bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solar Effects on Tensile and Optical Properties of Hubble Space Telescope Silver-Teflon Insulation
Authors: de Groh Kim K. , Dever Joyce A. , Snyder Aaron , Kaminski Sharon , McCarthy Catherine E. , Rapoport Allison L. , Rucker Rochelle N. 
Published: April 2011

ABSTRACTDuring the fourth servicing mission of the Hubble Space Telescope (HST), the second set of solar arrays (SA-II) was replaced with a third set and the SA-II was brought back to Earth. A section of the retrieved SA-II solar array drive arm (SADA) multilayer insulation (MLI), which experienced 8.25 years of space exposure, was provided to NASA Glenn Research Center for environmental durability analyses of the top layer of silver-Teflon fluorinated ethylene propylene (Ag-FEP). Because the SADA MLI had solar and anti-solar facing surfaces and was exposed to the space environment for a long duration, it provided a unique opportunity to study solar effects on environmental degradation of Ag-FEP, a commonly used spacecraft thermal control material. Therefore, the objective of this research was to characterize the degradation of retrieved HST SADA Ag-FEP with particular emphasis on solar radiation effects. Data obtained included tensile properties, solar absorptance, surface morphology and chemistry. The solar facing surface of the SADA was found to be extremely embrittled and contained numerous through-thickness cracks. Tensile testing indicated that the solar facing surface lost 60% of its mechanical strength and 90% of its elasticity while the anti-solar facing surface had ductility similar to pristine FEP. The solar absorptance of both the solar facing surface (0.155 ± 0.032) and the anti-solar facing surface (0.208 ± 0.012) were found to be greater than pristine Ag-FEP (0.074). Solar facing and anti-solar facing surfaces were microscopically textured, and locations of isolated contamination were present on the anti-solar surface resulting in increased localized texturing. Yet, the overall texture was significantly more pronounced on the solar facing surface indicating a synergistic effect of combined solar exposure and increased heating with atomic oxygen erosion. The results indicate a very strong dependence of degradation, particularly embrittlement, upon solar exposure with orbital thermal cycling having a significant effect.
High Density Addressable Protein and Cell Patterning via Switchable Superhydrophobic Microarrays
Authors: Shiu Jau-Ye , Chen Peilin 
Published: April 2011

ABSTRACTThere have been increasing research interests in the development of novel nano or micro-patterning techniques to create arrays of functional biomolecules for miniaturized assays, which could be used in various biomedical applications such as biosensors, proteomic, immunoassays or drug screening. Several techniques have been demonstrated capable of writing or printing biomolecules with very high degree of spatial control including dip-pen lithography, nanopipet, inkjet printing, photolithography, micro contact printing etc. The serial writing techniques provide the individual addressability whereas the parallel printing processes offer easy and fast protein patterning. However, it remains difficult to create complex patterns, such as functional multicomponent protein arrays, in parallel with individual addressability. Here we describe a novel approach to fabricate functional multicomponent protein and cell arrays where the electrowetting effect was employed to convert a water-repellent superhydrophobic surface into a wettable one allowing fast and high density addressable protein and cell deposition on the otherwise protein- and cell-resistant superhydrophobic surface. It has been shown that each element on the switchable superhydrophobic microarray could be addressed individually and different types of functional biomolecules could be selectively deposited on the microarray. Such protein patterning technique offers several advantages over other techniques including parallel protein deposition with individual addressability, possibility for large-scale patterning and easy integration with microfluidic system. The facts that the superhydrophobic surfaces can be fabricated from many hydrophobic materials and the electrowetting works for most dielectric materials allow great flexibility in the selection of the surface materials for protein deposition.
Silicon Nanocrystals Fabricated by a Novel Plasma Enhanced Hydrogenation Technique Suitable for Light Emitting Devices
Authors: Jamei Mehdi , Karbassian Farshid , Mohajerzadeh Shams , Abdi Yaser , Hashemi Pouya , Robertson Michael , Yuill Sandra 
Published: April 2011

ABSTRACTThe preparation of nano-crystalline silicon suitable for optoelectronic purposes by plasma-enhanced hydrogenation is reported. The method is compatible with mature ULSI technology because of its low temperature and non-wet processing environment. Visible light emission with peak wavelengths ranging from blue to red has been observed and could be tuned by varying the processing conditions. While the blue light emission may be due to surface defects present in the oxide layer, the green and red light emissions are believed to be due excitonic emission within the nano-crystalline grains as a result of quantum confinement effects. The layers were studied by SEM, TEM, CL and FTIR. A LED was fabricated and electroluminescence demonstrated.
Structural and Optical Properties of Al2O3 with Si and Ge Nanocrystals
Authors: Yerci Selcuk , Yildiz Ilker , Seyhan Ayse , Kulakci Mustafa , Serincan Ugur , Shandalov Michael , Golan Yuval , Turan Rasit 
Published: April 2011

