bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectroscopic Properties and Phase-separation Effect of Europium-doped Sodium Borosilicate Glasses
Authors: Ding J. Y. , Yin C.K. , Shih P.Y. , Yung S.W. 
Published: June 2019

AbstractEuropium oxide has been doped into sodium borosilicate (NBS) glasses (8Na2O-32B2O3- 60SiO2- xEu2O3) at various concentration levels. The glass raw materials were calcined at 800°C and melted at 1380°C and transparent glasses with slightly red color were obtained by quenching the melt in air. Thermal analyses and other experimental results showed excellent glass forming capability with Tg around 480 to 520°C at various doping concentrations. A typical deformation temperature of the europium-doped NBS glasses is around 570-660°C with densities around 2.45 to 2.6 g/cm3. The doped NBS glasses were further heat-treated at 560°C for phase-separation. Scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), thermomechanical analysis (TMA), optical absorption spectrometer and fluorescence emission spectrometer were used to explore properties of the glasses.
CW and Time-Resolved Photoluminescence Analysis of Silicon Implanted Glass Low-Temperature Annealed at Different Times
Authors: Lin Gong-Ru , Lin Chun-Jung 
Published: June 2019

AbstractThe effects of annealing time on continuous-wave (CW) and nanosecond time-resolved (TR) photoluminescence (PL) spectra of silicon-ion-implanted Borosilicate glass (BSO:Si+) annealing at 500°C are characterized. A broadband CWPL of the as-implanted BSO:Si+ at 450-530 nm is observed, and the luminescent peak is found to slightly red-shift after annealing for 90 min. The increasing CWPL intensity reveals that the natural oxygen vacancy (NOV, ΞSi Si-SiΞ) related irradiative defect is highly activated during 30-min annealing, however, which abruptly decreases with the annealing lengthens to 60-min or longer. The TRPL analysis indicates a non-radiative recombination process with a sub-picosecond lifetime for the blank BSO and the as-implanted BSO:Si+ samples, which gradually disappears as the BSO:Si+ is long-term annealed. The irradiative luminescent lifetime of the 60-min annealed BSO:Si+ is lengthened from 1.7 ns to 2.8 ns, which reveals that the density of the NOV defect is decreasing by at least one order of magnitude. A longer irradiative decay with nearly identical lifetime is also found in all annealed BSO:Si+. The ratios of TRPL peak intensities for different samples correlate well with those observed in CWPL measurement, however, the weighting factors of TRPL intensities for the latter two decaying components are vicissitudinous each other in different samples BSO:Si+. This interprets a significant evolution among different decaying mechanisms during the annealing process.
Hydrogen Passivation Kinetics of Si Nanocrystals in SiO2
Authors: Wilkinson Andrew R. , Elliman Robert G. 
Published: June 2019

AbstractHydrogen passivation of non-radiative defects increases the luminescence intensity from silicon nanocrystals. In this study, photoluminescence (PL) and time-resolved PL were used to investigate the chemical kinetics of the hydrogen passivation process. Isochronal and isothermal annealing sequences were used to determine the reaction kinetics for the absorption and desorption of hydrogen, using the generalised consistent simple thermal (GST) model proposed by Stesmans for Pb defects at planar Si/SiO2 interfaces. This included determination of the activation energies and rate constants for the forward and reverse reactions as well as the associated spread in activation energies. The reaction kinetics determined from such measurements were found to be in excellent agreement with those for the passivation of Pb defects at planar Si/SiO2 interfaces, suggesting the nanocrystal emission process is also limited by such defects. These results provide useful model data as well as insight into the processing conditions needed to achieve optimum passivation in H2. As an extension to the work, a preliminary study into passivation by atomic hydrogen was pursued via a post-metallization Al anneal (alneal). A considerable gain in luminescence efficiency was achieved over the previously optimised passivation in H2.
The Origin Of The 0.78 eV Luminescence Band In Strained Layer SiGe/Si
Authors: Kenyon Anthony J. , Steinman Edward A. , Pitt Christopher W. , Hole David E. , Vdovin Vladimir I. 
Published: June 2019

