Table of contents

We propose InGaAs nano-photodiodes incorporated with a ring-type polarization-insensitive surface-plasmon (SP) antenna, which consists of gold concentric-ring gratings. This ring antenna induces SP resonance for any polarization of incident light and enhances light absorption in a thin InGaAs layer owing to its symmetric structure. Finite-difference time-domain simulations suggest that the carefully designed ring SP antenna can achieve a quantum efficiency of more than 70% for a wide wavelength range and a maximum efficiency of about 80%. A 3 dB bandwidth of 21 GHz and an external responsivity of 0.39 A/W were experimentally demonstrated at a 1.55 µm wavelength.

We used transmission electron microscopy to analyse the microstructures in a thick AlN layer grown on a self-nucleated, columnar AlN seed crystal. The growth direction of the AlN layer grown by a new solution growth method was [1100]. The threading dislocation (TD) density near the epilayer-seed interface (on the seed crystal) was 10⁹ cm^-2. However, owing to dislocation annihilation, the TD density decreased to 10⁸ cm^-2 at a thickness of ∼5 µm. These results imply that the new solution growth method can grow high-crystalline-quality bulk AlN under moderate growth conditions (T ≈1200 °C, nitrogen pressure = 1 atm).

In this paper, we study the electrical properties and current-temperature stress (CTS) induced electrical instability of half Corbino and fork-shaped hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) fabricated on the same substrate. The influence on overall electrical properties of the threshold voltage shift of half Corbino a-Si:H TFT is discussed in comparison to fork-shaped a-Si:H TFT. The results indicate that half Corbino a-Si:H TFT has improved ON-current levels and electrical stability in comparison to fork-shaped a-Si:H TFT with the similar structural dimension.

We developed hydrogenated amorphous silicon (a-Si:H)/crystalline germanium (c-Ge) heterojunction solar cells for the first time to improve the open-circuit voltage (V_OC) at high temperatures. By using the optimum i layer thickness of 13 nm, we obtained V_OC of 0.266 V, that is comparable to the highest V_OC ever reported under 1 sun illumination. The temperature dependence of the a-Si:H/c-Ge heterojunction solar cell reveals a better temperature coefficient (-0.66%/°C) of V_OC than conventional homojunction solar cells. The high V_OC and low temperature coefficient are attributed to the benefit of the heterojunction and the excellent surface passivation capability of a-Si:H.

We have investigated the thermal stability of GaAs-oxides grown by atomic force microscope (AFM)-assisted anodic oxidation to identify the conditions suitable for fabricating oxide nanomasks for molecular beam epitaxy (MBE). The oxides grown at bias voltages, V_ox, less than 30 V were desorbed after standard thermal cleaning in MBE, while the oxide patterns fabricated at V_ox ≥40 V survived on the GaAs surfaces. From X-ray photoemission spectroscopy, we have found that the better thermal stability of AFM-oxides grown at V_ox > 40 V can be attributed to the formation of Ga₂O₃ and that Ga₂O₃ can be used as nanomasks for site-controlled MBE growth.

The ion incident angle dependences of the etching yields of SiO₂, polycrystalline silicon (poly-Si), and Si₃N₄ were studied using a plasma beam irradiation apparatus. The angle dependences were affected not only by the etchant chemistry produced by Ar and/or fluorocarbon gas plasmas, but also by the incident ion energy. Since the incident etchant characteristics were measured, the results are useful for constructing an etching profile simulator.

Lead-free ceramics (1-x)(K_0.48Na_0.52)(Nb_0.98Sb_0.02)O₃–xBiScO₃ + 0.8 mol % MnCO₃ have been fabricated by conventional sintering technique. The results of X-ray diffraction suggest that all samples show pure perovskite structure and the structure changes from orthorhombic to tetragonal with the increase of BiScO₃. At room temperature, the polymorphic phase transition (PPT) from orthorhombic to tetragonal phases was identified. With the increase in BiScO₃ content, both the cubic–tetragonal and tetragonal–orthorhombic phase transitions shift to lower temperatures; hence, the dielectric and piezoelectric properties are significantly enhanced. As a result, the ceramic with x=0.015 exhibits the following optimum properties: d₃₃=265 pC/N, k_p=0.509, k_t=0.503, ε_r =1409, tan δ=0.034.

Low-loss amorphous-silicon (a-Si) waveguides comprising three vertically stacked layers prepared on silicon-on-insulator substrates are demonstrated. We have fabricated multilayer a-Si waveguides and investigated their loss characteristics; this is the first such investigation to our knowledge. All the process temperatures were regulated below 400 °C for the complementary metal oxide semiconductor (CMOS) backend process compatibility. When the surface roughness and sidewall roughness were decreased, the propagation loss decreased to 3.7 dB/cm even in the case of the third layer a-Si waveguide. Such low-loss waveguides can be effectively applied to realize multilayer stacked optical devices.

We used pulsed electron deposition (PED) method to grow 50-nm-thick ZnO thin film on quartz and Si substrate at room temperature. X-ray diffraction (XRD) measurement shows the (002) peak with full width at half maximum (FWHM) of 0.87°. Photoluminescenct (PL) and IR transmission data exhibit the energy band gap (3.3 eV) and optical phonon frequency (50.7 meV) which are consistent with those of single crystal ZnO. Visible–UV transmission level is enhanced when oxygen partial pressure in the growth chamber increases. Our results prove that thin ZnO film with reasonable structural, surface and optical property can be grown at low temperatures using PED method.

The electron swarm parameters in HSi(OC₂H₅)₃ (triethoxysilane, TRIES) vapor have been investigated for relatively wide ranges of reduced electric field (E/N). Based on the arrival-time spectra (ATS) method for electrons using a double-shutter drift tube, the drift velocity and the longitudinal diffusion coefficient were measured for the E/N=20–5000 Td, and the ionization coefficient was obtained for E/N=300–5000 Td. The results were compared with those for SiH₄ and Si(OC₂H₅)₄ (tetraethoxysilane, TEOS), to show characteristics similar to the parameters in TEOS. We also determined the electron collision cross sections for TRIES by means of the Boltzmann equation analysis.

The spin-Seebeck effect (SSE) in magnetic insulators is shown to be applicable to two-dimensional (2D) position sensing using an Y₃Fe₅O₁₂ (YIG) slab covered with a Pt-film mesh. When a part of the YIG-slab/Pt-mesh sample was heated, the position of the heated part of the sample was found to be known from the measured SSE signals in the Pt mesh. Since the SSE-based position-sensing method allows commonly-used insulators to produce 2D position information, it may be useful for constructing versatile thermally-driven user-interface devices and image-information sensors.

