bluuebunny/crossref_metadata_2025_split huggingface dataset:
Innovative Diodes based on Amorphous-Porous Silicon Heterojunction
Authors: Rosa R. De , Ferrara V. La , Francia G. Di , Quercia L. , Roca F. , Tucci M. 
Published: April 2011

AbstractIn this paper we present an innovative diode based on the heterojunction between amorphous silicon and porous silicon grown on crystalline silicon. The device architecture gives several advantages. Deposition of amorphous silicon on porous material realises high performance junction at temperature less than 250°C and it passives the porous layer against the natural oxidation due to ageing in the environment. Porous technology allows to obtain a controlled textured silicon surface independently from crystalline silicon orientation just to give the opportunity to reduce surface reflectivity and the blue shift of the absorption spectra in solar cell application. Solar cells were characterised by I-V dark/light and quantum yield measurements. Under standard AM 1.5 light we obtained photovoltaic conversion efficiency greater than 10%. Change in photoluminescence in different gas environments showed for gas sensor applications give rise encouraging results. In dark condition we found the typical diode behaviour.
Structural and optoelectronic properties of amorphous and microcrystalline silicon deposited at low substrate temperatures by RF and HW CVD
Authors: Alpuim P. , Chu V. , Conde J. P. 
Published: April 2011

AbstractThe structural and optoelectronic properties of silicon thin films prepared by hot wire chemical vapor deposition and radio frequency plasma enhanced chemical vapor deposition are studied in the range of substrate temperatures (Tsub)from 100 °C to 25 °C. The defect density, structure factor and bond angle disorder of amorphous silicon films (a-Si:H) deposited by both techniques are strongly improved by the use of hydrogen dilution. Correlation of these structural properties with important optoelectronic properties, such as photo-to-dark conductivity ratio, is made. Microcrystalline silicon (μc-Si:H) is obtained using HW with a large crystalline fraction for hydrogen dilutions above 85% independently of Tsub. The deposition of μc-Si:H by RF requires increasing the hydrogen dilution and shows decreasing crystalline fraction as Tsub is decreased. The properties of the low Tsub films are compared to those of samples produced at 175 °C and 250 °C in the same reactors.
An Investigation of the Chromaticity of Blue Emitting Yttrium Silicate
Authors: Bosze E. J. , Hirata G. A. , Mckittrick J. 
Published: April 2011

ABSTRACTThis investigation studied the effects of Ho3+ and Er3+ on the luminescence of the blue emitting phosphor yttrium silicate, (Y1−mCem)2SiO5. Yttrium silicate has a large emission tail that extends into the red portion of the visual spectrum. To improve the chromaticity of this phosphor to give it a more saturated blue color, the emission intensity of the tail needs to be decreased. Photoluminscence and low-voltage cathodoluminescence measurements were performed on yttrium silicate phosphors with varying concentrations of Gd3+, Ho3+ and Er3+. It was found that when co-doping with Ho3+ and Er3+, the relative intensity of the emission tail was decreased, but so to was the overall luminescence intensity of this phosphor.
Ultrafast Silicon Based Internal Photoemission Detectors
Authors: Löken M. , Lipinsky Th. , Kappius L. , Mantl S. , Buchal Ch. 
Published: April 2011

ABSTRACTWe have studied different metal-silicon-metal (MSM) Schottky barrier photodiodes for the detection of visible and infrared light. We investigated the different Schottky barriers from Ti, Cr and Pt. At infrared wavelengths, the Schottky contacts provide electrons and holes by “internal photoemission” into the Si. The lowest Schottky barrier determines the long wavelength cutoff and the current noise. The temporal response was measured byultrashort (100 fs) laser pulses from a Ti:A1203 laser, which were converted by an optical parametric oscillator to a wavelength of 1.1 to 1.6 μm. The measurements were performed between 30 K and room temperature. The best detectors show a pulse width of 3.2ps FWHM at 1.25 μm wavelength and room temperature. To our knowledge this is the fastest infrared response for silicon based diodes ever reported.
A Projection-Type Excimer-Laser Crystallization System For Ultra-Large Grain Growth Of Si Thin-Films
Authors: Oh Chang-Ho , Nakata Mitsuru , Matsumura Masakiyo 
Published: April 2011

ABSTRACTWe have proposed a new excimer-laser crystallization system based on an optical projection concept. In the proposed system, a collimated excimer-laser light pulse is irradiated to Si thin-films on a glassy substrate, through a phase-shift mask and an optical lens system. Using oneand two-dimensional phase-shift masks, we have examined feasibility of the proposed method.
Stress and Dopant Activation in Solid Phase Crystalized Si Films
Authors: Kalkan A. Kaan , Fonash Stephen J. 
Published: April 2011

