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Reverse osmosis (RO) has been employed as a key separation process in many industrial applications. In recent years, the use of positron annihilation spectroscopy (PAS) including positron annihilation lifetime spectroscopy (PALS) and Doppler broadening of annihilation radiation to characterise the internal structure of the skin layer of thin film composite membranes has renewed research interest for further development and optimisation of the RO process. In this paper, we highlight the need for better understanding of the skin layer internal structure. We review relevant PAS techniques that could provide an unprecedented level of insight to our understanding of the internal structure of the active skin layer of RO membranes. PALS data reported in previous studies revealed that commercially available RO membranes have a mean free-volume hole-radius of 0.20–0.29 nm in the active skin layer. Data corroborated from the literature show a good correlation between the mean free-volume hole-radius of RO membranes and the rejection of boric acid which can be considered as a model small and neutral solute. The data also highlight the need for a comprehensive inter-laboratory study to standardise free-volume hole-radius measurement using PALS. In addition to free-volume hole-radius, free-volume fraction and thickness of the active skin layer appear to be important membrane properties governing neutral solute rejection. A roadmap is suggested to enhance the understanding of the transport of small and neutral solutes in RO. This includes integrating PAS with other techniques (e.g. molecular dynamics simulation) to describe the internal structure of RO membranes.

The electron emission properties of a coniferous carbon nano-structure (CCNS) based field emission electron gun have been measured. The CCNS was grown on a stainless steel substrate using chemical vapor deposition (CVD) and biased to about 50 kV. Stable, high-current-density electron emission (102 mA/cm 2 ) was measured continuously for more than 1300 h. This result compares favorably to printed and directly grown carbon nanotube (CNT) based emitters. A wide range of potential applications are foreseen for CCNS based electron emitters, such as high intensity X-ray sources.

The properties of materials involving polymer–solid interfaces are determined not only by the properties of the constituents but also by the interfacial region of the polymer near the solid, the so-called interphase. Here we report on positron annihilation lifetime spectroscopy (PALS) measurements of the free volume near the interface with a focused positron beam. The measurements were performed at an interface between a Teflon AF 1600 film and a 30 nm thick SiN membrane from the backside of a Si substrate which was locally etched away to expose the ultrathin SiN membrane. We were able to focus the positron beam onto the exposed region and to probe the SiN–Teflon AF 1600 interfacial region with low implantation energies, resulting in very narrow implantation profiles and excellent depth resolution. We found a pronounced decrease in orthopositronium lifetime close the interface. On the basis of modeling, we could estimate the interphase width and the average density increase in the interfacial region as ∼1...

The effects of heat treatment on membrane fouling resistance and the rejection of small and neutral solutes by reverse osmosis (RO) membranes were elucidated. RO membrane modification by heat treatment reduced fouling and improved boron rejection. However, heat treatment also caused a decrease in the water permeability of RO membranes. Significant improvement on fouling resistance by heat treatment was observed when RO concentrate was used to simulate a feed solution with high fouling propensity. The improved fouling resistance is likely to be due to changes in the hydrophobic interaction between the membrane surface and foulants. Boron rejection by the ESPA2 membrane was enhanced by heat treatment from 26 to 68% (when evaluated at the permeate flux of 20 L/m2 h). Positron annihilation lifetime spectroscopy revealed that heat treatment did not significantly influence the free-volume hole-radius of the membrane active skin layer. The results reported in this study suggested that changes in the other membrane properties such as free-volume fraction and thickness may be the main cause improving boron rejection.

This paper focuses on the innovative engineering design practice of the department of robotics at Kanazawa Institute of Technology in Japan.

