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In this study, we fabricated quasi-antiferromagnetic (AFM) layers and investigated the magnetic dynamics of quasi-AFM in both an experiment and simulation. Quasi-AFM has multi domains with alternating antiparallel magnetization, which can be realized by using 90 degrees magnetic coupling between two ferromagnetic layers. In magnetic resonance measurement, a frequency and damping constant of CoFe-based quasi-AFM are higher than those of conventional CoFe. Likewise, in micromagnetic simulation, we obtained the spin torque oscillation (STO) in Quasi-AFM with high frequency. This suggests the possibility of a novel material with the high frequency wave generator without a stray field, like antiferromagnetic materials.

In this paper, we demonstrate a wet treatment for the HfSix/HfO2 gate stack of n-type metal oxide semiconductor field effect transistor (nMOSFET) fabricated by a gate-last process in order to scale down the electrical thickness at inversion state Tinv value and reduce the gate leakage Jg. As a result, we succeeded in scaling down Tinv to 1.41 nm without mobility or Jg degradation by ozone–water-last treatment. We found that a high-density interfacial layer (IFL) is formed owing to the ozone–water-last treatment, and Hf diffusion to the IFL is suppressed, which was analyzed by high-resolution angle-resolved spectroscopy.

We propose a fluorine (F) treatment technique that is suitable for threshold voltage (Vth) modulation in p-channel metal–oxide–semiconductor field-effect transistors (PMOSFETs) with the atomic layer deposition (ALD) TiN/HfO2 gate structure. A work function near the band edge is achieved using the F treatment technique without the degradation of hole mobility in PMOSFETs. Vth shift value is almost the same regardless of gate length. The barrier height shift attributable to the F treatment corresponds closely to the Vth shift. It is found that the F treatment technique modulates the effective work function. No Vth shift in n-channel MOSFET (NMOSFETs), namely, the ALD-TiN/HfSix/HfO2 gate stack structure, is observed with F treatment. It is confirmed that F treatment is a suitable technique for complementary MOSFET (CMOSFETs) due to the confinement of Vth shift only to PMOSFETs.

The propagation of transverse waves generated acoustically in a piezoelectric element by colliding it with hypervelocity microparticles was studied. The propagation times were measured by a set of multiple electrodes on the surface of the element. The coordinates that the particles struck were determined by combining the propagation times and the velocity of the waves. By using the position-sensitive element, significant deviations between the prior indicated and actually measured orbits were observed. The potential of the present element as part of a steering system is discussed.

A short-pulse (~210 fs) high-power (~1 TW) laser was focused on a tape target 3 and 5 µm in thickness to a size of 11×15 µm2 with an intensity of 3×1017 W/cm2. Protons produced by this laser with an energy spread of 100% were found to be improved to create peaks in the energy distribution with a spread of ~7% by the application of the RF electric field with an amplitude of ±40 kV synchronous to the pulsed laser. This scheme combines the conventional RF acceleration technique with laser-produced protons for the first time. It is possible to be operated up to 10 Hz, and is found to have good reproducibility for every laser shot with the capability of adjusting the peak positions by control of the relative phase between the pulsed laser and the RF electric field.

We have developed a terahertz time-domain magnetooptical measurement system for investigating the carrier transport of semiconductors at low temperatures and high magnetic fields. To cool a superconducting magnet and a sample, Gifford–McMahon-type refrigerators were employed to avoid the use of liquid cryogen. However, the vibration of the refrigerator is a critical problem because it induces oscillation noise in measured waveforms of terahertz pulses. In order to overcome this problem, a synchronous data sampling method has been developed utilizing the sound of the refrigerator as a trigger for the waveform acquisition. This sampling method succeeded in eliminating the oscillation noise completely. Our measurement system enables us to obtain the magnetooptical spectra in the frequency range from 0.2 to 1.5 THz at temperatures between 5 and 300 K in magnetic fields of up to ±10 T. As an example, the measurement of the cyclotron resonances of a two-dimensional electron gas in a GaAs/AlGaAs heterostructure is demonstrated.

