bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanoindentaion and Wear Behavior of Nickel-Titanium Alloys and Thin Films
Authors: Ni Wangyang , Grummon David S.
Published: April 2011

The unusual constitutive behavior of NiTi alloys that display shape memory and transformational superelasticity may impart useful tribological properties. This paper presents some preliminary results on nanoindentation and pin-on-disk wear experiments that suggest potential tri-bological applications of NiTi alloys. It is shown that high levels of spring-back reversibility together with high hardness, as measured by nanoindentation experiments, correlate with improved wear resistance in bulk Nitinol alloys. Amorphous thin films of equiatomic NiTi, which are readily produced by physical vapor deposition, were found to be especially hard and wear resistant. Finally, stress induced B2-B19' transformation is shown to occur during wear-loading of martensitic NiTi, indicating that wear processes are capable of inducing superelastic effects in B2 NiTi alloys.
Effect of Tribological Properties of Undoped and Florine-Doped Silicon Di-Oxide Fims on Chemical Mechanical Planarization Process
Authors: Sikder A.K. , Thagella S. , Bandugilla U.C. , Kumar Ashok
Published: April 2011

Chemical mechanical planarization (CMP) occurs at an atomic level at the slurry/wafer interface and hence slurries and the interaction of the films and polishing pads play a critical role in the successful implementation of this process. Understanding the tribological properties of a dielectric layer in the CMP process is critical for successful evaluation and implementation of the materials. In this paper, we present the effect of tribological properties of undoped and florine doped silicon dioxide films on their CMP process. A micro-CMP tester was used to study the fundamental aspects of CMP process. We have studied the CMP process of oxides on polyurethane pads (IC1000-B4/SubaIV) with colloidal silica slurry at different conditions. The coefficient of friction (COF) and acoustic emission signal was monitored during process. The COF was measured during the process and was found to varies differently for different samples and with down force and platen roatation. The effects of machine's parameters on the polishing performance and correlation of physical phenomena with the process has been discussed.
All CO2-Processed Fluoropolymer-Containing Photoresist Systems
Authors: Flowers Devin , Hoggan Erik , DeSimone Joseph M. , Carbonell Ruben
Published: April 2011

Currently, the microlithography industry creates large amounts of organic and aqueous wastes in the production of semiconductors. Using carbon dioxide can possibly eliminate the majority of these waste solvents as well as eliminate the image collapse problems shown with aqueous base development. We will discuss the use of carbon dioxide to replace the most solvent intensive steps of the microlithography process, spin coating, developing, and stripping. However, before CO2 can replace conventional solvents, photoresist systems must be designed and synthesized to be compatible with CO2. These photoresist systems must be soluble in liquid CO2 to insure that thin-uniform coatings can be produced by spin coating while maintaining characteristics of conventional resist systems such as low absorbance, high sensitivity, solubility contrast, good resolution, and etch resistance. Using our CO2compatible resist system, we will demonstrate the ability of CO2 to spin coat uniform thin-films which (after exposing and PEB) can be developed using scCO2 to produce lithography features that may be stripped in CO2. Thus, revealing the enormous potential of CO2 to provide the microlithography industry an opportunity to escape its water and organic solvent dependence as it moves toward 157nm lithography.
EUV Lithography: Patterning to the End of the Road
Authors: Cobb Jonathan L. , Brainard Robert L. , O'Connell Donna J. , Dentinger Paul M.
Published: April 2011

Extreme Ultraviolet (EUV) lithography is gaining momentum as the patterning technology of choice for the semiconductor nodes with less than 70-nm half-pitch. As such, it must be ready for manufacturing in the 2006-2007 time frame, and it must be extendable to the lower limits of CMOS technology. Successful patterning of 40-nm dense lines in viable EUV photoresists indicates that today's resist materials may have the necessary resolution, but better optics are needed to verify this more rigorously. Although little is understood about the impact of line-edge roughness (LER) on device performance, it is generally assumed that EUV LER must be less than 3 nm 3σ. EUV lines have been printed with LER as low as 4 nm 3σ, but they were printed with unacceptable photospeed. Deliberate attempts to increase the photospeed while maintaining low LER have produced a resist with sizing dose of 1.7 mJ/cm2 and LER of 6.6 nm 3σ. Photospeed is important because EUV photons are difficult to create, and the photoresist must use them efficiently for economically acceptable throughput. Throughput models indicate that patterning doses may need to be 1-2 mJ/cm2, and only 30-40% of these photons will be absorbed, so the resists must be able to accommodate statistical dose fluctuations that are an appreciable fraction of the mean dose. Highly sensitive resists such as these have been produced with good LER. Since all resist materials absorb EUV radiation strongly, the photoresist layer will have to be less than 150 nm thick. Resists this thin pose problems for device manufacturing, largely because they will not have acceptable etch resistance, and this etch resistance will have to be recovered in some other way. Efforts have begun to integrate hard masks with thin resists in real device fabrication. Defect data indicate that defect densities do not increase in resist films less than 100 nm thick, and transistors, via chains, and microprocessors have all been fabricated with these thin-resist/hard-mask integrations.
Resistless Patterning of Magnetic Storage Media Using Ion Projection Structuring
Authors: Dietzel A. , Berger R. , Grimm H. , Schug C. , Bruenger W. H. , Dzionk C. , Letzkus F. , Springer R. , Anders S. , Bandic Z.Z. , Rettner C.T. , Terris B.D. , Eichhorn H. , Boehm M. , Adam D. , Loeschner H. , Platzgummer E. , Stengl G.
Published: April 2011