ABSTRACTSi and Ge nanocrystals were formed in alumina matrix by ion implantation and subsequent annealing. The phase separation of the Si nanocrystals was observed using X-ray photoelectron spectroscopy by monitoring Si 2p electrons. During nanocrystal formation with a high temperature annealing Si0 signals corresponding to Si nanoclusters increases while Si4+ signals related to a-SiO2 disappears from the spectrum. The transition from amorphous to nanocrystalline phase for both Si and Ge nanoclusters and the compressive stress exerted on the formed nanocrystals were also studied by Raman spectroscopy. Photoluminescence spectra of the Al2O3 containing nanocrystals were discussed by means of Ti and Cr impurities, as well as F centers. The existence of the amorphous Ge nanoclusters in alumina matrix significantly enhances the light emission of Ti3+ impurities.
DMC Study of the Optoelectronic Properties of Diamondoids
Authors: Drummond Neil , Williamson Andrew , Needs Richard , Galli Giulia 
Published: April 2011

ABSTRACTWe have performed density-functional theory (DFT) and quantum Monte Carlo (QMC) calculations of the optoelectronic properties of hydrogen-terminated carbon nanoparticles (diamondoids). Both the QMC and DFT results show that quantum confinement effects disappear in diamondoids larger than 1 nm in diameter, which have optical gaps below that of bulk diamond. Furthermore, our QMC calculations predict a negative electron affinity for diamondoids up to 1 nm in diameter. Both these properties result from the delocalized nature of the lowest unoccupied molecular orbital.
Ni-Fe Competition in the Catalytic Growth of Carbon Nanotubes
Authors: Mordkovich Vladimir. Z. , Kharitonov D. N. , Maslov I. A. , Mitberg E. B. 
Published: April 2011

ABSTRACTThe paper presents the results of competitive catalysis investigation of the carbon nanotube growth in situ of the partial oxidation process of methane. The competition between Ni and Fe results in suppression of Ni catalytic activity and the growth of Fe-capped carbon nanotubes. The discrimination is so strong that iron is segregated from Ni-Fe based stainless steel alloy leaving characteristic Ni-enriched corrosion caverns. The process strongly depends on temperature. Depending on particular catalyst bed composition, the nanotubes of various morphology may occur. In particular, the use of perovskite-type catalyst leads to formation of “olive-branch”-like peculiar carbon nanostructures.
Theoretical Analysis of Non-Catalytic Growth of Nanorods on a Substrate
Authors: Kwon S. Joon , Park Jae-Gwan 
Published: April 2011

ABSTRACTA theoretical analysis explaining non-catalytic growth of one-dimensional (1D) nanorods on a substrate is presented. The nuclei undergo cluster migration which continues until the mean free time of the adatoms is larger than surface diffusion time during several consecutive nuclei growth steps. The most probable mechanism is the migration of six adatoms into one fixed adatom. After the cluster migration, the nuclei grow in an isotropic manner, until the nucleus reaches the size limit. The 1D growth of nanorods on the nuclei begins when the reactant dose is smaller than a certain value. The growth rate of the height is greater than that of the radius. This difference in the growth rate causes the aspect ratio to increase with growth time. The presented analysis explains well the experimental results of the non-catalytic growth of nanorods.
A Facile Solution Method to Synthesis of C60 Nanorods
Authors: Liu Bing bing , Wang Lin , Zou Guang tian , Iwasiewicz A. , Sundqvist Bertil 
Published: April 2011

ABSTRACTWe report here a facile solution method to synthesis of C60 nanorods. A very simple and effective solvent, neat m-xylene, from which C60 can rapidly grow into individual novel nanorods with widths and thicknesses of the order of nanometers was found as a shape controller. These unusual nanorods can easily grow on various substrates such as glass and silicon, and nanorods with different diameters and length-to-diameter ratios can be synthesized under different growth conditions. The smallest nanorods we obtained have widths smaller than 30 nm. The nanorods obtained are highly crystalline and single phase.
Thermal Transport in MWNT Sheet: Extremely High Radiation From The Carbon Nanotube Surface
Authors: Aliev Ali E. , Guthy C. , Zhang M. , Zakhidov A. A. , Fischer J. E. , Baughman R. H. 
Published: April 2011