ABSTRACTDefect creation mechanisms during solid phase crystallization (SPC) of Si thin films were investigated with PECVD amorphous precursor samples produced with various deposition temperatures and thicknesses. These precursor films were implanted with dopant and then crystallized to obtain both SPC and dopant activation. The doping efficiency was found to decrease with the tensile stress level as measured by Raman shift. The stress shows a decrease as the precursor deposition temperature and thickness are lowered. Furthermore, a lower level of stress is induced by rapid thermal annealing when the annealing temperature is high enough to soften the glass substrate on which the films were deposited. We show that by control of stress during the SPC step, intragrain defect density can be lowered and electronic quality of the resulting polycrystalline Si films can be improved. Based on these observations, we propose the following tentative model to explain the defect creation: during SPC, tensile stress evolution is considered to result from the volumetric contraction of Si film when it transforms from the amorphous to crystalline phase. This contraction is retarded by the substrate, which imposes a tensile stress on the film. A high level of stress leads to formation of structural defects inside the grains of the resulting polycrystalline material. These defects trap carriers or complex with the dopant reducing doping efficiency.
Thin-Film Oxide Phosphors as Electroluminescent Materials
Authors: Minami Tadatsugu 
Published: April 2011

ABSTRACTIn this paper, we introduce rare earth- or transition metal-activated oxide phosphor thin films prepared by magnetron sputtering and dip-coated solution deposition. Thin-film electroluminescent (TFEL) devices using these oxide phosphor thin films as the emitting layer were investigated with a single insulating layer device structure using a thick ceramic sheet insulating layer. High-luminance multicolor emissions and high luminous efficiencies were obtained in TFEL devices using various oxide phosphors: binary compound, Ga2O3; ternary compound, Zn2SiO4, CaGa2O4 and ZnGa2O4; and multicomponent oxide, Zn2SiO4-Zn2GeO4 system. Luminances above 2000 cd/m2were obtained in CaGa2O4:Mn and Zn2Si1-XGeXO4:Mn TFEL devices driven at 1 kHz. Maximum luminous efficiencies of 2.53, 1.7 and 1.2 Im/W were obtained in Zn2Si0.7Ge0.3O4:Mn, Ga2O3:Mn and ZnGa2O4:Mn TFEL devices, respectively. Stable long-term operation was obtained in dip-coated and sputtered Ga2O3:Mn phosphor TFEL devices even when driven at 10 kHz. Various thin-film oxide phosphors activated with transition metals are suitable for the emitting layer of full-color electroluminescent displays (ELD) without the use of color filters. In particular, Ga2O3 is very promising as a phosphor host material for ELDs.
Simulations of Passive Matrix Polymer Image Sensors
Authors: Braun D. , Yu G. 
Published: April 2011

ABSTRACTTwo-dimensional passive photodiode matrices are hardly useful for image sensing due to the crosstalk between pixels. This crosstalk makes it difficult to recover information from individual pixels. A switching unit attached to each sensing unit has been the common solution in image sensors (such as in CMOS sensors and in TFT-PiN a-Si photosensors). A novel organic photodiode with voltage-switchable photosensitivity was developed recently. Passive photodiode matrices made with such organic photodiodes can be used for image sensing applications. This circuit simulation study demonstrates an effective scheme to extract images from passive photodiode matrices, concluding that individual photodiode parameters determine the contrast and resolution of N by M image sensors.
The photoluminescence temperature dependence of aluminium tris(8-hydroxyquinoline) as a function of excitation energy
Authors: Curry R.J. , Gillin W.P. 
Published: April 2011

ABSTRACTThe temperature dependence of the photoluminescence as a function of excitation energy has been investigated for aluminium tris(8-hydroxyquinoline) (AlQ). It was observed that the peak position of the photoluminescence is a function of both temperature and excitation energy. The observed photoluminescence spectra can be deconvolved into three peaks, with varying weighting factors, the positions of which do not change with temperature. Using these three peaks the measured photoluminescence data was then modeled using a rate-equation approach.
Characterisation of the physico-chemical properties of surface-treated indium tin oxide anodes for organic light-emitting diodes
Authors: Kima J. S. , Granströma M. , Friend R. H. , Johansson N. , Salaneck W. R. , Cola A. , Gigli G. , Cingolani R. , Cacialli F. 
Published: April 2011

