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We have developed indirectly heated hollow cathode electrodes and a cascade arc discharge apparatus with different channel diameters to realize plasma windows (PWs) as virtual vacuum interfaces. A compact arc discharge source with a channel diameter of 3 mm is fabricated to realize windowless vacuum–atmosphere separation. An atmospheric high-density Ar thermal plasma is generated, and a PW that produces 100 kPa and 81 Pa separation is demonstrated. An 8 mm channel diameter arc device is also constructed for application as an alternative differential pump with the separation of low- and high-pressure vacuum chambers, and the production of a high-density He plasma. Pressure differences of 2.5 kPa and 16 Pa between PWs are realized. Moreover, vacuum ultraviolet and visible emission spectroscopy reveal the characteristics of expanding plasmas and the plasma parameters.

Aiming at applications of ferroelectric and optical devices, we investigated the fabrication of one-axis-oriented lead zirconate titanate Pb(Zr,Ti)O3 (PZT) thin films on glass substrates with a processing temperature below the glass-transition point of the substrate. Chemical solution deposition (CSD)-derived PZT thin films with a preferential crystal orientation of (00l)/(h00)PZT were grown on an ITO/glass substrate with a crystalline buffer layer of calcium niobate Ca2Nb3O10 (ns-CN). This ns-CN buffer layer lowered the crystallization temperature of the CSD-derived thin films, resulting in crystalline PZT thin films with one-axis (00l) orientation and ferroelectricity of P r = 4 μC cm−2 deposited on transparent glass substrates at a crystallization temperature of 500 °C.

Wafer warpage occurs during the fabrication process, which induces many issues such as wafer handling, lithography alignment, device reliability. The efficiency of dicing street on wafer warpage reduction is investigated by varying the width, depth, and pitch of dicing. With the finite element method simulation results, decreasing the dicing pitch to a quarter-pitch shows a 43.7% warpage reduction. We reveal that the method of decreasing the dicing pitch is more efficient on wafer warpage reduction than that of increasing the dicing width or depth. Furthermore, the efficiency of warpage reduction by decreasing the dicing pitch is confirmed by experiments, which shows a good agreement with the simulated results. The method of decreasing the dicing pitch cut each part smaller. These small parts deform locally instead of continually over the whole wafer, resulting in an efficient wafer warpage reduction. This research provides guidelines for chiplet design or optimization of chip size to reduce the wafer warpage.

Diamond solid-state devices are very attractive to electrically control the charge state of nitrogen-vacancy (NV) centers. In this work, p-type vertical diamond Schottky diodes (VDSDs) are introduced as a platform to electrically control the interconversion between the neutral charge NV (NV0) and negatively charged NV (NV−) centers. The photoluminescence of NV centers generated by ion implantation in VDSDs shows an increase in NV−zero phonon line (ZPL) and phonon sideband intensities with reverse voltage, whereas the NV0ZPL intensity decreases. Thus, NV centers embedded in VDSDs are converted into NV−under reverse bias voltage. Moreover, the optically detected magnetic resonance (ODMR) of NV−exhibits an increase in the ODMR contrast with reverse bias voltage and splitting of the resonance dips. Since no magnetic field is applied, the dip splitting in the ODMR spectrum is ascribed to the Stark effect induced by the interaction of NV−with the electric field existing within the depletion region of VDSDs.

Herein, carbon films, including pentacene oligomers and pentacene-based precursors, were prepared from pentacene and H2 by hot mesh deposition. Ge and Ni films were used as catalytic underlayers to facilitate the polymerization of the pentacene-based precursors. Thereafter, the hot mesh-deposited C films on the Ge and Ni underlayers were irradiated with soft X-rays of high photon flux density in the NewSUBARU synchrotron facility. The Raman spectra of the Ni underlayer exhibited sharp peaks of the G and D bands, which possibly originated from the nanographene formed after soft X-ray irradiation. Conversely, for the amorphous and the polycrystalline Ge underlayers, broad peaks corresponding to amorphous C or small-sized graphite were observed despite the high-temperature treatment at approximately 1000 °C during soft X-ray irradiation. Results suggest that the differences between the properties of the Ge and Ni underlayers lead to the observed difference in their catalytic activities.