When products requiring careful handling such as semiconductor wafers and food (hereinafter called “workpieces”) are transported in manufacturing processes, problems can occur due to malfunctions that degrade sanitary conditions during the transport of workpieces through contact. An excellent device for transporting workpieces is a pneumatic non-contact holder (hereinafter called “cup”). This device holds a workpiece without contact by using pneumatic pressure, and so a workpiece doesn’t suffer damage or contamination. The purpose of this paper is to propose a method for overcoming the weaknesses in vortex-type non-contact holders, which is a cup that can hold a workpiece by using the negative pressure generated by the centrifugal force of a swirling flow, and propose a shape of cup which will generates a larger holding force from the point of view of energy saving. Specifically, we changed the shape of the chamfer in the swirling chamber exits and the number of the nozzles, and measured the holding force characteristics and the pressure distribution of the cup, thereby examining the performance of the cups. The experimental results indicate that the holding force is strongly related to both the shape of the chamfer in the swirling chamber exits and the number of the nozzles.Copyright © 2017 by ASME

Slow positron beam and optical absorption measurements are carried out to study structural defects and positronium formation in 40 keV B(+)-implanted polymethylmethacrylate (B:PMMA) with ion doses from 6.25 × 10(14) to 5.0 × 10(16) ions/cm(2). Detailed depth-selective information on defects in implanted samples was obtained by measuring of Doppler broadening of positron annihilation γ rays as a function of incident positron energy and these experimental results were compared with SRIM (stopping and range of ions in matter) simulation results. Two general processes, appearance of free radicals at lower ion doses (10(16) ions/cm(2)) and carbonization at higher ion doses (10(16) ions/cm(2)), are considered from the Doppler S-E and W-E dependences in the framework of the concept of defects formation during radiation damage of polymer structure. Probabilities of ortho-positronium (o-Ps) formation are analyzed using S-W plot and slow positron annihilation lifetime measurements. Dose dependence of o-Ps lifetime τ3 and intensity I3 at the incident positron energy of 2.15 keV correlates well with the dose dependence of S-parameter and seems to account for the existence of the expected two processes, i.e., scission of polymer chains and appearance of free radicals preceding the aggregation of the clusters resulting in the formation of network of conjugated bonds at lower ion doses and carbonization at higher ion doses. The increase of optical absorption observed with increasing ion implantation dose also suggests a formation of carbonaceous phase in the ion-irradiated PMMA.

Open spaces in polyethylene terephthalate (PET) coated with aluminum silicate (Al x Si 1 − x O y ) were probed using monoenergetic positron beams. The energy distributions of the annihilation γ rays and the positron lifetime spectra were measured for 60-nm-thick Al x Si 1 − x O y ( x = 0–1) deposited on PET using electron-beam evaporation. A clear correlation was obtained between the line-shape S parameter of the annihilation γ rays, water vapor, and oxygen transmission rates. The results suggest that open spaces in the Al x Si 1 − x O y layers play an important role in water/oxygen diffusion in Al x Si 1 − x O y /PET, where the concentration/size of such spaces showed its minimum value at x = 0.2–0.3. The free volume fraction below the interface between Al x Si 1 − x O y and PET (region width = 100–400 nm) was decreased by the deposition of the coating layer, and this region was also considered to act as a barrier against penetrations of gasses and molecules.

We investigated the residual defects in low-dose (1013 cm−2) arsenic implanted Si after high-temperature (1100 °C) annealing. The presence of residual damage was successfully revealed after using a rapid thermal process for heat treatment. This damage was identified as vacancy-type defects distributed near the surface, such as tetravacancies or pentavacancies. When O2 gas was introduced to the annealing chamber, vacancy-type defects were transformed into divacancy and carbon–oxygen complex. They were confirmed to be created by a non-equilibrium reaction during the rapid cooling-down step in the annealing sequence.

The paper presents an assistive devices for health care workers and nurses. A new controlled assistive device for feeding gastrostomy and its control technique have been developed. The proposed controller scheme based on the internal model control (IMC) is able to generate appropriate pressure for the pressurized bag. Effectiveness of the assistive device has been verified by experiments.

Pore entrance size of cage-like pores in mesoporous silica films is difficult to be determined by conventional techniques. A simple expedient is proposed by using positron annihilation lifetime spectroscopy (PALS) based on a slow positron beam. Because of the nature of positronium (Ps, the bound state of a positron and an electron) in mesoporous silica, almost no Ps annihilates in the smaller connecting channels of cages. By trimethylsilylation of the silica, an appreciable fraction of Ps can be trapped and annihilate in the channels, which renders the possibility to estimate the pore entrance size from Ps lifetime in it.

