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We have investigated the optical properties in GaNAs/GaAs multiple quantum wells (MQWs) with various GaNAs layer widths and N contents, which were fabricated on GaAs(001) substrates by molecular beam epitaxy using an RF-plasma source. In particular, when the GaNAs layer thickness, LW, was 3 monolayers (ML), the photoluminescence (PL) peak intensity around 1.31 eV was approximately 70 times stronger than that in the case of LW=10 ML. Moreover, the full width at half maximum of the dominant PL peak became narrow as GaNAs layer thickness decreased, even though N content was increased.

A submicron soft X-ray beam is generated by a highly coherent soft X-ray laser at 13.9 nm with a Fresnel phase zone plate. The focused X-ray beam profile is measured using a knife-edge scan method, and the spot diameter and peak intensity are 0.5 µm at full width at half maximum and 1 ×1011 W/cm2, respectively.

Pure ZnO was prepared at lower temperature (30 °C) by electrodepositing at higher temperature (50 °C), and Zn-incorporated ZnO was prepared. They were thermally treated in oxygen at different temperatures to investigate their optical characteristics using photoluminescence. The UV band from the band-edge emission is observed in the treated Zn incorporated ZnO but not in the thermally treated pure ZnO. The UV emission is proposed to be from the ZnO oxidized from Zn. The peak intensity of visible emission for the thermally treated Zn-incorporated ZnO is about 10 times that of emission from pure ZnO at 900 °C. The blue-green band of visible emission results from the defects in ZnO oxidized from Zn and, its enhancement may be related to the thermal stress and the improvement of the interface between ZnO and ZnO oxidized from Zn.

A defect mode in a one-dimensional (1D) photonic crystal (PC) with an in-plane switchable nematic liquid crystal (NLC) as a defect layer has been investigated. Two types of defect modes appear in the photonic band gap of the transmission spectrum. They are associated with the extraordinary and ordinary refractive indices of the NLC in the defect aligning perpendicular to the propagation direction of the light. The defect mode position does not shift upon the in-plane reorientation of the NLC molecules, but the peak intensity changes with rotating the director of the NLC around the light propagating axis. On the basis of these defect modes, the polarization direction of the light passing through the 1D PC with the in-plane switchable NLC can be electrically controlled by changing the field direction in the defect layer.

The origin of N–H related local vibration modes (LVMs) in GaAsN grown by chemical beam epitaxy is discussed on the basis of the change in peak intensity caused by annealing. The peak areas at 973 and 3124 cm−1 increase as the annealing temperature increases. Their ratio is almost one, independent of the annealing temperature and time. On the other hand, the intensities at 960, 2952, 3014, and 3098 cm−1 decrease owing to annealing. Although the peak area at 960 cm−1 becomes half after annealing at 700 °C, those at 2952, 3014, and 3098 cm−1 to almost zero. These results indicate that the wagging mode at 973 cm−1 and the stretching mode at 3124 cm−1 are originated from the same N–H related defect in GaAsN, and that the wagging mode at 960 cm−1 does not correspond to the stretching modes at 2952, 3014, and 3098 cm−1.

In this paper, we report on numerical and experimental results for the peak intensity stabilization of a fundamental laser through the second-harmonic generation process by introducing a phase-mismatching factor. The peak intensity fluctuation of a nanosecond-order fundamental laser at 1064 nm is reduced from 7.0 to 1.1% with a type-I noncritical phase-mismatching lithium triborate crystal heated at a phase-mismatching temperature of 146.7 °C. The method is applicable to the power stabilization of the laser with a flat-top beam profile.

We report a green phosphor Zn2SiO4:Mn2+ with a surface modified by coating SiO2 nanoparticles. The phosphor was coated with SiO2 nano-particles using a modified sol–gel method. The pH levels of phosphor solution were changed to investigate its effect on the phosphor characteristics. The SiO2 nano-particles are coated uniformly on the surface of phosphors at pH 3.9. The surface coating of SiO2 nano-particles on the phosphor leads to an increase in the intensity of the 515 nm peak of the phosphor and yields more increase in the peak intensity at pH 3.9 being the isoelectric point of the phosphor solution.

