bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermomechanical stress in silicon on quartz wafer bonding and Smart Cut® process
Authors: Chao Yu-Lin , Tong Qin-Yi , Gösele Ulrich M.
Published: April 2011

The thermal stress behavior of silicon/quartz bonded wafer pairs is examined. Sliding, debonding, and cracking are the observed mechanisms of relaxation. When the elastic energy due to the different thermal expansion coefficients of silicon and quartz exceeds the bonding energy, sliding will start and lead to a serrated curve on the curvature-versus-temperature graph. Finally, debonding will occur once the peeling stress exceeds the interface bonding strength. The debonded parts crack due to the overhang structure, and debonding-cracking processes continue during a further temperature increase. The stress behavior of the hydrogen-implantation induced layer splitting process (the so-called “Smart-Cut process”) of silicon/quartz pairs is also monitored in a stress measurement setup. It is observed that Smart-Cut process is a sudden process in agreement with the observations reported in the literature.
Characterization of Optical Lifetime in Silicon-on-Insulator Wafers by Photoluminescence Decay Method
Authors: Ibuka Shigeo , Tajima Michio , Ogura Atsushi
Published: April 2011

We report observation of temporal decay of luminescence due to electron-hole condensation in silicon-on-insulator (SOI) wafers. The condensate luminescence was observable in SOI wafers under ultraviolet light excitation, because of shallow penetration depth of the light and confinement of photo-excited carriers in the top-Si layer. We found that the temporal decay of the luminescence depended on the surface/interface condition and fabrication method. These findings can be explained by the difference in the recombination process via surface, interface and defect states in the top-Si layer. We propose that the decay measurement of the condensate luminescence has great potential for characterization of SOI wafers.
Effect of Excimer Laser Annealing on Ultra-low Temperature Gate Dielectrics
Authors: Chung Wonsuk , Thompson Michael O.
Published: April 2011

The effect of excimer laser annealing on the properties of ultra-low temperature (150°C) plasma enhanced chemical vapor deposited (PECVD) oxides was investigated. Annealing was performed using a 308 nm excimer laser incident directly on the oxides, at fluences up to the melting of the silicon and for as many as 3000 pulses. Following multiple shot irradiations below the silicon melt threshold, the CV threshold voltage was observed to decrease by ≍15V volts, coupled with an increase in the slope near threshold. Leakage currents measured by IV were not significantly changed. Property modifications are shown to be comparable to a 450°C thermal soak anneal. These results suggest that excimer laser annealing has potential to improve ultra-low temperature gate dielectrics for poly-Si Thin Film Transistors (TFTs) on plastic substrates.
Double-Gated Singly-Addressable Polysilicon Tip Array Fabrication and Characterization
Authors: Chubun N.N. , Chakhovskoi A.G. , Hajra M. , Hunt C.E.
Published: April 2011

Polysilicon-on-insulator singly-addressable arrays, consisting of double-gated field emission cells, were fabricated and tested. The field-emission tips were formed by a subtractive technique, using 2.5 µm thick polysilicon stripes on an insulating substrate. The tip structure was oxidized for dielectric isolation and coated with a 0.4 µm polysilicon layer as a first gate electrode. The polysilicon layer was then subsequently oxidized to provide a second isolation layer for separation from a 0.1 µm gold film, deposited as a second gate electrode. Finally, the 1.5 µm aperture was formed, combining wet etching of the silicon dioxide and dry etching of the polysilicon layers. The matrix allows addressing electrically any emission cell at the intersection of a cathode column and an extracting gate line. An independent voltage can be applied to the second gate during operation to focus the electron beam of an operating tip.
A Novel Poly-Si TFT in Line-Crossover with High Aperture Ratio and Small Signal Delay of AMLCD Panel
Authors: Park Jin-Woo , Song In-Hyuk , Park Kee-Chan , Jung Sang-Hoon , Han Min-Koo
Published: April 2011

We have proposed and fabricated a novel poly-Si TFT that is integrated into the gate-data line-crossover in order to increase aperture ratio and to decrease signal delay of AMLCD panel and electrical characteristics of TFT integrated into gate-data line-crossover almost are identical to conventional TFT. The aperture ratio of AMLCD panel was increased considerably because the TFT was located under the opaque metal line. We employed a low dielectric air-gap between the gate-data line crossover, which reduced a capacitance between the gate and data lines so that the RC signal delay of the data line is decreased significantly. Our experimental result shows that the fabricated TFT was successfully operated and the proposed structure found to reduce the RC signal delay has been reduced by factor of 9 compared with conventional AMLCD panel that employs SiO2 for insulator between gate and data lines.
The Effect of Sputtering Gas on the Materials and Electrical Characteristics of p-Si Films Formed by DC Magnetron Sputtering
Authors: Voutsas A.T.
Published: April 2011

In this work we will discuss the feasibility of sputtered-Si as a precursor for low-temperature p-Si films. We used DC sputtering to deposit thin Si films (30-100nm) that were subsequently crystallized by excimer-laser annealing using XeCl (308nm) irradiation. The as-deposited films were sputtered with different gases including Ar, He and Ar-He mixtures. As expected, He sputtering led to less dense films that Ar. However, the plasma voltage (during deposition) was also lower in these cases. It was found that mixing of Ar and He gases within an appropriate ratio range produced sputtered films with good optical properties, at much lower plasma voltages that Ar alone. The lower voltage application could be beneficial from the point of view of reducing microarcing and allowing application of higher DC power levels (to improve deposition rate). Polysilicon TFTs fabricated with the optimum Ar-He ratio (>5% Ar in He) demonstrate similar performance between pure-Ar and Ar-He sputtered p-Si TFTs.
Origin of Inhomogeneity in Pulsed Excimer-Laser Crystallized Silicon Films Studied by Computer Simulation
Authors: Kudo Toshio , Ichishima Daiji , Jin Cheng-Guo
Published: April 2011