Data for detecting magnetic flux surfaces at the edge plasma in tokamaks are presented here. When magnetic flux surfaces are moved by a plasma jog, it is observed that a current increment appears in the two sets of double probes whose front surfaces are shifted by a small distance and that a difference between these two currents through the differential amplifier giving a signal of the arrival of the separatrix also appears; we refer to consider the separatrix point as a typical position of the magnetic flux surfaces. It is confirmed that magnetic flux surfaces are located a few cm outward from that calculated by the eqfit-code (EQFIT) and that the absolute value of its deviation is identified. This identification is supported by the result of the observation of the correlation of the floating potential fluctuation between two different points using one probe pin of the same differential as the same double probes. The ion temperature and the space potential are observed by the another use of the differential double probe are modified following the estimated real magnetic surfaces positions.

Highly c-axis-oriented aluminum nitride (AlN) films were deposited by reactive rf magnetron sputtering on molybdenum (Mo) films for film bulk acoustic wave resonators (FBARs). We investigated the effect of underlayer materials on the crystalline qualities of AlN/Mo bilayers. AlN/Mo bilayers were sputter-deposited on silicon, silicon dioxide and AlN underlayers under the same sputtering conditions. The results revealed that the AlN underlayer markedly improves Mo film quality, and this greatly affects the orientation of the upper AlN film. By applying the AlN underlayer, we obtained a full width at half maximum of 2.3° from the X-ray diffraction rocking curve of the AlN film grown on a Mo film. We propose that the large surface energy of AlN is the reason the AlN underlayer improves the quality of the Mo films. In the FBAR with the AlN underlayer, a quality factor of 800 and an effective electromechanical coupling coefficient of 5.7% were achieved.

The four-beam correlation method has a potential of measuring fine-scale fluctuations locally. In the method, many lines of sight are measured and the coherences among them are calculated. As a proof of principle experiment, a visible fluctuation measurement system has been fabricated and applied to the TST-2 spherical tokamak plasma. Using this system, fluctuations were measured and high-frequency components (100±12.5 kHz) were analyzed. Because of a long parallel correlation length, local information was not obtained directly. However, comparison of the experimental results and those of a model calculation suggests that (i) the fluctuating emission is relatively localized in the peripheral region of the plasma, (ii) the perpendicular correlation length is of the order of 1 cm, while the parallel one is much longer than it and (iii) the magnetic field angle in the peripheral region agrees with that estimated from magnetic measurements.

In this paper, we report the first measurement of the time-integrated spatial coherence of the Ni-like Ag X-ray laser at 13.9 nm pumped by a 1.5 ps, 20 J Nd glass laser, in which the transient collisional excitation (TCE) pumping scheme is realized. The time-integrated complex coherence factor (CCF) of the X-ray laser has been determined from partially coherent diffraction patterns of a multislit array placed 1 m away from the X-ray laser source. The transverse coherence lengths in the directions horizontal and vertical to the Ag target surface are estimated respectively to be within 110 µm to 140 µm at a position 1 m from the X-ray laser source. We tried to explain the profile of the CCF with a quasi-monochromatic incoherent source model with various profiles.

We propose and experimentally prove a new signal detection method for optical disc systems, named "modified correct far-field (MCFF)", which realizes a stable servo control to various digital versatile discs (DVDs) with different groove specifications with using one photo detector.

The bias-stress-induced degradation characteristics of p-channel polysilicon (poly-Si) thin film transistors (TFTs) hydrogenated by plasma, H2 and H2/plasma processes are investigated. It is found that the stress time dependence of the transfer characteristics and the threshold voltage shift is affected by the hydrogenation processes and the quantity of hydrogen in the active channel layer of TFTs. These behaviors are mainly caused by the difference in the generation of defect states, that is, band tail states, deep traps corresponding to dangling bonds at/near the poly-Si/SiO2 interface, and positively charged traps corresponding to Si+ atoms created by H+ ions in the oxide. We propose a model to explain these behaviors.