We have detected very intense bursts of terahertz synchrotron radiation at the UVSOR-II electron storage ring operated in single bunch mode. The bursts were observed in the wavelength range from 0.2 to 3.0 mm by using a liquid-helium-cooled InSb hot-electron bolometer. The typical duration and interval of the bursts were about 200 µs and 10–15 ms, respectively. Each burst shows the quasi-periodic structure of about 30 µs. The peak intensity of the bursts was about 10000 times larger than that of ordinary synchrotron radiation in the same wavelength region. The extremely high intensity strongly suggests that the bursts are coherent synchrotron radiation, although the radiation wavelength was much shorter than the electron bunch length.

Photoluminescence in dye-doped polymer-dispersed liquid crystals (PDLCs) has been studied. Gain narrowing in the photoluminescence spectra of dye-doped PDLC is observed. From the pumped area and temperature dependence of the peak intensity and the full width at half maximum of the emission band, it is found that multiple light scattering plays an essential role in the gain narrowing in dye-doped PDLC.

We attempted to prepare Ge1-y C y alloys by implantation of C atoms into Ge crystals and post-annealing. For samples annealed at temperatures higher than 450°C, X-ray diffraction (XRD) spectra indicated that the Ge1-y C y alloys were successfully prepared. The highest substitutional C content was about 1 at.%. The optimum annealing temperature to incorporate C atoms into the substitutional sites was 450–500°C. We also investigated the dependence of the Raman intensity of the Ge–C local mode on the substitutional C content. The intensity of the Ge–C local mode was found to increase in proportion to the substitutional C content. Furthermore, the relationship between Ge–C peak intensity and substitutional C content was relatively in good agreement with that theoretically predicted.

We measured the infrared absorption of GaInNAs to clarify the origin of the large bandgap shift induced by thermal annealing. In the as-grown sample, an absorption peak due to the transverse-optical (TO) mode of Ga–N bonds was clearly observed at 469 cm-1. At higher annealing temperatures, the peak intensity decreased, and a new peak with an increased intensity appeared at 489 cm-1. Because the total absorbance of both peaks after the annealing was almost the same as that before the annealing, this peak transition resulting from thermal annealing is probably due to the alternation of the Ga–N bonding state. Because absorption peaks of larger bandgap semiconductors are generally observed in the higher wavenumber region, the observed transition of the peaks to the higher wavenumber side is consistent with the increased bandgap of GaInNAs. Therefore, we found that the variation in bonding causes the blue shift in the bandgap of GaInNAs during thermal annealing.

The local vibration mode of substitutional C atoms (C-LVM) in high-quality Si1-x-y Ge x C y crystals was studied by infrared absorption spectroscopy. The peak intensity and full width at half maximum of C-LVM were found to change depending on Ge content as well as substitutional C content. However, the integrated intensity of C-LVM exhibited a linear dependence on the substitutional C content. These results demonstrate that the effective charge of substitutional C atoms in Si1-x-y Ge x C y crystals is independent of their atomic configurations. Moreover, the present results clearly indicate that the substitutional C content can be estimated from the integrated intensity of C-LVM.

In0.2Ga0.8N/In0.03Ga0.97N 3-period multiple quantum wells (MQWs) were grown by low pressure metalorganic chemical vapor deposition and the effects of pre-In flow prior to QW growth on its overall optical property were investigated. Pre-In flow did not change the structural property of the MQW structure such as In composition and period but strongly influenced its optical properties. MQW samples grown with pre-In flow exhibited longer peak wavelength and stronger peak intensity. CL measurement revealed more uniform and smaller emission centers in pre-In flow samples, implying a reduction of non-radiative defective regions and more In-rich regions. These results indicate that the In source introduced prior to QW growth preferentially gets incorporated around defect sites such as threading dislocations to inhibit their propagation while forming seeds for In-rich regions.

We used metal-induced-crystallization (MIC) to crystallize amorphous silicon (a-Si) films over 1 µm thick. We employed a Ni/Ti layer for MIC. The a-Si films with the Ni/Ti layer were annealed at 550°C. We found that a 6-µm-thick Si film was oriented in the direction by inserting a Ti layer between Ni and the glass substrate. If the thicknesses of the Ni and Ti layer were nearly the same, the peak intensity ratio of the (220) to (111) planes was 3%. This oriented growth tendency is maintained from the beginning of crystallization to the full-crystallized stage.