In the paper, a fast coalescence growth is introduced to the epitaxial growth of GaN on silicon substrate. With the fast coalescence growth method, a thin low pressure GaN (LP-GaN) layer used as a function layer, the GaN film could coalesce quickly within a thin thickness, additionally, a smooth surface and high crystal quality could be achieved. With further investigation, it was found that the general GaN coalescence thickness was mainly influenced by the thickness and the growth pressure of the LP-GaN interlayer. And the LP-GaN interlayer has a critical thickness, if over the critical thickness, the crystal quality would degrade. At the same time, it is found that the GaN quality was not affected by the coalescence thickness with a thin LP-GaN interlayer under critical thickness.

The properties of nonpolar a-plane GaN layers grown with different Mg doping levels were investigated. With increasing the Mg flow rate, the hole concentration initially increased and then decreased, indicating the formation of compensation centers. The dominant photoluminescence (PL) emission at relatively low Mg doping levels is the blue luminescence (BL) band due to the donor-acceptor pair (DAP) transition with Mg_GaV_N (deep donor) and Mg_Ga (acceptor). In addition to the weak BL band, both the ultraviolet luminescence (UVL) and yellow luminescence (YL) bands are observed at higher Mg doping level. The UVL band, especially dominant at 10 K, can be related to bound excitonic emissions involving Mg-induced extended defects, whereas one or more mechanisms may contribute to the YL band.

The physical properties of high-stable transparent Si-doped zinc oxide (ZnO) films were determined by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). From XPS, the peak corresponding to the energy of ionized silicon (Si 2p) was observed for all samples after damp heat exposure, even in the aluminum (Al)-doped Si-undoped zinc oxide (ZnO:Al) thin film. SIMS profiles showed an increase in silicon concentration at the surface of ZnO thin films after damp heat exposure. The Ar concentration determined from SIMS measurement showed a clear relationship between the stability and Ar concentration. This can be explained by the packing density of ZnO and a barrier model. Additionally, comparing ZnO:Si with ZnO:Al prepared under the same deposition conditions, we found that silicon can make ZnO thin films more stable.

Chalcopyrite CuInSe₂ thin films were formed from paste precursors including Cu and In₂O₃ fine particles. The compositions of the pastes were In- and Cu-rich. Paste was coated on Mo/soda-lime glass by screen printing. The precursors were annealed at 450 °C under N₂:H₂ (97:3) ambient to reduce them. The reduced films consisted of the Cu₁₁In₉ and In phases. The reduced precursor showed granular shape and poor adhesion with the Mo layer because the melting point of Cu₁₁In₉ was about 300 °C and Cu₁₁In₉ does not wet with Mo. The reduced precursors were annealed at 600 °C under Se and Ar ambient to form the CuInSe₂ thin films. The In-rich CuInSe₂ thin film consisted of small grains. The Cu-rich CuInSe₂ thin film was dense and consisted of large grains of about 3 µm.

We have investigated the effects of BF₂ ion implantation and subsequent annealing on the structure of epitaxial BaSi₂ thin films with the aim of the fabrication of a p-type B-doped BaSi₂ film. After 10 min of annealing at 600 °C and above, BaSi₂ is lost at least partly accompanied by appearance of Si as evidenced by X-ray diffraction and Raman spectroscopy. Element mapping by energy dispersive X-ray spectroscopy revealed that a barium oxide is formed on the surface, which indicates that BaSi₂ is oxidized into a barium oxide and Si during annealing. Such oxidation was found to be suppressed by employing rapid thermal annealing for 30 s even when the annealing temperatures of 700 and 800 °C were chosen. Analysis of the full width at half maximum of the Raman peak showed that the inhomogeneous stress in the film produced by ion implantation can be decreased to the as-grown level by rapid thermal annealing at 700 and 800 °C for 30 s. At the same time, the red shift of the Raman peak is shown, based on which the possibility of B substitution for Si is discussed.

In this paper, we report the possibility of forming a phosphorus (P)-doped layer on silicon (Si) at low temperatures. Using the radicals catalytically generated from phosphine (PH₃), a thin n-type layer is formed on a crystalline Si (c-Si) wafer at 150 °C. The secondary ion mass spectrometry (SIMS) profile of doped P atoms indicates that P atoms exist in the vicinity of the c-Si surface, and the depth at which P atom concentration decreases to 1/10 of the surface concentration is less than 12 nm for 300 s of radical treatment. The sheet carrier density on radical-treated c-Si wafers measured using the Hall effect shows that P atoms act as donors without annealing. The sheet carrier concentration of the P-doped layer is increased by adding hydrogen (H₂) to the PH₃ source gas. The effect of adding H₂ to PH₃ suggests that the surface reaction of atomic H plays an important role in the doping process.

The effects of Y₂O₃ on BaTiO₃–MgO–MnO₂–CaZrO₃ nonreducible ceramics were investigated. Specimens with Y₂O₃ contents ranging from 1.0 to 2.5 mol % were prepared via the solid state method. The Curie temperature (T_c) and the electrical properties were closely related to the occupation behavior of yttrium, which is known as an amphoteric element. T_c increased almost linearly as a function of Y₂O₃ content when the doping content was low. Transmission electron microscopy (TEM) indicated a typical "core–shell" structure. The lattice parameters corresponding to the grain cores and the shells were determined by X-ray diffractometry (XRD) separately. The relief of the internal stresses arising from the lattice mismatch was responsible for the T_c shift. The specimens doped by a high level of Y₂O₃ can fulfill the EIA X8R specification with a high dielectric constant (ε_RT > 2400) and a low dielectric loss (tan δ< 1.1%). A high insulation resistivity and a slow degradation rate were obtained when a sufficient amount of Y₂O₃ was incorporated, which were attributed to the substitution of Ti⁴⁺ and the formation of a donor–acceptor complex.

Fine-grained BaTiO₃-based nonreducible ceramics were obtained by a conventional mixing method and the dielectric and electrical properties were characterized. The average grain size was less than 200 nm. The materials provided a dielectric constant of 1300 and satisfied the Electronic Industries Association (EIA) X8R specification. Fine-grained ceramics showed a better performance under a direct current (DC) field at high temperatures, compared with coarse-grained ceramics. Impedance analysis was conducted to determine the activation energy and to evaluate the ionic transference number. Moreover, capacitance variation under a DC field was also largely improved for fine-grained ceramics and relative mechanisms were examined.

