be used separately or in combination for sample treatment. The results of treatment of a model plasma polymer film and vegetative Bacillus subtilis and Escherichia coli cells are shown and discussed. A simple model of the He gas flow and reaction kinetics of oxygen atoms in the gas phase and at the surface is used to provide a better understanding of the processes in the plasma effluent. The new jet modification, called X-Jet for its appearance, will simplify the investigation of interaction mechanisms of atmospheric pressure plasmas with biological samples.

We present details of an experimental facility developed for the diagnostics of highly charged ions produced during pulsed laser ablation of solid targets. A range of laser fluences (2–10 J cm⁻²) from a Q-switched Nd : YAG laser (wavelength = 1064 nm, pulse duration ∼10 ns) was used to generate a copper plasma. The ion diagnostics were based on the time-of-flight (TOF) methods; an ion collector and a 45° parallel plate electrostatic ion energy analyser were used. A channel electron multiplier located 1.31 m away from the Cu target was used to record the energy-resolved TOF ion spectrum. The effect of laser fluence on the total ion charge, average ion energy and charge state distribution was investigated. The estimated threshold fluence for the onset of the plasma was 2.5 J cm⁻². About four times increase in both average ion energy and total ion charge was observed in the investigated laser fluence range. The maximum attainable charge state of the Cu ions increased from 1+ to 7+ with the increase in laser fluence. The correlation between relative abundance of the various ion charge states indicated that the formation of Cuⁿ⁺ occurred through ionization from Cu⁽ⁿ⁻¹⁾⁺ by the impact of fast electrons or by multiphoton interactions.

Measurements are presented of the most probable time-averaged ion velocities within the acceleration channel and in the plume of a diverging cusped-field thruster operating on xenon. Xenon ion velocities for the thruster are derived from laser-induced fluorescence measurements of the 5d[4]_7/2–6p[3]_5/2 xenon ion excited state transition centred at λ = 834.72 nm. The thruster is operated in both a high-current mode, where the anode discharge current is shown to oscillate periodically, and a low-current mode where operation is relatively quiescent. In the low-current mode, ion emission is predominantly in the form of a conical jet, whereas in the high-current mode, the emission is still divergent but more diffuse throughout the cone angle. These time-average measurements provide insight into the structure of the acceleration region. However, discerning the mechanism for the diffuse ion emission in the strongly oscillating high-current mode will require ion velocity measurements capable of resolving the time-dependent behaviour of the discharge.

Rectification ratios of 10⁵ were observed in printed organic copper/polytriarylamine (PTAA)/silver diodes with a thin insulating barrier layer at the copper/PTAA interface. To clarify the origin of the high rectification ratio in the diodes, the injection, transport and structure of the diodes with two different copper cathodes were examined using impedance spectroscopy and x-ray photoelectron spectroscopy (XPS). The impedance data confirm that the difference in diode performance arises from the copper/PTAA interface. The XPS measurements show that the copper surface in both diode structures is covered by a layer of Cu₂O topped by an organic layer. The organic layer is thicker on one of the surfaces, which results in lower reverse currents and higher rectification ratios in the printed diodes. We suggest a model where a dipole at the dual insulating layer induces a shift in the semiconductor energy levels explaining the difference between the diodes with different cathodes.

The smart-cut™ process is based on inducing and processing structural defects below the free surface of semiconductor wafers. The necessary defects are currently induced by implantation of light elements such as hydrogen or helium. An alternative softer way to induce shallow subsurface defects is by RF-plasma hydrogenation. To facilitate the smart-cut process, the wafers containing the induced defects need to be subjected to an appropriate thermal treatment. In our experiments, (0 0 1) Si wafers are submitted to 200 and 50 W hydrogen RF-plasma and are subsequently annealed. The samples are studied by transmission electron microscopy (TEM), before and after annealing. The plasma-introduced defects are {1 1 1} and {1 0 0} planar-like defects and nanocavities, all of them involving hydrogen. Many nanocavities are aligned into strings almost parallel to the wafer surface. The annealing is performed either by furnace thermal treatment at 550 °C, or by in situ heating in the electron microscope at 450, 650 and 800 °C during the TEM observations. The TEM microstructural studies indicate a partial healing of the planar defects and a size increase of the nanometric cavities by a coalescence process of the small neighbouring nanocavities. By annealing, the lined up nanometric voids forming chains in the as-hydrogenated sample coalesced into well-defined cracks, mostly parallel to the wafer surface.

In this work, the damage formation in InN layers has been investigated subsequent to europium implantation at 300 keV and room temperature. The layers of several micrometres were produced by hydride vapour phase epitaxy and used as matrices for ion implantation experiments due to their good crystalline quality. From this investigation, it is shown that InN exhibits a low stability under rare earth ion implantation. Starting at a low fluence of around 5 × 10¹² Eu cm⁻², an extensive modification of the surface layer takes place. The dissociation of InN and the presence of misoriented nanograins are observed in the damaged area. Analysis by electron diffraction indicates that the nanograins correspond to indium oxide In₂O₃.