Using a thin aluminum wire, we have successfully synthesized aluminum nitride powders in N2/NH3 mixed gas. The powders were characterized by X-ray diffraction and specific surface area measurement. The results of X-ray diffraction indicated that the synthesized powders consist of wurtzite aluminum nitride. In the powders synthesized in N2 gas, a weak peak intensity of aluminum nitride was observed. However, it is significantly increased using a mixed gas of N2/NH3. The average particle sizes were 30–70 nm.

Photoluminescence measurements have been carried out for GaAs/AlGaAs single quantum well (SQW) structures grown without interruption by conventional molecular beam epitaxy. The full widths at half-maximum (FWHM) from QWs having thin well width were reduced monotonously with the decrease of growth temperature until 350°C to one-half. This reduction of FWHM was explained by the transition of the top and bottom heterointerfaces which became close to the effective smooth interfaces at 350°C. The peak intensity had only a weak dependence on the growth temperature at the same temperature.

Thin films of ZnS prepared by coevaporation of ZnS and MnF2 have been studied by XPS. It is found that the binding energies of Mn 3p and F 1s electrons, as well as the intensity ratio of the Mn 3p peak to the F 1s peak, depend on the concentration of Mn, and can be divided into three groups. A tentative model that permits the existence of molecular centers in a limited concentration region has been proposed on the basis of the results obtained. The spectral shape of the Mn 3p peaks also change noticeably with the concentration of Mn. This change does not conflict with the model. It has been confirmed by atomic absorption spectroscopy that the concentration of Mn can be estimated from the peak intensity ratio of Mn 3p to S 2p.

The interactions of Au with Ar and O2 plasmas, and of Ni with O2, N2 and C2H5OH vapor plasmas have been studied by TSEE and XPS. The TSEE was strongly influenced by the amount of oxygen incorporated at metal surfaces due to the effects of the plasmas, and was suppressed by the oxygen incorporated in excess. With Au samples, Ar plasma produced a TSEE peak at about 170°C and O2 plasma two peaks at about 180–190°C and 120°C; O2 plasma gave a much weaker emission than the Ar plasma. Au samples exposed to the plasmas gave XPS spectra of Au, C, O, Al and Si. The incorporation of Si and Al may be attributable to the plasma reactor. The TSEE was closely correlated with the composition ratio of O/Si, resulting in a maximum at the value of O/Si=0.4. With Ni samples, a TSEE peak appeared at about 177°C independently of the plasma atmospheres. The peak intensity was satisfactorily correlated with the ratios of O/Ni and O/C, giving a maximum at the values of O/Ni=8 and O/C=1.

A new method for detecting deep levels in semi-insulating GaAs crystals is proposed. With this method determination of deep level distributions over a wafer by a spectroscopic photoelectrochemical current is possible. The deep levels of 1.13 eV, 1.02 eV, 0.98 eV, and 0.70 eV have been detected in both undoped and Cr-doped materials. Two additional deep levels of 0.78 eV and 0.65 eV were detected in Cr-doped materials. A peak intensity ratio of the 1.13 eV band to the 1.43 eV increased linearly with increasing chromium content in the crystals. Nonuniform distribution of deep levels in LEC GaAs crystals has been found.

Optimization of the modified van-Cittert's method (by the authors) was carried out, using model calculation. In order to obtain sufficiently good results with this method, careful simulation is always necessary. The optimization process (smoothing fucntion, peak intensity, number of subdivisions, Wa/Wf, sampling interval, etc.) in this method is useful to deconvolute other spectral data. This method might be a useful tool, when used with proper care. Applications to Fe Kα1,2 from iron compounds were also presented. It is confirmed that Fe Kα1,2 from K3Fe (CN)6 has clear fine structures.

In order to explain several PSEE time-related phenomena regarding scaratched metals, the authors have proposed a reaction-kinetic model (the Two-Process model), in which particular attention is given to activating inactivated emission sources. On the basis of this model the authors have succeeded in elucidating such PSEE phenomena (mostly observed for scratched aluminum) as a storage effect, the relation between the peak intensity and the ambient pressure, and the dependence of the intensity on the stimulation intensty. In a discussion regarding the parameters involved in the model it is suggested that glow curves produce useful information about the PSEE emission mechanism as well as TSEE measurements.