ABSTRACTLaser flash and self-heating 3ω techniques were employed to determine the anisotropic thermal conductivity and thermal diffusivity of highly oriented free standing multiwalled carbon nanotube (MWNT) sheet drawn from a sidewall of a MWNT forest that was grown by chemical-vapor deposition. The thermal conductivity and the thermal diffusivity along the alignment are 50±5 W/m·K and 45±5 mm2/s, respectively, and are mostly limited by intrinsic defects of individual nanotubes and phonon-phonon interaction within bundles which form the supporting matrix of the MWNT sheet. The long tube-tube overlapping substantially decreases the electrical and thermal interconnection resistances which are usually dominate in randomly deposited mat-like nanotube assemblies. The extremely large surface area of the MWNT sheet leads to excessive heat radiation that dose not allow to transfer the heat energy by means of phonons to distances > 2 mm.
Preparation and Characterization of NPC/SWNT Nanocomposite
Authors: Yi Bo , Rajagopalan Ramakrishnan , Foley Henry C 
Published: April 2011

ABSTRACTA nanocomposite carbon composed with single wall carbon nanotube (SWNT) and nanoporous carbon (NPC) was prepared by grafting a carbonizable polymer, poly(furfuryl alcohol) (PFA) to a SWNT. The SWNT was first functionalized with arylsulfonic acid groups on sidewall (SA-SWNT) and then converted to PFA-functionalized SWNT (PFA-SWNT) by in situ polymerization of furfuryl alcohol (FA). SWNT/NPC nanocomposite carbon was generated by heating PFA-SWNT in argon at 600°C. A continuous phase was formed between SWNT and NPC. The deformation of the nanocomposite carbon at high temperature was studied by heating it at temperatures from 1200 to 2000 °C and characterized with HRTEM and Raman spectra. It was found that NPC tended to graphitize along the axis of neighboring nanotubes at temperature higher than 1400°C. Complete graphitization of NPC and SWNTs was obtained at 2000 °C, when the NPC transformed to graphitic nanoribbon (GNR) and SWNT or DWNT collapsed within the confines of the GNR. Nanocomposite polymer and carbon fibers were prepared by dispersing small amount of SA-SWNT in FA, followed with polymerization, thermosetting and pyrolysis. The composite polymer fibers' Young's modulus was lower than the pure PFA fibers prepared at the same conditions. However, after heated in argon at 300 °C, 400 °C, 500 °C and 600 °C respectively, the Young's modulus of the nanocomposite carbon fibers turned to be higher than the fibers derived from pure PFA and the enhancement by SWNT increase with increasing temperature. For the nanocomposite carbon fibers treated at 600 °C, the fibers had ∼20% increase of Young's modulus over the fibers from pure PFA with only 0.1wt% of SA-SWNT in FA.
Effects of Hydrogen Post Treatment and Duty Factor on Carbon Nanotube Field Emission Stability
Authors: Wang Sigen , Chang Sha 
Published: April 2011

ABSTRACTCarbon nanotubes (CNTs) have been investigated as field emission electron sources for a number of applications such as x-ray source and microwave power amplifier. These applications often require that nanotubes provide a stable field emission at a high emission current. In this paper, we investigated the emission stability of CNTs as functions of hydrogen post-treatment and duty factor. The experimental results show that the hydrogen plasma treatment and a reduced duty cycle from 100% to 35% can noticeably improve the emission stability of CNTs at a high current value of 4 mA. Our study also shows that emission induced anode heating at high duty factor and high emission current level degrades vacuum level and thus the emission stability of CNTs.
Investigation of DNA Decorated Carbon Nanotube Chemical Sensors
Authors: Chen Michelle , Khamis S. M. , Johnson R. R. , Staii C. , Klein M. L. , Fischer J. E. , Johnson A. T. 
Published: April 2011

