bluuebunny/crossref_metadata_2025 huggingface dataset:
The interaction of C60 with Si(111) and Co/Si(111)
Authors: Zilani M.A.K. , Xu H. , Wang X.S. , Wee A.T.S.
Published: April 2011

We have studied the interaction of C60 with clean Si(111) and sub-monolayer Co covered Si(111) using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Our STM results indicate that C60 has little mobility at room temperature (RT) on Co/Si(111). After annealing to 450 °C, STM images show a regular arrangement of partially decomposed C60. XPS reveals a partial decomposition of C60 on Co/Si(111) at 520 °C, and total decomposition to form a SiC-3×3 phase at 720 °C. These results show that Co catalyses C60 decomposition resulting in the formation of the ordered SiC-3×3 phase ∼200 °C below that on clean Si(111).
Study by Weak Beam and HRTEM of double stacking faults created by external mechanical stress in 4H-SiC
Authors: Idrissi Hosni , Lancin Maryse , Douin Joel , Regula Gabrielle , Pichaud Bernard , Bouayadi Rachid El , Rousse Jean-Marc
Published: April 2011

4H-SiC samples are bent in compression mode at 550°C and 620°C. The introduced-defects are identified by Weak Beam and HRTEM techniques. They consist of double stacking faults bounded by 30° Si(g) partial dislocations whose glide locally transforms the material in its cubic phase. The velocity of partial dislocations is measured after chemical etching of the sample surface. The formation and the expansion of the double stacking faults are discussed.
Investigation of the influence of different copper slurry systems on post CMP topography performance
Authors: Springer Goetz , Thieme Peter , Klose Pierre
Published: April 2011

Since the early days of copper CMP much research and development effort was put into formulation of new copper and barrier CMP slurries. Two major motivations for this effort are the improvement of process performance for currently used integration schemes and the preparation for new integration schemes using low-k and ultra low-k dielectric materials. In this paper a systematic procedure for topography investigation after copper and barrier CMP is presented. The procedure is applied to four different copper slurries in order to compare after copper and after barrier CMP topography performance. As a result of the post copper CMP topography investigations, a discussion of advantages and disadvantages of non-selective and selective barrier polish processes will be presented. To complete the discussion of potential topography correction during barrier CMP, an investigation of an observed pronounced dielectric erosion close to large metal features or within high metal density arrays with medium or high selective barrier CMP processes will be presented.
Novel Pure Organic Particles for Copper CMP at Low Down Force
Authors: Cheemalapati K. , Chowdhury A. , Duvvuru V. , Lin Yong , Tang Kwok , Bian Guomin , Yao Lily , Li Yuzhuo
Published: April 2011

It is generally accepted that there is a minimum hardness requirement for abrasive particles to be used in CMP (Chemical Mechanical Polishing) slurries. For copper CMP, the common abrasives are various types of alumina and silica. It has also long been suspected that a softer organic based abrasive could significant reduce the defects during polishing. In this study, for the first time, we demonstrated the usefulness of an organic particle as abrasive in formulating copper CMP slurry. The unexpected consequence of using such soft hydrophilic particles is its low sensitivity of material removal rate for copper towards polishing down force and platen speed. In addition, due to its unique particle surface properties, the slurry gives high selectivity in removal rate for copper over barrier, cap, and dielectric materials. In this paper, some basic physical and chemical characteristics of the particles and slurry will be first presented. The performance of this new slurry in relation to conventional slurries on blanket and patterned wafers will be discussed.
Effect of Nano-Size Silica Abrasives in Chemical Mechanical Polishing of Copper
Authors: Jung Su-Ho , Singh Rajiv K.
Published: April 2011

