As organic photodetectors with less than 1 μ m pixel size are in demand, a new way of enhancing the sensitivity of the photodetectors is required to compensate for its degradation due to the reduction in pixel size. Here, we used Ag nanoparticles coated with SiO x N y as a light-absorbing layer to realize the scale-down of the pixel size without the loss of sensitivity. The surface plasmon resonance appeared at the interface between Ag nanoparticles and SiO x N y . The plasmon resonance endowed the organic photodetector with boosted photon absorption and external quantum efficiency. As the Ag nanoparticles with SiO x N y are easily deposited on ITO/SiO 2 , it can be adapted into various organic color image sensors. The plasmon-supported organic photodetector is a promising solution for realizing color image sensors with high resolution below 1 μ m.

Trap levels play an important role in semiconductor power devices. The barrier height of a metal-semiconductor junction, one of the important factors of unipolar devices, is influenced by the trap levels at its interface, i.e., interface states. However, there has not been much research on the interface states of Schottky diodes yet. Here, we report newly found KI1, KI2, and KI3 interface states of 4H-SiC Schottky diodes. We observed their changes after the first deep-level transient spectroscopy measurements, in which temperature rises to 750 K, and discussed the origins of these changes by using X-ray photoelectron spectroscopy and scanning electron microscopy. The KI1 was related to oxygen and photoresist (PR) residue, the KI2 was related to oxygen, and the KI3 was related to the PR residue.

The realization and application of optoelectronics, photonics, and sensing, such as in solar diode sensors and photodiodes, which are potentially useful from ultraviolet to infrared light sensing, is dramatically advanced when ZnO is integrated into semiconductor nanostructures, especially when compatible with mature silicon technology. Here, we compare and analyze the fundamental features of the Si-ZnO coaxial nanorod heterostructures (Si@ZnO NRs) grown on semi-insulating (100)-oriented Si substrates at growing temperatures of 500°C, 600°C, 650°C, and 700°C of the Si layer for device applications. ZnO NRs were grown by a vapor phase transport, and Si layers were made by rapid thermal chemical vapor deposition. X-ray diffraction, field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy, and Raman experiments showed that ZnO NRs were single crystals with a würtzite structure, while the Si layer was polysilicon with a zincblende structure. Furthermore, FESEM revealed that Si shell thickness of the Si@ZnO NRs increases with increasing growing temperatures of Si from 500°C to 700°C.

Blue-emitting phosphors (Gd1-xCex)(5)Si3O12N (0 <= x <= 0.07) were prepared through a solid-state reaction under a reducing atmosphere. The excitation spectra exhibited several broad bands in the wavelength range from 240 to 400 nm, and the emission spectra consisted of a broad band covering from 360 to 550 nm. Two different emission centers corresponding to two different crystallographic sites in the host lattice were confirmed. The influence that the Ce3+ concentration had on the photoluminescence of the prepared samples was examined, and the results indicate that an increase in the Ce3+ concentration introduces a red-shift of the emission peak due to an increase in the Stokes shift. Concentration quenching occurs when the Ce3+ content exceeds 3 mol%. In addition, the configurational coordinate model was used to finely explain the thermal quenching behavior of the phosphors. (C) 2017 Elsevier Ltd. All rights reserved.

The presence of voids in perovskite solar cells influences the efficiency because of accelerated charge recombination. The induced electric field near voids due to band bending attracts photogenerated electrons and holes toward the voids, leading to carrier recombination. However, if the surface of the voids is coated by materials with a band gap higher than that of the perovskite layer, the strong electric field induced near the voids in the opposite way prevents carriers from recombining. We identified voids in the perovskite layer by using an electron beam-induced current technique and found the influence of field-assisted passivation by organic materials on the efficiency of the solar cell.

The band alignment and defect states of GaInZnO thin films grown on SiO2/Si via radio frequency (RF) magnetron sputtering were investigated by using X-ray photoelectron spectroscopy, reflection electron energy loss spectroscopy, thermally stimulated exo-electron emission and photo-induced current transient spectroscopy.The band gap via reflection electron energy loss spectroscopy was 3.2eV. The defect states via photo-induced current transient spectroscopy and thermally stimulated exo-electron emission were at 0.24, 0.53, 1.69 and 2.01eV below the conduction band minimum of GIZO thin films, respectively. The defect states at 0.24 and 0.53eV are related to the field-effect mobility, and the defect stated at 1.69 and 2.01eV is related to the oxygen vacancy defect. Copyright (c) 2016 John Wiley & Sons, Ltd.

