In the field of micro-LED displays consisting of UV or Blue-LED arrays and phosphors, where the chips used are very small, particle size of phosphors must be small to suppress variation in hue for each pixel. Especially, there is a strong demand for a red phosphor with small particle sizes. However, quantum yields of inorganic phosphors decrease as particles size of phosphors get smaller. On the other hand, in the case of organic phosphors and complexes, quantum yields don't decrease when particle size gets smaller because each molecule has a function of absorbing and emitting light. We focus on Eu(III) complexes as candidates of red phosphors for micro-LED displays because their color purities of photoluminescence spectra are high, and have been tried to enhance photoluminescence intensity by coordinating non-ionic ligand, specifically, newly designed phosphine oxide ligands. Non-ionic ligands have generally less influential on properties of complexes compared with ionic ligands, but have a high degree of flexibility in molecular design. We found novel molecular design concept of phosphine oxide ligands to enhance photoluminescence properties of Eu(III) complexes. This time, novel dinuclear Eu(III)-β-diketonates with a branched tetraphosphine tetraoxide ligand, TDPBPO and TDPPPO, were developed. They are designed to have two different phosphine oxide portions; one has aromatic substituents and the other has no aromatic substituent. TDPBPO and TDPPPO ligands have functions of increasing absolute quantum yields of Eu(III)-β-diketonates. Eu(III)-β-diketonates with branched tetraphosphine tetraoxide ligands have sharp red emissions and excellent quantum yields, and are promising candidates for micro LED displays, security media, and sensing for their pure and strong photoluminescence intensity.

High structural perfection, wafer uniformity, and reproducibility are key parameters for high-volume, low cost manufacture of resonant tunnelling diode (RTD) terahertz (THz) devices. Low-cost, rapid, and non-destructive techniques are required for the development of such devices. In this paper, we report photoluminescence (PL) spectroscopy as a non-destructive characterisation technique for high current densityInGaAs/AlAs/InP RTD structures grown by metal-organic vapour phase epitaxy (MOVPE) for THz applications. By using a PL line scanning technique across the edge of the sample, we identify characteristic luminescence from the quantum well (QW) and the undoped/n+ InGaAs layers. By using the Moss-Burstein effect, we are able to measure the free-electron concentration of the emitter/collector and contact layers in the RTD structure. Whilst the n+ InGaAs luminescence provides information on the doping concentration, information on the alloy composition and compositional variation is extracted from the InGaAs buffer layer. The QW luminescence provides information on the average well width and provides a monitor of the structural perfection with regard to interface and alloy disorder.

As one of organic electroluminescent (EL) materials, we developed a method of fabricating an ink using low molecular- weight materials with a long emission lifetime for application to the inkjet method. Although the emission lifetime is usually long for low molecular-weight materials, their high manufacturing cost due to the necessity of vapor deposition is a disadvantage. We utilized the low molecular-weight material, tris-(8-hydroxyquinoline) aluminum (Alq3), and investigated its dispersibility in a solvent in which it has low solubility. In addition, we ascertained whether the material could maintain its photoluminescence characteristic under the irradiation of ultraviolet rays by investigating the emission of photoluminescence. Alq3 was crystallized into nanosize crystals, whose surface was then coated with a primary amine by the gas evaporation method. The fabricated ink contained crystals with an average size of 250nm and high dispersibility in tetradecane, in which Alq3 is insoluble. Thus, we made it possible to carry out an inkjet method with low molecular weight EL materials.

A half-cylindrical BK-7 prism/dielectric film with a grating/Ag film/fluorescent polymer film structure was prepared, and its surface plasmon (SP) excitation property was investigated. It was confirmed experimentally that SP excitations are possible in this structure by using prism and grating couplings. The SP excitation property depended on the direction of the grating vector. Furthermore, intense photoluminescence was observed when the SPs were simultaneously excited at the Ag/polymer interface by prism coupling and at the Cytop/Ag interface by grating coupling.