The effect of nano-size silica abrasives in chemical mechanical polishing (CMP) of copper is studied in order to reduce mechanical stresses during polishing, which may minimize defects such as surface scratches, copper peeling, dishing and erosion. In order to achieve low stress polishing of copper while maintaining removal rate efficiency, the formation of chemically modified surface layer, which can be mechanically removed by small size and low hardness abrasives, is critical. Complexing agents play an important role in the formation of a removable surface layer in the presence of the oxidizer, which is responsible for oxide formation, and the inhibitor, which passivates the surface. A new removal mechanism is proposed by correlating results of surface roughness after polishing with removal and etch rates. The effects of large silica and alumina abrasives, ranging from 200-1000 nm in diameter, are also studied to compare the different removal mechanisms.
A Model of Cu-CMP
Authors: Paul Ed , Brusic Vlasta , Sun Fred , Zhang Jian , Vacassy Robert , Kaufman Frank
Published: April 2011

CMP has been described qualitatively in terms of alternating cycles of chemical formation and mechanical removal of a thin layer on the wafer surface. A quantitative model of CMP has been developed2-7 which is based on mechanisms for surface kinetics, treating mechanical removal as one step in the mechanism. This model has been used successfully to explain removal rates for tungsten and thermal oxide CMP. In particular, for tungsten CMP the removal rate increases steeply with increasing oxidizer concentration at low concentrations, and then approaches an asymptotic maximum removal rate at high concentrations. The model explains this by starting with the assumption that mechanical abrasion removes only tungsten oxide but not tungsten metal. It then focuses on the fraction of wafer surface covered by a tungsten oxide layer. At low oxidizer concentrations, the oxide formation rate is small compared the removal rate, so only a small fraction of the surface is oxidized and the removal rate is small. At high oxidizer concentrations, the oxide formation rate is large compared to the removal rate, so most of the surface is oxidized and the removal rate is large. Increasing the oxidizer concentration in the high oxidizer concentration region does not significantly increase the surface fraction of tungsten oxide, and the removal rate approaches a constant value.
Polish profile control using magnetic control head
Authors: Tsujimura Manabu , Ishii Yu , Kimura Norio , Ota Masahiro
Published: April 2011

Magnetic bearing technology is widely used in various technical fields, and is particularly appreciated in the semiconductor industry, where it is applied to the turbo molecular pump and wafer transfer system due to the excellent controllability it provides, even at speeds as high as 50,000 rpm. This report discusses the adoption of magnetic bearing technology to control the wafer carrier tilt angle during polishing. When the wafer is polished on a viscoelastic pad, the wafer carrier is inclined and pressed into the pad. Therefore, the reaction force on the wafer from the pad is concentrated at the wafer edge, increasing the polish rate at the edge relative to the rest of the wafer. Modification of the tilt angle is thought to offer a possible means of normalizing the distribution of the reaction force from the pad and correcting the nonuniformity of the polish rate. The wafer carrier was confirmed to press slightly into the pad and to be tilted 18 × 10-5 rad by the viscoelasticity of the pad (without tilt angle control). Constant current control led to better control of the polish rate profile relative to feedback control. The polish rate in the outer area of the wafer was increased by tilting the carrier to the positive side, and the polish rate of the wafer center area could be reduced by tilting it to the negative side. The best profile was obtained with control current of Im = -0.4 A. When the wafer carrier was tilted in the reverse direction, the polish rate became almost zero. It was concluded that hydro-planing occurred between the wafer and the pad. Accordingly, this report demonstrates the possibility of improving the polish rate profile by maintaining the wafer carrier in a horizontal position using magnetic control.
Modeling of Pattern Density Dependent Pressure Non-Uniformity at a Die Scale for ILD Chemical Mechanical Planarization
Authors: Choi Jihong , Dornfeld David A.
Published: April 2011