ABSTRACTWe demonstrate a versatile class of nanoscale sensors based on single-stranded DNA (ss-DNA) as the chemical recognition site and single-walled carbon nanotube field effect transistors (swCN-FETs) as the electronic readout component. Coating swCN-FETs with ss-DNA causes a current change when exposed to gaseous analytes, whereas bare swCN-FETs show no detectable change. The responses differ in sign and magnitude depending both on the type of gaseous analyte and the sequence of DNA. Our results suggest that the conformation of ss-DNA on swCN-FET plays a role in determining the sensor response to gaseous analytes. The conformation depends not only on the base content of the oligomer, but also on the specific arrangement of the bases in the ss-DNA. We compare our results with the molecular dynamic simulations for understanding of the sensing mechanisms. SsDNA/swCN-FETs possess rapid recovery and self-regenerating ability, which could lead to realization of large arrays for sensitive electronic olfaction and disease diagnosis.
Reliability Study of a Fluorescent Blue Organic Light-Emitting Device
Authors: Lee Jiun-Haw , Ho Yu-Hsuan , Lin Tien-Chun , Wu Chia-Fang 
Published: April 2011

ABSTRACTIn this paper, we measured and analyzed the operation lifetime of a high efficiency blue OLED which consists of N,N' –Vdiphenyl -N,N'-bis(1-napthyl) -1,1'-biphenyl-4,4'- diamine (NPB) as the hole-transport layer (HTL), 4,4'-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl (DPAVBi) doped in 9,10-bis(2';-naphthyl) anthracene (ADN) as the emitting layer (EML), and bis(10-hydroxyben-zo[h]quinolinato)beryllium (Bebq2) as the electron-transport layer (ETL). Due to the high electron mobility of the ETL (one order of magnitude higher than Alq3), the carrier balance is achieved and a blue OLED with a high external quantum efficiency of 8.32% is obtained. The device structure of our blue OLED device is ITO /HTL (40nm)/EML (45nm, 4% dopant)/ETL (15nm)/ LiF(1.2nm)/Al (100nm). In our operation lifetime measurement, we fixed the initial luminescence of the blue OLEDs at 12500, 10000, 7000, 5000 cd/m2 with a constant current driving. The resulting half-lifetime are 5.58, 16.56, 27, 109.819 hours, respectively. To estimate the half-lifetime of this device, we use a well-known relation in our fitting: L*t1/2n= constant where n is the acceleration coefficient, and t1/2 is the half-lifetime. In our blue OLED, the n value is 3.088. By using the equation, we can calculate that the estimated half lifetime at an initial luminance of 1000 cd/m2 achieves 15611 hours in our device. For further investigating the lifetime mechanism in our blue OLED, we fit all the luminance versus time curves obtained under different driving condition. We found that luminance is inversely proportional to the square of the time, rather than a typically stretched exponential decay which means the luminance decay is a second-order reaction in our blue OLED.
Fabrication of Organic Thin Film Transistors Using Low Temperature, Soluble Silicon Oxide as the Gate Dielectrics
Authors: Wei Jeng-Hua , Lin HorngJiunn , Chen Ying-Ren 
Published: April 2011

ABSTRACTIn this paper, a unique water-based, liquid phase deposited silicon oxide (LPD SiO2) is adapted to the fabrication process of the organic thin film transistor (OTFT). Through the use of this process, an OTFT with a silicon oxide gate insulator is successfully fabricated at 100°C or less. At this low process temperature, the SiO2 functions efficiently as a gate dielectric with the breakdown field being larger than 5 MV/cm, the leakage current being near 1 pA/um2 with a gate bias of 20 V and the surface roughness being less than 1nm. Due to the high quality silicon oxide, the oxide-gated OTFT shows the low threshold voltage (-1 ∼ -2V) and medium on/off current ratio (∼1000). Because this oxide is a water-based process, it is highly resistant to the following soluble semiconductor material and its solvent.
Gate Dielectric Dependent on Pentacene Growth and Electrical Stability in OTFTs
Authors: Chang Su Kim , Sung Jin Jo , Sung Won Lee , Hong Koo Baik 
Published: April 2011

ABSTRACTWe report on the effects of modifying the gate dielectrics by spin coating of HMDS, PVP and PVA which cause different surface energy and surface roughness owing to the different functional groups. In changing the surface state with applying various surface treatments, I-V and C-V measurements of the OTFTs were performed. The PVP-coated OTFTs, which has smoother and lesser amount of OH-groups on the gate dielectric surface, showed enhanced pentacene growth and nearly free hysteresis behavior than that of the HMDS and PVA-coated OTFTs.
Ab Initio Study of Switching Properties of Photochromic Dithienylethene Molecules
Authors: Odell Anders , Delin Anna 
Published: April 2011