ABSTRACTWe studied the surface properties of indium-tin oxide (ITO) modified by wet (aquaregia, ultrasonication, RCA) and dry (oxygen- and argon-plasma) treatments. The surface modification was investigated by surface energy, surface morphology, sheet resistance, carrier concentration, carrier mobility, and workfunction measurements. We report that the studiedoxygen-plasmatreatment induces: the highest surface energy with the highest polarity, the smoothest surface, the highest carrier density but the lowest mobility, the lowest sheet resistance, and the highest workfunction (stable in air). Polymer light-emitting diodes fabricated with the oxygen plasma treated substrates give the best performance in terms of electroluminescence efficiency and device lifetime. This is attributed to a favorable surface modification of ITO anodes by oxygen-plasma.
The Influence of Oxygen Content On Photoluminescence from Er-Doped SiOx
Authors: Chen W. D. , Liang J. J. , Hsu C.C. 
Published: April 2011

ABSTRACTSiOx films with oxygen concentrations ranging 13–46 at.% were deposited by plasma enhanced chemical vapor deposition (PECVD) technique using pure SiH4 and N2O mixture. Erbium was then implanted at an energy of 500 KeV with dose of 2×1015 ions/cm2. The samples were subsequently annealed in N2 for 20 sec at temperatures of (300–950°C). Room temperature (RT) photo-luminescence (PL) data were collected by Fourier Transform Infrared Spectroscopy (FTIS) with an argon laser at a wavelength of 514.5 nm and an output power from 5 to 2500 mw. The intense room-temperature luminescence was observed around 1.54 μm. The luminescence intensity increases by 2 orders of magnitude as compared with that of Er-doped Czochralski (CZ) Si. We found that the Er.- luminescence depends strongly on the SiOx microstructure. Our experiment also showed that the silicon grain radius decreased with increasing oxygen content and finally formed micro-crystalline silicon or nano-crystalline silicon. As a result, these silicon small particles could facilitate the energy transfer to Er3+ and thus enhanced the photoluminescence intensity.
The Optical and Crystalline Structure Properties of ZnO Thin Films Grown by Rf Magnetron Sputtering
Authors: Kim K. K. , Park S. J. , Song J.H. , Song J.-H. , Jung H.-J. , Choi W.K. 
Published: April 2011

ABSTRACTZnO thin films were epitaxially grown on A12O3 (0001) single crystalline substrate by RF magnetron sputtering. The films were grown at the substrate temperature of 550°C and 600°C for 1 h and at a power of 60–120 W. The crystalline structure of the ZnO films was analyzed by 4-circle X-ray diffraction and backscattering (BS)/channeling. The FWHM of XRD ø -rocking curve increase from 9.45 to 18 arc-min. as the RF power increased from 80 to 120 W at 550°C. In-plane ZnO growth on sapphire.(0001) substrate at 550°C and at 80 W was found to be ZnO [1010] |: A12O3[1120], indicating a 30° rotation of ZnO unit cell about the sapphire (0001) substrate. For a specimen that was grown at an RF power of 120 W, 550°C, 1 h, the FWHM of XRD ø -rocking curve was 7.79 arc-min. In BS/channeling studies, the films deposited at 120 W, 600°C showed good crystallinity with the channeling yield minimum (Xmin) of only 5%, but for films deposited at 550°C the yield was as high as 50-60%, was of lower crystalline qualilty. From the results of the AFM measurement, the grain size gradually increased as the growing temperature and power increased. In case of the film deposited at 120 W and 600°C. the hexagonal shape of the grains were clearly observed. In PL measurement, only the sharp near band edge (NBE) emission were observed at room temperature for the film deposited at 80-120 W and 550°C, but the emission from deep level were also detected in the films deposited at 60 W, 550°C and 120 W, 600°C. The FWFM was decreased from 133 meV to 89 meV as RF power increased from 80 to 120 W at 550°C, and that of film deposited at 120 W and 600°C showed 98 meV respectively. The results were somewhat opposite to those of XRD. In the present study, the relationship between optical properties and crystal structure is discussed in terms of the quality of grains and the defects.
Investigation of Coupling Mechanism between Erbium (Er3+) and Ytterbium (Yb3+) in Alumina (A12O3) Host
Authors: Chryssou C.E. , Kenyon A.J. , Pitt C.W. , Chandler P.J. , Hole D.E. 
Published: April 2011