In order to understand the occurrence and development of inhomogeneous poly-Si texture in the polycrystallization process of poly-SiTFT fabrication, we have simulated 1) the influence of pulse energy (PE) and optical axis (OA) fluctuations on the texture of poly-Si films and 2) the interference between both fluctuations, under the single-pulsed XeCl laser irradiation at the overlapping ratio 98%. The frequency of fatal irregular pulses in the PE fluctuation is much more than that in the OA fluctuation (pointing stability). Once the poly-Si texture suffers a fatal irregular pulse over the complete melting (CM) point, the inhomogeneous texture caused is never recovered by the following overlapping irradiation and no columnar structure is formed. However, when no irregular pulses exceed the CM point, the partial inhomogeneous texture caused in the poly-Si films is recovered by the thinning out of small Si grains in the texture and a columnar structure is formed. The key to the issue of fatal irregular pulses should be not only the reduction of PE and OA fluctuations but also the optimum selection of pulse energy not over the CM point.
Strained Ge Channel p-type MOSFETs Fabricated on Si1−xGex/Si Virtual Substrates
Authors: Lee Minjoo L. , Leitz Christopher W. , Cheng Zhiyuan , Pitera Arthur J. , Taraschi Gianni , Antoniadis Dimitri A. , Fitzgerald Eugene A.
Published: April 2011

We have fabricated strained Ge channel p-type metal oxide semiconductor field-effect transistors (p-MOSFETs) on Si1−xGex (x=0.7 to 0.9) virtual substrates. Capping the channel with a relaxed, epitaxial silicon layer eliminates the poor interface between silicon dioxide (SiO2) and pure Ge. The effects of the Si cap thickness, the strain in the Ge channel, and the thickness of the Ge channel on hole mobility enhancement were investigated. Optimized strained Ge p-MOSFETs show hole mobility enhancements of nearly 8 times that of co-processed bulk Si devices across a wide range of vertical field. These devices demonstrate that the high mobility holes in strained Ge can be utilized in a MOS device despite the need to cap the channel with a highly dislocated Si layer.
A Patterned Soi by Masked Anneal for System-on-Chip Applications
Authors: Cohen G. M. , Sadana D. K.
Published: April 2011

We present a method for fabricating pattern silicon-on-insulator (SOI) wafers that exploit internal thermal oxidation (ITOX) to control the BOX formation. We demonstrated the process by fabricating a pattern SOI having two different buried oxides (BOX) thickness. We also show that by using a very low oxygen dose the BOX can be quenched in the masked regions, while maintaining a continuous BOX in unmasked regions. Very low damage forms at the transition region from thick to thin BOX. Due to the oxygen diffusion the smallest patterned box feature we could obtain was limited to > 0.5 micron.
Channel Engineering of SiGe-Based Heterostructures for High Mobility MOSFETs
Authors: Leitz Christopher W. , Currie Matthew T. , Lee Minjoo L. , Cheng Zhi-Yuan , Antoniadis Dimitri. A. , Fitzgerald Eugene A.
Published: April 2011

Strained Si- and SiGe-based heterostructure metal-oxide-semiconductor field-effect transistors (MOSFETs) grown on relaxed SiGe virtual substrates exhibit dramatic electron and hole mobility enhancements over bulk Si, making them promising candidates for next generation complementary MOSFET (CMOS) devices. The most heavily investigated heterostructures consist of single strained Si layers grown upon relaxed SiGe substrates. While this configuration offers significant performance gains for both n- and p-MOSFETs, the enhanced hole mobility remains much lower than the enhanced electron mobility. By contrast, a combination of buried compressively strained Si1−yGey layers and tensile strained Si surface layers grown on relaxed Si1−xGex (x < y), hereafter referred to as dual channel heterostructures, offers nearly symmetric electron and hole mobilities without compromising n-MOSFET device performance. To investigate these heterostructures, we study the effects of alloy scattering on channel mobility in long channel MOSFETs. By using the combination of a buried Si0.2Ge0.8 channel and a strained Si surface channel grown on a relaxed Si0.5Ge0.5 virtual substrate, we have achieved nearly symmetric electron and hole mobility in the same heterostructure. By employing different virtual substrate compositions, we can decouple the effects of strain and alloy scattering in both tensile strained surface channels and compressively strained buried channels. We show that significant hole mobility enhancements can be achieved in dual channel heterostructures, even for buried channel compositions where alloy scattering is expected to be most severe. Furthermore, we show that alloy scattering in tensile strained SiGe surface channels impacts electrons much more severely than holes. Taken together, these results demonstrate that dual channel heterostructures can offer symmetric carrier mobilities and provide excellent performance gains for CMOS applications.
Design and Modelling of a Fourier Spectrometer Based on Sampling a Standing Wave
Authors: Knipp D. , Stiebig H. , Büchner H.-J. , Jäger G. , Rosa M. , Street R.A.
Published: April 2011