The electronic structure and the optical properties of Mn-decorated graphitic carbon nitride (g-C3N4) were investigated using the density functional method. The large absorption energy of the Mn atoms on the g-C3N4 surface was found to suppress the clustering of the Mn atoms, which led to a conservation of the photocatalytic activity. The electronic structures of the Mn-decorated g-C3N4 showed that impurity energy levels emerged in the forbidden band of g-C3N4 and that the band edge of g-C3N4 shifted upward to 0.40 eV. In addition, the calculated optical constants showed that the novel photon absorption in the range of visible light originated from electronic transitions from the N 2p states in the upper valence band to impurity Mn 3d states. Moreover, the photon absorption reached a maximum when all sites of triangular N holes were decorated with Mn atoms. Our results provide evidence that the Mn-decorated C3N4 system could be a highly-efficient photocatalyst for solar light due to the extension of the range of photon absorption to include almost all visible light.

Defect states of hydrogenated amorphous silicon nitride (a-SiNx:H) thin films were measured using the thermally stimulated exoelectron emission spectroscopic method. The defect states of films with nitrogen to silicon composition ratios (x) of 0.92,121, and 1.44 were found to be located 1.66, 1.77, and 1.82 eV below the conduction band minimum, respectively.We confirmed that the hydrogen concentration decreased as x was increased via an elastic recoil detection analysis experiment, while as the hydrogen concentration increased, the defect concentration decreased. From these results, we concluded that the defect centers could be related to dangling bonds, the so-called K centers, in silicon nitride. Furthermore, as the concentration of Si H was increased with decreasing x via the infrared spectroscopy, the defect density was reduced through the defect passivation. (C) 2016 Elsevier B.V. All rights reserved.

Defect depth profiles of Cu (In1−x,Gax)(Se1−ySy)2 (CIGSS) were measured as functions of pulse width and voltage via deep-level transient spectroscopy (DLTS). Four defects were observed, i.e., electron traps of ~0.2 eV at 140 K (E1 trap) and 0.47 eV at 300 K (E2 trap) and hole traps of ~0.1 eV at 100 K (H1 trap) and ~0.4 eV at 250 K (H2 trap). The open circuit voltage (VOC) deteriorated when the trap densities of E2 were increased. The energy band diagrams of CIGSS were also obtained using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and DLTS data. These results showed that the valence band was lowered at higher S content. In addition, it was found that the E2 defect influenced the VOC and could be interpreted as an extended defect. Defect depth profile images provided clear insight into the identification of defect state and density as a function of depth around the space charge region.

We investigated the relationship between band alignments and threshold voltage shifts of GaInZnO (GIZO) thin films grown on SiO2/p++-Si by the RF sputtering method via utilizing X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The band gap energies of the GIZO thin films are increased from 3.03eV to 3.43eV with the increase in their Gallium (Ga)/Indium (In) ratios of 0.83, 1.05, and 1.34. The barrier height of GIZO/Mo is also increased by increasing in the Ga/In ratio, and then the threshold voltages positively shift. From the result of DLTS, it is found that the D defect is located at 0.56eV below the conduction band, and its defect density shows the increasing tendency by the increase in the ratio of Ga/In (i.e. the decrease in In content). From the transfer curves of the GIZO thin films, the mobility shows the decreasing tendency by the increase in the ratio of Ga/In. As a result, it is suggested that the increase in the density of D defect density in the GIZO thin film plays a dominant role in the decrease in its mobility.

One-dimensional ZnO nanorods were grown vertically on a (100) Si substrate using a vapor phase transport method. Following the fabrication of ZnO nanorods, Si layers were deposited by rapid thermal chemical vapor deposition (RTCVD) directly on the ZnO nanorod/Si (100) substrate. Field emission scanning electron microscopy revealed that a Si/ZnO nanorod coaxial heterostructure were synthesized vertically oriented along the (002) plane on a Si substrate. X-ray diffraction, Energy dispersive X-ray and Raman spectroscopy revealed that the ZnO nanorods were single crystals with a hexagonal structure, and grew with a c-axis orientation perpendicular to the Si substrate, whereas the Si layer was poly-silicon with cubic structure. These results demonstrated the Si/ZnO nanorod coaxial heterostructure were synthesized successfully on a (100) Si substrate and the ZnO nanorod enables the synthesis of a vertically grown well-aligned Si/ZnO coaxial nanorod heterostructure.