AbstractThe photoluminescence band around 0.78 eV that is sometimes seen in strained layer SiGe samples or deformed silicon containing a high density of dislocations has been attributed to the presence of oxygen complexes. In this study we have prepared a set of Si0.9Ge0.1 samples by MBE which have then been implanted with iron, erbium, or oxygen in order to study the effect of implanted impurities on photoluminescence in the technologically important region around 1.5 microns.Following implantation with oxygen, two luminescence bands appear around 0.85 eV and 0.78 eV, respectively. However, these bands are not present in either the unimplanted sample or those subject to Er or Fe implantation. The correlation between oxygen doping and the appearance of these bands supports the conjecture that they are associated with oxygen complexes.
Experimental and Theoretical Joint Study on the Electronic and Structural Properties of Silicon Nanocrystals Embedded in SiO2: active Role of the Interface Region
Authors: Daldosso N. , Luppi M. , Dalba G. , Pavesi L. , Rocca F. , Priolo F. , Franzò G. , Iacona F. , Degoli E. , Magri R. , Ossicini S. 
Published: June 2019

AbstractThe local environment of light emitting silicon nanocrystals (Si-nc) embedded in amorphous SiO2 has been studied by x-ray absorption spectroscopy (XAS) and by ab-initio total energy calculations. Si-nc have been formed by PECVD deposition of SiOx with different Si content (from 35 to 42 at.%) and thermal annealing at high temperature (1250 °C). The comparison between total electron yield (TEY) and photoluminescence yield (PLY) spectra has allowed the identification of a modified region of SiO2 (about 1 nm thick) surrounding the Si-nc, which participates to the light emission of Si-nc. Total energy calculations, within the density functional theory, clearly show that Si-nc are surrounded by a cap-shell of stressed SiO2 with a thickness of about 1 nm. The optoelectronic properties show the appearance of localized states not only in the Si-nc core region but also in the modified SiO2 region.
Si Nanocrystals as Sensitizers for Er PL in SiO2
Authors: Forcales M. , Wojdak M. , Klik M.A.J. , Gregorkiewicz T. , Gusev O. B. , Franzò G. , Pacifici D. , Priolo F. , Iacona F. 
Published: June 2019

AbstractSensitization of Er3+ photoluminescence in SiO2 layers by silicon nanocrystals has been investigated under resonant and nonresonant pulsed optical pumping. We observed that the very efficient channel of erbium excitation introduced by the nanocrystals can be saturated when very high pulsed photon flux is used. While this channel is saturated, tuning to the resonant excitation wavelength results in an increase of erbium-related photoluminescence, indicating that direct and indirect excitations can take place simultaneously.
Microscopic Structure of Er-Related Optically Active Centers in Si
Authors: Przybylinska H. , Vinh N. Q. , Andreev B.A. , Krasil'nik Z. F. , Gregorkiewicz T. 
Published: June 2019

AbstractA successful observation and analysis of the Zeeman effect on the near 1.54 μm photoluminescence spectrum in Er-doped crystalline MBE-grown silicon are reported. A clearly resolved splitting of 5 major spectral components was observed in magnetic fields up to 5.5 T. Based on the analysis of the data the symmetry of the dominant optically active center was conclusively established as orthorhombic I (C2v), with g‼≈18.4 and g⊥≈0 in the ground state. The fact that g⊥≈0 explains why EPR detection of Er-related optically active centers in silicon may be difficult. Preferential generation of a single type of an optically active Er-related center in MBE growth confirmed in this study is essential for photonic applications of Si:Er.
Defect Mediated and Resonant Optical Excitation of Er3+Ions in Silicon-rich Silicon Oxide
Authors: Kuritsyn D. , Kozanecki A. , Przybylińska H. , Jantsch W. 
Published: June 2019

AbstractWe study sensitization of the4I13/2–4I15/2Er3+luminescence at 1.54 μm in silicon-rich silicon oxide (SRSO) in the whole range of blue-green pump wavelengths. We show that, in general, defects due to excess Si in silica act as luminescence sensitizers. They cause a wide excitation band with a long wave length limit of 600 nm. For monochromatic excitation the maximum luminescence yield is still smaller than for resonant excitation within the 4f shell of Er without additional Si. The large enhancement of the excitation cross section for electrical excitation reported in the literature is plausible, however, as the wide excitation band makes good use of the wide energy distribution of hot carriers. We suggest that the dominant factors, which limit the excitation efficiency of Er3+, are distance dependence of the transfer rate and little spectral overlap of the interacting states.
Self-Assembly Optical Components
Authors: Lazarev Pavel I. , Paukshto Michael V. , Sidorenko Elena N. 
Published: June 2019