We report Ultraviolet (UV)-induced visible light luminescence in artificial-lattice thin films of ion-doped silica glass (silica superstructure thin films). The film was composed of periodic nanometer layers of germanium-doped silica (Ge:SiO2), titanium-doped silica (Ti:SiO2), and tin-doped silica (Sn:SiO2). The thickness of each layer was between 10 and 30 nm. Despite the small thickness of the film (few microns), a relatively bright luminescence of white light was observed, along with cathode-ray luminescence in the superstructure film. In addition, irradiation of the superstructure film with UV light led to light amplification by stimulated emission at 405 nm. The experimental results suggest the potential application of silica superstructure thin films as optical amplifiers.

We carried out degradation analysis of a blue phosphorescent organic light emitting diode by both impedance spectroscopy and transient electroluminescence (EL) spectroscopy. The number of semicircles observed in the Cole-Cole plot of the modulus became three to two after the device was operated for 567 hours. Considering the effective layer thickness of the initial and degraded devices did not change by degradation and combining the analysis of the Bode-plot of the imaginary part of the modulus, the relaxation times of emission layer and hole-blocking with electron transport layers changed to nearly the same value by the increase of the resistance of emission layer. Decay time of transient EL of the initial device was coincident with that of the degraded one. These phenomena suggest that no phosphorescence quenching sites are generated in the degraded device, but the number of the emission sites decrease by degradation.

The historical review of Taiwan's researching activities on the features of PECVD grown SiOx are also included to realize the performance of Si nanocrystal based MOSLED made by such a Si-rich SiOx film with embedded Si nanocrystals on conventional Si substrate. A surface nano-roughened Si substrate with interfacial Si nano-pyramids at SiOx/Si interface are also reviewed, which provide the capabilities of enhancing the surface roughness induced total-internal-reflection relaxation and the Fowler-Nordheim tunneling based carrier injection. These structures enable the light emission and extraction from a metal-SiOx-Si MOSLED.

A novel sensing system for glucose in aqueous solution based on cataluminescence(CTL) is proposed. CTL is a kind of chemiluminescence emitted in a course of catalytic oxidation of combustible substances. A sensing system consisting of a CTL-based chemical-sensor made of the γ-Al2O3 catalyst activated with Tb and an ultrasonic nebulizer is developed. CTL is emitted by injection of air containing mist of a glucose solution prepared by the nebulizer on the catalyst. The CTL intensity measured by a photomultiplier is reproducible for the repeated injection of the mist, and the system can measure glucose concentration in a range of 1-200 mg/dl.

We prepared transparent polymer films doped with π-conjugated organic dyes around a multimode silica fiber and observed very narrow fluorescence peaks as compared with the fluorescence in solution. The peak position showed no dependence on the excitation wavelength, indicating that it could not be explained by a whispering gallery mode in a medium with broad optical gain. The peaks can be explained by amplified spontaneous emissions (ASE) because the intensity depended linearly on the excitation intensity with a threshold. When the dye-doped film was formed on the portion of a fiber with the clad etched out and was excited by the polarized laser propagating inside the fiber core, we observed ASE peaks not of the dyes but of the optical fiber itself, suggesting the possibility that the dyes were oriented with their transition moment pointing parallel to the film surface. These fiber ASE peaks shifted to longer wavelength when we varied the excitation wavelength to shorter wavelength, which clearly ruled out the possibility of silicate Raman scattering as the origin.

A new technique incorporating combinatorial deposition to develop thin-film phosphors by r.f. magnetron sputtering is demonstrated using subdivided powder targets. In comparison with development using conventional r.f. magnetron sputtering, the atomic ratios of Si and Ge as well as the Mn content in Zn2Si1-XGeXO4:Mn thin film phosphors could be more efficiently optimized in order to obtain the highest intensity in electroluminescent and photoluminescent emissions. High luminances of 11800 and 1536 cd/m2 were obtained in Zn2Si0.6Ge0.4O4:Mn thin-film electroluminescent devices fabricated under optimized conditions and driven at 1 kHz and 60 Hz, respectively.