Co/Pt thin film multilayers with strong perpendicular anisotropy and out-of-plane coercivities of 5-11 kOe were magnetically altered in areas of local ion beam interaction. The ion irradiations were performed by ion projection through silicon stencil masks fabricated by silicon on insulator (SOI) membrane technology. The ion projector at the Fraunhofer Institute for Silicon Technology (ISiT) was operated at 73 keV ion energy and with a 8.7- fold demagnification. After exposure to 3 × 1014Ar+/ cm2 magnetic islands smaller than 100 nm in diameter were resolved in the Co/Pt multilayersby means of magnetic force microscopy. The impact of different ion species (He+, Ar+ and Xe+) and ion energies (10 – 200 keV) on the multilayer structure was evaluated using Monte Carlo simulations. The ballistic interface intermixing was used to predict magnetic coercivity changes for various irradiation conditions. The simulations revealed that with 73 keV Ar+ and Xe+ ions the irradiation dose could be reduced by a factor of 100 and 400 respectively in comparison to 73 keV He+which was verified in the experiments. X-ray reflectivity measurements confirmed that the Co/Pt superlattice structure is slightly weakened during the irradiation and that the surface smoothness of the media is preserved. Using the Ion Projection Process Development Tool (PDT) at IMS-Vienna concentric data tracks including head positioning servo informations were patterned onto a 1” IBM microdrive™ glass disk which was coated with Co/Pt multilayers. In a single exposure step several tracks within an exposure field of 17 mm in diameter were structured by 2 × 1015He+/ cm2 at 45 keV using a 4- fold demagnification set-up.
Nanoscale Pattern Transfer Using Sputter-Induced Corrugations Formed at the Si/SiO2 Interface
Authors: Allen Cary G. , Daniels Matthew , Umbach Christopher C. , Blakely Jack M.
Published: April 2011

A conventional ion mill used for thinning transmission electron microscope samples has been used to produce nanoscale surface corrugations on the thermal oxide of Si. Using Ar ions with energies from 1.1 to 2.5 keV in an off-normal incidence geometry, the corrugations were produced with wavelengths from 30 to 80 nm and amplitudes of ~1 to 2 nm. The corrugated pattern in the oxide has been transferred to the underlying Si substrate by reactive ion etching, producing structures that have a much higher aspect ratio than the original corrugations.
Large Scale Periodic Magnetic Nanostructures Fabricated by Optical Interference Lithography
Authors: Carl A. , Kirsch S. , Wassermann E.F.
Published: April 2011

Large scale periodic arrays of Co/Pt multilayer dots with perpendicular magnetic anisotropy are fabricated utilizing optical interference lithography with Ar+ ion lasers operating at wavelengths of 457nm and 244nm, respectively. The experimental technique allows us to fabricate dot-arrays with periodicities ranging between 125nm and 1100nm and with corresponding dot diameters between 70nm and 740nm. The dot-arrays are prepared on (100)-silicon substrates covering a total area of up to 20cm2 with a maximum dot density of about 4.1x1010dots/in2 as well as within the surface of (110)-silicon substrates. The global magnetic properties of the dot-arrays are characterized by the magneto-optical Kerr effect. The micromagnetic properties of a single Co/Pt dot are measured with quantitative magnetic force microscopy (QMFM) by using a MFM-tip, the magnetic properties of which have been calibrated within the point probe approximation with nanofabricated current carrying rings. This allows us to measure quantitatively the z-component of both the magnetization and the stray field of a Co/Pt dot on the nanometer scale.
Dual-Mode Optical Molecular Switching Systems for Organic Memories
Authors: Galvão D.S. , Braga S.F. , Barone P.M.V.B. , Dantas S.O.
Published: April 2011

The synthesis of dual-mode optical molecular switching systems has been recently achieved. These systems were based on chiral helical-shaped alkenes in which the chirality can be reversibly modulated by light. In this work we report a theoretical study on the geometric and spectroscopic properties of these structures using the well-known semi-empirical methods PM3 (Parametric Method 3) and ZINDO/S-CI (Zerner's Intermediate Neglect of Differential Overlap -Spectroscopic - Configuration Interaction). Our results show that there are two stable conformers very close in energy for each possible molecular helicity presenting a barrier of ∼40 kcal/mol for bond rotation along the main molecular axis. Under protonation these barriers increase significantly and might explain why the protonation leads to the blocking of the switching process. We propose a scheme for the switching mechanism based on charge transfer and conformational changes during the isomer interconversion.
Generation and Transport of Photocarriers in Head-Tail Poly(3-Alkylthiophene) Films
Authors: Rikitake Koichi , Takashima Wataru , Kaneto Keiichi
Published: April 2011

Photovoltaic effects in Schottky Junction cells composed with Au/head-tail poly(3-hexylthiophene) (HT-P3HT)/Al have been studied as a function of excitation photon energy and temperature. It has been found that photocarriers are effectively generated at the interface of HT-P3HT/Al from the excitation spectra of photocurrents (photoaction spectra), which were obtained upon illumination to the Au or Al sides. The photoaction spectra also suggest that the photocarrier generation occurs at around 2.3 eV and 3.5 eV, which correspond to the peak of φ-φ* absorption and the photon energy with lower optical density region, respectively. The mechanisms of photocarrier generation are discussed taking the role of the Schottky junction into consideration.
Optical Spectroscopic Studies of a Soluble Fluorene-Based Conjugated Polymer: A Hydrostatic Pressure and Temperature Study
Authors: Guha S. , Rice J.D. , Martin C. M. , Graupner W. , Chandrasekhar M. , Chandrasekhar H.R. , Scherf U.
Published: April 2011