Transparent clay films were prepared using tetraphenyl phosphonium (TPP) modified smectites (TPP-SA, TPP-HE, and TPP-SA-HE), which were prepared by ion exchange of either synthetic saponite (SA) or synthetic hectorite (HE) as well as a mixture of these two kinds of smectites (SA-HE) with TPP-bromide (TPP-Br). Uniform liquid dispersions of these TPP-smectites were successfully prepared by adding N,N-dimethylformamide (DMF) to hydrous gels of TPP-smectites. Finally, transparent self-supported films of about 30 µm thickness were prepared by casting these dispersions. From the optical studies, it was confirmed that the transparent clay films maintained their optical transparency in the visible range even after annealing at 350 °C for an hour. Particularly, haze value of the TPP-SA-HE film decreased by one-third compared to TPP-SA, and it was also confirmed that the flexibility of TPP-SA-HE film was better than that of TPP-HE. From the cross-sectional scanning electron microscope (SEM) images, it was confirmed that TPP-SA film has large voids, which causes scattering of light compared to TPP-HE. Finally, the average void size was reduced by mixing these two TPP-smectites with different particle size.

The synthesis and properties of water wheel-like cyclic oligomer (noria_PY) derivatives (noria_PY-ADs) with pendant adamantyl ester (AD) groups were examined for their application as extreme ultraviolet (EUV) resist materials. Noria_PY-ADs with various degrees of introduction (DI values) of AD groups were synthesized by adjusting the reactant feed ratios and reaction concentration. Solubility, film-forming property, and thermal stability were consistent with differences in DI values. The patterning properties of noria_PY-AD₂₅ (DI= 25%) were examined in an EUV resist system, and noria_PY-AD₂₅ provided a clear line-and-space pattern with 30 nm resolution and a line width roughness (LWR) of 11.3 nm.

Small-molecule p–n heterojunction organic photovoltaic (OPV) devices with a two-component donor layer composed of tetrabenzoporphyrin (BP) and titanyl phthalocyanine (TiOPc) can utilize near-infrared (NIR) light up to 950 nm and shows a 2.4% power conversion efficiency (PCE) (J_sc = 7.7 mA/cm²; open circuit voltage, V_oc = 0.61 V; and fill factor, FF= 0.50) under AM1.5G illumination at an intensity of 100 mW/cm². This value is higher than the 2.0% value obtained by an archetypal device composed of a single-component BP layer. The device performance was improved by the exposure of the TiOPc layer to toluene, which induced a rapid change in the morphology of the TiOPc layer from what is called Phase I to Phase II. The acceptor layer comprising 1,4-bis(dimethyl-phenylsilylmethyl)[60]fullerene (SIMEF) showed higher V_oc and PCE than that comprising popular PCBM, because the lowest unoccupied molecular orbital (LUMO) level of SIMEF is higher than that of PCBM.

We report here electric-field-induced conductive pathway formation in a multiwalled carbon nanotube nematic liquid crystal blend. Experiments have performed by inserting the blend into a 10 µm planar, pre-aligned indium-tin-oxide coated sandwiched type electro-optical cell. The conductive pathway formation process have confirmed by in-situ porarized optical microscopy, dielectric monitoring and conductance measurements as a function of bias voltage. When bias voltage increases, conductivity and imaginary part of the dielectric constant (ε'') increases dramatically upto six and four order of magnitude respectively. Low electric field disordered state of nanotubes causes transition to the directionally aligned conductive state after some critical electric-field had applied. From our experimental results we have found that the critical field is ∼15 kV/cm. This electric-field controllable low conductive disordered to directionally aligned conductive transition technology is promising for the fabrication of low-dimensional conductive materials and applications of voltage-switch devices.

In this study we propose a resistive random-access memory (RRAM) using stacked GeO_x and PbZr_0.5Ti_0.5O₃ (PZT). Under unipolar-mode operation, the bilayers Ni/GeO_x/PZT/TaN RRAM shows a large resistance window of >10², for 85 °C retention, and a good DC cycling of 2000 cycles, which are significantly better than those shown by the single-layer Ni/PZT/TaN RRAM without the covalent-bond-dielectric GeO_x.

Tungsten silicide (WSi_x) peeling is a noticeable issue from the manufacturing viewpoint, especially as WSi_x is widely applied in very large scale integrated circuit (VLSI) fabrication as a gate and interconnecting material, even on a 25-nm-node NAND flash device. In this study, we attempt to determine the margin of the Si/W atomic ratios and the mechanism of WSi_x film peeling after thermal annealing. The use of an as-deposited WSi_{x > 2.0} film and 30 s rapid temperature annealing (RTP) at least 750 °C for a tungsten-rich WSi_1.85 film are the minimal conditions for preventing peeling. Moreover, we found that silicon and phosphorus atoms diffuse upward on WSi_x films, driven out of the underlying doped poly-Si film, while they acquire sufficient thermal budgets based on energy dispersive X-ray (EDX) analysis and secondary-ion mass spectroscopy (SIMS). During this process, the strong mutual interaction and the rough interface formation between the tetragonal phase of WSi_x and polycrystalline silicon (poly-Si) enhance the adhesion of WSi_x films. A strong adhesion might reduce the risk of peeling in the subsequent processes.

In this study, we investigated the galvanic effect between the Cu metals and ruthenium nitride (RuN_x) films that were deposited at various nitrogen (N₂) gas flow rates in chemical mechanical polishing slurries. It was found that the galvanic corrosion of the RuN_x films was inhibited with increasing N₂ gas flow ratio, whereas the galvanic corrosion of the Cu seed layers was enhanced. Electrochemical impedance spectroscopy showed that the galvanic corrosion resistance of RuN_x increased and that of the ruthenium oxide layer decreased as N₂ flow ratio increased. This was because the increase in the N content in the RuN_x films inhibited the corrosion and oxidation of the Ru metals.

AlGaN-based deep ultraviolet light-emitting diodes (LEDs) with aluminum reflective electrodes deposited to cover both p- and n-mesh contact electrodes have been fabricated. A 1.55-fold increase in light extraction efficiency has been demonstrated. Despite their reduced contact area, the LEDs exhibited only a slight increase in forward voltage of 0.45 V at 20 mA. Also, their 50% lifetime was estimated to be about 10,000 h at 20 mA DC at room temperature by extrapolation. Owing to the reflective electrodes, a 288 nm LED with external quantum efficiency as high as 5.4% was achieved. The light output power was 4.6 mW at 20 mA.