We studied the grain size dependence of the defect evolution that occurred in a nanocrystalline (NC) Ni and its coarse-grained counterpart under irradiation. The vacancy defects produced during irradiation were investigated via in situ observations of the positron annihilation Doppler broadening spectra. The annihilation line-shape parameter S was measured under beam-on (during irradiation) and beam-off (after irradiation) conditions. We found that different variations in S were observed depending on the grain size; for the coarse-grained specimen, the S measured under beam-on conditions was larger than that observed under beam-off conditions, while for the NC specimen, the S value remained unchanged under beam-on and beam-off conditions. The former result indicated that the vacancy concentration was enhanced during irradiation, due to transient vacancy production. The latter result may imply that defect accumulation was strongly suppressed under irradiation. We also studied the flux dependence of the radiation damage effects for the NC specimen, using high-flux He ions in the flux range of 1.2 × 10 13 –6 × 10 14 ions/(cm 2 s). A slight flux dependence was observed, which was due to microstructural changes at the intersections of the crystallite interfaces under the highest flux irradiation studied.

Free-volume hole-radii of the active skin layer of one seawater and two low pressure reverse osmosis (RO) membranes – namely SWC5, ESPAB, and ESPA2 respectively – were evaluated using positron annihilation lifetime spectroscopy (PALS) with a slow positron beam. The results were related to the rejection of boric acid and eight N-nitrosamines to provide insights to the transport of these small solutes through RO membranes. At pH 8 (which is the experimental pH in this study), these solutes are uncharged. PALS analysis showed that the SWC5 has the smallest mean free-volume hole-radius (0.259 nm) among the three RO membranes investigated here. Correspondingly, the SWC5 membrane exhibited the highest rejection of boric acid and all N-nitrosamines. Results reported here also showed that the rejection of these chemicals increased in the order of increasing molecular volume. In addition, the difference in their rejection amongst the three RO membranes investigated here was most apparent for those (i.e., boric acid and N-nitrosodimethylamine (NDMA)) with a small molecular volume. The EPSA2 and ESPAB were determined to have mean free-volume hole-radius of 0.289 nm. However, the ESPAB membrane had lower water permeability and showed considerably higher rejection of boric acid and NDMA than the ESPA2 membrane. These results suggest that in addition to the mean free-volume hole-radius, other membrane parameters and properties such as the free-volume hole-radius distribution and thickness of the active skin layer can also play a role in governing the rejection of small and uncharged solutes by RO membranes.

P-selectin glycoprotein ligand-1 (PSGL-1) is an adhesive molecule that is known to be a ligand for P-selectin. An anti-adhesive property of PSGL-1 has not been previously reported. In this study, we show that PSGL-1 expression is anti-adhesive for adherent cells and we have elucidated the underlying mechanism. Overexpression of PSGL-1 induced cell rounding and floating in HEK293T cells. Similar phenomena were demonstrated in other adherent cell lines with overexpression of PSGL-1. PSGL-1 overexpression inhibits access of antibodies to cell surface molecules such as integrins, HLA and CD25. Cells transfected with PSGL-1 deletion mutants that lack a large part of the extracellular domain and chimeric construct expressing extracellular CD86 and intracellular PSGL-1 only showed rounded morphology, but there are no floating cells. These results indicated that PSGL-1 causes steric hindrance due to the extended structure of its extracellular domain that is highly O-glycosylated, but intracellular domain also has some effect on cell rounding. This study implies that PSGL-1 has Janus-faced functions, being both adhesive and anti-adhesive.

Commercial composite membranes for water purification were studied by means of the variable-energy positron annihilation γ-ray technique. The positron incident energy E dependence of R parameter (3γ/2γ ratio) analyzed from positron annihilation γ-ray spectra revealed the layer structure consisting of a dense top layer and a porous substrate for the membranes. Thickness of the dense layer for each membrane was evaluated from the R(E) based on a positron implantation stopping profile.

Mesoporous silica films on Si wafers were prepared via a sol-gel process using a triblock copolymer as the structural template. Spin-coated films were dried and subsequently subjected to Ar plasma treatments for decomposing the polymeric porogen. Mesopore formation in the silica film upon Ar plasma treatments was investigated by positron annihilation lifetime spectroscopy. In comparison with calcined silica film, much larger pores, more heterogeneous in size were found in silica film prepared with Ar plasma decomposition of the porogen.