Local material removal rate is inversely proportional to the local pattern density in ILD CMP. With the assumption that the local velocity and Preston coefficient are constant across a chip, local MRR non-uniformity is mainly attributed to the local pressure non-uniformity. Pressure distributions on two different test patterns consisting of five different pattern density sections were obtained with a finite element model. These pressure distributions were compared with output from a semi-empirical pattern dependent oxide CMP model (MIT model) with three different weighting functions. Result showed that pressure distribution could be well approximated with the pattern density dependent oxide CMP model. This FEM model was further taken to evaluate the effects of thickness and material properties of each layer on the degree of pattern dependant pressure non-uniformity at a die scale for a typical polishing pad made up of a hard and a soft layer. The analysis shows that the degree of pressure nonuniformity at a die scale increases with the combination of a stiff hard layer and a thick soft layer, while it decreases with the combination of a stiff soft layer and a thick hard layer.
Advances in the CMP Process on Fixed Abrasive Pads for the Polishing of SOISubstrates with High Degree of Flatness
Authors: Kulawski Martin , Luoto Hannu , Henttinen Kimmo , Suni Ilkka , Weimar Frauke , Mäkinen Jari
Published: April 2011

The new approach using Fixed Abrasive (FA) pads for polishing thick film Silicon-on- Insulator (SOI) wafers after bonding and grinding process [1] has been further developed. The aim is a practicable industrial manufacturing process, where the major specifications especially in long term stability and removal rate should be achieved. In base line studies a stable removal rate on suitable level has been reached, while the degeneration of the total thickness variation (TTV) was limited to a clearly smaller value than that being typical for the standard stock removal polishing. The overall removal in these tests was adjusted to 2-3 μm, which removes all sub surface damage (SSD) from wafers ground by ultra fine grinding wheels with very small average abrasive particle size. The process has been able to remove all visible grindlines after removing less than 1.5 μm. In another test with a further developed high density FA pad, removal rates up to ∼0.6 μm/min were achieved. The polished samples were further processed and characterized by capacitive thickness measurements gauges, optical surface inspection tool (“Magic mirror”), atomic force microscopy (AFM) and optical reflection measurements.
Pad Asperity Parameters for CMP Process Simulation
Authors: Yoshida Takafumi
Published: April 2011

This paper reviews the contact mechanics between the surface of a wafer and the asperity of the polishing pad for CMP from basic asperity such as spherical, rectangular, and conical shapes to more general asperity with a height distribution. This paper also proposes a practical method to bridge a measured profile of pad asperity in microscopic scale to a set of simple parameters which describe the elastic behavior for CMP process simulation in larger scale. We show a scalable CMP simulation using the proposed pad asperity parameters.
Assessment of Planarization length variation by the Step-Polish-Response (SPR) Method
Authors: Bartha Johann. W. , Bormann Tilo , Estel Kathrin , Zeidler Dieter
Published: April 2011

In spite of the fact, that the main purpose of CMP is the planarization of surfaces, most processes are optimized with respect to the removal rate. This might be due to a lack in techniques for the determination of the planarization behavior. The commonly used expression “Planarization Length” implies a maximum lateral extension over which the planarization is obtained and which can not be improved. Several attempts have been made to determine the planarization length by studying the CMP on different test patterns. The general problem in the interpretation of the data is the interaction of neighboring pattern with different pattern densities. This problem does not apply to the most simple pattern possible, which is a single step with an extension of the up and down areas much larger than the planarization length. In this case the spatial derivative of the resulting contour after CMP is directly the demanding transfer function to be used for the convolution. This concept, initially proposed by Boning et. al., was applied to evaluate the polish of copper and silicon oxide. Wafers with concentrically steps in Cu or SiO2 films with an extension of 1 to 5 cm have been prepared. During polish, the initially infinite steep step widens up, yielding the planarization length as a function of the removal respective the polishing time. Significant differences in the evaluation of the planarization length could be quantified depending on the pad, slurry and tool parameters. Our first experiments revealed a decrease in planarization length by the addition of BTA in a copper slurry. We believe that the SPR method enables a unambiguous, pattern independent determination of the planarization capability in CMP.
Quantum confinement effect of silicon nanocrystals in situ grown in silicon nitride films
Authors: Kim Tae-Youb , Park Nae-Man , Kim Kyung-Hyun , Ok Young-Woo , Seong Tae-Yeon , Choi CheolJong , Sung Gun Yong
Published: April 2011