The design of a novel spectrometer based on a thin film diode in combination with an electro statically tunable micro machined mirror will be presented. The semi transparent diode is introduced into a standing wave created in front of a reflector to sample the profile of the standing wave. Varying the position of the reflector results in a shift of the phase of the standing waves and thus in a change of the optical generation profile within the detector. The spectral information of the incoming light can be determined by the Fourier transformation of the transient response of the sensor. An analytical optical model will be presented which facilitates the evaluation of different detector concepts. The model will be applied to discuss different device designs regarding the resolution of the spectrometer, the spectral range and the linearity.
Silicon Microfabrication: Laser Ablation vs. Inductively Coupled Plasma (ICP) Etch
Authors: Owens Megan M. , Soucy Joseph W. , Marinis Thomas F.
Published: April 2011

Mechanical prototypes of a silicon interposer device, having high-aspect ratio straight walls, were required for experiments to qualify various packaging assembly options. The ideal solution would yield expendable, quickly made, and relatively inexpensive replica parts.

This need led to the investigation of micromachining of silicon via laser ablation. We sought to optimize the results by varying several parameters, the most influential of which was shown to be laser wavelength. Silicon wafers of thickness 500 νm were machined using laser wavelengths of 10,600 nm, 1064 nm, and 355 nm. As was predicted according to the theoretical silicon absorption profile, the best results were obtained using 355 nm wavelength light from an ultraviolet laser source. Several post-machining cleaning routines, to remove melted silicon debris, were evaluated as well. Pictorial results of both laser processing and cleaning are shown and discussed.

ICP was concurrently investigated as a viable alternative to laser machining. These cuts were markedly cleaner and straighter than those induced by laser; additionally, cut features were more well defined. Pictorial results are compared and contrasted with those of laser ablation.

Cost and time are traded for quality when choosing between laser ablation and ICP etch. Therefore, process choice should be application-dependent. For wafers with moderately complex cutout features, laser micromachining is significantly lower in cost and manufacturing time. However, the laser process does produce residual thermal stress surrounding the cut region, machined edges are relatively rough, and fine features are more difficult to produce. Laser ablation is an attractive manufacturing option for quick-turnaround prototyping as well as high-volume production; ICP is better suited to producing high-definition parts without potential for thermal stress damage.
Metastable Superstructures in RuSr2Gd1.4Ce0.6Cu2O10-δ?Superconductor Based on TEM Observation at Room Temperature
Authors: Yang Li , Vieira J. M. , Tang Kaibin , Zhou Guien
Published: April 2011

Three types of metastable modulations in Ru-based superconductor RuSr2Gd1.4Ce0.6Cu2O10-δ are observed by electron diffraction at room temperature and reported in this paper. The modulations are sensitive to the irradiation of the electron beam and the sample storage time. Having the tetragonal symmetry (I4/mmm) with a=0.384nm, c=2.864nm, the structure of RuSr2Gd1.4Ce0.6Cu2O10-δ?resembles that of YBa2Cu3O7-δ by inserting a fluorite type Gd1.4Ce0.6O2 layer instead of the Y layer and Ru ions residing in the Cu(1) site. In this compound, superconductivity is confined to the CuO2 layer while magnetism stems from the RuO2 layer. The metastable modulations display the interaction between the two layers from the structural point of view. The results suggest that although, superconductivity and magnetism are decoupled from each other in the unconventional superconductor, the effect may be limited by metastable lattice modulation.
Orientation Control of HTS Thin Films
Authors: Endo K. , Ishikawa H. , Yoshizawa T. , Abe K. , Itoh J. , Kajimura K.
Published: April 2011

The preparation of non c-axis oriented HTS films with longer coherence length is one of key technologies toward realisation of viable Josephson devices. We reports on the successful growth of (119)Bi-2223 films by MOCVD using a two-step growth temperature procedure and on AFM observation of the film surface. This temperature procedure was found to be effective for orientation control and phase control in comparison with a fixed growth temperature procedure. As a result, superconducting properties were much improved. The surface morphology observed by AFM showed a mountain-range-shaped one, which strongly reflects the epitaxial relationship between the (119)Bi-2223 film and (110) SrTiO3 substrate.
Preparation of [Ba2CuO2(CO3) ]m[ACuO2]n(A=Sr,Ca) Films by MBE Technique
Authors: Adachi Yutaka , Matsui Yoshio , Sakaguchi Isao , Haneda Hajime , Takahashi Koichiro
Published: April 2011

[Ba2CuO2(CO3)]m[ACuO2]n(A=Sr) superlattices containing oxycarbonate blocks as charge reservoir have been prepared on SrTiO3 using the molecular beam epitaxy technique. First, thin films of the oxycarbonate cuprate Ba2CuO2(CO3) have been prepared on SrTiO3(001) using NO2 gas as an oxidant and CO2 gas. The films have been grown at 500°C. At higher substrate temperature or at lower CO2 pressure Ba2CuO3 was formed instead of Ba2CuO2(CO3), and the films becomes amorphous at lower temperature. X-ray diffraction and reflection high-energy electron diffraction observations indicated that (BaxSr1−x)2CuO2(CO3) grew along the [001] crystal orientation on SrTiO3(001) with the following epitaxial relationship: Ba2CuO2(CO3)[100]//SrTiO3[110] and Ba2CuO2(CO3)[110]//SrTiO3 [100]. Depth profile of secondary ion mass spectrometry signals indicated the incorporation of carbon into the films. Secondly, the oxycarbonate cuprates and infinite layers have been alternately stacked. It was confirmed that Ba2CuO2(CO3)was inserted between several unit cells of SrCuO2. Electrical measurements show the as grown films to have a semiconducting behavior.
The Progress on Low-Cost, High-Quality, High-Temperature Superconducting Tapes Deposited by the Combustion Chemical Vapor Deposition Process
Authors: Shoup Shara S. , White Marvis K. , Krebs Steve L. , Darnell Natalie , King Adam C. , Mattox Dave S. , Campbell Ian H. , Marken Ken R. , Hong Seung , Czabaj Bolek , Paranthaman M. , Christen Hans M. , Zhai Hong-Ying , Specht Eliot
Published: April 2011