We describe the recent installation of a new slow positron beamline at AIST and our plans to develop a dedicated superconducting accelerator for positron production. The new positron beamline is already installed and should be operational by the end of this fiscal year (March 2012). Initially positrons will be generated using a 70 MeV electron beam from the existing accelerator directed onto a newly installed converter and moderator assembly. The beamline has two experimental ports both dedicated to positron lifetime spectroscopy, one port with a focused beam (diameter ~ 30 microm) and the other unfocussed (~ 10 mm). A superconducting accelerator for positron production is currently under development. When completed, it will deliver a high frequency (~ MHz), high current (~ mA), short pulse length (< 100 ps) beam to the positron production target. We investigate the possibility of transporting the positron pulses thus produced directly onto samples for lifetime measurement. Such a scheme would remove the necessity for pulse stretching and chopping which is required with the existing LINAC and should allow for greatly increased slow positron transport efficiency.

Nafion® is one of the most popular proton conducting membranes for polymer electrolyte fuel cells (PEFCs). For the integration of Nafion® to the catalyst layers, very thin layers of the polymer are often formed on the catalysts of PEFC from dilute solutions. We applied energy variable positron annihilation to characterizing the structure of thin Nafion® films prepared by spin and dip coating from ethanol/water solutions of Nafion® on Si substrates. Experimental data suggest that the nano-structure of 23 nm thick spin coated Nafion® film is different from 220 nm thick film and also from 26 and 227 nm thick dip coated films, possibly due to the preservation of the unique rod-like structure of Nafion® in the dilute solution.

This study aimed to elucidate the optimum usage parameters of low reactive-level laser therapy (LLLT) in a rat incisional wound model. In Sprague-Dawley rats, surgical wounds of 15-mm length were made in the dorsal thoracic region. They were divided into groups to receive 660-nm diode laser irradiation 24 h after surgery at an energy density of 0 (control), 1, 5, or 10 J/cm2. Tissue sections collected on postoperative day 3 were stained with hematoxylin-eosin and an antibody for ED1 to determine the number of macrophages around the wound. Samples collected on day 7 were stained with hematoxylin-eosin and observed via polarized light microscopy to measure the area occupied by collagen fibers around the wound; day 7 skin specimens were also subjected to mechanical testing to evaluate tensile strength. On postoperative day 3, the numbers of macrophages around the wound were significantly lower in the groups receiving 1 and 5 J/cm2 irradiation, compared to the control and 10 J/cm2 irradiation groups (p

Depth profiling experiments by positron annihilation spectroscopy have been used to investigate the free volume element size and concentration in films assembled using the layer-by-layer (LbL) adsorption method. Films prepared from strong polyelectrolytes, weak polyelectrolytes, hydrogen-bonding polymers, and blended polyelectrolyte multilayers have different chain packing that is reflected in the free volume characteristics. The influence of various parameters on free volume, such as number of bilayers, salt concentration, solution pH, and molecular weight, has been systematically studied. The free volume cavity diameters vary from 4 to 6 Å, and the free volume concentrations vary from (1.1-4.3) × 10(20) cm(-3), depending on the choice of assembly polymers and conditions. Films assembled from strong polyelectrolytes have fewer free volume cavities with a larger average size than films prepared from weak polyelectrolytes. Blending the weak polyanion poly(acrylic acid), PAA, with the strong polyanion poly(styrene sulfonate), PSS, to layer alternately with the polycation poly(allyamine hydrochloride), PAH, is shown to be a viable method to achieve intermediate free volume characteristics in these LbL films. An increase in salt concentration of the adsorption solutions for films prepared from strong polyelectrolytes makes these films tend toward weaker polyelectrolyte free volume characteristics. Hydrogen-bonded layered films show larger free volume element size and concentration than do their electrostatically bonded counterparts, while reducing the molecular weight of these hydrogen-bonded polymers results in slightly reduced free volume size and concentration. A study of the effect of solution pH on films prepared from weak polyelectrolytes shows that when both polyelectrolytes are substantially charged in solution (assembly pH = 7.5), the chains pack similarly to strong polyelectrolytes (i.e., lower free volume concentration), but with smaller average cavity sizes. These results give, for the first time, a clear indication of how the free volume profile develops in LbL thin films, offering numerous methods to tailor the Ångström-scale free volume properties by judicious selection of the assembly polymers and conditions. These findings can be potentially exploited to tailor the properties of thin polymer films for applications spanning membranes, sensing, and drug delivery.