Silicon nanocrystals were in situ grown in a silicon nitride film by plasma enhanced chemical vapor deposition. The size and structure of silicon nanocrystals were confirmed by high-resolution transmission electron microscopy. Depending on the size, the photoluminescence of silicon nanocrystals can be tuned from the near infrared (1.38 eV) to the ultraviolet (3.02 eV). The fitted photoluminescence peak energy as E(eV) = 1.16 + 11.8/d2 is an evidence for the quantum confinement effect in silicon nanocrystals. The results demonstrate that the band gap of silicon nanocrystals embedded in silicon nitride matrix was more effectively controlled for a wide range of luminescent wavelengths.
Electro-Optical Properties of Na0.5K0.5NbO3Films on Si by Free-Space Coupling Technique
Authors: Grishin Alexander M. , Khartsev Sergey I.
Published: April 2011

We report electro-optic performance of highly polar axis oriented Na0.5K0.5NbO3(NKN) films grown directly on Pt(100nm)/Ti(10nm)/SiO2/Si(001) substrates by rf-magnetron sputtering. Semitransparent gold electrodes (diameter Ø= 2 mm) were deposited ontop the NKN films by a thermal evaporation through the contact mask. Processing parameters have been specially optimized to obtain “electrosoft” NKN films with a non-linear fatigue-free P-E characteristics: low remnant Pr = 3.6 μC/cm2 and high induced polarization P = 26 μC/cm2 @ 522 kV/cm, and the coercive field Ec= 39 kV/cm. Electro-optical characterization of NKN/Pt/Si films has been performed using waveguide refractometry: a free-space coupling of a light beam into the thin-film waveguide modes. Intensity of TM- andTE-polarized light of 670 nm laser diode reflected from the free surface of NKN film and Au-cladding NKN/Pt/Si waveguide was recorded at zero and 30 V (100 kV/cm) bias electric field. Extraordinary and ordinary refractive indices as well as electro-optic coefficient have been determined by fitting these experimental data to the Fresnel formulas. Applying 160 V (530 kV/cm) across the parallel plate NKN capacitor (Ø= 2 mm, thickness 3 μm), modulation of the reflected light as high as 40% was achieved.
Carbon Layer as a New Material for Optics
Authors: Clergereaux R. , Escaich D. , Martin S. , Raynaud P. , Gaillard F.
Published: April 2011

Plasma enhanced CVD produces carbon layers with various properties which are highly correlated to the different process parameters such as monomer structure, plasma type or plasma power. For example, the modification of monomer (CH4 to C4H10) or the plasma source and the increase of plasma power lead to an optical band-gap which runs from 0.9 to 4.3eV, a conductivity from 5·103 to 5·105S.m−1 and a refractive index from 1.47 to 2.76. Then, it is able to control the optical and electrical film properties from the external process parameters. This paper will thus be focused on the description of relation between deposition parameters, structural characteristics of material and film properties. These materials can then be used for optoelectronics applications.
The characteristics of joints with Indium-silver alloy using diffusion soldering method
Authors: Kim Je Yoon , Park Sang Won , Yoon Jee Young , Kim Hwa Young , Lee Dae Yeon , Kim Gyu Tae , Sung Man Young , Kang Ey Goo
Published: April 2011

Bonding process using indium-silver alloy which can withstand high temperature was investigated at relatively low temperature. We used a thermal evaporator and vacuum coater for making indium-silver contact. From the result of experiment, we observed that indium and silver films which have good quality are formed. From phase diagram of In-Ag alloy, we can find that melting point of these compounds increases with the silver content, i.e. eutectic (144° C) <AgIn2 (166° C) < (300° C) < (670° C) < (695° C). And these compounds are determined by the composition ratio of the source metal. Now we confirmed the thermal characteristics of Indium-Silver alloy is controlled by silver. Consequently we have developed Ag/In/Ag multi-layer composite which has higher melting point than that of normal contact. The melting point of Ag/In/Ag multi-layer is about 700° C. The joint cross-sections are studied using SEM(scanning electron microscopy) and EDX(Energy Dispersive X-rays). From these data, we observed that the composition and microstructure of Ag/In/Ag multi-layer were reliable and this bonding procedure is a better technique compared to the conventional structure of quantum well LED and GaN/Si LED structure was made by using sapphire for substrate and might be good for high temperature electronic devices in the future.
White-Light Emitting Diode through Ultraviolet InGaN-pumped Sr2Si1−xGexO4 : Eu2+ phosphors
Authors: Kim J.S. , Jeon P.E. , Kim W.N. , Choi J.C. , Park H.L. , Kim G.C.
Published: April 2011