ABSTRACTPlasma-enhanced CVD (PECVD) deposited alumina (A12O3) thin films and single sapphire crystals were co-doped with both erbium and ytterbium using ion implantation. Yb3+ and Er3+ concentrations ranged from 2.4At% to 8At% and from 0.4At% to 0.8At%, respectively. The samples show relatively strong, broad, room-temperature photoluminescence (PL) at λ=11.53µm corresponding to the intra-4f transitions between the 4I13/2 (first excited) and the 4I15/2 (ground) state of Er3+. The full width at half maximum (FWHM) of the emission spectrum is as high as 67nm for the A12O3 thin films; for the sapphire crystals it is 45nm. The fluorescence lifetime of the samples has been measured to be as high as 4.2ms at 50mW laser pump power. The indirect pumping of erbium through the transfer of energy from ytterbium has been demonstrated and the PL peak intensity has been studied as a function of the Yb3+/Er3+ concentration ratio when the samples are pumped at 514nm and 850nm; the PL excitation spectrum (PL at 1.53gm as a function of pump wavelength) of an Er3+/Yb3+ co-implanted sample is also presented. Both the PL peak intensity at 1.53µm and the fluorescence lifetime have been studied as functions of annealing temperature. Luminescence spectra attributed to defects in the alumina matrix are presented for as-implanted samples and following thermal annealing.
Effects of Co-Dopants on the Microstrucutre and El Properties of the Zns:Mn Luminescence Materials
Authors: Zhai Qing , Li Jinghong , Lewis Jay , Waldrip Karen , Jones Kevin , Holloway Paul , Puga-Lambers M. , Davidson Mark 
Published: April 2011

ABSTRACTThin films of zinc sulfide (ZnS) doped with Mn, were deposited using magnetron sputter source. The electroluminescent properties of the as-deposited films were relatively poor. Post- deposition rapid thermal annealing (RTA) with and without co-dopants was studied. Significant changes in microstructure and EL performance were observed on the samples after post-sputter processing. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were employed to characterize the microstructure. Both inter-grain and intra-grain distributions of the co-dopants were measured using energy dispersive X-ray spectra (EDX) and the distribution versus thickness was determined by dynamic secondary ion mass spectrometry (SIMS). A correlation between electroluminescent properties and the microstructure is obtained.
The Origin of Luminescence From Cerium Oxide on Silicon
Authors: Choiv Won Chel , Lee Ho Nyung , Kim Yong , Kim Eun Kyu 
Published: April 2011

ABSTRACTAs the ultra-violet/blue luminescent material, we will introduce the thermal treated cerium oxide on silicon. It has been confirmed a violet/blue luminescence ranging from 358 rim to 450 rnm at room temperature from the thermally treated cerium-dioxide thin films on silicon. As a results of AES and HR-TEM measurement, it was confirmed that cerium silicates were generated by thermal treatment. These cerium silicates such as Ce4.667(SiO4)3O and Ce2Si2O7 are the source of the ultra-violet (UV) emission ranging from 358 nim to 450 nm (maximum at 388 rim).
Evidence for Energy Transfer Mechanisms in Er3+-Doped Pmma Paac Copolymer Samples
Authors: F. R. Sosa , Flores M. , Rodríguez T. R. , Muiñoz F. A. 
Published: April 2011

ABSTRACTThe Judd-Ofelt intensity parameters for f-f transitions of Er3+ ions in PMMA:PAAc copolymer samples were determined from optical absorption measurements and their dependence on the erbium content investigated within the range of 0.1 to 3.0 % mol. The densities, refractive indices and emission spectra have been measured. For our Er-PMMA:PAAc samples an effective radiative transfer between the copolymer host and the erbium ions is observed and discussed.
Survey of Recent Research Results for New Fluor Materials
Authors: Hollerman William A. , Glass Gary A. , Allison Steven A. 
Published: April 2011

ABSTRACTThere is worldwide interest in the use of fluor materials that emit visible light when exposed to ionizing radiation. Typically, fluors are used as components in high performance electromagnetic calorimeters, down-hole oil well loggers, temperature sensors for equipment with high speed moving parts, and beam positioning systems for large particle accelerators. A candidate fluor should have a large fluorescence efficiency, small reduction in output as a function of exposure, intense visible fluorescence spectrum, large material density, and small prompt fluorescence decay time.Over the last few years, new fluor materials have been located by organizations such as Oak Ridge National Laboratory, Lawrence Berkeley National Laboratory, and the Department of Defense. These new fluors, such as YAIO3:Ce, YSiO5:Ce, GdSiO5:Ce, Y2O2S doped with Tb, Pr, and Eu, and Gd2O0S doped with Th, Pr, and Eu, show a great deal of promise for use in the applications listed above.This paper will present a summary of fluor research completed by the authors over the last ten years. These results will be used to establish a fluor characterization program at the Acadiana Research Laboratory (ARL) that will move it to the front of this developing technology.
Porous Polymer/Ceramic Composites for Luminescence-Based Temperature and Pressure Measurement
Authors: Scroggin A.M. , Slamovich E.B. , Crafton J.W. , Lachendro N. , Sullivan J.P. 
Published: April 2011