Thermally stimulated current spectra were investigated for ion-injected teflon-FEP film electrets which were positively charged by the liquid-contact charging method using water or aqueous solutions of various electrolytes such as LiNO3, NaCl, RbCl, MgCl2, AlCl3, KI and CaCl2. TSC from these electrets showed two peaks at about 90°C and 130°C. The relative peak intensity of the sharp peak at 90°C was strongly affected by the kind and the concentration of the electrolytes used for charging, and it is concluded that this sharp peak is due to the mobile ions injected into the polymer.

The IR stimulation of a commercial ZnS:Cu, Al phosphor was observed at room temperature within the ranges 1350 to 1050 nm and 715 to 688 nm. The trap depths estimated from the thermoluminescence are in or near the range of the former values. It is concluded from measurements of the peak intensity and the decay of the IR stimulation that the probability for a retrapping of optically released electrons increases with an increase in the number of empty shallow traps.

Undoped LEC SI–GaAs crystals can be classified into two groups with respect to the deep PL emission band. One group dominantly exhibits emission peak energy at 0.8 eV, and the other at 0.65 eV. The profile along the growth direction and the wafer diameter for resistivity was similar to that for the 0.8 eV PL peak intensity in the 0.8 eV dominant crystals, while it was opposite to that for the 0.65 eV PL peak intensity in the 0.65 eV dominant crystals. The presence of these emission bands was found to depend on the growth conditions. Results suggest that two deep levels related to different origins are present in undoped LEC SI–GaAs.

TSEE from MgO single crystals, undoped (3-nine and 4-nine purities) and doped with titanium (240 ppm), was observed after cleaving without any other excitation. The TSEE peaks were at 110, 180, 210, and 330°C, except crystals with a 4-nine purity. These showed only 110 and 330°C peaks. The peak intensity at 110°C decayed to one half the initial value after the sample was kept at room temperature for about an hour. (The initial value was determined several minutes after cleaving.) An analysis of this decay process shows 2nd-order kinetics. Intense MgO:Ti (240 ppm) TSEE was observed at temperatures of 180, 210, and 330°C.

We have studied the effect of thermal cyclic annealing (TCA) on the crystal quality improvement of MOCVD grown InP on GaAs substrates. The crystal quality has been evaluated by the etch pit density (EPD), X-ray diffraction and photoluminescence (PL) measurement. It is found that the TCA is effective in reducing the dislocation density, and that the annealing at 700°C is essential to confine the point defects near the InP/GaAs interface. The EPD is reduced from 6×107 cm-2 to 3×107 cm-2, and the defect-related PL peak intensity is decreased below the residual level in the 5 µm-thick InP on GaAs.

In order to examine the physical meaning of the parameters involved in the two-process model previously proposed by the authors, the following experimental studies were conducted for scratched Al specimens. (1) It was found that the statistical fluctuation in the PSEE yield obeys a Poisson distrubution. This indicates that not only the exo-emission process but also the process of reactivating inactive emission sources should be regarded as a stochastic process. (2) The rate of exo-activation was found to be insensitive to specimen temperatures between 100 and 300 K, and to agree well with the theoretical value obtained from a simple tunneling model. (3) Abrasion did not affect the frequency of the photoluminescence at peaks which were observed at 2.6, 3.0, 3.8 and 4.8 eV. The peak intensity, however, increased after abrasion and then gradually decreased. This is similar to the intensity change in a PSEE yield.

Photoluminescence measurements were carried out to study the annealing effect of Zn-doped p-type InSe. The diffusion constant of Zn atom along the c-axis in InSe was estimated to be D=2.7×107 exp (-2.5 eV/k T)cm2s-1 from the depth profiles of the 1.17 eV emission peak intensity. The isochronal annealing behavior of this peak showed that the activation energy for a dissociation of Se vacancy-Zn acceptor complex was 0.4 eV.

We have carried out a Raman spectroscopic study on the effect of substituting trivalent rare-earth ions (Ln=Eu, Sm and La) for Ba in LnBa2Cu3O y (y=6–7) into the chemical form of Ln1+x Ba2-x Cu3O y (0≤x≤0.4). The oxygen vibrational mode in the BaO plane is influenced by the substitution through significant changes in the phonon frequency and peak intensity. On the other hand, the bending mode in the CuO2 plane does not show appreciable variation with an increase in x. These results are common to the cases where Ln=Eu, Sm and Nd, but not to Ln=La, and are interpreted in terms of the oxygen defect and hole-concentration compensation.