After the nuclear power plant accident in Fukushima, a significant amount of radioactive materials were released into the environment. The radiation exposure has brought lots of concerns about environments contamination, as well as economic and social consequences. Japan governmental agencies have started to continuously monitor and collect radiation levels by monitoring posts, probe cars and airborne surveys. These monitoring data contribute to estimate the external dose levels of radioactive materials and analyze human effects in the future. In this paper, we introduce the RALFIE (RAdiation Exposure LiFelog Indicator) system to help residents and experts to search for contaminated spots in daily activities and develop a reference guideline for reducing external exposures for individuals with their own data. First we design a model to integrate personal spatio-temporal positions with air dose rates on the real-time radiation monitoring data. Then we compare the relationship between ambient dose equivalent and individuals from D-shuttle sensors. Finally, we discuss how to create semantic trajectories with users' real-time annotation and geographic features with future directions.

The purpose of this research is to develop an assistive device for upper limbs. The disturbance estimation property of the internal model control is applied to detect motion intention of users. The experimental prototype of the assistive device for upper limbs is developed to evaluate the proposed control method. Effectiveness of the proposed method is verified by experiments. The experimental results include also that muscular activities occur in several muscles using surface electromyography. The proposed device is expected to maintain residual function of upper limbs.

Wood cellulose nanofibril films with sodium carboxylate groups prepared from a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized pulp exhibited an extremely low oxygen permeability of 0.0008 mL μm m(-2) day(-1) kPa(-1) at 0% relative humidity (RH). Positron annihilation lifetime spectroscopy (PALS) was used to determine the pore sizes in wood and tunicate TEMPO-oxidized cellulose nanofibril (TOCN-COONa) films in a vacuum (i.e., at 0% RH). PALS analysis revealed that the pore size of the wood TOCN-COONa films remained nearly at 0.47 nm from the film surface to the interior of the film. This is probably the cause of this high oxygen-barrier properties at 0% RH. The crystalline structure of TOCN-COONa also contributes to the high oxygen-barrier properties of the wood TOCN-COONa films. However, the oxygen permeability of the wood TOCN-COONa films increased to 0.17 mL μm m(-2) day(-1) kPa(-1) at 50% RH, which is one of the shortcomings of hydrophilic TOCN-COONa films.

The nanoscopic structure of three kinds of commercially available composite membranes (LF10, NTR729HF, and NTR7250) for water purification has been studied by energy-variable positron annihilation. The membranes consist of a functional polymer film and porous polysulfone substrate supported on a nonwoven polyester fabric. Positron annihilation γ-ray and positron lifetime techniques were employed to probe the layer structure of the composite membranes and subnanometer-sized free-volume holes in the functional films, respectively. It was found that the functional film on the porous substrate in LF10 contains two different layers on the substrate, while that in NTR729HF and NTR7250 consists of a single top layer. Comparison of the rejections of different uncharged solutes, determined by a pressure-driven experiment, with the hole size of the functional film, obtained from the positron lifetime data, revealed that the holes probed by positrons can well explain the hindering effect of molecular transport. More...

Thirteen different monoclonal antibodies against canine P-selectin glycoprotein ligand-1 (cPSGL-1) were obtained by immunization of rats with cells of a canine lymphoma cell line (Ema). O-sialoglycoprotein endopeptidase treatment of Ema cells showed that all of these antibodies recognized O-glycosylated peptides of canine PSGL-1. Experiments using deletion or point mutants of cPSGL-1 indicated that these antibodies could be categorized into several groups based on their cPSGL-1 recognition characteristics. These anti-cPSGL-1 monoclonal antibodies will be useful for analysis of the canine P-selectin and PSGL-1 system.