AbstractWe report a new method of Thin Crystal Film deposition. In the present paper we describe the method of crystallization, structure, and optical properties of Bisbenzimidazo[2,1-a:1',2',b']anthra[2,1,9-def:6,5,10-d'e'f']-diisoquinoline-6,9-dion (mixture with cis-isomer) (abbreviated DBI PTCA) sulfonation product. The Thin Crystal Film has a thickness of 200-1000 nm, with anisotropic optical properties such as refraction and absorption indices. X-ray diffraction data evidences a lyotropic liquid crystalline state in liquid phase and crystalline state in solid film. Anisotropic optical properties of the film make it useful in optical devices, e.g. liquid crystal displays.
Absorption and Luminescence Properties of Sequentially Random- and Defined Copolymers Based on Poly(fluorene-benzothiadiazole)
Authors: Herguth Petra , Kim Joo Hyun , Jiang Xuezhong , Liu Michelle S. , Jen Alex K-Y. 
Published: June 2019

AbstractThe emission wavelength in conjugated copolymers is determined by the various monomers used, their sequence in the polymer backbone, the effective conjugation length of the material, and intra- and intermolecular interactions of the different units. This paper will discuss the influence of conjugation length as well as the influence of intramolecular charge-transfer on the absorption and emission properties. Fluorene, benzothiadiazole and a third comonomer (fluorene, xylene or triphenylamine) were used as building blocks. The influence of monomer sequence is probed as well by comparing sequentially random copolymers to their sequentially defined ones with identical monomer ratios. Model oligomers were also made for comparison.
Novel Divalent Osmium Complexes: Synthesis, Characterization, Tuning of Emission, and use in Organic Light Emitting Diodes
Authors: Carlson Brenden , Phelan Gregory D. , Kim Joo H. , Jen Alex K.-Y. , Dalton Larry 
Published: June 2019

AbstractIn this work we present the synthesis and characterization of several novel osmium complexes of the form [Os(N-N)2 L-L]2+ 2Ts- or [Os(L-L)2 N-N]2+ 2Ts- designed for organic light emitting device (OLED) applications. In the complex notation N-N represents a derivative of 2,2'-bipyridine or 1,10-phenanthroline and L-L represents a strong π-acid arsine or phosphine ligand. Several counterions have been used and include tosylate, hexafluorophosphate, triflate, heptafluorobutyrate, chloride, bromide, and iodide. The complexes feature 3MLCT emission that ranges from 611-650 nm, which makes them suitable as an emission source for red OLEDs. Phosphorescent quantum yields as high as 45% and emission lifetimes as short as 400 nanoseconds have been reached. The complexes were incorporated into OLED and give off red, orange, yellow, and green electrophosphorescence. Red devices have been created using polyvinylcarb/2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole, polyvinylnapthalene/2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole, and polyfluorene host materials. OLEDs have been created which give brightness up to 3000 cd m-2 and efficiency up to 2.2% at 632 nm emission.
Energetics of mer/fac isomers in metal tris(8-hydroxyquinoline) chelates: Implications on charge conduction in organic light-emitting devices
Authors: Ferris Kim F. , Sapochak Linda S. , Rodovsky Deanna , Burrows Paul E. 
Published: June 2019

AbstractElectronic structure calculations for the mer and fac-isomers of aluminum tris (8-hydroxyquinoline) (Alq3) and the methyl-substituted series, nMeq3Al (n = 3 - 7) are presented. From these data, we estimate their relative abundances in Alq3 thin films and the resultant trap state energies. Ab initio computations performed at the SCF level suggest a significantly higher stability (6 - 7.5 kcal/mol) of the mer-isomer over the facial form, whereas MP2 treatment of electron correlation effects lowers the difference to (4 - 4.5 kcal/mol). Substitution of the Al+3 metal ion with the larger ions Ga+3 and In+3 increases the energetic preference of the meridianal form by 2.7 kcal/mol and decreases it by 0.8 kcal/mol, respectively. Trap state energies calculated by previously proposed methodologies show little difference between mer and fac trap states. These results suggest that the existence of the facial isomer in thin films of metal trisquinolates is unlikely to significantly affect charge conduction.
Imaging individual chains and aggregates on conjugated polymer films
Authors: Kemerink M. , van Duren J.K.J. , Jonkheijm P. , Koenraad P.M. , Janssen R.A.J. , Salemink H.W.M. , Wolter J.H. 
Published: June 2019