Newly designed cyclometalated iridium phosphors bearing 2,3-diphenylquinoxalines were characterized to provide highly efficient and vivid-red emitting materials for electrophosphorescent organic light-emitting devices. Excellent quantum efficiencies for photoluminescence (PL) within a range 50-79% were observed in dichloromethane solutions at room temperature. A greatly improved PL decay lifetime of 1.1 µsec was also observed in CBP coevaporated film. Luminescence peak wavelengths of the phosphors lay within a preferable range 653-675 nm in evaporated films. The most vivid-red electroluminescence with 1931 CIE chromaticity coordinates of (x=0.70, y=0.28) was successfully attained.

Theoretical calculation has been done on the decay time of photoluminescence of Ir(ppy)3 dissolved in tetrahydrofuran and its temperature dependence at 1.2-300 K. Taking into account that the emitting triplet state consists of three zero-field splitting substates and taking into account one-phonon non-radiative transitions among these substates, the rate equations for the populations of these substates have been obtained. Three decay components are derived by solving not only the secular equation but also the rate equations, where the slow decay time shows decrease from 145 to 2 µs with increasing temperature from 1.2 to 300 K. A good agreement has been obtained for the temperature dependence between the calculated slow decay time and the observed one.

Time resolved photoluminescence measurements of lanthanide and group III metal chelates of 8-hydroxyquinoline (Q) have been performed as a function of temperature and excitation wavelength. For the lanthanide complexes it has been shown that either singlet or triplet luminescence can be observed depending on the excitation wavelength. Lifetime measurements of these emissions show that competing non-radiative paths are very important in the performance of these molecules. For ErQ we have shown that it is the singlet state that couples most efficiently to the ion. Radiative lifetime measurements of the ion emission show relatively short lifetimes that are indicative of quenching mechanisms. For the group III metal chelates at room temperature the luminescence is dominated by the singlet emission but at 80 K there is evidence that triplet emission can occur when the molecule is excited at long wavelengths. Luminescence lifetime measurements of the emission from the lanthanide ions: erbium, neodymium and ytterbium all show effective lifetimes of the order of microseconds which is very fast compared to the lifetimes of the free ions. Using excitation directly into the lanthanide ion (e.g.980 nm excitation for erbium) and via the organic ligands (400 nm excitation) we have seen that there are no changes in the emission lifetimes and hence the exciton transfer from the ligand to the lanthanide ion is not a rate limiting step.

The driving frequency dependence of EL characteristics were investigated in thick ceramic insulating type thin-film electroluminescent (TFEL) devices with various Mn-activated Y2O3-based phosphor thin-film emitting layers driven by a sinusoidal wave voltage. High luminous efficiencies of approximately 10 and 1 lm/W were obtained in the TFEL devices driven at 60 Hz and 1 kHz, respectively. The difference in luminous efficiency was mainly caused by the increase of input power in 1 kHz-driven-devices resulting from a dielectric loss of a thick BaTiO3 ceramic sheet used as the insulating layer. The correlation between the sound emission from the devices and the effective power consumed in the devices was found with variations in both the applied voltage and the frequency. The higher input power of the 1 kHz-driven-device may be attributable to sound emissions resulting from the piezo-electricity of BaTiO3 ceramics.