Granulocyte and monocyte adsorptive apheresis (GMA) has shown efficacy in patients with active ulcerative colitis (UC). However, with routine weekly treatment, it may take several weeks to achieve remission, and to date, the efficacy of a more frequent treatment schedule remains unknown. The aim of this study was to assess the clinical efficacy and safety of intensive GMA treatment in patients with active UC.This was an open-label, prospective, randomized multicenter study to compare an intensive, two GMA sessions per week, with the routine, one GMA session per week. A total of 163 patients with mild-to-moderately active UC were randomly assigned to routine weekly treatment or intensive treatment. The maximum number of sessions of GMA permitted was 10. However, when patients achieved remission, GMA was discontinued. Remission rate at the end of the study, time to remission, and adverse events were assessed in both groups.Of the 163 patients, 149 were available for efficacy analysis as per protocol, 76 were in weekly GMA, and 73 were in intensive GMA. At the end of the study period, clinical remission was achieved in 41 of 76 patients (54.0%) in weekly GMA and in 52 of 73 patients (71.2%) in intensive GMA (P=0.029). The mean time to remission was 28.1+/-16.9 days in the weekly GMA treatment group and 14.9+/-9.5 days in the intensive GMA group (P0.0001). Intensive GMA was well tolerated without GMA-related serious adverse side effects.Intensive GMA in patients with active UC seems to be more efficacious than weekly treatment, and significantly reduced the patients' morbidity time without increasing the incidence of side effects.

The influence of physical aging on the profile of free volume characteristics in thin polysulfone (PSF) films was investigated using variable energy positron annihilation lifetime spectroscopy. The PSF films exhibited decreasing o-Ps lifetime during physical aging, while o-Ps intensity remained constant. The o-Ps lifetime was reduced at lower implantation energies, indicating smaller free volume elements near the film surface (i.e., in the top ∼50 nm). These near-surface regions of the films age dramatically faster than bulk PSF. The accelerated aging is consistent with the notion of enhanced mobility near the film surface, which allows polymer near the surface to reach a lower free volume state more quickly than the bulk. No influence of the silicon wafer support on aging behavior was detected. Additionally, the impact of CO2 conditioning on physical aging was briefly examined. The results from these studies were compared to aging behavior of ultrathin PSF films tracked by gas permeability measurements, and favorable agreement was found.

Positron annihilation gamma energy distribution, lifetime spectroscopy and time-of-flight method were used to study surfactant-templated mesoporous silica films deposited on glass. The lifetime depth profiling was correlated to Doppler broadening and 3γ annihilation fraction measurements to determine the annihilation characteristics inside the films. A set of consistent fingerprints for positronium annihilation, o-Ps reemission into vacuum, and pore size was directly determined. The lifetime measurements were performed in reflection mode with a specially designed lifetime spectrometer mounted on a slow positron beam system. The intensity of the 142 ns vacuum lifetime component was recorded as a function of the energy of the positron beam. In a film with high porosity a reemission efficiency of as high as 40 % was found at low positron energy. Positron lifetime in samples capped by a thin silica layer was used to determine the pore size. The energy of the reemitted o-Ps fraction was measured by a time-of-flight detector, mounted on the same system, allowing determination of both o-Ps re-emission efficiency and energy in the same sample. We demonstrate the potential of the simultaneous use of different positron annihilation techniques in the study of thin porous films.

To improve the spatial resolution of positron annihilation spectroscopy (PAS), a system to produce an intense positron microbeam was developed in AIST. A slow positron beam, which was produced by an electron linear accelerator, was focused by a lens onto a remoderator to enhance its brightness. The brightness-enhanced beam with an intensity of ≈1 × 106 e+/s was extracted from the remoderator and focused onto the sample by a lens. The beam size at the sample was 25 μm, which is more than two and half orders of magnitude smaller than that in the magnetic transport system (≈10 mm). Hence, the spatial resolution of PAS with an AIST positron microbeam can be drastically improved relative to PAS using conventional methods.

