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Self-assembled monolayers (SAMs) of three thiol derivatives with a COOH group at the terminus of the molecule were prepared on Au(111) substrates as templates for immobilization of DNA molecules. The adsorption states and the structures were examined by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. S 2p XPS results showed that these molecules are mostly chemisorbed on the Au(111) surface through S–Au bonds. The molecular orientation in these SAMs was elucidated using the polarization dependence of the C K-edge NEXAFS spectra. These results suggested that the film structure and the molecular packing differ among these SAMs. We compared the amounts of the amino-terminated DNA molecules adsorbed on these SAMs estimated from the peak intensity of the N 1s XP spectra. These results show that the adsorption efficiency of the DNA molecules depends on the structures of the COOH-terminated SAMs.

Out of two species of fluorescence of polyethylene terephthalate (PET), intrinsic fluorescence (I), which was caused by short-wavelength ( 320 nm), was much more intense for thick films. This fact was confirmed, and explained by an elementary formula. Effects of polymerization catalysts onto the fluorescence spectra were found to be indirect; namely, peak positions of the fluorescence were not affected by catalyst systems, while fluorescence intensity was sensitive not only to catalyst systems but also to minute differences in local surroundings. Effects of catalyst systems on the weak absorption bands at 338 nm and 354 nm were examined. Integrated excitation spectra were resolved; therein, a hidden n→π* state was found. Most likely, this is related with the weak absorptions at 338 nm and 354 nm, which are the major origins of fluorescence (II).

We present a type of lateral shearing interferometer (LSI) for at-wavelength characterization of the projection lens for use in extreme-ultraviolet lithography (EUVL). LSI is one of the potential candidates for high Numerical Aperture (NA) optics testing at the EUV region. To address the problem of multiple-beam interference, we propose a general approach for derivation of a phase-shift algorithm that is able to eliminate the undesired 0th order effect. The main error source effects including shear ratio estimate, hyperbolic calibration, and charge coupled device (CCD) size, etc. are characterized and the measurement accuracy of the LSI is estimated to be within 7 mλ rms (0.1 nm rms at 13.5 nm wavelength) for testing the wavefront of EUVL projection optics.

Various models have been proposed, to date, to explain the improvement in organic electroluminescent devices by the insertion of an insulating layer such as LiF between the light emitting tris-(8-hydroxyquinolinato) aluminum (Alq3) layer and the cathode metal deposited on it. Although the average thickness of the LiF for the optimal performance is typically only 0.5 nm, the layer structure of the inserted LiF has been assumed explicitly or implicitly. In order to clarify the growth mode and electronic structure of LiF in the system, the Alq3–LiF–Al system was investigated by ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and metastable atom electron spectroscopy (MAES). We found island formation of LiF on the Al substrate, and also that the Al surface is only partly covered when a 0.5-nm-thick LiF layer is deposited on it. MAES measurements revealed that island-grown LiF has density of states similar to that of a thick LiF layer except for the existence of defect states, which is probably due to Li vacancies near the interface. MAES also suggested a slight difference in the spatial extention of the wave function of LiF between a 0.5-nm-thick island and a 2.0-nm-thick film, while a distinct difference was found between LiF and Alq3 films. These findings are important in order to discuss their attenuation lengths in relationship to electron injection. We have constructed a realistic energy diagram of the interface, taking account of the island nature of the 0.5-nm-thick LiF layer. This energy diagram suggests it is necessary to reexamine the proposed models.

Nonlinear optical responses of a self-assembled monolayer (SAM) containing merocyanine chromophore, 1-alkyl-4-(4-hydroxystyryl) pyridinium bromide (HSP), on gold in water and in ethanol were studied by second-harmonic generation (SHG). The pH dependence of the SHG response clearly showed a solvatochromic characteristic of the merocyanine from a protonated form to a zwitterionic form. A large second-order susceptibility χzzz=5.0×10-7 esu (2.1×102 pm/V) was found in a basic solution of ethanol where the merocyanine is in the zwitterionic form. Combination of the SHG and surface plasmon resonance (SPR) spectroscopy measurements also provides us with details of the formation process of the merocyanine SAMs in the ethanol solution of the HSP-terminated-alkyldisulfide, ω,ω'-dithiodi[1-undecyl-4-(4-hydroxystyryl)pyridinium bromide](HSPC11SS). A considerable difference was found in the kinetics between SPR and SHG, because SHG probes the molecules in a noncentrosymmetric fashion on the gold surface while SPR probes the optical thickness of the film. The difference enabled us to separate the chemisorption from the physisorption in the adsorption process. Interestingly, both probes showed slower kinetics in the solution of higher concentration, suggesting association of the disulfide molecules in the solution of high concentration.