Phosphorescent white organic light-emitting devices (PhWOLEDs) with a double emitting layer (EML) structure were fabricated. The EMLs were doped with blue and yellow phosphors of iridium(III) bis[4,6-(difluorophenyl)-pyridinato-N,C2'] picolinate and [2-(4-tert-butylphenyl)benzothiazolato-N,C2'] iridium (acetylacetonate). Comparing the performance of PhWOLEDs with the host of yellow EML varying from p- to n-type materials, the results showed that the PhWOLED fabricated with 4,7-diphenyl-1,10-phenanthroline (BPhen) as the yellow host had the highest performance, exhibiting a peak current efficiency of 31.7 cd/A, a peak power efficiency of 17.1 lm/W, and the Commission Internationale del'Eclairage coordinates of (0.33, 0.41) at a bias of 9 V. The enhancement was attributed to the improved charge carrier balance, broadened recombination region, and adequate energy levels between the BPhen host and the dopants, which made distinct roles for the dopants to effectively harvest the charge carriers.

On the basis of mode competition, we propose a novel bistable device that has the potential to improve the degrees of freedom of optical input-output directions. Unlike the conventional mode competition in a single cavity, the proposed device uses two cavities that are cross-coupled between an in-plane laser diode (LD) and a vertical-cavity surface-emitting laser (VCSEL). We calculated rate equations using the cross-gain saturation model in order to elucidate the conditions under which the proposed device may have bistability. We also analyzed the static and dynamic responses. From the calculations, we found that the product of the optical confinement factor and the photon lifetime of the two lasers should have almost equal values. The results show that by coupling two cavities having similar characteristics, the switching characteristic becomes comparable to those of other reported bistable devices. In the case of static operations, switching powers of less than 2 mW and about 20 fJ could be achieved; these are some of the smallest operational performances.

We demonstrate the potential of a hydrothermal method-grown ZnO as a high-spatial resolution imaging device for in-situ soft X-ray laser diagnostics by characterizing the exciton emission patterns. By plotting the emission pattern radii at each position, we estimated the evolution of the beam radius around the focal point. The beam profile of the Ni-like Ag ion plasma laser was estimated from the waist radii as 29 and 21 µm, the divergence angle as 7.2 and 11 mrad and the M² factor as 47 and 50 in the horizontal- and vertical-axis, respectively. Spatial resolution of the magnifier was estimated to be 6 µm and is expected to improve by optimizing the optics of the magnifier and using a telescope. Our results would enhance the use of ZnO as an imaging device that would play a crucial role in the development and application of soft X-ray light sources.

Photocurrents induced by two-photon absorption (TPA) at a wavelength of 1.55 µm in GaAs and Si photodiodes (PDs) were measured and compared. The photocurrent generated by a GaAs PD depends strongly on the linear polarization direction, which is consistent with the anisotropic nature of TPA in GaAs. In contrast, the photocurrent of a Si PD has a negligible dependence on the polarization direction, indicating that TPA is isotropic in this PD at a wavelength of 1.55 µm. The photocurrents generated by GaAs and Si PDs by elliptically polarized light are consistent with analysis based on the third-order nonlinear susceptibility tensor.

We present optical modeling and physical analysis results of thin-film organic solar cells (OSCs) based on a generalized transfer matrix method, which can calculate, with a simple matrix form, the mixed coherent and incoherent interaction of an incoherent glass substrate with other coherent layers. The spatial distribution of the electric field intensity, power density, and power dissipation are calculated in both coherent and incoherent layers with respect to the optical spacer thickness. By decomposing the power density and power dissipation into forward-propagating, backward-propagating, and their interference components, we demonstrate that the dependence of the spacer thickness on the total device reflectance plays an important role in determining the light absorption efficiency of the OSC.

This paper proposes that the cylindrical cavity around a circular light source can decrease the divergence angle without changing the emission energy and source size. This result can provide a way to reduce the etendue of the light source by scrambling the rays inside the cavity with a lossless scattering surface. The experiment demonstrated that the metallic cavity around the surface source reduced the divergence angle. However, the metallic surface also absorbed quite a large portion of the light energy. The Lambertian nature of the sidewall surface changed the directions of the rays into horizontal directions. It increased the number of reflections inside the cavity and amplified the small amount of absorption at a single reflection. This effect of the cavity on the etendue of the light source can contribute to providing more design flexibility in various lighting applications.

To clarify the excitation mechanism of hydrogen in transversely excited atmospheric-pressure (TEA) CO₂ laser-induced helium gas plasma, atomic emission characteristics of H, C, F, and He were studied using a Teflon sheet (thickness of 2 mm) attached to a metal subtarget. The TEA CO₂ laser (750 mJ, 200 ns) was focused on the Teflon sheet in the surrounding He gas at 1 atm. Atomic emissions of H, C, F, and He occurred with a long lifetime, a narrow spectrum width, and a low-background spectrum. The correlation emission intensity curves of H–He and F–He indicated a parabolic functions. To explain the emission characteristics, we offered a model in which helium metastable atoms (He^*) play an important role in the excitation processes; namely, atoms collide with helium metastable atoms (He^*) to be ionized by the Penning effect, and then recombine with electrons to produce excited states, from which atomic emissions occur.

Photochemical surface and interface modifications of Al thin films on silica glass were successfully carried out using a 157 nm F₂ laser for micropatterning. The surface modification phenomenon was discussed in relation to by changing the laser wavelength using a 193 nm ArF laser or a 266 nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. The ArF laser could induce the surface modification of Al thin films to form a protective Al₂O₃ layer resistant to KOH aqueous solution, similarly to the F₂ laser. However, the mechanical hardness of the ArF-laser-irradiated sample was clearly lower than that of the F₂-laser-irradiated sample. The origin of the surface modification was examined by irradiating the F₂ laser in vacuum. The interface modification phenomenon was analyzed by X-ray photoelectron spectroscopy in the three cases. The adhesion strengths of the samples were also compared. The 266 nm Nd:YAG laser was not effective for the present photochemical modifications.

We report on a passively mode-locked Nd:YVO₄ laser using a single-walled carbon nanotube saturable absorber (SWCNT-SA) fabricated by vertical evaporation. An 880 nm laser diode pump source was used to reduce the thermal load of the laser crystal. At a pump power of 11.8 W, a 1.8 W average output power was achieved for a continuous wave mode-locked laser with an optical conversion efficiency of 15.3%. The repetition rate of the passively mode-locked pulse was 90 MHz with a 15 ps pulse width. The pulse energy and peak power of the mode-locked laser were 20 nJ and 1.3 kW, respectively.