The molecular orientation and partial density of states were evaluated using NewSUBARU by soft X-ray absorption spectroscopy (XAS) and soft X-ray emission spectroscopy measurements. The degree of molecular alignment was degraded by increasing mesh temperature in hot mesh deposition (HMD), in other words, was changed from pentacene (Pn) to 6,13-dihydropentacene (DHP). At a mesh temperature of 1450 °C, the different XAS was obtained due to the mixing effect of Pn and DHP, and presence of Pn oligomer. The HMD carbon film transformed into the graphite-like film and the graphene on the quartz substrate and the Ni/quartz substrate after soft X-ray irradiation, respectively. The HMD carbon film after soft X-ray irradiation showed the peaks due to terminal carbon such as CH n and COOH in comparison with the reported large graphene sheet. It indicates that the flake size of the graphene on the Ni/quartz substrate was small and had many edges.

We elucidate the carrier transport mechanism from the p+-layer (metallic-conduction) to the n-layer (band-conduction) in a diamond p+–n junction, which is the basic structure of diamond devices. We fabricate Schottky–pn diodes containing p+–n junctions and analyze the temperature dependence of electrical properties in the forward bias region. At temperatures higher than the cryogenic region, free holes transport from the p+-layer to the n-layer. In the cryogenic region, which is insufficient to excite holes to the valence band, the direct transport of holes from the effective carrier conduction level in the p+-layer to the n-layer by tunneling becomes dominant.

Defects in vertical diamond Schottky barrier diodes have been investigated by photocurrent spectroscopy in supercontinuum light photon energy ranging from 1.24 to 3.1 eV, and from 170 to 296 K. The photocurrent spectra exhibit three thresholds located around 1.3, 2.2 and 2.5 eV, which are related to defects energy levels in the active layer of diamond Schottky diodes (a slightly doped boron layer). Although the origin of the reported defects is still under discussion, they can be ascribed to hydrogen and nitrogen related defects. Moreover, the generated photocurrent can be explained by a two-photon process.

We measured in-plane X-ray diffraction and investigated the strained lateral structure and its relaxation in a Cu2O thin crystal epitaxially grown in a small gap between paired MgO substrates. Although one side MgO was peeled off to irradiate Cu2O with X-ray, a thin MgO layer remained on Cu2O, and diffraction peaks of (400)-planes in both MgO and Cu2O were detected. The peak has four-fold symmetry on sample rotation, and the lattice constant estimated from the diffraction angle is 4.254 A. The lattice constant is larger than that of MgO and smaller than that of strain-free Cu2O. Furthermore, it was found that the lattice strain in Cu2O relaxes at a depth of ≈0.15 μm from MgO on the basis of the estimated X-ray penetration depth under consideration of low incident angle, absorption and refraction of X-ray.

In this article, diffractive imaging using electron beams, in particular, the approach using the selector aperture in a TEM is reviewed. The experimental setups and the reconstruction algorithms suitable for the atomic-resolution mode and medium-resolution mode are proposed, respectively. In the medium-resolution mode, a phase distribution of the wavefield transmitted through the sample is obtained across a FOV more than 100 nm with the phase accuracy of 0.1-0.2 rad. Through the phase imaging, a thickness map of the sample and an electrostatic potential map in/around the sample are visualized. In the atomic-resolution mode, its high-resolution ability better than aberration-corrected TEM imaging is confirmed based on the experiments and theory, in which the ability is explained to be attributed to the lack of direct influence of the objective lens chromatic aberrations.

We characterized OH-terminated diamond (111) surfaces which show step-terrace (ST) and bunching-step (BS) regions from contact potential difference (CPD) and current to investigate the relationships between surface topography and generation of interface states on the surfaces. The OH-termination was performed using water vapor annealing. The CPD and current measurements were conducted by conductive-probe AFM and Kelvin-probe force microscopy. The CPD and current were highly correlated with the surface topography. The I–V characteristics shows typical ideality factors (n) of about 1.5 and 2.0 in the ST region and the BS region, respectively. As the n were higher than that of an ideal Schottky contact (n = 1.0), we concluded that a metal insulator semiconductor diode structure, whose n increases as its interface state density increases, was formed. Considering that step density in the BS region was much higher than that in the ST region, the steps seemed to have generated the interface states.

We have developed organic photoconductive film (OPF) CMOS image sensors with pixel structures different from those of a conventional silicon image sensors, in which, the organic thin film for photoelectric conversion and the charge storage part for signal charge accumulation are completely independent. In this paper, we focus on two unique features of the OPF image sensor: (1) technology that realizes over 120 dB simultaneous-capture wide dynamic range, (2) global shutter technology achieving high saturation signals per unit square that is 10 dB higher than that of silicon image sensors with the global shutter function, without sacrificing pixel area. In addition, we have developed a test chip that realizes a high resolution of 8K4K, a high frame rate of 60 fps, a high saturation signals of 450 ke−, and the global shutter function simultaneously. These features of the OPF image sensor will contribute to significant progress in imaging and sensing fields.