The degradation characteristics under various bias stress conditions are systematically investigated in hydrogenated n- and p-channel polysilicon thin film transistors (poly-Si TFTs) with a sidewall spacer. The device characteristics after a relatively long stress in the p-channel TFTs exhibit more serious degradation than those in the n-channel TFTs. Moreover, the stress time dependence of the threshold voltage shift in the former devices shows more complicated behavior than that in the latter. These serious and complicated time-dependent degradation characteristics (induced only in p-channel devices) can be explained by the generation of two defect states in which hydrogen plays an important role: one is positively charged traps that correspond to Si+ atoms generated by the injection of H+ ions into the gate oxide near the source and appear after a certain stress time. The other is deep traps that correspond to dangling bonds generated by the dissociation of Si–H bonds at/near the interface near the source and appear after a long stress time.

A submicron soft X-ray beam is generated by a highly coherent soft X-ray laser at 13.9 nm with a Fresnel phase zone plate. The focused X-ray beam profile is measured using a knife-edge scan method, and the spot diameter and peak intensity are 0.5 µm at full width at half maximum and 1 ×1011 W/cm2, respectively.

A freestanding (0001)AlN substrate with a thickness of 112 µm was successfully prepared by hydride vapor phase epitaxy (HVPE) of AlN at 1230 °C on a (111)Si starting substrate and subsequent removal of the Si substrate using a chemical etchant. The AlN substrate was transparent and displayed a smooth surface without cracks. Plan-view transmission electron microscopy (TEM) observations at the top surface of the AlN substrate revealed that an average dislocation density of 3 ×109 cm-2 was achieved. The dislocations were found to run inclined from the direction of growth. The AlN substrate exhibited a near-band-edge emission at 209.4 nm in the room-temperature photoluminescence spectrum.

A T-shaped high-power switching device composed of circular corrugated waveguides with three ports and double dielectric disks made of sapphire was proposed as a fast switching device based on a new principle in electron cyclotron current drive systems. This switching device has the advantages of operating at a fixed frequency and being compact. The design of the prototype switch was obtained by numerical simulations using a finite-difference time-domain (FDTD) method. The size of these components was optimized for the frequency band of 170 GHz. Low-power tests were carried out in a cross-shaped model.

We demonstrate a method for manufacturing wire-grid-type polarizers using a general-purpose printer and a general-purpose printing spot-color ink. The transmission characteristics are examined by terahertz (THz) time-domain spectroscopy. The wire grid sheet prepared in this study has a polarization factor larger than 0.90, which is comparable to that of commercial metal wire grids in the sub-THz range. This simple manufacturing method could be applied to one- or two-dimensional metallic photonic crystals.

We have designed and fabricated a contact grating device to increase diffraction efficiency on the basis of the principle of the Fabry–Perot resonator. The grating structure and layer thicknesses were carefully determined by considering the electric field strength in the device and the fabrication accuracy of the grating. The prototype device had a peak diffraction efficiency of 71% at an incident angle of 42°; these values were slightly different from the design values of 78% and 44.5°, respectively. Numerical calculations revealed that this deviation was caused by the fabricated grating structure. A higher terahertz power will be expected with a device as per the design.

We have demonstrated a high gain neon-like argon ion X-ray laser using a gas puff target. The elongated X-ray laser plasma column was produced by irradiating the gas puff target with line-focused double picosecond laser pulses with a total energy of 9 J in a travelling-wave excitation scheme. Strong lasing was observed, and a high gain coefficient of 18.7 cm-1 and a narrow beam divergence of less than 3.7 mrad were measured on the transient collisionally excited 3p1S0-3s1P1 transition for neon-like argon at 46.9 nm with targets up to 0.45 cm long.