The innovative Combustion Chemical Vapor Deposition (CCVD) process is a non-vacuum technique that is being investigated to enable next generation products in several application areas including high-temperature superconductors (HTS). In combination with the Rolling Assisted Biaxially Textured Substrate (RABiTS) technology, the CCVD process has significant promise to provide low-cost, high-quality lengths of YBCO coated conductor. The CCVD technology has been used to deposit both buffer layer coatings as well as YBCO superconducting layers. A buffer layer architecture of strontium titanate and ceria have been deposited by CCVD on textured nickel substrates and optimized to appropriate thicknesses and microstructures to provide templates for growing PLD YBCO with high critical current density values. The CCVD buffer layers have been scaled to meter plus lengths with good epitaxial uniformity along the length. A short sample cut from one of the lengths enabled high critical current density PLD YBCO. Films of CCVD YBCO superconductors have been grown on single crystal substrates with critical current densities over 1 MA/cm2. Work is currently in progress to combine both the buffer layer and superconductor technologies to produce high-quality coupons of HTS tape made entirely by the non-vacuum CCVD process.
Critical Currents at Grain Boundaries in High Temperature Superconductors
Authors: Agassi D. , Pennycook S. J. , Christenb D. K. , Duscher G. , Franceschetti A. , Pantelides S. T.
Published: April 2011

We present atomic resolution Z-contrast images, electron energy loss spectroscopy (EELS) and theoretical calculations in support of a band-bending model for the effect of grain boundaries on critical currents. In the high angle regime, dislocation cores are closely spaced and the boundary is modeled as a continuous junction, with a width determined by the dislocation density per unit boundary length. This quantitatively explains the approximately exponential reduction in critical current. In the low angle regime, where dislocations are separated by substantial good passages, explicit calculations of flux pinning are presented. Significant differences are found between a strain and band-bending mechanism. Recent data fit the band-bending model and suggest substantial improvement is possible through doping to a flat band condition.
Continuous YBCO – Tape Coating by Thermal Evaporation
Authors: Nemetschek Ralf , Prusseit Werner , Holzapfel B. , Eickemeyer J. , deBoer B. , Miller U. , Maher E.
Published: April 2011

Currently, due to simultaneous large area coating thermal evaporation (TE) allows the highest YBa2Cu3O7 (YBCO) volume deposition rates among various coating techniques. The simultaneous large area deposition translates into long length when the deposition area is closely filled up with metal tape. On short RABiTS samples thermal evaporation has already established critical current densities in excess of 1 MA/cm2 at 77K. Recently, the deposition technique has been scaled up using a multi-turn tape winder for a simultaneously coatable length of 4 meters of 1 cm wide tape. The reel to reel tape deposition system is designed for long term operation based on a vapor composition control by atomic absorption spectroscopy and in situ refillable evaporation sources. In the initial setup phase the system has been able to reproduce the above results on small samples. The first results on continuously moving tape substrate coating up to a length of several meters will be reported.
Effect of Sulfur Surface Structure on Nucleation of Oxide Seed Layers on Textured Metals for Coated Conductor Applications
Authors: Cantoni C. , Christen D. K. , Goyal A. , Heatherly L. , Ownby G. W. , Zehner D. M. , Norton D. P. , Rouleau C. M. , Christen H. M.
Published: April 2011

We present a study of the {100}<100> biaxially textured Ni (001) surface and oxide seed layer nucleation by in situ reflection high-energy electron diffraction and Auger electron spectroscopy. Our observations revealed the existence of a c(2×2) superstructure on the textured Ni surface due to segregation of sulfur contained in the bulk metal. The sulfur superstructure promotes the epitaxial (002) nucleation of seed layers such as Y2O3-stabilized ZrO2 (YSZ) and CeO2 on the metal and optimizes the biaxial texture necessary for high Jc superconductors on RABiTS.
Pattern Shape-Controlled Self-Assembly of Bi0.90Si0.10 Nanocrystallites
Authors: Fang Jiye , Stokes Kevin L. , He Jibao , Zhou Weilie L. , O'Connor Charles J.
Published: April 2011

Nanometer-sized Bi0.90Sb0.10 has been, for the first time, prepared using a hightemperature organic solution reducing method. With the presence of proper capping and stabilizing agents, we were able to produce Bi0.90Sb0.10 nanoparticles as small as ∼12 nm. Nearly monodisperse distributions were obtained through a size-selective post treatment. Transmission electron microscope characterization reveals that the as-prepared particles have a highly crystalline single rhombohedral phase. Self-assembled patterns of Bi0.90Sb0.10 were successfully achieved upon evaporation of the solvent from the nanoparticle colloids. As a step toward possible applications of these particles in thermoelectric device structures, we have also demonstrated that we are able to control the pattern of Bi0.90Sb0.10 self-assembly from 2D to 1D by employing different solvent systems with varying ratios of polar and non-polar components.
Annealing Studies of Re Doped AlPdMn Quasicrystals
Authors: Winkler Donny W. , Tritt Terry M. , Gagnon Robert , Strom-Olsen J.
Published: April 2011