The size evolution of gold (Au) nanoparticles (NPs) on the sidewall surface of silicon (Si) nanowires (NWs) has been investigated by thermal treatments, using high-angle annular dark field scanning transmission electron microscopy. The Si NWs grown at 550°C by rapid thermal chemical vapour deposition have been observed to be surrounded by Au NPs with less than 5 nm diameter and ∼1012 cm−2 density on the whole Si NW surface. To explore the size change of Au NPs, the Au NPs on the Si NW were annealed ex situ at the temperature range of 700–900°C for 20 min. The sizes of NPs for samples annealed at 700, 800 and 900°C represent Gaussian distribution with the average size of 4, 6 and 7 nm, respectively, while at high temperatures above 900°C, they change to a bimodal distribution. It is suggested that the surface diffusion rate of Au NPs on Si NW is much lower than that on the Si substrate because of the substitutional diffusion mechanism.

BACKGROUND/AIMS:Fructose malabsorption (FM) mimics symptoms of irritable bowel syndrome (IBS), and its prevalence has increased. Diagnosing FM in IBS is challenging because of its overlap with small intestinal bacterial overgrowth (SIBO). We assessed the prevalence of FM by comparing patients with IBS with asymptomatic control individuals after excluding SIBO using the glucose hydrogen breath test (HBT).METHODS:Patients diagnosed with IBS and asymptomatic control individuals were enrolled prospectively. Dietary habits were assessed with the Food Frequency Questionnaire. After excluding SIBO, participants underwent HBTs with both 15 g and 25 g of fructose.RESULTS:Thirty-five patients with IBS and 35 age- and sex-matched asymptomatic control individuals were enrolled. The 15-g fructose HBT yielded positive results in 7 of the 35 (20.0%) patients with IBS and in 2 of 35 (5.7%) controls (P = 0.070). The 25-g fructose HBT was positive in 16 of the 35 (45.7%) patients with IBS and in 8 of the 35 (22.9%) controls (P = 0.040). Analysis of the Food Frequency Questionnaire responses showed no significant differences between the 2 groups in dietary intake, although patients with IBS showed a significantly higher mean fiber intake than controls (21.24 ± 11.35 g vs 15.87 ± 7.07 g, respectively, P = 0.040).CONCLUSIONS:The 25-g fructose HBT identified FM in a significantly higher percentage of SIBO-negative patients with IBS than in asymptomatic control individuals, suggesting that FM may correlate with IBS. Education regarding dietary control of foods containing fructose may be useful for the management of patients with IBS.

The behavior of deep level defects by a voltage-induced stress for CuInGaSe2 (CIGS) solar cells has been investigated. CIGS solar cells were used with standard structures which are Al-doped ZnO/i-ZnO/CdS/CIGSe2/Mo on soda lime glass, and that resulted in conversion efficiencies as high as 16%. The samples with the same structure were isothermally stressed at 100°C under the reverse voltages. The voltage-induced stressing in CIGS samples causes a decrease in the carrier density and conversion efficiency. To investigate the behavior of deep level defects in the stressed CIGS cells, photo-induced current transient spectroscopy was utilized, and normally 3 deep level defects (including 2 hole traps and 1 electron trap) were found to be located at 0.18eV and 0.29eV above the valence band maximum (and 0.36eV below the conduction band). In voltage-induced cells, especially, it was found that the decrease of the hole carrier density could be responsible for the increase of the 0.29eV defect, which is known to be observed in less efficient CIGS solar cells. And the carrier density and the defects are reversible at least to a large extent by resting at room-temperature without the bias voltage. From optical capture kinetics in photo-induced current transient spectroscopy measurement, the types of defects could be distinguished into the isolated point defect and the extended defect. In this work, it is suggested that the increase of the 0.29eV defect by voltage-induced stress could be due to electrical activation accompanied by a loss of positive ion species and the activated defect gives rise to reduction of the carrier density.