Spectroscopic properties of conjugated molecules/polymers have varying degrees of sensitivity to backbone conformation. Optical studies are presented as a function of temperature and hydrostatic pressure, using photoluminescence and Raman scattering from two polymers with distinct differences in their backbone conformation, namely, polyfluorene (PF) and ladder type poly(para-phenylene)(m-LPPP). In contrast to the photoluminescence (PL) vibronics in mLPPP, the 0-0 PL vibronic peak in PF shows a red-shift with increasing temperatures. Pressure studies reveal that the PL spectrum of PF red-shifts and broadens with increasing pressures. The phonon lines in PF show an antiresonance effect at higher pressures indicating a strong electron-phonon interaction.
Electrophosphorescent Light Emitting Devices Using New Iridium(III) Complexes
Authors: Das Rupasree Ragini , Lee Chang-Lyoul , Kim Jang-Joo
Published: April 2011

We have synthesized a new tris-orthometalated Ir(mpp)3 and several bis-orthometalated Ir(III) complexes of 3-methyl-2-phenylpyridine(Hmpp). The influence of the methyl substituent in Hmpp and different ligand environments on the optical, electrochemical and electroluminescence properties of the orthometalated complexes are examined by varying the donor acceptor properties. This includes several uninegative bidentate ligands consisting of different organic functional groups. Absorption, excitation and emission spectra in solution and solid state of these complexes agree with a strong electronic excitation to 1MLCT in Ir(mpp)3 and preferably to 3MLCT in other complexes. These complexes demonstrate strong phosphorescence at room temperature with a lifetime of 1-2 μs. Multilayer organic light emitting devices using these complexes as the triplet emitter are studied using PVK (poly(9-vinyl carbazole)), CBP (4,4'-N,N'-dicarbazole-biphenyl) and TAZ (3-phenyl-4-(1'-napthyl)-5-phenyl-1,2,4-triazole) as the host materials. Ir(mpp)3exhibits quite different behavior in different host materials.
Design of Luminescent Polymers for Leds
Authors: Holmes A. B. , Bond A. D. , Davies J. E. , Fischmeister C. , Frey J. , Hennecke U. , Li J. , Ma Y. , Martin R. E. , Rees I. D. , Robinson K. , Sano T. , Cacialli F. , Lim S. F. , Friend R. H.
Published: April 2011

A 2,3-dibutoxy-1,4-phenylenevinylene comonomer was incorporated into a distyrylbenzene derivative 11. Novel 1,2-disubstituted-3,6-dibromobenzene comonomers 15 and 18 were prepared by directed metallation. Copolymerization of 11with a 9,9-dioctylfluorene-2,7-diboronate ester 1 yielded a green fluorescent polymer while copolymerization of 15 and 18 with the 9,9-dihexylfluorene-2,7-diboronate 22 afforded promising blue fluorescent polymers 23 and 24 respectively.
The Effects of Processing Conditions on the Efficiency and Lifetime of Organic Light Emitting Devices Incorporating a New Oxadiazole Derivative
Authors: Jung G.Y. , Wang C. , Cea P. , Pearson C. , Bryce M.R. , Petty M.C.
Published: April 2011

The effects of processing conditions on the properties of organic light emitting devices (LEDs) based on rubrene-doped poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] and a new electron transporting material, 2,5-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazol-5-yl]pyridine, are reported. These dual-layer LEDs exhibited a higher quantum efficiency than observed for structures incorporating the more widely used electron transport compound 1,3-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazol-5-yl]benzene (OXD-7). However, the as-prepared devices degraded relatively rapidly on storage (10-1 mbar, no applied bias). Thermal annealing of the degraded devices at 160 °C for 30 minutes restored the currents and light outputs close to those measured for fresh devices. The annealed LEDs exhibited a significant increase in their operating lifetime. Lifetime improvements could also be achieved by increasing the deposition rate and thickness of the thermally evaporated aluminium top electrode. These effects are attributed to better adhesion between the aluminium top electrode and the underlying electron transport layer.
Organic Solar Cells Based on Evaporated Planar and Bulk Heterojunctions of a PPVpentamer and C60
Authors: Geens W. , Aernouts T. , Poortmans J. , Hadziioannou G.
Published: April 2011

The technique of vacuum evaporation has been applied to deposit organic photovoltaic active layers. The five-ring PPV-type oligomer 2-methoxy-5-(2'-ethylhexyloxy)-1,4-bis((4',4”-bisstyryl)styrylbenzene) (MEH-OPV5) and C60 act as respectively donor and acceptor materials in planar heterojunction (MEH-OPV5/C60) and bulk heterojunction (MEH-OPV5:C60) devices. These devices were fabricated with ITO/PEDOT:PSS bottom electrodes and Al top contacts. The performance of both solar cell configurations has been compared. It was found that under AM1.5 illumination the MEH-OPV5/C60 cells exhibit a higher open-circuit voltage (∼ 1.00 V) than the MEH-OPV5:C60 devices (∼ 0.92 V). On the other hand, the limited exciton diffusion length in these materials was reflected in the lower short-circuit current density of the planar heterojunction cells as compared to the bulk heterojunction structures. Overall AM1.5 power conversion efficiencies reaching 2 % are reported. Also the influence of the organic layer thickness and the substrate temperature during deposition on the device performance has been addressed. Thick organic films generally induce a high series resistance that limits both the short-circuit current density and the fill factor. An elevated substrate temperature during deposition of the MEH-OPV5:C60 layers onto ITO/PEDOT:PSS led to the formation of nucleated islands of 100 - 150 nm diameter with holes in between. As a result, no reliable photovoltaic devices could be realized with such organic films. AFM analysis and spectral response measurements supported these findings.
Corrosion Performance Projection of Yucca Mountain Waste Packages
Authors: Sagüés Alberto A.
Published: April 2011