The Sr2Si1−xGexO4 : Eu2+ phosphors are formed by means of a new synthesis method. The Sr2Si1−xGexO4 : Eu2+ have the mean particle size of 200 nm and the spherical shape. The Sr2Si1−xGexO4 : Eu2+ show two emission colors : the blue color of 480 nm and the green color of 525 nm. The intensity of green band with respect to blue band is significantly decreased in comparison with that of solid-reacted bulk sample, described by the hindrance of the energy transfer between the blue and green band by numerous nanoparticle boundaries. As the increase of Ge4+ ions, the 480 nm emission intensity of the Sr2Si1−xGexO4 : Eu2+ are more dominant. This behavior can be understood in terms of the effect of Ge4+ ions on the energy transfer from 480 nm band to 525 nm band. The fabricated white-light emitting diode using ultraviolet InGaN chip with the blue and green emitting Sr2Si1−xGexO4 : Eu2+ phosphor shows warm white light of 4300 K and higher color stability against input power in comparison with a commercial blue GaN-pumped YAG:Ce3+.
Structure of Cobalt Nanosphere Superlattice Films by Small Angle X-ray Scattering
Authors: Beerman Michael , Ohnuma Masato , Bao Yuping , Krishnan Kannan M.
Published: April 2011

Cobalt nanocrystals, recently synthesized with narrow size distributions and controlled shapes, organize in a wide range of arrays as a function of shape, size and interparticle interactions. The nanocrystals (NCs) consist of a cobalt metal core with a nominal diameter of 11 nm, and an organic surfactant surface layer with a chain length of ∼1.7 nm. For the simplest case (ε-Co nanospheres, super-paramagnetic at room temperature) a hexagonal arrangement of NCs is observed in transmission electron microscope (TEM) images when precipitated from solution onto carbon films. For practical applications and for further understanding of the self-assembly process, long range order of the super lattice must be probed over regions that are greater in extent than may be examined by TEM. Hence, small angle x-ray scattering (SAXS) measurements were performed on cobalt nanospheres randomly dispersed in solution and assembled on glass substrates. Least squares fit to the intensity distribution as a function of the scattering vector q gave an average particle diameter of 11.0 ± 0.8 nm. Structure factor contribution to the intensity profile agrees well with a quasi-random model for scattering from a face centered cubic (FCC) superlattice composed of uniform radius cobalt spheres. The measured nearest neighbor interparticle spacing, 14.1 nm, agrees to within 2% of the predicted value of 14.4 nm based on a free energy model that governs the self-assembly of the nanoparticle system.
Transmission Electron Microscopy (TEM) Studies of Ge Nanocrystals
Authors: Xu Q. , Sharp I.D. , Liao C.Y. , Yi D. O. , Ager J.W. , Beeman J.W. , Liliental-Weber Z. , Yu K.M. , Zakharov D. , Chrzan D. C. , Haller E.E.
Published: April 2011

