Yoshio Taniguchi

Chalcogenide thin films for laser‐beam recordings by thermal creation of holes

The shapes of holes thermally created by a laser beam in thin films of wide range of materials are studied. The most cleanly shaped holes, which measure up to recent requirements for direct‐read‐after‐write video recordings by submicron dots, are obtained in some compositions of amorphous chalcogenide thin films such as As‐Te system, Ge‐Te system, As‐Se system, Ge‐Se system, and Sb‐S system thin films. The experiments clarify several important conditions helpful in obtaining cleanly shaped holes. The most important condition is that the viscosity of the material in liquid or softened state should be high. The required incident laser‐beam power for recording in an As‐Te system thin film on a polymethyl methacrylate substrate rotating at 1800 min−1 is about 10 mW. Addition of Se to the As‐Te system thin films greatly increases film stability. A signal‐to‐noise ratio of about 45 dB is obtained in reproduced color video signals.

Large second-harmonic generation coefficients of bis(benzylidine) cycloalkanones estimated by the second-harmonic wave generated with the evanescent wave technique

Abstract The second-harmonic generation (SHG) coefficients ( d ) in a series of novel organic materials, i.e. bis(benzylidene)cycloalkanones derivatives, were estimated by means of the second-harmonic wave generated with the evanescent wave (SHEW) technique. As a result, it is found that several compounds exhibit a large d coefficient, in pentanone (MBCP). An X-ray crystallographic study reveals that the symmetry of MBCP is orthorhombic mm2. Comparison between d coefficients estimated by the SHEW and the Kurtz technique is also made.

Fluorescence spectra of vacuum-deposited films of ω-(1-pyrenyl)alkanoic acids

Abstract Vacuum-deposited films of ω-(1-pyrenyl)alkanoic acids with different chain length were prepared using a deposition rate of ≈1 nm min . Their fluorescence spectra consist of pyrene monomer fluorescence and two new emissions; no excimer-like emission was detected as a major component. These fluorescence results are considered in terms of pyrenyl aggregates characteristic of a deposited film.

Fluorescence characterization of ablated polymeric materials: Poly(methyl methacrylate) doped with 1‐ethylpyrene

Fluorescence spectra and rise as well as decay curves of 1‐ethylpyrene (EPy) in poly(methyl methacrylate) films changed using a XeCl (308‐nm) excimer laser as an ablation source. This phenomenon was observed not only for the ablated area but also for the masked region of about 20 μm around the ablated area and was attributed to the change of the dispersion condition of EPy. Effects of laser ablation upon properties of polymer films were elucidated by analyzing fluorescence dynamics using a microscope and under a total internal reflection condition.

Fluorescence spectral changes of vacuum-deposited films of ω-(1-pyrenyl)alkanoic acids induced by an excimer laser: molecular aspects of laser annealing

Abstract Vacuum-deposited films of ω-(1-pyrenyl) alkanoic acids showed fluorescence spectral changes upon irradiation with an excimer laser and a Xe lamp, although no absorption spectral change was detected. It was confirmed that this characteristic phenomenon depends on the number of methylenes in the chain and that a non-linear photochemical process (with respect to irradiation intensity) is involved.

Fluorescence characteristics, formation mechanism and chromophore association of ω-(1-pyrenyl) alkanoic acid films prepared by vacuum deposition

Abstract Thin films of ω-(1-pyrenyl) alkanoic acid were prepared by vacuum deposition and their fluorescence properties were studied using a picosecond single-photon counting method. Their fluorescence spectra exhibited a structured emission ascribable to a new aggregate. The deposition mechanism and the resulting chromophore association in the film were examined by varying deposition rate and chromophore content. The emission with long lifetime characteristic of a 1-substituted pyrene suggested that the compound was evaporated as a single molecule.

In situ observation of vacuum deposition process of 10-(1-pyrenyl) decanoic acid by fluorescence measurement

Abstract Fluorescence spectra of 10-(1-pyrenyl) decanoic acid were measured during vacuum deposition on hydrophilic and hydrophobic quartz substrates. On the basis of the observed thickness-dependent fluorescence spectra, the formation mechanism of excimer sites and pyrenyl aggregates characteristic of the deposited films is discussed in terms of the interaction between the substrate and the compound.

Quantification and mitigation strategies of neutron induced soft-errors in CMOS devices and components

As semiconductor device scaling is on-going far below 100nm design rule, terrestrial neutron-induced soft-error typically in SRAMs is predicted to be worsen furthermore. Moreover, novel failure modes that may be more serious than those in memory soft-error are recently being reported. Therefore, necessity of implementing mitigation techniques is rapidly growing at the design phase, together with development of advanced detection and quantification techniques. The most advanced such techniques are reviewed and discussed.

Second-order nonlinear optical susceptibility measurement of crystal with a glass prism in total-reflection geometry

Second-harmonic generation in a uniaxial crystal in total-reflection geometry is precisely measured. A Y-cut plate and a Z-cut plate of quartz crystals were used as samples. The incident wave is totally reflected by a glass prism in contact with the sample crystal, and an evanescent wave penetrates into the sample as a fundamental wave. The results gave the quantitative values of the components for a nonlinear optical susceptibility tensor with various polarizations and with Y-cut and Z-cut quartz plates. This technique can be applied to various samples to evaluate their nonlinear optical efficiencies.

Quasi‐epitaxial growth of diacetylene films by vacuum deposition

The quasi‐epitaxial growth of vacuum‐deposited films of diacetylenes on various substrates, including uniaxially aligned polymer surfaces formed with rubbing treatment or Langmuir–Blodgett technique, is reported. The oriented polydiacetylene (PDA) films are readily obtained from these monomer films using photopolymerization. Highly oriented PDA films with excellent optical qualities have been obtained on rubbed polyethylene terephthalate surfaces. The typical dichroic ratio of these oriented PDA films is more than 100:1. This ratio is high enough to permit the application of these films to optical waveguide devices. The method for obtaining these highly oriented PDA films is described in detail. In addition, the structure, the morphology, and the optical anisotropy of these PDA films is examined by x‐ray and electron diffraction, electron microscopy, and other optical means.