The proposed high-level nuclear waste repository at Yucca Mountain relies heavily on the corrosion resistance of waste packages (WP) emplaced in tunnels bored through tuffaceous rock for adequate performance during the anticipated 10,000 years regulatory period. Present WP design uses a ∼20-mm-thick outer shell of Alloy 22 as the main corrosion-resistant barrier. The operating conditions may include an initial high-temperature (>96 °C) pulse that will last approximately several hundred to a thousand years. Ti-alloy shields are envisioned to prevent water from directly dripping on the WP. However, recent findings suggest that deliquescent salts and other contaminants on the WP surfaces may cause liquid water to form there, even at high temperatures. Current performance projections predict that during the anticipated regulatory period localized corrosion modes will be unlikely and that the Alloy 22 barrier will degrade primarily by very slow uniform dissolution, essentially under passive surface conditions. A review is presented of the assumptions and experimental findings leading to those projections, as well as a discussion of findings of a recent Workshop on the challenges involved in extrapolating limited information on corrosion behavior over an extremely long service period that extends beyond the time frame of common engineering experience. Potential mechanisms for deterioration of the passive regime that may be encountered under those circumstances are discussed.
Synthesis and Examination of New Actinide Pyrochlores
Authors: Laverov N.P. , Yudintsev S.V. , Stefanovsky S.V. , Jang Y.N. , Ewing R.C.
Published: April 2011

Pyrochlore is a complex oxide with general formula VIIIA2VIB2O6X (X – additional anion in specific position, usually O2-). It has a fluorite-derived structure (space group Fd3m) where one-eighth of oxygens are missing. Two different structural sites for cations exist, resulting in the cell parameter of pyrochlore is twice that of the fluorite lattice. Some pyrochlore-based actinide waste forms have been produced in the systems: CaO-CeO2-TiO2, CaO-UO2(ThO2)-ZrO2, CaO-UO2(ThO2)-Gd2O3-TiO2-ZrO2, and CaO-ThO2-SnO2. The oxide precursors were cold pressed at 200 – 400 MPa and sintered at 1500 – 1550 °C for 6-10 hours in air or at 1300 – 1350 °C for 5-50 hours in pure oxygen (Ce-doped batches only). The use of pure oxygen was used to try to put Ce in the tetravalent state required to form a pyrochlore.

The products were examined with XRD, SEM/EDS, and TEM. In the ceramics with bulk compositions: CaCeTi2O7, CaThZr2O7, (Ca0.5GdTh0.5)(TiZr)O7, (Ca0.5GdU0.5)(TiZr)O7, and CaThSn2O7, pyrochlore was the major phase, but fluorite-structured oxide was also present. In the samples with target compositions CaUZr2O7 and (Ca0.5GdU0.5)Zr2O7 pyrochlore was not identified, rather a fluorite-structured oxide appeared. Different occurrences of pyrochlore and defect fluorite in the ceramics produced are due to crystal chemical constraints.
Sorption-Reagent Method in Liquid Radioactive Waste Management
Authors: Avramenko Valentin A. , Zheleznov Veniamin V. , Kaplun Elena V. , Marinin Dmitri V. , Sokolnitskaya Tatiana A. , Yukhkam and Anna A.
Published: April 2011

Methods of liquid radioactive waste (LRW) decontamination from radionuclides including their co-precipitation at specific conditions or adsorption on selective sorption materials are well known and extensively used in LRW management technologies. At the same time, it was shown in a number of papers that some forms of organic and inorganic ionexchangers react with solutions containing specific components that results in formation of virtually insoluble precipitates inside the sorbent matrix or on its surface. Here in some cases the sorbent selectivity to some radionuclides increases substantially.

The sorption-reagent materials synthesized for decontamination purposes are the most highly selective in regard to such difficult to remove radionuclides as strontium-90 and cobalt-60. It was shown by comparative analysis of radionuclide removal efficiency by traditional selective sorbents and developed sorption-reagent materials that the latter have the highest distribution coefficients in systems too complex for “pure” sorption/ion-exchange decontamination. For example, the sorption-reagent materials have strontium distribution coefficients several dozens higher than those of commercially available sodium titanates and silicotitanates.

The mechanism of radionuclide sorption on sorption-reagent materials of different types was studied. It was shown that this is a multi-stage process and the course of different stages of chemical reactions and sorption is determined by the parameters of medium from which radionuclides are sorbed. It was also shown that these materials application in liquid radioactive waste management enables one to develop simple technological setups combining the advantages of sorption and precipitation methods.

One of the main fields of the sorption-reagent materials application can be decontamination of high-salinity radioactive waste formed whether as a result of ionexchanger filters regeneration in LRW management systems or in reverse osmosis installations. Use of sorption-reagent materials for high-salinity waste management enables one to reduce several ten-fold or even hundred-fold the volume of solid radioactive waste (SRW) to be sent for final disposal and, therefore, to decrease the cost of LRW management. The approach consisting in combined application of reverse-osmosis and sorption-reagent methods for LRW decontamination is suggested.
General Approach Used in the Performance Assessment for the Waste Isolation Pilot Plant
Authors: Rechard Rob P.
Published: April 2011