74Ge nanocrystals were formed by ion beam synthesis in SiO2. Transmission Electron Microscopy was used to characterize the structure and properties of these Ge nanocrystals before and after liberation from the matrix. The liberation from the SiO2matrix was achieved through selective etching in a HF bath. High-resolution micrographs and selective area diffraction confirm that the crystallinity is retained in this process. Transfer of released nanocrystals is achieved through ultrasonic dispersion in methanol and deposition onto lacey carbon films via evaporation of methanol. In an effort to determine the melting point of Ge nanocrystals and observe the growth and evolution of nanocrystals embedded in the amorphous SiO2during heat treatment, as-grown nanocrystals were heatedin-situup to 1192°C±60°C in a JEOL 200CX analytical electron microscope. Electron diffraction patterns are recorded using a Charge-Coupled Device. A large melting hysteresis was observed around the melting temperature of bulk Ge.
Image-Based Nanocrystallography in Future Aberration-Corrected Transmission Electron Microscopes
Authors: Moeck P. , Qin W. , Fraundorf P. B.
Published: April 2011

Since the crystallographic phase and morphology of many materials changes with the crystal size in the one to hundred nanometer range and the potential technological applications of nanoparticles are enormous, a need arises to determine the crystallography of nanoparticles individually. Direct space high- resolution phase-contrast transmission electron microscopy (TEM) and atomic resolution Z-contrast scanning TEM when combined with goniometry of direct and/or reciprocal lattice vectors offer the possibility of developing dedicated nanocrystallography characterization methods for such small nanoparticles. Although experimentally feasible for cubic nanocrystals with lattice constants larger than 0.4 nm in contemporary high-resolution TEMs with modest tilt range, image-based nanocrystallography by means of transmission electron goniometry has so far only been employed by a few specialists worldwide. This is likely to change in the future with the availability of aberration-corrected TEMs. The reasons why this change is likely to happen are outlined in this paper.
Fabrication of CdTe Quantum Dot Arrays on GaAs utilizng Nanoporous Alumina Masks
Authors: Jung Mi , Lee Hong Seok , Park Hong Lee , Mho Sun-Il
Published: April 2011

The uniformity and reproducibility of the CdTe QD arrays on the GaAs substrates can be improved by using a nanoporous mask. The CdTe QDs on the GaAs substrate were grown by a molecular beam epitaxy (MBE) method. The nanoporous alumina masks used for the fabrication of QD arrays have the thickness from 0.3 νm to 5 νm with the nanochannels of ∼ 80 nm diameter and the pore density of ∼ 1010cm−2. When the thickness of the alumina mask used for the CdTe QD growth was about 300 nm, the CdTe QD arrays formed as a replica of the nanochannels of the mask. Smaller self-assembled CdTe QDs located randomly were produced by using the thicker nanochannel mask than 0.5 νm. The thickness of the nanochannel mask controls the size of the CdTe/GaAs QDs.
Formation of an Ordered Array of Nanocrystalline Si Dots by Using a Solution Droplet Evaporation Method
Authors: Tsuchiya Yoshishige , Iwasa Tatsuya , Tanaka Atsushi , Usami Ko-Ichi , Mizuta Hiroshi , Oda Shunri
Published: April 2011

This paper reports on a new bottom-up technique of forming silicon nanostructures based on natural aggregation of nanocrystalline (nc) -Si dots in the solution. We first study how the nc-Si dots deposited on the Si substrate get mobile in the solution by simply dipping the substrate with the nc-Si dots on into various solutions. We then demonstrate a solution droplet evaporation method that utilizes aggregation of the dots when we evaporate a solution droplet applied onto the nc-Si dots randomly deposited on the Si substrate. It is shown that the nc-Si dots are assembled well in a droplet of the hydrofluoric acid solution, resulting in various regular patterns on the substrate.
Photochromic Nanofiber Aggregates of PVA/H3PMo12O40 Hybrid
Authors: Gong Jian , Gao Fengmei , Pan Yan , Cui Xiujun , Qu Lunyu , Wang Rongshun
Published: April 2011