ABSTRACTWe report an ab initio study of a photochromic dithienylethene derivative. The mechanisms for switching between open and closed conformations are investigated based on total energy calculations for the ground and excited state. An explanation for the central ring closure based on relaxation of the excited state is presented.
Controlling the pKa for Protonic Doping of Polyaniline by Non-covalent Complexation
Authors: Wan Hui , Yang Sze C 
Published: April 2011

ABSTRACTWe report a synthetic method for shifting the pKa for the deprotonaton of polyaniline by the formation of non-covalent complexes between polyaniline and a polyanion. Depending on the choice of the polyanion and the condition of the synthesis, we can control the pKa value for the dedoping reaction to spread the pH range from 5.5 to 9.0. From a systematic study of the structural influence on the pKa values, we have verified that the electrostatic stabilization of the polaron is the origin for this unusually large pKa shift.
Molecular-Scale Structure of Pentacene Interfaces with Si (111)
Authors: Seo Soonjoo , Evans Paul G. 
Published: April 2011

ABSTRACTThe morphology and crystal structure of the first few molecular layers of organic semiconductor thin films at organic-inorganic interfaces are important from both electronic and structural perspectives. The first upright layer of pentacene on Si (111) forms on top of a disordered layer of strongly bonded pentacene molecules in a structure similar to the pentacene monolayers formed on insulators. We describe a high-resolution structural study of this crystalline phase of pentacene using low-temperature scanning tunneling microscopy (STM). The arrangement of molecules in these layers observed with STM agrees the results of with structural studies using scattering techniques. The imaging conditions and sample preparation techniques necessary to achieve molecular resolution can be adapted to subsequent STM and scanning tunneling spectroscopy experiments probing individual structural defects including vacancies, dislocations and grain boundaries within and between islands.
In-plane Structure and Polymorphism of Pentacene Thin Films
Authors: Kakudate Toshiyuki , Yoshimoto Noriyuki , Saito Yoshio 
Published: April 2011

ABSTRACTThe structure and polymorphism of pentacene thin films on SiO2 substrate were investigated by grazing incidence x-ray diffractometry (GIXD). The in-plane GIXD patterns were successfully obtained from vacuum deposited ultra-thin films of a few monolayers thick. The two-dimensional lattice constants were determined for both thin-film and bulk phases from the observed GIXD patterns. Considering the obtained unit cell parameters, the mechanism of the transformation between polymorphs was discussed using the classical nucleation theory.
Electronic Structure of Ionic Liquids Studied by UV Photoemission and Inverse Photoemission Spectroscopy
Authors: Nishi Toshio , Kamizuru Yasunori , Kanai Kaname , Ouchi Yukio , Seki Kazuhiko 
Published: April 2011

ABSTRACTElectronic structures of the ionic liquids were studied by ultraviolet photoemission spectroscopy (UPS) and inverse photoemission spectroscopy (IPES). The sample materials contain 1-buthyl-3-alkylimidazolium ion [Cnmim]+ (n=4, 8, 10) as the cation in combination with fluorine-containing anions (tetrafluoroboronate BF4−, hexafluorophosphate PF6−). Comparing the calculated density of states with the observed spectra, we found that the ionization thresholds of these ionic liquids are determined by the highest occupied molecular orbitals (HOMO) of the cation, although the calculated HOMOs of the isolated anions are higher than that of isolated cation. The combination of the UPS and IPES results reveals that the band gaps of these ionic liquids are determined by only cation.
The Effect of Ultraviolet Light Curing on the Material and Fracture Properties of a k∼2.5 Low-k Dielectric
Authors: Smith Ryan S. , Tsui Ting , Ho Paul S. 
Published: April 2011

ABSTRACTIn this paper, we investigated the role of ultra-violet light (UV) curing on the molecular structure and fracture properties of a porous organosilicate glass (OSG) dielectric with k∼2.5. A correlation between material properties, including fracture toughness, and molecular structure was found. Multiple analytical techniques including Fourier Transform IR (FTIR) Spectroscopy, x-ray photo-emission spectroscopy (XPS) and x-ray reflectivity were used to investigate changes in the molecular bonding and material properties with UV curing. Overall, UV seems to be highly penetrating leading to uniform composition and density changes in the low k film to improve its properties. The decrease of methyl and hydrogen content relative to the Si-O-Si bonding structures led to increasing density and dielectric constant with UV exposure. UV curing increases the critical fracture toughness, while the sub-critical fracture toughness is insensitive to UV cure. The correlation between critical fracture toughness and material properties is discussed.