The molten pool depth measurement method using an ultrasonic phased array system has been developed. The molten pool depth distribution is evaluated by comparing the times taken by the ultrasonic wave to propagate through a molten pool and a solid-phase and through only the solid-phase near the molten pool. Maximum molten pool depths on a flat type-304 stainless-steel plate, formed with a gas tungsten arc welding machine for different welding currents from 70 to 150 A, were derived within an error of ±0.5 mm.

A plasma-irradiated poly(ethylene terephthalate) (PET) film has a long lifetime of bonding capability. To clarify its origin, a PET film was irradiated with oxygen plasma. It was then exposed to normal atmosphere including water vapor. FTIR absorption on the irradiated and non-irradiated films was measured at different times after the start of evacuation. The irradiated film has a larger amount of OH than the non irradiated film, and OH is generated on the film surface. The irradiated film has a larger amount of adsorbed water, because the surface is activated by the created OH. The adsorbed water is desorbed rapidly with increasing evacuation time in the non irradiated film, but it is desorbed more gradually in the irradiated film. Water has hydrogen bonds with OH; thus, the water desorption is suppressed. The OH absorption band is shifted to the lower wave number side owing to the hydrogen bonds. The irradiated surface may be protected by the water from the atmosphere.

We present the memristive switching properties in a single nanowire device made of titanium dioxide. We constructed the single oxide nanowire device made of titanium dioxide on a Si substrate. First, we confirmed the existence of memristive switching in a 10nm scale nanowire device. We successfully extracted the carrier-types for memristive switching by utilizing atmosphere control measurements. Although cobalt oxide and nickel oxide showed the p-type behavior reported previously, the present titanium dioxide nanowire memristor exhibited n-type behavior. Our results highlight the fact that carrier-type of memristive switching seems to be consistent with that of a bulk material, but this is in fact somehow contradictive to a model based on precipitation of metals within an oxide matrix. Since, in conventional capacitor-type memristors, it has been impossible to measure the carrier-type in memristive switching because memristive events are buried within a solid, the open-top planar-type ‘‘nanowire memristor’’ is clearly a powerful device for extracting the intrinsic features of memristive switching phenomena. # 2012 The Japan Society of Applied Physics

Poly(ethylene terephthalate) (PET) films can be bonded directly by oxygen plasma irradiation and heat press at low temperatures of 100–160 °C. The irradiated films were kept in the atmosphere for six years, yet they can be bonded tightly. The irradiated surface is extremely active just after the irradiation, and it is considerably active after five years. Dry- and wet-peel tests suggest hydrogen bonding and chemical bonding. The films are bonded by these two elements at lower press temperatures, while by the pure chemical bonding at higher temperatures. Fourier transform infrared spectroscopy (FTIR) results on the non-irradiated, irradiated and bonded samples indicate that OH and COOH groups are created at the surface, they are responsible for the both bondings. Dehydrated condensation reaction is proposed for the chemical bonding. The hydrogen bonding is broken by water penetration, causing smaller peel strength under the wet-peel test. Cross-linking layer may be the origin for the long lifetime.

A major clinical concern in coronary intervention for cardiovascular disease is late stent thrombosis after the implantation of drug eluting stents (DES). DES widely used in clinical settings currently utilize polymer coatings, which can induce persistent arterial wall inflammation and delayed vascular healing, resulting in impaired endothelialization. We examined the viability of human umbilical vein endothelial cells (HUVECs) for fluorine-incorporated amorphous carbon (a-C:H:F) coatings, which are known to be anti-thrombogenic. a-C:H:F and a-C:H were synthesized on the tissue culture dishes using radio frequency plasma enhanced chemical vapor deposition by varying the ratio of hexafluoroethane and acetylene. HUVECs were seeded on coated dishes for 6 days. The results indicate that the a-C:H:F surface does not disturb HUVEC proliferation in 6 days of culture and is promising for stent materials that allows the preservation of endothelialization, even if the fluorine concentration of a-C:H surface affects the early adhesion of endothelial cells.