This paper discusses the technical approach and rationale of the performance assessments (PAs) conducted for the Waste Isolation Pilot Plant that contributed to the success of the certification in 1998. The PAs were iterated: there were four preliminary PAs between 1989 and 1992 and the certification PA in 1996. Although many changes occurred between the 1992 PA and 1996 PA, the preliminary iterations provided a strong foundation on quality assurance, parameter and model databases, documentation, and peer review. The seven general steps of a PA are used to provide a brief overview of their history. The paper then delves into the rationale used for the most computationally intense step of a PA, the consequence evaluation. For this evaluation, Sandia National Laboratories mostly used detailed models when evaluating the probabilistic performance of the repository under the stylized conditions specified by the U.S. Environmental Protection Agency (EPA). A computational tool, CAMCON, was specifically tailored for this approach. Many advantages were gained by using detailed models directly in the PA, rather than using simplified results of these models. One important advantage was that models and parameters remained fairly unbiased (i.e., the analysis had only a few major conservative assumptions rather than many, unquantified conservatisms). This approach allowed Sandia to faithfully provide a “reasonable expectation” of repository performance, as specified by the EPA.
Radioelement transport in the Bangombé nuclear reactor zone (Gabon) – Evidence from U and Sm isotopes
Authors: R. Bros , G. Kamei , T. Ohnuki
Published: April 2011

As a natural analogue study of relevance to the safety margin of radioactive waste repository conditions, mineralogical and isotopic studies were carried out to assess the effects of the alteration of the Bangombé natural nuclear reaction zone. Mobilization and retention of reactor products were identified around the reactor. The high temperature alteration associated with the heat released during nuclear reactions lead to the partial dissolution of uraninite and the sorption of released U mostly by Al-chlorite. This was followed by the precipitation of secondary U-phases such as Zr-bearing uraninite and U-Ti oxides. The recent (<1 Ma) low temperature alteration lead to further dissolution of reactor core uraninite and mobilization of U and fissiogenic REE. Migrations took place laterally through hydraulically conductive fractures within sandstones and vertically through compacted shales, likely by diffusion-type process. Adsorption onto clays and Fe-oxides is the dominant mechanism of retention as inferred by the results of selective extraction experiments. The amounts released appear to be low compared with the quantities initially produced in the core and the transfers may have been limited within several meters around the reactor.
Synthesis of Cobalt Nanoparticles, Nanorods and Nanowires assisted by Oleic Acid and Oleylamine based Mixtures.
Authors: Dumestre F. , Amiens C. , Chaudret B. , Fromen M. C. , Casanove M. J. , Renaud P. , Zurcher P.
Published: April 2011

In this paper we report on the synthesis in solution of cobalt nanoparticles, nanorods and nanowires achieved through the decomposition of an organometallic precursor Co(η3-C8H13)(η4-C8H12) and stabilized by carboxylic acid / amine based mixtures. Through decomposition of the precursor in the presence of a 1/1 mixture of oleylamine / oleic acid during 3 hours, the formation of 3 nm spherical nanoparticles is observed while hcp-cobalt nanorods are obtained if the reaction is pursued for 48 hours. Increasing the amount of oleic acid to 2 equivalents with respect to the amine results in the formation of hcp-cobalt nanowires, micrometers in length and 6 nm mean diameter‥ By using amines with various chain lengths we have observed a modification of the aspect ratio of the cobalt nanorods1. For example, the decomposition of Co(η3-C8H13)(η4-C8H12) in the presence of octadecyl-, hexadecyl-, dodecyl- and octylamine in association with oleic acid allows to selectively produce nanorods of varying aspect ratio.

Physical characterization using TEM and HRTEM, shows that the nanoparticles, nanorods and nanowires are all hcp single crystals. The magnetic properties reveal a saturation magnetization similar to that of bulk and a ferromagnetic behavior at room temperature for the nanorods and nanowires while the 3 nm nanoparticles remain super-paramagnetic.
Production Of CoPt Alloy Grains Within Protein Templates
Authors: Warne Barnaby , Mayes Eric L.
Published: April 2011

The spherical protein ferritin can be used as a generic reaction vessel for the production of a variety of materials, such as iron and manganese oxides. Here, its use for the aqueous production of nanoparticles of equiatomically alloyed CoPt is demonstrated. These have been considered for ultrahigh density magnetic recording as well as permanent magnetic materials. This monodisperse protein strictly regulates the maximum diameter of nanocrystals synthesized within its 8 nm diameter cavity. As a consequence of its external uniformity, it decouples the formation of highly regular self-patterned films from any size distribution associated with the synthesized material. Further, its 2 nm-thick protein coating discourages sintering of particles at temperatures required for the transformation to theL10phase required for magnetic recording applications.
Capacitance-Voltage Characterization of Pulsed Plasma Polymerized Allylamine Dielectrics
Authors: Xu Yifan , Berger Paul , Cho Jai , Timmons Richard B.
Published: April 2011

Polyallylamine films, deposited on Si wafers by radio frequency (RF) pulsed plasma polymerization (PPP), were employed as insulating layers of metal-insulator-semiconductor (MIS) capacitors. The insulating polymer films were deposited at substrate temperatures of 25°C and 100°C. Multiple frequency capacitance-voltage (C-V) measurements indicated that an in-situ heat treatment during film deposition increased the insulator dielectric constant. The dielectric constant, calculated from the C-V data, rose from 3.03 for samples with no heat treatment to 3.55 for samples with an in-situ heat treatment. For both sample sets, the I-V data demonstrate a low leakage current value (<20fA) up to 100V with an area of 0.0307 mm2, resulting in a current density of <0.65 pA/mm2. Hysteresis in the C-V curves with differing sweep directions was more pronounced for in-situ heat-treated samples indicative of positive mobile ions.
Hyper-Rayleigh Scattering and Fluorescence of CdS-ZnS Nanoparticle Composites
Authors: Zhang Yu , Wang Xin , Ma Ming , Fu Degang , Zhang Haiqian , Gu Ning , Liu Juzheng , Lu Zuhong , Ma Yi , Xu Ling , Xu Jun , Chen Kunji
Published: April 2011