Quasicrystals have properties associated with both crystalline and amorphous materials. These properties appear to be sensitive to both composition and annealing conditions. Therefore, it is important to investigate the influence of the microstructure on the electrical and thermal transport properties of quasicrystals. AlPdMn quasicrystal samples were prepared with various levels of Re substituted for the Mn (Al70Pd20Mn10−XReX) and then subjected to different annealing conditions. Electrical resistivity, thermopower and thermal conductivity were measured on each as grown and annealed sample over a broad range of temperature, 10 K < T < 300 K. The relationship between the electrical and thermal transport properties and microstructure will be presented and discussed.
Enhancement of Thermal to Electrical Energy Conversion with Thermal Diodes
Authors: Hagelstein P. L. , Kucherov Y.
Published: April 2011

Experiments demonstrating thermal to electrical energy conversion using thermal diodes have shown an enhancement of the open circuit voltage over the thermoelectric open circuit voltage. Two different physical mechanisms are proposed to be responsible for the effects seen: (1) Thermionic injection from the emitter can occur when a temperature gradient is present, which induces an increased ohmic return current under zero-current conditions. (2) Blockage of the ohmic return current leads to a voltage increase for both thermoelectric and thermionic forward currents. Both effects increase the efficiency of energy conversion. Experiments show enhancements of the figure of merit in the range of 5-8 over the thermoelectric values. The best results are consistent with a single-side conversion efficiency in excess of 30% of the Carnot limit.
Electronic Structure and Thermoelectric Property of Skutterudite CoSb3
Authors: Koga Kenji , Akai Koji , Oshiro Kazunori , Matsuura Mitsuru
Published: April 2011

Electronic structure of CoSb3 is calculated by means of full-potential linearlized augmented plane wave (FLAPW) method with the generalized gradient approximation (GGA). The calculated band gap of CoSb3 with the consideration of spin-orbit (SO) interaction is 110meV, which is about a half of that without SO interaction. It is found that simple four bands model with the Kane's nonparabolic valence and conduction bands, two parabolic conduction bands describe calculated electronic structure near band edge very well. Using the simple four bands model, thermoelectric properties are calculated and are discussed. Larger band gap, e.g., Eg=200meV with the microscopic mechanism such as phonon scattering yields a fair agreement with the experiment in a wide range of temperature.
Kinetic Monte Carlo Simulations of Dislocation Etch-Pits
Authors: Bentz Daniel N. , Jackson Kenneth A.
Published: April 2011

Chemical mechanical polishing and stress corrosion cracking result from chemical attack at stressed regions. To better understand the combined effects of chemical attack and stress, a kinetic Monte Carlo (kMC) study of the formation of dislocation etch pits is being pursued. In the simulations, atoms from a diamond cubic lattice are irreversibly removed with a probability which depends on an atom's number of nearrest neighbors as well the local stress developed from its physical location with respect to a dislocation in the lattice. In accordance with experimental observations, both faceted and non-faceted dislocation etch-pits have been observed. Simulations have been performed for various values of the strength to the etchant attack and the magnitude of the stress produced by the dislocation.
Novel Preparation Method of Thin Films by Ablation Plasma produced by Intense Pulsed Ion Beam Evaporation
Authors: Yatsui Kiyoshi , Suematsu Hisayuki , Jiang Weihua , Suzuki Tsuneo , Yang Sung-Chae , Kinemuchi Yoshiaki , Hirai Makoto , Kato Keizo
Published: April 2011

A novel preparation method of thin films has been successfully developed by high-density ablation plasma produced by pulsed ion-beam evaporation method. The preparation is available with extremely high deposition rate (with cm/s), without heating the substrate, in a vacuum, with good stoichiometry. As an example, the preparation of phosphoresecent SrAl2O4:Eu, Dy thin films will be shown. Furthermore, a new method has been developed of the synthesis of ultrafine nanosize powders by use of microexplosion of pulsed wire discharge. As an example, the synthesis of NiFe2O4 powders will be shown, where two wires of nickel and iron were exploded by pulsed current. In addition, we have succeeded in the preparation of tungsten thin films within via holes in LSI by use of pulsed ion beam-evaporation method. In addition to the huge power per shot, a new machine has been developed of highly repetitive, pulsed power machine for the industrial applications.
Fabrication of CaO Insulator Coatings by MOCVD for Application in Fusion Reactor Blankets
Authors: Zeng Z. , Natesan K.
Published: April 2011

The liquid lithium blanket for fusion reactors requires an electrically insulating coating on the duct to minimize the magnetohydrodynamic pressure drop that occurs during the flow of liquid metal in a magnetic field. Calcium oxide (CaO) is a good candidate for the coating material because it is an excellent electrical insulator and it is stable in a liquid lithium environment. In this paper, details are presented on metalorganic chemical-vapor deposition method that was used to fabricate the CaO coating. Composition and phase analyses of the coating were performed by energy dispersive X-ray analysis and X-ray diffraction. Scanning electron microscopy images show that the coating did not crack after several thermal cycles from room temperature to 715°C. The resistance of the coating is high enough for an insulating coating on the liquid lithium blanket of fusion reactors.
Formation and Conductive Properties of Miniaturized Fullerite Sensors
Authors: Berdinsky Alexander S. , Fink Dietmar , Petrov Alexander V. , Müller Manfred , Chadderton Lewis T. , Chubaci Jose F. , Tabacniks Manfredo H.
Published: April 2011