We excited a transition between ground-state Zeeman sublevels in ⁴⁰Ca⁺ using a radio frequency (RF) magnetic field. We discuss methods for generating an RF magnetic field of sufficiently large amplitude and for estimating the amplitude of the RF field to observe Rabi oscillations with high Rabi frequencies. A maximum Rabi frequency of ∼250 kHz was obtained. We also demonstrate a simple quantum gate operation on a combined system using the S_1/2–D_5/2 transition in ⁴⁰Ca⁺.

The tunnel magnetoresistance (TMR) and the structure of full-Heusler CoFeAlSi (CFAS)–Al₂O₃ granular films have been investigated. It was found that the most part of the film was in discontinuous layers after annealing at 673 K. A maximum MR ratio of about 18% was obtained at room temperature under a magnetic field of 8 kOe. The X-ray diffraction pattern of the film exhibited a weak peak of CFAS(220) and/or MgO(200) at about 45°, and a halo-like pattern with two peaks within the range 20–30°. These results suggest that the high MR ratio observed is related to the existence of granules with high spin polarization.

Simultaneous measurements of electron and ion transfers were performed in an all solid ion-transfer device made of transition metal cyanide films, indium–tin oxide (ITO)/Na_xNi[Fe(CN)₆]_0.68·5.1H₂O (NNF68)/Na_xCo[Fe(CN)₆]_0.90·2.9H₂O (NCF90)/ITO, against time (t) and temperature (T). At 330 K, the current density (I) steeply decreases below 10 s, and then becomes nearly constant above 10 s. We found that there exists time-lag between the electron and ion transfers. We analyzed the I–t curves with an equivalent circuit, which consists of the external component (R_ex) of resistance, the bulk component (R') resistance, the leak current component (R_leak), and the capacitance (C). The large R' component was ascribed to suppressed current density owning to the local charge neutrality.

The authors present a highly efficient program method for high-speed, low-voltage, and multi-bit/cell operation in the conventional silicon/oxide/nitride/oxide/silicon structure. This method uses a forward bias for collecting the electrons into the substrate whilst both substrate and drain biases are used for injecting the electrons into the nitride layer. With an aid of the substrate bias for electron injection, we obtained a program time as short as 600 ns and an ultralow-voltage operation with a drain voltage of 2 V and a substrate voltage of -3 V. In addition, a localized charge-injection near the junction edge was confirmed with a threshold voltage difference of 1 V between the forward and reverse read.

Nanoscale tantalum nitride–aluminum oxide–silicon nitride–silicon oxide–silicon (TANOS) memory devices utilizing a recess region were investigated to improve device performance and reduce cell-to-cell interference. The dependence of electrical properties on the depth of the recess region in the TANOS flash memory devices was simulated by using Synopsys TCAD Sentaurus. The cell-to-cell interference characteristics of the TANOS flash memory devices dependent on the recess region were investigated. The drain current at an on-state in the TANOS flash memory devices increased with increasing depth of the recess region owing to the existence of the fringe field generated from the recess region. The coupling ratio of the TANOS flash memory increased with increasing depth of the recess region. The simulation results showed that the cell-to-cell interference in the TANOS flash memory devices decreased with increasing depth of the recess region.

Fullerene (C₆₀)-based organic field-effect transistors (OFETs) were fabricated using lithium fluoride (LiF)/silver (Ag) as source/drain electrodes. Field-effect mobility increased from 2.74 to 5.07 cm² V^-1 s^-1 after modifying single Ag electrodes with the proper thickness of LiF layer. Meanwhile, the contact resistance could be reduced from 25 to 10 kΩ. The performance improvement of the OFETs was attributed to the realignment of the energy band, which could reduce the charge carrier injection barrier at the C₆₀/Ag interface. Moreover, the electronic tunneling enhancement was also analyzed in detail to discuss the effect of the LiF layer.

Radio frequency (RF) performances of hetero-gate-dielectric tunneling field-effect transistors (HG TFETs) have been compared with those of SiO₂-only and high-k-only TFETs in terms of f_T, f_max, gate capacitance, channel resistance, and transconductance. HG TFETs can have higher f_T/f_max and smaller switching time than SiO₂-only TFETs and high-k-only TFETs because they have higher g_m and current drivability than SiO₂-only TFET and smaller gate capacitance than high-k-only TFET.

Reducing the size of semiconductor devices causes contact in deca-nano size. Substantial fluctuation of contact resistance is anticipated owing to the reduction of impurity atoms in the contact holes. In this study, the impact of the random dopant fluctuation on the contact resistance is revealed by three-dimensional device simulation with a Schottky contact model. The standard deviation of the contact resistance could become 50%, dominated by the number of impurity atoms in the depletion layer formed by the Schottky barrier. The average value of the contact resistance could increase as the impurity concentration decreases because of the reduction of the tunneling path.

In this paper, a new rounded edge fin field-effect transistor (RE-FinFET) is proposed, where the edges of fins near source and drain regions are rounded in order to reduce self-heating effects. The key idea in this work is to control self-heating by reducing the thermal resistance. Moreover, our simulation results demonstrate that current of the device increases. Also, the series resistance reduces due to the rounded edges of fins near source and drain. Furthermore, using three-dimensional (3D) and two-carrier device simulator, we have examined various design issues of the RE-FinFET and provided the reasons for the improved performance in terms of self-heating and short channel effects. Our results suggest that RE-FinFET is an alternate structure for FinFETs, and expands the application of FinFETs to high temperature.

Cu₂ZnSnS_xSe_4-x nanocrystallines have been synthesized via solvothermal route in ethylenediamine using CuCl, ZnCl₂, SnCl₄·5H₂O, Se, and S powders as reaction reagents. The as-synthesized products were characterized by X-ray powder diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy. The results confirm that the Cu₂ZnSnS_xSe_4-x (0≤x ≤4) is a complete solid solution with single phase and uniform composition. The solid solutions Cu₂ZnSnS_xSe_4-x (0< x <4) are single crystalline nanoplates with the diameter of 20–50 nm. Raman spectra of the Cu₂ZnSnS_xSe_4-x nanocrystallines revealed that vibrating modes were modulated by x-values. Photoluminescence spectra of the as-prepared Cu₂ZnSnS_xSe_4-x nanocrystallines showed that one wide emission band with peak position around 1.40 eV which slightly changed with x-values.