ABSTRACTPorous Polymer/ceramic films were processed via tape casting. Upon doping with luminescent molecules such as platinum(II) octaethylporphine and [Ru(4,7-diphenyl-1,10-phenanthroline)3]C12, the films were used as pressure sensors, yielding a Stern-Volmer constant of A ranging from 0.02 to 0.61. These films also exhibited very fast response times (∼I ms). Tape cast films doped with Rhodamine B were used as temperature sensors under cryogenic conditions. The temperature sensitivity of the doped films increased with increasing Rhodamine B concentration.
Thin-Film Oxide Phosphors as Electroluminescent Materials
Authors: Minami Tadatsugu 
Published: April 2011

ABSTRACTIn this paper, we introduce rare earth- or transition metal-activated oxide phosphor thin films prepared by magnetron sputtering and dip-coated solution deposition. Thin-film electroluminescent (TFEL) devices using these oxide phosphor thin films as the emitting layer were investigated with a single insulating layer device structure using a thick ceramic sheet insulating layer. High-luminance multicolor emissions and high luminous efficiencies were obtained in TFEL devices using various oxide phosphors: binary compound, Ga2O3; ternary compound, Zn2SiO4, CaGa2O4 and ZnGa2O4; and multicomponent oxide, Zn2SiO4- Zn2GeO4 system. Luminances above 2000 cd/m2 were obtained in CaGa2O4:Mn and Zn2Si1−XGeXO4:Mn TFEL devices driven at 1 kHz. Maximum luminous efficiencies of 2.53, 1.7 and 1.2 lm/W were obtained in Zn2Si0.7Ge0.3O4:Mn, Ga2O3:Mn and ZnGa2O4:Mn TFEL devices, respectively. Stable long-term operation was obtained in dip-coated and sputtered Ga2O3:Mn phosphor TFEL devices even when driven at 10 kHz. Various thin-film oxide phosphors activated with transition metals are suitable for the emitting layer of full-color electroluminescent displays (ELD) without the use of color filters. In particular, Ga2O3 is very promising as a phosphor host material for ELDs.
Enhancement of Nonlinear Optical Properties Through Supramolecular Chirality
Authors: Elshocht S. Van , Busson B. , Verbiest T. , Kauranen M. , Snauwaert J. , Hellemans L. , Persoons A. , Nuckolls C. , Katz T.J. 
Published: April 2011

ABSTRACTWe study second-order nonlinear optical properties of enantiomerically pure and racemic Langmuir-Blodgett films of a chiral helicenebisquinone. Supramolecular aggregation of the material enhances the nonlinear efficiency of the enantiomerically pure material. We also show that the material is potentially useful for constructing quasi-phase-matched structures for frequency conversion.
El Behavior of Stylyl Compounds with Benzoxazole and Benzothiazole for Organic Light-Emitting-Diode
Authors: Yamashita Koichi , Imaizumi Kaname , Mori Tatsuo , Mizutani Teruyoshi , Miyazaki Hiroshi 
Published: April 2011

ABSTRACTWe studied the EL behaviors of benzoheterocyclic derivatives as emitting and hole transport layers for organic light-emitting-diodes (OLEDs). First, we studied the benzoheterocyclic derivatives having stylyl group, triphenylamine group and benzoxazole or benzothiazole group as an emission layer. These devices emitted a blue-green light. The current densities of the OLED having these benzoheterocyclic derivatives as an emission layer were higher than that of the Alq3 OLED at same applied voltage. However, these devices did not have a high EL efficiency (maximum 0.1 lm/W). From these results, in these benzoheterocyclic derivatives having a triphenylamine group, we thought that holes could flow out from hole transport to cathode. We newly synthesized dimer-type benzoheterocyclic derivatives without a triphenylamine group, which have benzoheterocycle at both sides. The current densities of the OLEDs having dimer-type benzoheterocyclic derivatives was more strongly suppressed than that of the OLEDs having benzoheterocyclic derivatives with a triphenylamine group at same applied voltage, but the EL efficiency could not be improved by dimerization and eliminating of a triphenyldiamine group obtained. Next, we studied the TPD derivatives having benzoxazole, benzothiazole and stylyl groups as hole transport layer. In new TPD derivatives, the EL efficiency the OLEDs having the TPD derivatives with stylyl groups was the best efficiency of all. The EL efficiency of ITO/a TPD derivative with stylyl groups/Alq3/AlLi is 1. 1 lm/W (max. luminance 12000cd/m2).