Fullerite nanotubules of 100 nm to 2 μm radius, up to 200 nm wal thickness and 10 μm length were produced inside etched swift heavy ion tracks in a polymer, by letting fullerence precipitate from a concentrated C60 solution within the tracks. After contacting the tubules on both sides with silver paste, their resistivity was measured as a function of temperature. All of the 13 prepared samples show a complex behaviour that can be described by tw Arrhenius curves, the low temperature branch with activation energy Eact = (1.77 ± 0.2) eV stemming from pure C60, and the high temperature branch being tentatively ascribed to C60Agx with x ≍ 12.4 and Eact = (0.68 ± 0.2) eV, as the letter compound has found to be produced at ambient temperature by C60 / Ag thermal intermixture. Such samples with tw branches of negative temperature coefficients of resistance might be useful to construct advanced thermoresistors.
Building Two and Three-dimensional Structures of Colloidal Particles on Surfaces using Optical Tweezers and Critical Point Drying
Authors: Vossen Dirk L. J. , Hoogenboom Jacob P. , Overgaag Karin , Blaaderen Alfons van
Published: April 2011

We describe a method for patterning substrates with colloidal particles in any designed two-dimensional structure. By using optical tweezers particles are brought from a reservoir to a surface that carries a surface charge opposite to that of the particles. Using this technique large, two-dimensional patterns can be created, where the pattern can be manipulated on a single particle level. We show that these structures can be dried using critical point drying thus preventing distortions due to surface tension forces. After drying patterned surfaces can be used for further processing, which includes repeating the procedure of patterning. We show some first results of three-dimensional structures created using this layer-by-layer method. The method is generally applicable and has been demonstrated for a variety of (core-shell) colloidal particles including particles that are interesting for photonic applications like high-refractive index (ZnS)-core – silica shell particles, metallodielectric (gold)-core – silica-shell particles, fluorescently labeled particles and small (several nanometers large) gold particles. Particle sizes used range from a few nanometers to several micrometers.
Patterned Nanoparticle Assembly as Novel Chemical and Biological Platforms
Authors: Maye M.M. , Luo J. , Han L. , Kariuki N. , Zhang F.X. , Zhong C.J.
Published: April 2011

The ability to self-assemble nanoparticles into thin films and subsequently characterize the structural or morphological responses to interfacial chemical/biological reactivity is increasingly important. Surface patterning and tailoring us ing nanoparticle assemblies are expected to provide such abilities for selective immobilization and chemical and biological recognition. We describe herein recent results of an investigation of hydrogen-bonding based self-assembly of core-shell nanoparticles onto monolayer-patterned surfaces, and its potential utility for in-situ atomic force microscopic characterizations of interfacial chemical and biological reactivities. This system is potentially useful for immunoassays based on topographical height changes with well-defined internal morphological standard.
Investigation of the Temperature-Dependent Surface Morphology of p-Sexiphenyl Thin Films on KCl(001)
Authors: Kintzel E.J. , Gillman E.S. , Skofronick J.G. , Safron S.A. , Smilgies D.-M.
Published: April 2011

Investigation into the temperature dependence of the surface morphology of a thin film of p-sexiphenyl (p-6P) on KCl(001) was carried out by atomic force microscopy (AFM). An individual p-6P film was prepared by vapor deposition at a base pressure of ∼1x10-8 mbar onto a KCl(001) surface which was maintained at 323 K during deposition. The AFM was carried out in a separate vacuum chamber, in situ, at a base pressure of ∼1x10-6 mbar. The p-6P film was cooled and maintained at discrete temperatures in the range from 294 K to 128 K as AFM measurements were performed. Similar surface morphologies are observed for film temperatures maintained at 294, 264, and 227 K, and 188 and 128 K during the AFM measurements. AFM images for the first set of film temperatures (294 - 227 K) indicate the presence of block-like islands of p-6P, with well-defined crystallite boundaries. AFM images of the films in the second set (188 and 128 K) indicate the presence of triangular wedge-shaped structures of p-6P preferentially aligned nearly in the direction of the [110]KCl. Comparison of these wedge-shaped structures at the indicated film temperatures reveals they are rotated by approximately 180° with respect to each other. Subsequent images of the surface of the p-6P film captured again at 294 K, after the final 128 K temperature study was completed, revealed the same surface features found for the initial 294 K film temperature.
Rigid Optical Chromophore: The Photophysical Properties of p-Phenylene Benzobisthiazole Derivative
Authors: Lee Seung-Hwan , Otomo Akira , Nakahama Tatsuo , Yamada Toshiki , Yokoyama Shiyoshi , Mashiko Shinro
Published: April 2011

