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Blue-emitting phosphors (Gd 1- x Ce x ) 5 Si 3 O 12 N (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 Ce 3+ concentration had on the photoluminescence of the prepared samples was examined, and the results indicate that an increase in the Ce 3+ concentration introduces a red-shift of the emission peak due to an increase in the Stokes shift. Concentration quenching occurs when the Ce 3+ content exceeds 3 mol%. In addition, the configurational coordinate model was used to finely explain the thermal quenching behavior of the phosphors. [ABSTRACT FROM AUTHOR]

Single crystalline Si epilayers were grown on sapphire (1 1¯ 0 2) substrates through a three-step growth method by rapid thermal chemical vapor deposition (RTCVD). Hydrogenation of the epilayers was performed by the hydrogen-plasma exposure (HPE) in a remote plasma chemical vapor deposition (RPCVD) system, following rapid thermal annealing. It was found that the hydrogenation treatment improves the crystallinity of the Si epilayer as well as the electrical properties of Si epilayers. After hydrogenation, especially, the intensity of the deep level defects which are responsible for the lattice mismatch between Si and the sapphire substrate decreases. Also, dislocations and microtwins are reduced remarkably, improving the crystallinity. In Schottky diodes fabricated on hydrogenation-processed Si epilayers, the leakage current decreases one order of magnitude in comparison to non-hydrogenated samples. It is suggested that these characteristics could be explained by the hydrogen incorporation at defects. [Copyright &y& Elsevier]

We have fabricated Si nanocrystals utilizing nanometer-sized Pt islands acting as etching-masks on SiOx/amorphous-Si/SiOx/p-Si (1 0 0) thin films. In the measurement of transmission electron microscopy the Si nanocrystals embedded in SiO2 were observed, and in the measurement of cathodoluminescence spectroscopy at 77 K Si nanocrystal-related peaks were observed at 462 and 647 nm. For the Al/SiO2/nanocrystalline-Si/SiO2/p-Si capacitor structure, a hysteretic behavior with the flatband voltage shift of 0.592 V was observed in the measurement of capacitance–voltage characteristic at 300 K. These results indicate that Si nanocrystals can be formed by using a nanosized Pt island etching-mask, and that Si nanocrystals embedded in SiO2 layer act as Si quantum dots which hold promise potential applications. [Copyright &y& Elsevier]

We investigated the relationship between band alignments and threshold voltage shifts of GaInZnO (GIZO) thin films grown on SiO 2 /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 3.03 eV to 3.43 eV 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 0.56 eV 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. [ABSTRACT FROM AUTHOR]

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, 1.21, 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. [ABSTRACT FROM AUTHOR]

Abstract: The effects of varying the conditions for the chemical bath deposition (CBD) of cadmium sulfide (CdS) layers on CdS/Cu(In,Ga)Se2 (CIGS) hetero-junctions were investigated using photoluminescence (PL), electroluminescence (EL), deep level transient spectroscopy (DLTS), and red-light-illuminated current-voltage (I–V) measurements. We demonstrated that varying CBD-CdS conditions such as the temperature and time influenced the recombination pathways around the CdS/CIGS junction via the formation of different electronic defects, which eventually changed the photovoltaic conversion efficiency. As the CBD-CdS time and temperature were increased, the cell efficiency decreased. PL measurements revealed that this degradation of the cell efficiency was accompanied by increases in the defect-related recombination, which were attributed to the existence of donor defects around CdS/CIGS having an energy level of 0.65eV below conduction band, as revealed by DLTS. Increasing distortions in the red-light-illuminated I–V characteristics suggested that the related defects might also have played a critical role in metastable changes around the CdS/CIGS junction. Because the CBD-CdS time and temperature were considered to influence the diffusion of impurities into the CIGS surface, the evolution of the efficiency, PL spectra, defect populations, and red-light-illuminated I–V characteristics observed in this work could be attributed to the diffusion of impurities during the CBD-CdS process. [Copyright &y& Elsevier]