Poly (vinyl alcohol) (PVA)/H3PMo12O40ultra-fine fiber aggregates contained differential weight percentage of H3PMo12O40 to PVA (20, 50 and 80 wt.%, respectively) have been successfully prepared by electrospinning technique. By means of IR spectrum, wide-angle X-ray diffraction, and scanning electron microscope (SEM) techniques, the fiber aggregates were characterized. The result from scanning electron microscopy (SEM) showed that the average diameter of the fibers was between 240-900 nm. The photochromic behavior of the fiber aggregates was investigated by means of IR, UV-Vis spectra and electron spin resonance (ESR). The results showed that the Mo atom of H3PMo12O40 was reduced via one-electron step and the PVA was oxidized to unsaturated ketone after the PVA/H3PMo12O40 fiber aggregates was irradiated under UV light. The color of the fiber aggregates changed from white to blue under ultraviolet irradiation and the photochromism of the fiber aggregates was reversible in air condition.
Nucleation and Growth of Gold Nanoparticles Deposited by RF-Sputtering: An Experimental Study
Authors: Barreca Davide , Gasparotto Alberto , Pierangelo Elisabetta , Tondello Eugenio
Published: April 2011

Gold nanoparticles were deposited on SiO2, Si(100) and HOPG (Highly Oriented Pyrolitic Graphite) by RF-sputtering from Ar plasmas. Sample preparation was performed at temperatures as low as 60°C under different total pressures, RF-powers and deposition times, with particular attention to the influence of process parameters and growth surface on nanosystem properties. In this paper, the most important results regarding the compositional, structural and morphological features of the obtained specimens, are presented and discussed.
Nanolithographic Manipulated Cutting of Aligned Metal Oxide Nanowires
Authors: Campbell L.J. , Chen Y.X. , Zhou W.L.
Published: April 2011

Controlling the characteristics of nanowires in order to later construct nanoarchitecture and nanocomponents for nanodevice and nanosensor applications is essential. Metal oxide nanowires are aligned using the Langmuir-Blodgett (LB) technique to uniaxially compress the nanowires. A surfactant monolayer of metal oxide nanowires is fabricated, and then compressed on an aqueous subphase. The compression yields an array of aligned nanowires, which is transferred to a planar substrate. Cutting areas of the array are defined by electron beam nanolithography. After an etching process, it is shown that the metal oxide nanowires have been successfully cut. With further refinement of this technique, the nanowires can be used to construct basic building blocks of nanodevices and nanosensors.
Synthesis of Indium Tin Oxide Nanoparticles and Application to Near IR-reflective Film
Authors: Song Ja Eun , Kang Young Soo
Published: April 2011

ITO nanoparticles were synthesized by coprecipitation method in an aqueous solution and thermal method in an alcohol solution. The coprecipitate prepared at room temperature showed the crystal structure of indium oxide in X-ray diffraction when it was annealed above 300°C. In thermal method, the nanoparticles have two phase crystal structure of indium oxide hydroxide (InOOH) and indium hydroxide (In(OH)3). Annealing at the temperature above 300 °C, it showed the rhombohedral crystal structure of indium oxide (In2O3). The phase transition of ITO nanoparticle was also detected with DSC. Near IR-reflective film was prepared by spin coating using ITO sol solution. Transmission electron microsopy (TEM) and energy dispersive X-ray spectrometer (EDS) were used to characterize the morphology and composition of ITO nanoparticles. Near-IR (NIR) spectrometer was used to determine reflectance on the surface of ITO film in the NIR-radiation region.
Photoluminescent Enhancement of Ruthenium Complex Monolayers by Surface Plasmon Resonance of Silver Nanoparticles
Authors: Pan Shanlin , Wang Zhenjia , Rothberg Lewis J.
Published: April 2011

The photoluminescence intensity from a bis (2,2'-bipyridine)-(5-isothiocyanato-phenanthroline) Ruthenium (RuBICP) monolayer covalently bound to a glass substrate is found to be enhanced up to 20 times when silver nanoparticles are deposited on top. The emission spectra are blue shifted by interactions with the silver nanoparticles. Field enhancement is found to be able to enhance the radiative decay rate by over three orders of magnitude but fewer than 2 % of the molecules in the sample experience this large enhancement. Increased absorption rates also increase the luminescence but to a much smaller degree.
Effect of Template Materials on the Top Morphologies of Cu Nanowires
Authors: Lin Ran-Jin , Wu Luh-Huei , Tsai Ching-Hsiang , Sung Chien-Min
Published: April 2011