We investigated the electrical resistance dependence on temperature of a single carbon nanotube (CNT) in vacuum, air, and water by heating the end of the CNT locally. The device used for investigation consisted of a microheater for local heating, four electrodes for measuring resistance on a silicon-on-insulator wafer, and a trench for further heat insulation. Then, the resistance of a single CNT assembled on the device was measured as a function of added heat quantity. The temperature coefficients of resistance of the CNT were 0.214×10^-3, 0.422×10^-3, and 0.735×10^-3/°C in vacuum, air, and water, respectively. Moreover, the heat quantities required to raise the temperature of a CNT in air and water are 1.2- and 1.3-fold that in vacuum, respectively. Thus, CNTs, mainly used as thermal sensors in vacuum, may also be suitable for use in air and water.

An impact production of carbon nanoclusters is carried out in nitrogen gas using a two-stage light-gas gun. A small polycarbonate ball (or a stainless steel ball) is injected at about 6.5 km/s into a pressurized target chamber to collide with an aluminum target (or a hexane + aluminum target) in 1 atm of nitrogen gas. We can confirm the production of many types of carbon nanoclusters such as aluminum-encapsulated carbon nanoparticles, carbon nanotubes, and balloonlike nanocarbons. Therefore, it is expected that many types of carbon nanoclusters are produced by impact reactions of asteroids in space, when such reactions take place in a carbon-rich atmosphere. Particularly on Titan satellite, a large number of carbon clusters produced by impacts of asteroids are expected to be stored.

We report the enhanced light output power of GaN-based light-emitting diode (LED) by using graphene film as a transparent conducting electrode. Monolayer graphene was synthesized on copper foil by using chemical vapor deposition method and directly transferred onto the GaN-LED as a top electrode. Compared to the conventional LEDs using indium tin oxide (ITO) layer for an electrode material, the light output power of LED with graphene electrode was improved by ∼25%. This was attributed excellent graphene characteristics of high electrical conductivity, high optical transmittance of nearly 97% over a wide range of infrared, visible, and ultraviolet region and large area uniformity with fewer defects.

Aluminum-doped zinc oxide ceramics were used to study oxygen self-diffusion by the vapor–solid exchange method. The diffusion profile and the quantitative analysis of impurities (H, Li, and Al) were performed by secondary ion mass spectrometry. The concentrations of Al and H in ZnO were evaluated to be 3.2×10¹⁹ and below 1.5×10¹⁷/cm³, respectively. The simultaneous diffusion of oxygen tracer and Li impurity were detected in the analysis, and the diffusion profiles were analyzed to evaluate the diffusion coefficients. Enhanced oxygen diffusivity and increased Li impurity concentration was obtained in Al-doped ZnO. We discuss the defect equations for enhancing oxygen diffusivity and increasing Li concentration in Al-doped ZnO.

CuGaSe₂ single-crystal films are grown on the As-stabilized (2×4) surface of (001) GaAs by migration-enhanced epitaxy (MEE), where Cu+Ga and Se are alternately deposited. The growth process is monitored by refraction high-energy electron diffraction (RHEED) in the [110] azimuth. Under the Cu-enriched growth condition, a deformed 4-fold pattern is observed in both Cu+Ga and Se deposition periods. The deformed 4-fold pattern is found to be related to the segregation of Cu₂Se on the CuGaSe₂ surface as confirmed by the results of X-ray diffraction (XRD) measurement. By reducing the beam equivalent pressure of Cu (Cu-BEP), clear 4-fold patterns appear in both Cu+Ga and Se deposition periods instead of deformed 4-fold patterns. Further reduction of Cu-BEP results in clear 4- and 2-fold patterns for Cu+Ga and Se deposition periods. Under these growth conditions, Cu₂Se-segregation-free CGS growth is achieved. Thus, the CuGaSe₂ single-crystal layers without Cu₂Se-segregation are successfully grown on GaAs(001) substrates by optimizing the Cu-BEP.

The heteroepitaxial growth of (0001) ZnO on (0001) sapphire substrates by halide vapor phase epitaxy using a two-step growth procedure was investigated. X-ray diffraction analysis revealed that single-crystal (0001) ZnO layers on (0001) sapphire substrates were grown at 400 °C. High-temperature heteroepitaxy at 1000 °C on (0001) sapphire substrates was realized by two-step growth using the ZnO layer grown at 400 °C as a buffer layer. Two-dimensional layer growth at 1000 °C was realized on buffer layers thicker than 0.4 µm. Photoluminescence (PL) measurements performed at room temperature for the ZnO layer grown on the 0.4-µm-thick buffer layer showed a significant blueshift of near-band-edge emission (NBE). A thick buffer layer of 0.8 µm was found to be necessary for a successful two-step growth without a blueshift of NBE in the PL spectra, which is caused by a large compressive stress.

In this work, we investigate GaN(0001) crystal growth focusing on gas-phase and surface reactions from the viewpoint of metalorganic chemical vapor deposition (MOCVD) by ab initio calculations. We consider the adsorption of compounds of Ga and N atoms on a Ga-covered surface cluster model. For the adsorption of these compounds, it is found that Ga–Ga bonds undesirable for the steady growth appear for alkylgallium with amino group, and the compounds which have coordinate bonds with NH₃ can be a solution for this problem, since they do not make Ga–Ga bonds.

In the present investigation we study the effects of film-deposition time duration on thermal diffusivity (α) of hydrogenated amorphous carbon (a-C:H) thin-films grown in a radio-frequency (RF) plasma enhanced chemical vapor deposition system. A set of films was deposited at 50 W RF power for 40, 60, 80, and 100 min. Film characteristics were determined from the optical transmission spectroscopy, Fourier Transform Infrared spectroscopy, and Raman spectroscopy. Thermal diffusivity of a-C:H films was evaluated using the optical pump-and-probe technique on the aluminum-coated samples. Results show a trend of increase in α as the deposition time increases due to the microstructural changes associated with longer exposure to ion bombardment effects on the growth surface of the films.

An RF magnetron sputtering technique was used to deposit Ge and stacked Si/Ge films for infrared imaging sensors; the electrical characteristics of these films were estimated. The cross-sectional scanning electron microscope (SEM) image obtained confirmed that a layered Si/Ge structure was deposited on the SiO₂ substrate. The layered film, annealed in an Ar atmosphere, exhibited a large temperature coefficient of resistance (TCR) (-3.63%/K) and a low resistivity (64.5 Ω·cm). The conductivity and TCR of Si/Ge films depend on the thickness of the Ge layer. A significant improvement in TCR was achieved by decreasing the thickness of the Ge layer. Ge thin films sandwiched between amorphous silicon layers facilitate the realization of a noncooled bolometer.