A spin metal–oxide–semiconductor field-effect transistor (MOSFET) is a promising spintronics device for future low-power electronics. In this paper, we demonstrate the successful improvement of the performance of a spin-MOSFET-type device, a ferromagnetic-semiconductor GaMnAs-based vertical spin electric double-layer transistor (EDLT); the magnetoresistance ratio reaches 37%, which is 7 times larger than those obtained in previous studies. Furthermore, we find that the magnetic anisotropy of our device is modulated by changing the gate voltage. Our results open up the possibility of realizing novel functional devices, in which both current and magnetic anisotropy can be controlled by the gate electric field.

Thermally produced SiC/SiO2 stacking in SiC MOSFETs creates defect-related interfacial states in and around the band gap of SiC. These interfacial states can cause serious reliability problems such as threshold voltage shift, as well as efficiency problems such as channel mobility degradation. Carbon species having C=C double bonds have been suggested as one of the origins of these interfacial states. We have theoretically shown that this type of defect produces interfacial states in and around the band gap of SiC, and that they can be removed by saturating the C=C double bond by reactions with H2 and F2. The single-bond products of these reactions are found to be stable at regular device operation temperatures.

The electrical properties of Al2O3/p-type diamond (111) MOS capacitors were studied with the goal of furthering diamond-based semiconductor research. To confirm the formation of an inversion layer in the p-type diamond body, an n-type layer for use as a minority carrier injection layer was selectively deposited onto p-type diamond. To form the diamond MOS capacitors, Al2O3 was deposited onto OH-terminated diamond using atomic layer deposition. The MOS capacitor showed clear inversion capacitance at 10 Hz. The minority carrier injection from the n-type layer reached the inversion n-channel diamond MOS field-effect transistor (MOSFET). Using the high-low frequency capacitance method, the interface state density, D it, within an energy range of 0.1–0.5 eV from the valence band edge energy, E v, was estimated at (4–9) × 1012 cm−2 eV−1. However, the high D it near E v remains an obstacle to improving the field effect mobility for the inversion p-channel diamond MOSFET.

In this paper, we present and discuss a simple estimation method for the life expectancy of optical disks using resampling (bootstrap) statistical analysis in order to roughly estimate the lifetime of archival-grade disks. The performance of this method was examined experimentally using the Eyring acceleration test with four stress conditions. Results demonstrated the capability of this bootstrap analysis for estimating life expectancy compared with conventional statistical analysis using the Eyring acceleration test.

Lifetimes of positrons in perfect crystals having band gaps are calculated using the two-component density functional theory. For electron–positron correlation, we use the local density approximation (LDA) and the correction of the LDA using a high-frequency dielectric constant. While the LDA is found to slightly underestimate positron lifetimes, the correction of the LDA well reproduces experimental lifetimes. We discuss the quality of crystals used in a positron annihilation experiment by comparing theoretical and experimental positron lifetimes.

The change in electrical characteristics due to mechanical stress is studied for short-channel metal–oxide–semiconductor field effect transistors (MOSFETs) fabricated on (001) substrate in advanced 65 nm technology. An experimental trial is carried out to investigate the effect of three independent components of mechanical stresses orthogonal to one another on drain current and threshold voltage using a pin-pressing apparatus and the cantilever method. The change in drain current agrees with the signs and magnitudes shown in the literature for surface stress on the (001) plane. On the other hand, the change versus stress vertical to the plane shows a peculiar phenomenon for pMOSFET. That is, the change decreases with the expected rate up to 90 MPa, but increases rapidly above 450 MPa. Although the physical mechanism is unclear at present, simultaneously generated biaxial horizontal strains possibly cause this peculiar phenomenon.

Near-field technology has been expected as one of the promising techniques for increasing the recording density in an optical storage disk system since it was introduced. In a near-field optical disk drive system (NFDD), the gap between a disk and a solid immersion lens (SIL) is required to be less than one-tenth laser wavelength with a high accuracy in order to generate an evanescent wave for reading or writing a signal. This is because the gap performance has detrimental effects on the RF amplitude vibration in a reading channel and on the signal laser peak power vibration in a writing channel. In this study, we first clarify whether specific disk resonances cause the deterioration of the gap performance in the NFDD. We then demonstrate an approach of improving the disk mechanical performance in order to achieve a highly precise gap performance. Finally, we investigate a high-performance gap servo system by utilizing the disk substrate suitable for the NFDD.