A type of carbon nanoform (carbon nanowalls: CNWs) has been successfully deposited on both Ni wafers and Ni wires using dc plasma chemical-vapor-deposition (CVD) method. Transmission electron microscopy (TEM) and Raman spectroscopy were used to characterize CNWs' microstructure. It is found that CNWs are well crystallized, and each CNW consists of several pieces of curved graphene sheets, presenting a quasi-two-dimensional geometry. The average length and width of CNWs are about 2-4µm, while their thickness is less than 7nm. Field emission measurement showed that such CNW films exhibited the excellent electron emission efficiency, comparable to the high-grade carbon nanotube (CNT) emitters. The threshold field defined as the field to obtained 1µA/cm2 is less than 1V/µm and the electrical field for 1mA/cm2 current density is only about 1.5V/µm. Moreover, the CNWs have stable emission behaviors, and we have successfully fabricated a kind of high-brightness lamps based on the CNW coated Ni wires.

Electroluminescence (EL) under alternating-current (ac) operation is first reported for n+-polysilicon/SiO2/p-Si MOS capacitors with 50 nm Si-implanted SiO2. Visible EL can be observed with the naked eye in the dark. The ac operation by pulse-wave distinctly enhances the EL intensity and its lifetime. The pulse frequency affects the EL spectrum and thus the EL color. A model of EL mechanism is proposed for the Si-implanted MOS EL device, which has a possibility of visible light emitting device.

Thin-film electroluminescent (TFEL) devices have been newly developed using Y2GeO5 oxide phosphor thin films prepared by r.f. magnetron sputtering. Multicolor emissions were observed in TFEL devices fabricated using various impurity-activated Y2GeO5 phosphor thin films. A high-luminance TFEL device was fabricated using a Y2GeO5:Mn thin film prepared with a Mn content of 2 at.% and postannealed at 1020: luminances of 414 and 3020 cd/m2 and luminous efficiencies of 6.7 and 0.93 lm/W for yellow emission when driven at 60 Hz and 1 kHz, respectively. Newly developed oxide Y2GeO5:Mn phosphors are very promising for use as the thin-film emitting layer of TFEL devices.

Photoelectric techniques, such as photoluminescence are commonly used to evaluate and qualify heterostructure materials. These studies provide invaluable information on the energy configuration of these devices. In this paper, we extend photoelectric techniques to the evaluation of fully fabricated HBTs. We describe photoconduction measurements performed on the base/collector junctions in GaAs based HBTs. The devices studied contained a window in the emitter metal and monochromatic, chopped light was focused through a microscope into the window. The measurements are performed on wafer at room temperature. The spectral characteristic of the photocurrent provides information on the material and allows the determination of the source of the measured photocurrent. The dependence of the photocurrent on the junction bias allows the profiling of the junction. Three different collector structures were investigated, containing GaAs, AlGaAs, and InGaP. The effects of electron and hole barriers are evaluated. The information obtained allows for the design of improved HBTs.

BaAl2S4:Eu thin-film EL device using a new blue emitting EL phosphor was prepared by the two targets pulse-electron-beam evaporation. The maximum luminance level was 65 cd/m2 under the 50 Hz pulse voltage. The EL spectrum had blue emission with a peak around 470 nm due to the transition for Eu2+ ion. The CIE color coordinates of BaAl2S4:Eu EL device were x = 0.12 and y = 0.10. The performance of blue-emitting BaAl2S4:Eu EL devices is shown to be sufficient for commercial color EL display in color purity and luminance level.

Photonic crystals have optical properties characterized by photonic bandgap, large anisotropy and high dispersion, which can be applied to various optical devices. We have proposed an autocloning method for fabricating 2D or 3D photonic crystals and are developing novel structures and functions in photonic crystals. The autocloning is an easy process based on the combination of sputter deposition and sputter etching and is suitable for industry. We have already demonstrated devices or functions such as polarization splitters and surface-normal waveguides. In this paper, we describe our latest work on photonic crystals utilizing the autocloning technology. Phase plates and polarization selective gratings for optical pick-ups are demonstrated utilizing TiO2/SiO2 photonic crystals. The technology to introduce CdS into 3D photonic crystals is also developed and photoluminescence from the introduced CdS is observed, which is the first step to realize luminescent devices with 3D confinement or high polarization controllability.