The cation extraction process in the bilayer cyanide film with an epitaxial interface, Na_0.84-yCo²⁺[Fe_y³⁺Fe_1-y²⁺(CN)₆]_0.713.8H₂O (NCF71)/Na_1.60-x(Co_x³⁺Co_1-x²⁺)[Fe²⁺(CN)₆]_0.902.8H₂O (NCF90), was investigated by depth-resolved X-ray absorption spectroscopy. Assuming stepwise depth (z) distributions of Co³⁺ and Fe³⁺, we estimated the step depths, d_Co and d_Fe, and concentrations, δ_Co and δ_Fe, of the respective ions against the average quantity (δ_av) of cation extraction. The Na⁺ extraction was found to be dominant in the NCF90 surface layer, consistent with the lower redox potential in the NCF90 layer. We found that the magnitude of d_Fe (∼600 nm) is much deeper than the actual depth (d = 200 nm) of the NCF71/NCF90 interface, and interpreted the behavior in terms of the redox interaction in the vicinity of the interface.

Nanocomposite alloys with the nominal compositions Nd_xY_6-xFe₆₈Mo₄B₂₂ (x=1–5) were prepared directly by devitrification of amorphous rods and ribbons. The effect of Y doping on the glass-forming ability (GFA) of the alloys has been investigated. It was found that the GFA of the alloys was enhanced by the substitution of Y for Nd and increased with increasing Y content. The best glass former was Nd₁Y₅Fe₆₈Mo₄B₂₂ with a critical diameter of 4 mm. A comparison of microstructures and magnetic properties between ribbon and bulk magnet with the same composition after optimally annealing treatment was presented in detail. Compared to the Nd₃Y₃Fe₆₈Mo₄B₂₂ ribbons, the better hard magnetic properties have been obtained in the Nd₃Y₃Fe₆₈Mo₄B₂₂ nanocomposite bulk magnet, which can be attributed to much higher relative content of hard magnetic Nd(Y)₂Fe₁₄B phase in the crystallized rod sample.

Gas permeation through smectic C^* free-standing films causes a unidirectional director rotation, occasionally accompanied by a unidirectional vortex-like hydrodynamic flow. In this study, by placing ZrO₂ micro-particles on the film subjected to methanol vapor transport, we observed the particle motions and measured a drag force acting on them. The particles underwent a unidirectional quasi-circular motion with the velocity linear to the methanol transfer rate with the magnitude of the drag force being on the order of several pN that increased approximately linearly with the velocity of the flow. A simple analysis shows that the conversion efficiency from the transmembrane methanol current to the drag force on the particles is ∼1.4×10^-10 N·s·m²/mol in our system. The present hydrodynamic experiment is complementally to the previous observations of linear director rotation in the Lehmann effect, which well supports Leslie's phenomenological theory.

Shock recovery experiments at pressures of up to 22 GPa on BaSi₂ powder are performed using a propellant gun. The shocked samples are characterized using X-ray diffraction analysis, Raman spectroscopy, and scanning electron microscopy (SEM). Only the orthorhombic BaSi₂ phase is detected and no evidence of amorphization or phase transition is obtained. The SEM images reveal that the BaSi₂ powder is consolidated at pressures below 10 GPa, whereas many cavities in addition to whiskers with diameters of several hundreds of nanometers are formed on the surface of the sample shocked at 10 GPa. These whiskers are due to the eruption of BaSi₂ vapor from the cavities and the subsequent mixing of this vapor with air. The shock-induced heat may be the cause of this vaporization.

Ti–Al–Cr–N coatings, characterized by a nanocomposite comprising nano-sized TiN crystallites embedded in amorphous AlN or CrN matrix, could be successfully synthesized on Si(111) and WC–Co cemented carbide substrates by a closed field unbalanced middle frequency magnetron sputtering method. The Cr content in the Ti–Al–Cr–N coatings linearly increased from 11.2 to 32.8 at. % raising the Cr targets currents from 5 to 15 A, whereas the Ti content decreased from 63 to 47 at. %. The high resolution transmission electron microscope (HRTEM) image and diffraction patterns clearly show that the Ti–Al–Cr–N coatings were composites of crystallites and amorphous phase, which were distinguished from each other by lattice fringe contrast. The hardness and Young's modulus value of the Ti–Al–Cr–N coatings increased with incorporation of Cr, and had the maximum value of 38.9 and 475 GPa at the Cr content of 17 at. %, respectively. The average friction coefficient of the Ti–Al–Cr–N coatings largely decreased with an increase of the Cr content when compared to the TiN coatings.

We examined the effects of a supersonic wave on laser-induced plasma and ablation-induced cavitation bubbles in liquid-phase laser ablation. The effect of the supersonic wave on laser-induced plasma was the change in the optical emission intensity. We observed an intense optical emission when the ablation target was irradiated with a laser pulse at a negative phase of the sound pressure of the supersonic wave. The effect of the supersonic wave on ablation-induced cavitation bubbles was the repetitive formation and collapse of the bubbles at the same frequency as the supersonic wave. The ablation-induced cavitation bubbles served as a "seed", and the repetitive formation and collapse of the cavitation bubbles were driven by the sound pressure of the supersonic wave.

The resist materials are evaluated using their resolution, line edge roughness (LER), and sensitivity. However, the evaluation of chemically amplified resists is tricky because of the trade-off relationships between resolution, LER, and sensitivity. In this study, we investigated a chemically amplified resist with a fullerene matrix by analyzing the dose-pitch matrices of line width and LER. The effective quencher concentration of the fullerene resist obtained by the analysis was higher than those of typical polymer-type resists. This suggests that the quantum efficiency of acid generation in the fullerene matrix is slightly lower than those of polymer-type resists. The effective reaction radius was 0.06 nm, which was smaller than those of polymer-type resists. The proportionality constant between LER and the chemical gradient of the fullerene resist was smaller than those of polymer-type resists, probably owing to its molecular size.