A novel rigid and planar chromophore, p-phenylene benzobisthiazole unit with donor and acceptor groups, has been synthesized for second-order nonlinear optical applications. The first hyperpolarizability, β, of the nonlinear optical (NLO) chromophore has been measured by a Hyper-Rayleigh Scattering technique at 1064 nm in 1,1,1,3,3,3-hexafluoro-2-propanol solution. The β value of the NLO chromophore is 405E-30 esu, which is about seventeen times that of the p-NA (nitroaniline) value. The chromophore showed good thermal stability up to 330 °C in nitrogen atmosphere.
Theoretical Study of The Luminescence Effects in Trinuclear Silver Organometallic Compounds
Authors: Salcedo Roberto , Sansores L. Enrique , Martínez Ana
Published: April 2011

The luminescence and related phenomena of a trinuclear silver organometallic complex has been studied from a theoretical viewpoint (B3LYP/6-31G* level). The study takes into account the relation between this compound and the [Au(CH3N=COCH3)3] that has been characterised and studied on the base of its solvoluminescence behaviour.
Line Shape Analysis of Photoluminescence Spectra on Solutions of MD-PPV
Authors: Santos L. F. , Marconi F.M. , Bianchi R.F. , Marletta A. , Nunes L. A. O. , Faria R. M. , Balogh D.T.
Published: April 2011

In this work, we study the influence of organic solvents on the absorption and emission spectra of solutions and films of a soluble poly-(p-phenylenevinylene)- PPV derivative, the poly(3-methoxy-5-dodecoxy-p-phenylene-vinylene)- MD-PPV. We carried out absorption in the UV-Vis range, photoluminescence (PL) and photoluminescence excitation (PLE) measurements of MD-PPV solutions and cast films from five different solvents at room temperature. UV-Vis measurements show a solvatochromic effect, presenting a blue shift of the lowest-energy edge of the φ-φ* transition band for different solvents. PL spectra, on the other hand, show a multi-peak behavior, which is fitted considering an excitonic transition model followed by vibronic structure replica. It is observed that the first vibronic peak intensity tends to increase in comparison to the excitonic peak as δH increases, indicating that the solubility parameter of the solvent has a direct influence on the electron-phonon coupling. In addition, deviations from the intrachain model were observed for aromatic solvents, suggesting that aggregate formation can take place in the emission spectrum. Excitation spectra show that a new excitation peak comes out around 550 nm for poorer solvent solutions at higher PLE detection wavelengths, which is consistent with aggregate states emission.
Resonant Tunneling and the Substituent Effect on Negative Differential Resistance in a Molecular Junction
Authors: Matsunaga Nikita , Sohlberg Karl
Published: April 2011

Recently there has been an explosion of interest in the potential use of individual molecules as electronic device elements. The electrical characteristics of molecular junctions, individual molecules spanning the gap between two metal electrodes, have been reported and certain molecular species have been found to exhibit highly nonlinear current versus applied-voltage (I/V) properties. Intriguingly, these nonlinearities (pronounced peaks) in the I/V behavior are extremely sensitive to the functionalization of the molecule forming the junction. The substitution of a single functional group can completely eliminate the nonlinear behavior. Many have suggested that resonant tunneling could lead to the observed nonlinearities. Resonant tunneling requires a double potential barrier along the electron transfer coordinate. We propose a possible physical origin for such a double potential barrier and support the model with first principles electronic structure calculations. Next we discuss a quantum mechanical tunneling model for electron transport through the double potential barrier. The model gives insight into the origin of nonlinear I/V behavior in molecular junctions and the effect of substituent functional groups on the junction molecule.
The Precursor Polymer Approach to Electrodeposition and Patterning of Conjugated Polymer Ultrathin Films
Authors: Advincula Rigoberto , Xia Chuanjun , Taranekar Prasad , Deng Suxiang , Onishi Ken
Published: April 2011

In this paper, we report strategies for electrodepositing and patterning ultrathin films of conjugated polymers on flat electrode surfaces using the precursor polymer approach. This involves a rational synthesis design of the precursor polymer followed by careful electrodeposition and characterization of ultrathin films on conducting substrates. This has resulted in the preparation of smooth, high optical quality films, which should be important for applications involving flat electrode surfaces in devices. Characterization was made using surface sensitive spectroscopic and microscopic techniques. Copolymerization with monomers, polymer backbone design, and grafting on modified surfaces are key points in this strategy. Novel methods of in-situ characterization techniques have also been developed combing electrochemistry and surface plasmon resonance techniques.
Thermo-optical switches using coated microsphere resonators
Authors: Tapalian C. , Laine J.-P. , Lane P. A.
Published: April 2011

We report optical switching by a silica microsphere optical resonator coated by a conjugated polymer. Microspheres were fabricated by melting the tip of an optical fiber and coated by dipping in a 1 mg/ml toluene solution of poly(2,5-dioctyloxy-1,4-phenylenevinylene) (DOOPPV). The resonator properties were characterized by evanescently coupling 1.55 μm light propagating along a stripline-pedestal anti-resonant reflecting optical waveguide into optical whispering gallery modes (WGMs). WGM linewidths less than 2 MHz were measured, corresponding to cavity Q > 108. WGM resonant frequency shifts as large as 3.2 GHz were observed when 405 nm pump light with a power density of ∼100 mW/cm2 was incident on the microsphere. The time constant of the observed frequency shifts is approximately 0.165 seconds, leading us to attribute the frequency shift to thermo-optic effects. Such a system should be capable of thermo-optically switching at speeds on the order of 10 kHz.
Radionuclide Uptake and Transport on Microbes in Potential Repository Drifts at Yucca Mountain, Nevada
Authors: Jolley Darren M.
Published: April 2011