The thermal characteristics of thin-film vertical-cavity surface-emitting lasers (VCSELs) have been studied by means of finite element analysis. The thin-film VCSELs transferred onto a selected substrate, which we have already demonstrated, are very attractive for integrated optoelectronic devices. However, structural design based on thermal analysis is required to improve the performance especially for small aperture VCSELs. We confirmed that an AlN submount used as the transferred substrate was satisfactory from the viewpoint of thermal conductivity. We also numerically showed that an Au plating layer on the top surface and an oxide-defined layer would improve the thermal characteristics. Although the thermal resistance Rth of 5 µm air-post thin-film VCSEL is very high, the 5 µm oxide-defined aperture with 35 µm mesa and an Au plating layer of 3 µm thickness can reduce Rth by about 27%.

A simple optoelectronic packaging method for integrating plastic optical fibers (POFs) with vertical-cavity surface-emitting lasers (VCSELs) is described. Passive alignment was performed using polymer guide holes, which were directly patterned on the top of VCSELs by means of standard photolithography. The direct formation of the polymer guide holes and the connection of POFs did not degrade the light-current characteristics or thermal characteristics of the VCSELs. As a transmitter module, we confirmed low optical crosstalk between adjoining fibers and the capability for high-bit-rate data transmission.

A liquid crystal (LC) microlens for obtaining an erect image is designed using LC director orientation simulation and ray tracing, where relationships between LC material and structural parameters of the double-layered LC microlens cell and its optical properties are calculated. Then, the double-layered LC microlens is fabricated based on the simulation results. The dependence of the working distance on the magnification of the image is discussed experimentally and theoretically. An erect image of unit magnification with a designed working distance is obtained by the double-layered structure. Lens properties such as magnification are continuously controlled and image direction can be switched by changing the voltage applied to the LC microlens cell.

Advanced metamorphic high-electron-mobility heterostructures were grown by gas-source molecular beam epitaxy (gas-source MBE). These structures included an InGaAs/InAsP composite channel layers to improve breakdown voltage and a thin InP stopper layer under the n-InGaAs contact layer to provide long-term reliability and highly selective etching for mass production. Even though the graded buffer layer was thin (0.45 µm), misfit dislocations, observed by transmission-electron microscopy (TEM), were confined effectively to this thin buffer layer. High mobilities of over 9000 cm2 V-1 s-1 were obtained with the thin compositionally graded InAlAs buffer layer when the As composition of the InAsP sub-channel layer was less than 0.2.

We devised a new method of determining the temperatures of materials with their electron-energy distributions. The Fermi–Dirac distribution convoluted with a linear combination of Gaussian and Lorentzian distributions was fitted to the photoelectron spectrum measured for the Au(110) single-crystal surface at liquid N2-cooled temperature. The fitting successfully determined the surface-local thermodynamic temperature and the energy resolution simultaneously from the photoelectron spectrum, without any preliminary results of other measurements. The determined thermodynamic temperature was 99 ± 2.1 K, which was in good agreement with the reference temperature of 98.5 ± 0.5 K measured using a silicon diode sensor attached to the sample holder.

We investigated the dependence of terahertz (THz) wave intensity on ex situ annealing temperature of low-temperature-grown gallium arsenide (LT-GaAs). THz waves excited by femtosecond laser pulses were emitted from photoconductive antennas (bow-tie type) formed on LT-GaAs, and the radiation intensity was measured with a Si bolometer. LT-GaAs ex situ annealed at temperatures of 700 °C and above generated 1.4 times higher radiation intensity than unannealed LT-GaAs. Transmission electron microscopy images revealed apparently improved crystal quality, explaining the observed higher carrier mobility and associated radiation intensity.

We have fabricated a simple-cubic-lattice photonic crystal (PhC) device based on high-resistivity silicon in the terahertz (THz) range by micro-electro-mechanical system (MEMS) techniques. The lattice constant of the three-dimensional (3D) PhC device is 120 µm, resulting in a photonic band gap (PBG) centered at 1 THz. The 3D PhC device was constructed by stacking ten 120-µm-thick chips with periodic pillars and holes patterned respectively on both of their sides by Si deep reactive ion etching. By THz time-domain spectroscopy, the PBG of the device was observed between 0.83 and 1.17 THz in the Γ–Z direction with a transmittance attenuation of about 35 dB, which is in good agreement with a numerical calculation result.