Both hardness (H) and rate sensitivity (m) of nanocrystalline NiFe alloys were studied by nanoindentation testing. It was found that H increases, and m decreases after rolling in the alloys. It is interesting that the decrease in m by rolling is totally contrary to the conventional coarse grain alloys. The dislocation density is remarkably enhanced by rolling deformation, which leads to the hardening behaviour of the samples. The dislocation absorbed at the grain boundary (GB) and/or sub-GB and grain growth by rolling are responsible for the reduced m of the rolled alloys.

The ternary chalcogenide of Cu₃SbSe₄ is demonstrated to be a novel p-type thermoelectric material, by doping Sn in the Sb site. The figure of merit (ZT) in Cu₃Sb_0.975Sn_0.025Se₄ reaches 0.75 at 673 K. Such excellent thermoelectric properties are attributed to the crystal structure of Cu₃SbSe₄, consisting of the three-dimensional Cu/Se framework acting as the hole conduction pathway and the [SbSe₄] tetrahedra. The Cu/Se framework is suitable to tune the electrical conductivity by doping. The insertion of tetrahedral [SbSe₄] causes a more distorted diamond-like structure, providing a relatively lower lattice thermal conductivity and a relatively large Seebeck coefficient. The origin of the structure–electrical property relationship and ZT enhancement by Sn doping is elucidated.

Thermally transferred optically stimulated luminescence (TT-OSL) of quartz is the low intensity OSL measured after heating a previously optically zeroed quartz to temperatures below that erasing the OSL electron trap. We identify the source traps contributing to TT-OSL by studying the changes in TT-OSL and thermoluminescence (TL) caused by optical bleaching at various temperatures and by repeated TT-OSL measurements, and quantify source-trap parameters using the Hoogenstraaten method. We find that both the single transfer mechanism and the double transfer mechanism are contributing to TT-OSL production. Three source traps are identified when the samples are heated to 300 °C for 10 s to induce the thermal transfer. The first one corresponds to a TL peak at ∼200 °C. It captures electrons during the optical bleaching and releases these charges during subsequent heating. It provides ∼10% of the electrons that give rise to TT-OSL. The second trap corresponds to a TL peak at 290–300 °C and provides ∼80% of the electrons for TT-OSL through the single transfer mechanism. This electron trap has a depth of 1.34 ± 0.05 eV and a frequency factor in the order of 10¹¹ s⁻¹. It has a mean lifetime of 0.24 Ma at 10 °C. The third trap corresponds to a TL peak at ∼380 °C and provides ∼10% electrons for TT-OSL through the single transfer mechanism. It has a depth of 1.66 ± 0.07 eV and a frequency factor in the order of 10¹² s⁻¹. To validate the techniques used we also determined the parameters of the fast component OSL trap and received results consistent with published values. Most importantly, our results show that the relatively short lifetime of the main TT-OSL source trap limits possibilities of using TT-OSL to extend the age range of quartz OSL dating, as has been suggested by various authors.

This paper reports the design of an electromagnetic vibration energy harvester that doubles the magnitude of output power generated by the prior four-bar magnet configuration. This enhancement was achieved with minor increase in volume by 23% and mass by 30%. The new 'double cell' design utilizes an additional pair of magnets to create a secondary air gap, or cell, for a second coil to vibrate within. To further reduce the dimensions of the device, two coils were attached to one common cantilever beam. These unique features lead to improvements of 66% in output power per unit volume (power density) and 27% increase in output power per unit volume and mass (specific power density), from 0.1 to 0.17 mW cm⁻³ and 0.41 to 0.51 mW cm⁻³ kg⁻¹ respectively. Using the ANSYS multiphysics analysis, it was determined that for the double cell harvester, adding one additional pair of magnets created a small magnetic gradient between air gaps of 0.001 T which is insignificant in terms of electromagnetic damping. An analytical model was developed to optimize the magnitude of transformation factor and magnetic field gradient within the gap.

On page 4 in the second paragraph, the first sentence should read:

The delay time of the current source, which is realized by an electronic device, varies so much in dependence on the operating parameters that the 'sync' output of the signal generator, by which the current source is controlled, is unsuitable to provide an appropriate trigger pulse.

This paper reported on highly transparent self-cleaning surfaces of zinc oxide synthesized via the sol–gel route. The results, including the x-ray diffraction, optical transmittance spectra, atomic force microscopy and the contact angles, were also reported in the paper, along with a discussion on the hydrophobic properties of zinc oxide. However, upon further investigation of the hydrophobicity of zinc oxide thin films, we found that the contact angles originally reported were not reproducible, and hence this might have led to incorrect and ambiguous analysis of the properties of zinc oxide thin films. The inconsistency in the data and the ambiguities oblige the authors to retract the above article.