We report the optical modification of gallium nitride by femtosecond laser irradiation. A 5-nm-band-gap shift, observed by spectral ellipsometry, results a reduction of 0.01 in the refractive index at a wavelength of 400 nm. An indistinct circular pattern was also observed using nano-beam diffraction. These results suggest that femtosecond-laser irradiation induces stress–strain, rather than slight amorphization. We also observed that the angle of first-order diffraction from the grating with a 1.0 µm period, fabricated by interferometric irradiation using a femtosecond laser without any damage, corresponds to the calculated angle. The first-order diffraction efficiency for a wavelength of 403 nm was estimated to be 4.0×10-3%.

The visibility of breast cancer was studied by two types of Laue angular filter (LAF) under x-ray dark field imaging. One was designed so that a field size of 90 ×90 mm2 was available by a 2.124-mm-thick LAF with a 35 keV x-ray energy. The second was a thin LAF of 125.6 µm thickness with a view field of 10 ×10 mm2 using a 13.7 keV x-ray. The estimated spatial resolutions for the cases of the 2.124-mm-thick LAF and the 125.6-µm-thick LAF were 139 and 23 µm, respectively. This is in good agreement with our experiment.

Eddy current testing utilizing a cooled normal pickup coil and a high-Tc superconducting quantum interference device (SQUID) picovoltmeter was performed both experimentally and analytically. In the experiment, we successfully detected a small crack on the back surface of a Cu plate by moving the coil in an unshielded environment. First, we developed a method of avoiding the drift of the detected signal that was caused by the variance of lift-off. Next, we clarified the dependences of the detected signal on the excitation frequency and the thickness of the Cu plate. It was shown that an optimum frequency that maximizes the detected signal exists. Because this frequency changed with the thickness of the Cu plate, the frequency dependence could be used to estimate the depth of the crack from the surface of the Cu plate. The experimental results were analyzed taking into account the phase and amplitude of the signal field caused by the crack. Good agreement was obtained between experiment and analysis.

We developed a new UV-Raman spectroscopy system for local and global strain measurements in Si. Using a 364 nm excitation laser, strain in an ultra-thin Si film can be measured. Because of the resonance effect using this particular wave length, reasonably short measurement time is realized to obtain strain mapping with keeping the sample at sufficiently low temperature. An in situ wavenumber calibration system has been newly developed for superior wavenumber resolution and precision of approximately 0.1 cm-1. A quasi-line shape excitation light source has also been developed to verify the effective spatial resolution. Strain mapping and spectral measurements for relaxation by rapid thermal annealing in strained-Si substrates are demonstrated.

The growth and differential conductivity (dI/dV) spectra of ultrathin Fe films on Cr(001) were studied at room temperature (RT) by scanning tunneling microscopy, together with the spin-resolved image of the Cr(001) film. It is found that 2 ML Fe films deposited at RT and postannealed at 300 °C show atomically flat terraces and a distinct peak at +300 mV in the dI/dV spectrum, which corresponds to the spin-polarized surface state of the Fe(001) surface. These features were not observed for submonolayer Fe films on Cr(001) substrates or at postannealing temperatures lower than 200 °C. The spatially resolved dI/dV signal maps of the 2 ML Fe films show a distinct contrast. This contrast may not be of magnetic origin, but a result of the Fe layer dependence of the local density of states.

We report photoacid-induced nonerasable recording in tert-butoxycarbonyl-protected quinizarin methacrylate polymers for three-dimensional optical memory. 1 m/s-speed recording was achieved using an 800 nm femtosecond laser at an 80 MHz-repetition rate, without a postexposure bake after laser irradiation. Three-layer recording indicates that no optical damage during recording enables modulation of the Compact Disc type memory. The linewidth of recorded marks of 0.4 µm indicates a 49 Gbits/cm2 areal density when the numerical aperture is 1.35.

In this paper, we propose a new advanced push–pull (APP) method as a new one-beam tracking detection method suitable for a dual-layer Blu-ray disc (BD) system. This method overcomes two issues. One of them is tracking error signal (TES) offset at the boundary between recorded tracks and unrecorded tracks, and the other is TES offset caused by the stray lights from the other layer of dual-layer discs. The new APP-TES is stable at the boundary in the dual-layer BD system, because the dividing area of a far-field pattern is optimized and the detecting areas are allocated to avoid stray lights from the other layer. Its stable characteristics are confirmed experimentally.