Hyper-Rayleigh scattering (HRS) or incoherent second-order light scattering technique has been used to investigate the second-order optical nonlinearities of nanoparticles and seems sensitive to nanoparticle aggregation. In the present work, CdS and ZnS nanoparticle colloids are prepared by the method of colloidal chemistry. From absorption spectra their average diameters are determined to be 5.0 nm for CdS and 2.5 nm for ZnS. Composite CdS-ZnS colloids are obtained by mixing the two colloids at different concentration ratio. The formation of the composites is confirmed by fluorescence measurement. The reduction of emission intensity of the ZnS colloid at 428 nm is observed with increasing CdS concentration, due to fluorescence quenching of the ZnS colloid after forming CdS-ZnS composites. The apparent combining constant of the two nanoparticles is determined to be 8.1×104 mol−1.L by fitting the relative fluorescence intensity of F0/F vs. the added CdS concentration. Upon 1064 nm laser pulse excitation, HRS signal is determined at frequency-doubling wavelength (532 nm) using photomultiplier tube (PMT). HRS experiments show that the composite CdS-ZnS colloids exhibit stronger HRS signal than both CdS and ZnS colloids, and a maximum of HRS signal appears at concentration ratio of [CdS]/[ZnS]=1. This is attributed to that the composite CdS-ZnS nanoparticles have lower symmetry which contributes substantially to the second-order optical nonlinearity of nanoparticles in the electric dipole approximation.
Occurrence of ‘Accidental’ inn Quantum Dots in Indium Gallium Nitride/Gallium Nitride Heterostructures
Authors: O'Donnell K. P. , Martin R. W. , White M. E. , Pereira S. , Mosselmans J. F. W. , Tobin M. J. , Grandjean N. , Damilano B.
Published: April 2011

Nakamura and co-workers were first to report the observation of spontaneously formed In-rich clusters in InGaN quantum wells (QW), using transmission electron microscopy (TEM) [1,2]. Some of the present authors have argued that the exceptional optical efficiency of nitride devices is due to the presence of nearly pure InN QD which form accidentally during crystal growth [3]. Pure InN QD with very small radius would emit light in the required spectral region, under the opposing effects of intrinsic electric fields and quantum confinement [4]. We have recently used extended X-ray absorption fine stucture to examine nanostructure [5]of molecular beam epitaxial (MBE) quantum boxes (QB), and photoluminescence excitation spectroscopy to examine their optical properties [6]. As revealed by AFM, QB are densely packed mesoscopic structures, 10–40 nm wide and 2–3 nm high. Our analysis of the QB EXAFS shows that the filling factor is of order 1%: each QB therefore contains a single QD. The optical evidence suggests that InN dots may be cubic. In contrast, TEM shows that QD in thick epilayers are sparsely distributed [7]. We re-examine recent TEM data on QW in the light of these results.
1.6 μm Emission from InAs Quantum Dots grown on a GaAs Substrate using an AlGaAsSb Metamorphic Buffer
Authors: Balakrishnan G. , Birudavolu S. , Dawson L. R. , Huffaker D. L. , Xu Huifang , Jiang Yingbing
Published: April 2011

We report 1.6 μm emission from InAs QDs (QDs) grown on a GaAs substrate. The ensemble is grown on a graded digital alloy (DA), which increases the matrix lattice constant from 5.65 Å to 5.77 Å. The reduced lattice mismatch between the InAs and matrix material produces larger QDs and thereby allows longer wavelength emission compared to standard growth techniques. The resulting QD density ranges from 2×1010 to 8×1010/cm2 with QD dimensions of 5nm x 30nm measured using atomic force microscopy (AFM). According to x-ray diffraction (XRD) data and transmission electron microscopy (TEM), the metamorphic buffer is unstrained with low defect density.
Self Assembled PbSe Quantum Dots with Almost Equal Sizes Grown by MBE on PbTe/Si(111)
Authors: Alchalabi Karim , Zimin Dmitri , Zogg Hans
Published: April 2011

We report on PbSe QDs grown on a few μm thick PbTe(111) layers on Si(111). The QDs form as pyramids with three (100) side faces and (111) base. Their sizes are almost equal, the standard deviation of their heights can be as low as 2–3%. This seems to be the narrowest distribution ever observed for self assembled QDs. Similar QDs of PbSe have first been described by Pinczolits et al. (Appl. Phys. Lett. 73, 250, 1998). These authors used cleaved BaF2 as a substrate, they observed two types of dots with somewhat wider size distributions. The results are compared and explained on the basis of nucleation and growth theories.
Spectroscopic Ellipsometry Studies of Nanocrystalline Silicon in Thin-Film Silicon Dioxide
Authors: Jellison Gerald E. , Jaiswal Supriya , Rouleau Christopher M. , Simpson John T. , White Clark W. , Owen C.
Published: April 2011

Nanocrystalline silicon (n-Si) is formed in a silicon dioxide thin-film matrix by ion implantation followed by thermal annealing in forming gas at 1100 °C for 1 hour. The ion implantation is performed using multiple implants with different implantation energies and doses to create a quasi-flat concentration of silicon atoms throughout the silicon dioxide film. These samples are then analyzed using spectroscopic ellipsometry to characterize their linear optical properties. Implantations with small doses (5 × 1020 Si atoms/cm3) increase the refractive index by a small amount (δn∼0.006 at 600nm), while implantations with moderate dose (5 × 1021 Si atoms/cm3) have a larger increase in refractive index and exhibit optical absorption above ∼1.9 eV (650 nm).
Control of Silicon Quantum Dots nucleation and growth by CVD
Authors: Mazen F. , Baron T. , Hartmann J. M. , Semeria M. N. , Brémond G.
Published: April 2011

To be successfully integrated in nano-electronics devices, silicon quantum dots (Si-QDs) density, density uniformity, size and size dispersion must be controlled with a great precision. Nanometric size Si-QDs can be deposited on insulators by SiH4 CVD. Their formation includes two steps : nucleation and growth. We study the experimental parameters which influence each step in order to improve the control of the Si-QDs morphology.