Mesoporous silica films were synthesized via a sol–gel process under an acidic condition. Various amounts of triblock copolymer F38 were loaded to precursor sols as the pore generator. The evolution of the pores generated by porogen decomposition was investigated as a function of F38 loading by positron annihilation gamma-ray energy spectroscopy and positron annihilation lifetime spectroscopy based on slow positron beams. The threshold of pore percolation is found to be around 10 wt% of F38 loading by positron annihilation gamma-ray energy spectroscopy. Positron annihilation lifetime spectroscopy in the films show that the pore size increases from 1 nm to 3 nm with increasing F38 loading from 5 wt% to 30 wt%.

Plasma-enhanced chemical vapor deposition (PE-CVD) low-dielectric (low-k) film was irradiated with ultra violet (UV) light of wavelength 172 nm to enhance mechanical strength and reduce dielectric constant (k value). The thickness measurement method for the UV annealed low-k film is discussed. The effects of UV irradiation on dielectric constant, shrinkage, stress, density, pore size, mechanical strength, and structure are clarified and the mechanism is discussed.

The impact of TiN deposition on thin high-k (HfO2 and HfSiON) films formed on Si substrates was studied using monoenergetic positron beams. For the predeposition sample, the positrons implanted into Si diffuse toward the high-k/Si interface under the influence of the electric field, suggesting the presence of negative charges in the high-k films. After TiN was deposited on HfO2, positive charges were introduced at the TiN/HfO2 interface, which were associated with the incorporation of nitride into HfO2, resulting in the formation of positively charged oxygen vacancies (VOs). From the isochronal annealing experiments for TiN/HfSiON/Si, it was found that positively charged defects (such as VO) were introduced into HfSiON after annealing at 700–900 °C. These defects were introduced by the interaction between TiN and HfSiON, resulting in the formation of polycrystalline TiO2 at the interface. The positively charged defects were annealed out at 1100 °C, but the dielectric properties of HfSiON degraded.

Positron annihilation was used to probe vacancy-type defects in electroplated Cu fabricated using different electrolytes. Isochronal annealing experiments revealed that the agglomeration of vacancy-type defects in grains was observed below 200 °C and that their concentration started to decrease above 300 °C. The observed annealing stages of the defects agree with those for pure Cu irradiated with light particles such as electrons. The size and concentration of vacancies decreased with decreasing concentrations of residual impurities in Cu films. A decrease in the impurity concentration, however, increased the failure rate of Cu interconnects in a stress-induced voiding test. Thus, void formation related to stress-induced failure can be reduced through the introduction of vacancy clusters into grains.

Positron annihilation lifetime spectroscopy (PALS) based on a pulsed slow positron beam was applied to study mesoporous silica films, synthesized using amphiphilic PEO–PPO–PEO triblock copolymers as structure-directing agents. The pore size depends on the loading of different templates. Larger pores were formed in silica films templated by copolymers with higher molecular-weights. Using 2-dimensional PALS, open porosity of silica films was also found to be influenced by the molecular-weight as well as the ratio of hydrophobic PPO moiety of the templates.

Subnanoporosity was introduced into SiOCH-based thin films by mixing tetraethyl orthosilicate with hexamethyldisiloxane (HMDSO) in the plasma enhanced chemical vapor deposition process, and was evaluated by the variable-energy positron annihilation lifetime technique. It was found that with increasing the HMDSO fraction both porosity and pore size were enhanced, as evidenced by the decreased refractive index and increased ortho-positronium lifetime. The lifetimes from 2.0 to 6.8 ns suggested the tunable pore volumes within a range of 0.1–0.7 nm3.

Positron annihilation spectroscopy (PAS) based on an intense pulsed slow positron beam was applied to the study of mesoporous silica films, synthesized using tetraethyl orthosilicate (TEOS) as the network precursor and a triblock copolymer (EO 106 PO 70 EO 106 ) as the structure-directing agent. With positron annihilation lifetime spectroscopy (PALS), pore sizes were obtained from ortho -positronium ( o -Ps) lifetimes of the films capped with a 20 nm thick SiO 2 layer. Influences of preparation conditions such as heating, TEOS vapor infiltration and precursor solution ageing on the pore size were studied. Moreover, the effect of ageing of the precursor solution on film pore interconnectivity/open porosity was investigated through lifetime–energy correlation measurements by observing intrinsic annihilation of o -Ps diffused out from the uncapped film surface.