Radionuclide adsorption onto microbes, microbial retention in the engineered barrier system (EBS), and their potential release from the EBS as microbial colloids have been investigated. The microbial source term for these calculations was derived using MING V 1.0 software code [1]. Multiple model calculations from MING representing variations in possible microbial communities in the EBS were abstracted into two equations representing one meter segments of potential repository drift containing either commercial spent nuclear fuel (CSNF) or defense high level waste (HLW) packages. These two equations (Equations 1 and 2) represent the average cumulative microbial biomass generated in the EBS at any given time. A distribution for uranium uptake onto microbes (162.88 ± 133.05 mg U/gm dry cell) was applied to the microbial source term. The distribution was derived from the data set in Suzuki and Banfield [2] representing 45 different species of bacteria and fungus, covering uranium uptake at optimum pH values of 1 to 7. The mass of uranium sorbed onto the biomass was either sequestered in the EBS or transported as a microbial colloid based on a regression of data from Jewett et al. [3] representing microbial sorption onto air-water interfaces in unsaturated column experiments. Over one million years, it is estimated that EBS microbes may adsorb from 77 to 2302 kg of uranium [2302 kg U > 100% of the uranium available in a one meter segment of a CSNF waste package] per meter of waste package depending on the saturation of the invert and type of waste package. Over the same time, microbial colloids may transport from 8 to 1250 kg of adsorbed uranium per meter of waste package from the EBS.
Characterization and Dissolution of ZrTh3UO10 and Th3UO8 Ceramics
Authors: Curran Gini , Sevestre Yoann , Rattray Wendy , Allen Patrick G. , Czerwinski Ken R.
Published: April 2011

Thoria-urania-zirconia ceramics were studied in order to investigate the long-term behavior of potential thorium fuels in a repository environment. The ceramics were prepared by coprecipitation of the metal salts. Zirconia was added to determine if further stabilization against dissolution of the thoria-urania system could be achieved. In addition, 0.5 wt% MgO was added to some samples to increase stability and density. The inclusion of Zr in the ceramics did not dramatically decrease the leaching of thorium from the matrix.

Material properties of the ceramic were analyzed using electron microscopy techniques such as Energy Dispersive X-ray (EDX) analysis and Electron Energy Loss Spectroscopy (EELS). X-ray diffraction and synchrotron-based x-ray absorption studies including extended xray fine structure (EXAFS) and x-ray absorption near edge spectroscopy (XANES) were also used to reveal elements of the phase structure and chemistry of the ceramics. X-ray diffraction (XRD) and EDX show that these ceramics separate into a zirconium-based phase and an actinide-based phase with low mutual affinity of thorium and zirconium, as well as partial solubilization of uranium in zirconium. The comparison of EELS spectra collected for the ceramics with spectra collected for UO2 and U3O8 reference materials also allow the assessment of uranium oxidation state independently in the two separate phases. Assessment of the bulk oxidation state using XANES correlated well with the EELS analysis. Interatomic distances and the bulk crystal structure were determined using EXAFS.
Depleted Uranium Dioxide Waste Package for Spent Nuclear Fuel
Authors: Forsberg Charles W. , Dole Leslie R.
Published: April 2011

Depleted uranium dioxide (DUO2) waste packages (WPs) for disposal of spent nuclear fuel (SNF) are being investigated to (1) reduce radionuclide releases from WPs, (2) decrease the potential for repository nuclear criticality events, (3) provide radiation shielding, and (4) provide a means to beneficially use excess depleted uranium (DU). The DUO2 is incorporated into the WP as (1) a particulate fill for void spaces within the package and (2) a component of a DUO2-steel cermet (DUO2 embedded in steel) that replaces the steel components of the WP. Depending upon the design, there is 3 to 8 times as much DUO2 as SNF UO2 in the WP. Most radionuclides in the SNF cannot be released until the UO2 crystal structure is destroyed. The DUO2 surrounding the SNF slows the degradation of the SNF UO2 in the interior. This behavior is similar to the mechanisms that slow the degradation of natural uranium ore bodies containing UO2. The results of initial investigations and the expected thermodynamic WP behavior are described.
Neptunium Incorporation into Uranium(Vi) Compounds formed During Aqueous Corrosion of Neptunium-Bearing Uranium Oxides
Authors: Finch Robert J. , Fortner Jeffery A. , Buck Edgar C. , Wol Stephen F.
Published: April 2011

We report results of experimental studies on the behavior of Np during aqueous corrosion of unirradiated Np-bearing U oxides. Np-doped U oxides were reacted in humid air at 90°C and 150°C for several weeks within sealed stainless-steel vessels. Reacted solids were examined by scanning and transmission electron microscopies (SEM and TEM), electron energy-loss spectroscopy (EELS), and X-ray powder diffraction (XRD). Dehydrated schoepite, (UO2)O0.25-z(OH)1.5+2z (0 ≤z ≤0.15), is the predominant U(VI) compound formed in these experiments. Preliminary EELS analysis on crushed grains verify that dehydrated schoepite formed at 150°C contains up to approximately 2 wt.% Np, corresponding to a maximum Np:U molar ratio of approximately 1:40. These are maximum values because the degree to which surface-sorbed Np is present on the grains analyzed is not yet known. Crystalline NpO2 also precipitated during these experiments, and the concentration of Np in dehydrated schoepite may represent the maximum amount of Np that can be incorporated into dehydrated schoepite under the experimental conditions.