A liftoff process was used to fabricate nanoimprint molds with dense patterns below 50 nm pitch. Circumferentially aligned patterns were defined by electron-beam lithography (EBL) using an electron-beam recorder with a rotary stage. Undercut profiles suitable for liftoff were fabricated by etching multilayered resist systems that use a hydrogen silsesquioxane (HSQ) layer as an etching mask for the underlying resin, and liftoff was performed by dissolving the HSQ layer on an insoluble resin layer. By using an undercut profile that was formed in a trilayered stack after EBL, a mold with high-density (42 nm pitch) and large-area (2.5 in.) pillar patterns was fabricated. Quartz replica molds were also fabricated by the liftoff process combined with UV nanoimprint. It was possible to fabricate molds with both a positive tone and a negative tone, and the fabrication of a replica mold with pillar patterns (49 nm pitch) was demonstrated.

On the basis of the main physical processes of secondary electron emission, the relationships among the incident energy (W_p0) of primary electrons, the number of secondary electrons (δ_PEθ) released per primary electron entering the metal at high electron energy and incident angle θ and incident angle (θ) are deduced. In addition, the relationship between the number of secondary electrons (δ_PE0) released per primary electron entering the metal at θ= 0° and W_p0 is determined. From the experimental results, the relationships among the ratio β_θ (the subscript θ means the primary electron is incident at θ in this paper), the ratio at θ= 0° (β₀) and θ are obtained. On the basis of relationships among δ_PEθ, δ_PE0, β_θ, β₀, backscattered coefficient η_θ, backscattered coefficient at θ= 0° (η₀), secondary electron yield δ_θ, and secondary electron yield at θ= 0° (δ₀), the universal formula for expressing δ_θ using δ₀, η_θ, η₀, and θ is deduced. The secondary electron yield calculated from this universal formula and the yields measured experimentally from aluminum and copper are compared. The results suggest that the proposed formula is universal for the estimation of secondary electron yields in the angle range of 0–80° and the energy range of 10–102 keV.

We studied the electrophoretic migration of electrophoretic inks by measuring the total reflection at the interface between the electrode and the ink solvent simultaneous with the current response to a cyclic-polarity-reversed triangular voltage. We demonstrated that the current peaks and optical responses to the cyclic-polarity-reversed triangular voltage are effective for the easy evaluation of mobility, the charge amount of ions and ink particles, and the interactions of particles with the electrode and inter-particles. The mobility of the ink particles was measured from the slopes of these peak voltages as functions of the square root of the time rate of the scanning voltage. The offset of line extrapolation indicated the interaction of the particles with the electrode. The optical response was effective for measuring the mobility even when the conductivity of the cell was too large to detect the drift current peaks.

The interface of Ag(In,Ga)Se₂ (AIGS) and Cu(In,Ga)Se₂ (CIGS) solar cells was investigated by high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) imaging method. It was found from the results that the AIGS film had Ag-rich and Ag-poor layers. The CdS layer in the CIGS solar cell had a denser structure and a better connection with the CIGS layer than the CdS layer in the AIGS solar cell. The lattice between CIGS and CdS was continuous and ordered. However, there were some defects in CdS and the lattice arrangement was distorted at the AIGS/CdS interface in the AIGS solar cell, resulting in the poor performance of the AIGS solar cell compared with the CIGS solar cell.

We have developed a system for performing optical-pumping and double-resonance NMR of semiconductors simultaneously or sequentially. The components include a cryosystem equipped with a Gifford–McMahon (GM) cryocooler, which cools the samples via thermal contact. The following benefits are derived from this feature. (1) A pickup coil and tank circuits for NMR can be built in a vacuum, which excludes rf discharges and/or arcing (breakdown) occurring in conventional systems employing a helium-gas atmosphere, allowing application of the stronger and more stable rf-pulses required for broad-line double-resonance NMR. (2) Heat around a sample generated by light irradiation can be drained through the thermal connection to a heat anchor, permitting the use of a light-power high enough to achieve large nuclear polarization by optical pumping. (3) A bottom-loading style can be adopted for the installation of a cryostat and a probe to an NMR magnet, allowing a more compact system.

In this study, we have investigated real-time decoding feasibility of magnetic micro-barcodes in a microfluidic channel by using numerical analysis of magnetic field distribution of the micro-barcodes. The vector potential model based on a molecular current has been used to obtain magnetic stray field distribution of ferromagnetic bars which consisting of the micro-barcodes. It reveals that the stray field distribution of the micro-barcodes strongly depends on the geometries of the ferromagnetic bar. Interestingly enough, we have found that one can avoide the miniaturization process of a magnetic sensor device needed to increase the sensitivity by optimizing the geometries of micro-barcodes. We also estimate a magnetic sensor response depending on flying height and lateral misalignment of the micro-barcodes over the sensor position and found that control of the flying height is crucial factor to enhance the detection sensitivity and reproducibility of a magnetic sensor signal in the suspension assay technology.

A nanopore protein biosensor using a copolymer and diffusive flow of the test sample was developed. The copolymer coated within the nanopore can capture the antibody, which then captures the antigen. Diffusive flow of a test sample can be obtained using a concentration gradient between the nanopore and the micropore sides. No applied voltage was used to create the electrokinetic flow of the test liquid. The present nanopore protein biosensor showed high sensitivity and detected antigen quantities as low as 0.15 nM (4 pg/mL).

A Cu₂ZnSnS₄ (CZTS) single crystal was grown at 900 °C, which is less than its melting point (962 °C) using a traveling heater method, which is one of the solution growth methods. No twins and no secondary phases could be distinguished from the Laue and X-ray diffraction patterns, respectively.

Photoluminescent emissions of zinc sulfide–silica–cerium thin films deposited by magnetron sputtering were observed. The films consisted of ZnS nanocrystals embedded in amorphous SiO₂ matrices. ZnS–SiO₂:Ce films exhibited photoluminescence even without postannealing. Their emission spectra showed broad patterns in the visible range; the emitted colors depended on film composition.

A water-repellent silicon (Si) surface with a nanostructure was formed by simple wet chemical etching using catalysis of a silver nanoparticle. Water repellency can be increased by forming micro- or nanostructures on the Si surface. A single nanosized silver particle dispersion solution was coated onto a Si(100) substrate with a polished surface. The samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. The roughness and depth of the surface structure increased with increasing etching time. The Si surface with the nanostructure had a contact angle of 130°, indicating a water-repellent surface, whereas the surface without the nanostructure had a contact angle of 68°.

We describe a method for evaluating the power linearity over a wide dynamic range of a terahertz time-domain spectroscopy (THz-TDS) system. The dynamic range is achieved by means of metalized film attenuators (MFAs). The evaluation was based on repeated measurements of transmittance in a particular sample at different incident power levels. We apply the method to both focused- and collimated-beam systems and show that the method can be applied to reflectance measurements as well.