AbstractWe demonstrate a novel method to visualize individual molecular chains in the surface layer of organic semiconducting polymer films of arbitrary thickness. The method is based on scanning force microscopy and employs a combination of a sensitive phase detection system and metal coated tips with a low (∼1 N/m) spring constant and a relatively high Q factor (∼200). The molecularly resolved morphology is observed in phase images that are taken simultaneously with the topography. Surprisingly, we found that, when the tip apex radius exceeds the intermolecular spacing in the surface layer, surface aggregates –when present- are visualized. In both cases, the phase contrast is shown to result from van der Waals interaction between the conjugated backbone of the polymer chains and the metallic tip, and can quantitatively be described by a simple harmonic oscillator model. We have employed this method to study the morphology of poly(p-phenylene vinylene) (PPV) derivatives with different substitutions.
Halogenation of ORMOSIL: A Promising Rout for Tailoring Optical Absorptions
Authors: Fardad Amir , Liang Wei , Zhang Yadong , Case Bryson , Jiang Shibin , Peyghambarian Nasser 
Published: June 2019

AbstractFluorinated and photo-imageable precursors are synthesized through a Barbier-Grignard reaction for 1550-nm window. The precursors are used for the sol-gel process of integrated optic components for silica-on-silicon technology. Material compositions and process parameters are optimized to achieve internal absorptions >0.1 dB/cm and propagation losses of about 0.5 dB/cm at 1550 nm. Compact 1×16 Beam splitters are designed and fabricated which exhibit >0.3 dB power uniformity, >0.1 dB PDL and 1.5 dB coupling loss. By hybrid integration of the passive splitters and in-house fiber amplifiers, amplifying splitters are demonstrated at various signal intensities.
Electrosynthesis and Properties of Conducting Polythiophene Derivative Using Co-surfactants in Aqueous Medium.
Authors: Moustafid T.El. , Gregory R.V. , Brenneman K.R. , Lessner P.M. 
Published: June 2019

AbstractThe electrosynthesis of poly (3, 4-ethylenedioxythiophene) from its monomer 3, 4-ethylenedioxythiophene with doping by a mixture of lithium tosylate and co-surfactants sodium dodecylsulfate and sodium poly (4-styrenesulfonate) was performed. An anionic surfactant in aqueous solution was used to increase monomer solubility in water and reduce the potential oxidation relative to acetonitrile medium. Polymer films were synthesized by cyclic voltammetry and galvanostatic methods and characterized by IR, AFM and SEM spectroscopy.
Synthesis and Characterization of Novel Platinum Acetylide Oligomers
Authors: Cooper Thomas M. , Hall Benjamin C. , McLean Daniel G. , Rogers Joy E. , Burke Aaron R. , Turnbull Kenneth , Weisner Andrew 
Published: June 2019

AbstractAs part of an effort to develop a spectroscopic structure-property relationship in platinum acetylide oligomers, we have prepared a series of bidentate Pt(PBu3)2L2 compounds. The ligand was the series o-syd-C6H4-CΞC-(C6H4-CΞC)n-H, n = 0,1,2. The terminal oligomer unit consisted of a sydnone group ortho to the acetylene carbon. The compounds were characterized by various methods, including 13C-NMR, ground state absorption, fluorescence, phosphorescence and laser flash photolysis. The acetylenic 13C-NMR resonances showed sydnone influences that decreased with increasing number of monomer units. The ground state absorption spectra were slightly red shifted from those of the baseline oligomers not having a sydnone group. The low temperature emission and excitation spectra showed complex dependence on excitation and emission wavelengths, suggesting the chromphores resided in a distribution of solvent environments and conformations. Finally, broad triplet state absorption spectra were observed, with absorption throughout the visible and near infrared regions.
Green OLED's: Electroluminescence and the electrical carrier transport
Authors: Pereira L. , Pontes R. , Lopes P. 
Published: June 2019

AbstractOrganic Light Emitting Diodes (OLED) based on metal chelate complexes (Alq3) as the emmiting layer has been prepareded and studied in order to characterise their optical and electrical properties. Electrical measurements have been performed in order to establish the nature of carrier transport. The results point to a trap charge-limited conduction (TCL) with characteristic trap energy near 0.13 eV. In electroluminescence a large green band with a maximum at 2.4 eV was found as a result of three overlapping bands that are correlated with the organic layers. The origin of this luminescence spectrum was analysed.
Oligo(phenylenevinylene)s end-capped with phenothiazine or triphenylamine
Authors: Detert H. , Sadovski O. 
Published: June 2019