Aiming at avoiding strong surface oxidization at the regrowth interface of InGaAlAs materials, we investigated hydrogen-chloride (HCl) in situ gas etching of various materials in a metalorganic–vapor–phase–epitaxy (MOVPE) reactor. The etching patterns at the mask edge in all cases were limited by the (111)B plane. The etching rates for InP and InGaAs were similar. In the case of InGaAlAs, the etching rate decreased because surface oxidization occurred at a higher aluminum content. Moreover, in the case of InAlAs, in situ gas etching was not possible without an InP cap layer. Furthermore, after HCl in situ mesa etching, a high crystalline quality was obtained, even in the case of InP regrowth on an InGaAlAs structure.

To accurately measure closed crack length, we proposed an imaging method using a subharmonic phased array for crack evaluation using surface acoustic waves (SAW SPACE) with water immersion. We applied SAW SPACE to the hole specimen in a fundamental array (FA) image. The hole was imaged with high resolution. Subsequently, SAW SPACE was applied to fatigue crack and stress corrosion crack (SCC) specimens. A fatigue crack was imaged in FA and subharmonic array (SA) images, and the length of this particular fatigue crack measured in the images was almost the same as that measured by optical observation. The SCC was imaged and its length was accurately measured in the SA image, whereas it was underestimated in the FA image and by optical observation. Thus, we demonstrated that SAW SPACE with water immersion is useful for the accurate measurement of closed crack length and for imaging the distribution of open and closed parts of cracks with high resolution.

Undrawn and drawn polyester films were stretched by 1% between the clamps of a tensile tester, and the effects of infrared exposure on the stress relaxation were observed. Upon exposure for 5 s, the stress deceased sharply, and after stopping, it recovered nearly to the extended level of the original stress relaxation, except for the uniaxially drawn films stretched along the machine direction which showed a complex behavior.

Photoreflectance (PR) measurement was carried out for ordered/disordered GaAs0.5Sb0.5 layers grown on (001) InP and (111)B InP substrates by molecular beam epitaxy. A marked band-gap reduction and valence-band splitting due to point-group symmetry breaking was observed for the ordered GaAs0.5Sb0.5 layer grown on (001) InP, but not for the disordered GaAs0.5Sb0.5 layer grown on (111)B InP. The result of the PR measurement is in agreement with that of the optical absorption measurement.

To increase the hole mobility of heavily-doped GaAsSb layers lattice-matched with InP substrates, GaAs/GaSb short-period superlattices were grown by molecular beam epitaxy. The hole mobility of a 50-nm-thick GaAsSb layer increased from 35 to 55 cm2V-1s-1 by changing the layer structure from a random-alloy one to short-period-superlattice one (doping concentration: about 3×1019 cm-3). The mobility was further increased to 68 cm2V-1s-1 by thinning the first layer of the short-period superlattice.

The crystallographic and luminescent characteristics of Ba2ZnS3:Mn thin film electroluminescent (EL) devices have been investigated. Ba2ZnS3:Mn thin films have been prepared by electron-beam evaporation and postdeposition annealing at 600°C. It has been found that the suitable molar fraction of Ba/Zn in a deposition source pellet for suppressing impurity phases formed in thin films is about 1.8. The Ba2ZnS3:Mn EL devices show an efficient reddish-orange luminescence with the Commission Internationale de l'Eclairage (CIE) color coordinates of (x, y) = (0.60, 040). The luminance and efficiency at 1 kHz are 250 cd/m2 and 0.09 lm/W, respectively. Since the Ba2ZnS3:Mn thin films are crystallized even at 600°C, Ba2ZnS3:Mn is a promising red EL phosphor for a low-temperature process.

The n-type doping ability of the electron-donating organic molecule tetrathianaphthacene (TTN) was examined by ultraviolet photoemission spectroscopy (UPS) for two kinds of matrix organic semiconductors, hexadecafluorophthalocyaninatozinc (F16ZnPc) and tris(8-hydroxyquinoline)aluminum (Alq3). The observed dependence of the UPS spectra suggests that TTN acts as a good donor in F16ZnPc, while the effect was not so significant for Alq3. These results and the consideration of the energy parameters of these molecules indicate that a close match between the highest occupied molecular orbital of the dopant and the lowest unoccupied molecular orbital of the matrix is important for efficient n-type doping.

InGaAsSbN quantum well diodes operating at 2 µm wavelength region were grown by molecular beam epitaxy (MBE) on InP substrates. The emission wavelength of the electroluminescence (EL) was as long as 2.43 µm at room temperature for the quantum well diode with 1.4% nitrogen. It was found from the temperature dependence of the EL spectrum that the introduction of nitrogen induced a marked reduction of temperature dependence of the band-gap energy of the InGaAsSbN layer.