We show that the nucleation step is governed by the reactivity of the substrate with the Si precursors. On SiO2, OH groups are identified as nucleation sites. By controlling the OH density on the SiO2 surface, we can monitor the Si-QDs density on more than one decade for the same process conditions. Moreover, Si-QDs density as high as 1.5 1012 /cm2 can be obtained. On the contrary, the growth step depends on process conditions. By modifying the gas phase composition, i.e by using SiH2Cl2 as Si precursor, we can grow the nuclei already formed during the nucleation step without formation of new Si-QDs. We discuss the advantages of this process to improve the control of the Si-QDs size and limit the size dispersion.
Anomalous X-Ray Scattering On Self-Assembled Islands: Direct Evaluation Of Composition Profile, Strain Relaxation, And Elastic Energy
Authors: Malachias A. , Magalhães-Paniago R. , Medeiros-Ribeiro G. , Kycia S. , Kamins T.I. , Stan R.
Published: April 2011

The growth of Ge on Si(001) produces a wealth of morphologies of nanocrystals. After the deposition of a two-dimensional Ge film 3.5 monolayers thick, islands are formed, and several shape transitions can be observed depending on the growth temperature, rate and deposited thickness. In this work we combine atomic force microscopy and two different types of measurements of anomalous x-ray scattering to determine this elastic energy both in pyramid and dome shaped islands. By comparing pyramids and domes data, we have observed both an increase of lattice parameter and enhancement of interdiffusion for the domes. These results show that there is a drastic decrease of the elastic energy stored per atom upon this particular shape transition.
Sol-Gel derived Bi4-xNdxTi3O12 Thin Films and Their Characterization
Authors: Melgarejo R.E. , Tomar M.S. , Hidalgo A. , Katiyar R.S.
Published: April 2011

Nd substituted bismuth titanate Bi4-xNdxTi3O12 were synthesized by sol-gel process and thin films were deposited on Pt substrate (Pt/TiO2/SiO2/Si) by spin coating. Thin films, characterized by X-ray diffraction and Raman spectroscopy, shows complete solid solution up to the composition x < 1. Initial results indicate that the ferroelectric polarization increases with increasing Nd content in the film with 2Pr = 50μC/cm2 for x = 0.46, which may have application in non-volatile ferroelectric memory devices.
The Effect of Hydrogen Incorporation on the Performance of Nanocrystalline Silicon Thin Film Transistors Fabricated by Microwave ECR Plasma CVD
Authors: Teng Lihong , Anderson Wayne A.
Published: April 2011

Nanocrystalline silicon (nc-Si:H) TFT's with the active layers deposited by microwave ECR-CVD were fabricated and characterized using hydrogen dilution as a variable during the Si film deposition. The bottom-gated TFT's were fabricated on SiO2, glass and polyimide substrates at a temperature of 200–400°C with the introduction of 4–12 mTorr H2. The correlation between the H2 dilution and the TFT characteristics was studied and the experimental results were correlated with some theoretical considerations. The TFT on a glass substrate deposited at 400°C with 10 mTorr H2 showed a field effect mobility of 13.3 cm2/V-s and an ON/OFF current ratio of 4.9×106 with the OFF-state leakage current of 3.7×10−11 A. We found that, for the same Si film deposition conditions, the TFT's fabricated on polyimide foil have comparable characteristics to the TFT's on glass substrates.
Nano-Scale Morphology and Electron Spectrum of Defect States in Low-k SiOCH Films
Authors: Ligatchev V. , Wong Rusli T.K.S. , Liu B. , Ostrikov K.
Published: April 2011

Results of experimental investigations on the relationship between nanoscale morphology of carbon doped hydrogenated silicon-oxide (SiOCH) low-k films and their electron spectrum of defect states are presented. The SiOCH films have been deposited using trimethylsilane (3MS) - oxygen mixture in a 13.56 MHz plasma enhanced chemical vapor deposition (PECVD) system at variable RF power densities (from 1.3 to 2.6 W/cm2) and gas pressures of 3, 4, and 5 Torr. The atomic structure of the SiOCH films is a mixture of amorphous-nanocrystalline SiO2-like and SiC-like phases. Results of the FTIR spectroscopy and atomic force microscopy suggest that the volume fraction of the SiC-like phase increases from ∼0.2 to 0.4 with RF power. The average size of the nanoscale surface morphology elements of the SiO2-like matrix can be controlled by the RF power density and source gas flow rates.