AbstractMonodisperse oligo(phenylenevinylene)s end-capped with arylamines have been prepared via Horner Olefinations from bisphosphonates and arylaminobenzaldehydes. The influences of the conjugation length, different arylamine end groups, and of side chains with various electronic character on the electrical and optical properties of the chromophores are investigated. The elongation of the π-conjugated segment from 3 to 5 rings gives rise to bathochromic shifts of the electronic spectra and a slight increase of the oxidation potential. The same but more pronounced is true when the central electron donating ethers are replaced by the strong acceptor alkylsulfone. The electronic spectra of chromophores with triphenylamine and with N-alkylphenothiazines as end groups are quite similar, but the heterocyclic unit reduces the oxidation potential. The incorporation of a chromophor into a segmented copolymer has only negligible effect on the optical and electrical properties.
Chemical Environment Effects on the Photophysical Behavior of Two-Photon Materials
Authors: Collette Jeremy C. , Harper Aaron W. 
Published: June 2019

AbstractA set of six new two-photon engineered diethylamino-substituted styryl pyrazine (DEASP) dyes have been developed as chemically responsive chromophores. This work employs UV/Vis spectroscopy to draw structure-optical property relationships and to quantify the solvatochromic effect observed for these dyes. Absorbance profiles for each of these dyes have been measured in 22 solvents ranging from very nonpolar (TMS) to very polar (water). Absorbance maxima of the longest wavelength π→π transitions have been correlated to nine empirical scales of solvent polarity, and a comparative analysis is presented. Dimroth & Reichardt's and Kamlet & Taft's single parameter scales have been recalculated with spectral data obtained for the six DEASP dyes. The correlation of these established and recalculated scales are shown and discussed. DEASP chromophores are found to exhibit high sensitivity to their chemical environment and exceptional range as solvatochromic probes. Current models of solvatochromism, based on dipolar probes, cannot account for the solvatochromism observed in our quadrupolar dyes, and fail to describe the effect of the chemical environment on this family of twophoton dyes. The need to develop a more universal model of solvation incorporating higher order moment contributions is apparent.
Gated Nonlinear Transport in Organic Thin Film Transistors
Authors: Hamadani Behrang H. , Natelson Douglas 
Published: June 2019

AbstractCharge transport in poly(3-hexylthiophene) field effect transistors has been studied in a series of devices with channel lengths ranging from 3 μm down to 200 nm over a broad range of temperatures and gate voltages. We report gate-modulated highly nonlinear transport at temperatures below ∼200 K that is consistent in form with a Poole-Frenkel-like hopping mechanism in the space charge limited current regime. There is also consistency between this behavior and the hypothesis that density of localized states is strongly energy dependent. We also observe what appears to be a crossover from thermally activated to nonthermal hopping below 30 K.
Intra-Grain and Oligo-Grain Top-Contact Organic Thin film Transistors
Authors: Verlaak Stijn , Jonge Stijn De , Noppe Stijn , Janssen Dimitri , Steudel Soeren , Vusser Stijn De , Heremans Paul 
Published: June 2019

AbstractWe describe and demonstrate a micromachined shadowmask that allows the realization of intra-grain and oligo-grain top-contact organic thin film transistors (OTFTs). First experimental results of OTFT's show that for small channel lengths, grain boundary barriers indeed appear to dominate the output characteristics of OTFTs.
Field Effect of Fullerene Thin Film Studied by Displacement Current Measurements and Infrared Absorption Spectroscopy in The Multiple Reflection Geometry
Authors: Ogawa S. , Kimura Y. , Ishii H. , Niwano M. 
Published: June 2019

AbstractAu/fullerene(C60)/SiO2/Si field effect transistor (FET) has been investigated to examine the behavior of carrier injection by using displacement current measurement (DCM) and infrared absorption spectroscopy in the multiple internal reflection (MIR-IRAS). At the first scan of DCM, an increasing displacement current due to electron injection was clearly observed above a threshold voltage in forward scan, while no flow-back of the injected electrons was observed, indicating that almost all electrons injected in the scan were trapped. The capacitance obtained from the increasing current suggests that the electrons injected from a Au electrode spread laterally along C60/SiO2 to some extent. At the further scans of DCM, the threshold voltage was shifted to higher voltage, and the lateral spread of the electron was quite suppressed due to the space charge of the filled traps. These results clearly demonstrate that DCM is a useful method to examine the behavior of carriers in field effect transistor (FET) devices. The spectral change in MIR-IRAS observed under bias voltage for electron injection is also reported.