Electron density of the defect states N(E) of the SiOCH films has been investigated with the DLTS technique in the energy range up to 0.6 eV from the bottom of the conduction band. Distinct N(E) peaks at 0.25 - 0.35 eV and 0.42 - 0.52 eV below the conduction band bottom have been observed. The first N(E) peak is identified as originated from E1-like centers in the SiC-like phase. The volume density of the defects can vary from 1011 - 1017 cm-3 depending on specific conditions of the PECVD process.
The effect of chemical treatment on porous silicon: the role of alcohol
Authors: Ohmukai Masato , Honda Mei , Kodama Yumiko , Tsunekuni Hiroshi , Tsutsumi Yasuo
Published: April 2011

We investigated the effect of the chemical etching on light-emitting porous silicon. It is well known that the treatment with the mixture of HF acid and ethanol noticeably enhances photoluminescent efficiency but the mechanism is not clarified yet. We found that ethanol plays a key role to oxidize silicon hydride species that dissolves with the aid of HF acid. In addition, the chemical treatment with methanol or propanol instead of ethanol gave the same result.
Effects of Amorphous Carbon Films on the Performance of Porous Silicon Electroluminescence
Authors: Gelloz Bernard , Koshida Nobuyoshi
Published: April 2011

Efficient electroluminescence (EL) is obtained at low operating voltages (<3 V) from n+-type silicon- electrochemically oxidized thin nanocrystalline porous silicon (PS)-amorphous carbon-Indium tin oxide (ITO) junctions. The effects of a few nanometer thick amorphous carbon film between PS and ITO on the EL characteristics have been investigated. The carbon film enhances the stability. The EL efficiency is improved due to a reduction of current density and an increase in EL intensity. In addition, the reproducibility from device to device is very much improved by the carbon film. The enhancement in stability should originate from the capping of PS by the carbon film and the high chemical stability of carbon and Si-C bonds, which should prevent PS oxidation. The carbon film acts as an efficient buffer layer between PS and ITO, resulting in enhanced mechanical, electrical and chemical stability of the top contact and providing high reproducibility. The thin carbon film has only positive effects on all the EL characteristics. This is a very important step towards application.
The Pile-Ups Of Aluminum And Boron In The Sige(C)
Authors: Li Hong-Jyh , Onsongo David , Kirichenko Taras A. , Kohliand Puneet , Banerjee Sanjay K.
Published: April 2011

Dopants diffusion, activation and pile-up due to rapid thermal annealing of implanted Al and B in a thin (∼200Å) Si cap layer on top of Si1-x-yGexCy layer were studied. Experimental results show that both the lattice strain and differential diffusion flux can cause atomic pile-up at the interface and the evidences of those effects were shown independently to each other in this paper. In addition, the pile-up can be extended from the interface to the surface by incorporating C in the underlying layer where B diffusion is much less than in the cap Si. Material analysis shows that both B atomic and activated concentrations in the Si cap layer are increased by 50 %, which suggests that the dopant activation can be increased and junction depth can be decreased at the same time using the inserted Si1-x-yGexCy diffusion blocking layer.
Influence of Different Atmospheres on the Life Time of Porous Silicon Light-Emitting Devices
Authors: Jumayev B.R. , Tam H.L. , Cheah K.W. , Korsunska N.E.
Published: April 2011

In present report, we investigated the degradation processes in porous silicon light-emitting devices (LED) in different atmospheres (O2, N2, air and vacuum) by photoluminescence (PL), electroluminescence (EL), lifetime (LT) and I-V characteristic measurements as well as by Energy Dispersive X-ray Spectroscopy (EDS). The contacts were made by evaporation of Au and Au/Cu alloy. The LEDs emit in visible range at forward and reverse bias. As a rule, full width at half maximum of EL spectrum is wider than that of PL spectrum. The bias direction of applied voltage during degradation change EL, PL, I-V characteristics, and LT of the LEDs. At forward bias, LT degradation is less than that in reverse bias.

The degradation of LEDs during forward bias did not produce any change in the spectral shape of EL and PL. At reverse bias, degradation led to red shift in the peak of EL and PL. The results show that the lifetime of LEDs with Au contact is longer than Au-Cu. Operating in different atmospheres, the LT in vacuum is longest and is more than 100 hours in reverse bias at room temperature.

Possible mechanisms of degradation of LEDs are discussed. It is proposed that degradation is connected mainly with two processes: oxidation and metal diffusion. It is shown that the oxygen and metal in ionic state can diffuse quickly. Hence, in forward bias, the diffusion of metal would dominate, and in reverse bias, diffusion of oxygen dominates.
Generation of Silicon Nanocolumns by Nanosecond Pulsed-Excimer Laser Irradiation and Their Field Emission Properties
Authors: Guan Yingfeng , Pedraza A. J. , Ellis E. D. , Baylor L. R.
Published: April 2011

Laser-generated silicon microcone arrays were used as templates for the growth of nanocolumns using laser irradiation as well. The formation mechanism of the microstructure is briefly reviewed, and the origin and growth of nanocolumns are discussed. The formation mechanism of nanocolumns requires highly localized melting, which explains why they fail to form on a flat surface but can grow atop the microcones. Field emission properties from both microcolumns and nanocolumns have been measured. The high aspect ratio (height/tip radius) of nanocolumns makes them suitable for various field emission applications.
Low-Cost, Large-Area Nanocrystalline TiO2 -Polymer Solar Cells on Flexible Plastics
Authors: Mandal Krishna C. , Smirnov Anton , Peramunage D. , David Rauh R.
Published: April 2011

This paper describes our recent research on the development of fully flexible and low-cost dye-sensitized nanocrystalline TiO2 solar cells (DSSC). At EIC Laboratories, we have developed various large-area solid-state versions, which include both ionically, and hole-conducting allpolymer DSSCs made by continuous coating and lamination process. Various critical steps involve ∼10 micron thick nanocrystalline TiO2 film deposition on conducting PET plastics by various methods such as spraying, spin coating, and screen printing, a low temperature sintering (∼150°C) process, and polymer laminated electrolyte have been demonstrated as valuable active components. The photovoltaic (PV) performance presented in this paper show the fabricated solar cells of ∼1.2 cm2 area with reproducible AM1.5 (Air Mass 1.5) efficiencies of 4.7%. A prototype solar cell with a new hole conducting star polymer with AM 1.5 efficiency ∼2.12% has been thoroughly characterized and discussed.