An array of copper nanowires (50-110 nm in diameters) was deposited by the electrolysis of CuSO4-H2SO4 solution at room temperature using DC current. The array was created by forcing deposited copper to follow a pattern of nano tunnels. These nano tunnels were formed with two different methods: anodizing an aluminum film that coated on a silicon wafer to form nano holes within oxidized alumina, and etching the ion-tracked polycarbonate membrane.

The difference in top morphologies of the Cu nanowires in these templates is very marked. The copper nano wires deposited in anodized alumina template form the separate spherical balls with diameter of about 10 νμ on the surface of the alumina film, in spite of the template thickness of only 0.5 νm. In contrast, no such Cu agglomeration was formed with copper nano wires deposited in holes of polycarbonate. This variance in copper morphologies is likely due to the difference of the interface energy between Cu and anodic alumina and that of Cu and polycarbonate.
Synthesis and Characterization of Novel Au(core)-Au/Pt Alloy(shell) Nanostructure
Authors: Liu Ru-Shi , Chen Hau-Ming , Hu Shu-Fen
Published: April 2011

A systematic study is reported about the amount-dependent morphology change in a series of Au-Pt bimetallic nanoparticles synthesized using chemical reduction. The amount of Au precursor is kept constant throughout whole series of compounds to obtain fixed Au core size (∼7.5 nm). The Au/Pt ratio is varied from 1/1 to 1/4 in order to synthesize Pt shell layer of different thickness. We observed a remarkable shift of surface plasmon band around 410 nm. With the aid of high resolution transmission electron microscope (HRTEM) and energy-dispersive spectrometer (EDS), the composition of shell layer is found to be Pt enriched Au-Pt alloy. As the amount of Pt increases, the Pt clusters formed a string-like shape on the surface of nanoparticles. The average diameter of these Pt clusters is about 2 nm. This special structure may exhibit unique catalytic property.
Covalent Coupling of Gold Nanoparticles to Multiwalled Carbon Nanotubes for Electronic Device Applications
Authors: Ma Xicheng , Lun Ning , Li Xia , Wen Shulin
Published: April 2011

Creating hybrid nanostructures of disparate nanoscale blocks is of interest of exploring new types of electronic devices and networks. Here, we demonstrate the novel coupling of gold nanoparticles of 3-4 nm diameters to sidewall of multiwalled carbon nanotubes (MWNTs) using the electroless plating technique. MWNTs were initially chemically modified with an H2SO4-HNO3 acid treatment, and subsequently activated with Pd-Sn catalytic nuclei via a one-step activation approach. When the activated MWNTs were immersed in a gold-containing electroless plating bath, gold deposition occurred at the catalytic sites. The deposited gold clusters then catalyze further gold deposition on the tube surface (autocatalytic process). Novel hybrid nanostructures with gold nanoparticles homogeneously distributed on MWNTs resulted. High-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) were used to characterize the conjugation process.
Spherical Aberration Corrected Z-STEM Characterization of CdSe and CdSe/ZnS Nanocrystals
Authors: McBride James , Kippeny Tadd C. , Pennycook Stephen J. , Rosenthal Sandra J.
Published: April 2011

Spherical aberration corrected Atomic Number Contrast Scanning Electron Microscopy (Z-STEM) has recently demonstrated an amazing ability to not only obtain sub-angstrom levels of detail but also yield chemical information at that level as well. With an optimal probe size of 0.8 Å, extremely detailed images of CdSe nanocrystals were obtained showing the lattice structure and surface morphology. As an example of the usefulness of this technique, a sample of CdSe nanocrystals prepared using trioctylphosphine oxide (TOPO) as the surfactant was compared to a sample of CdSe prepared using a mixture of TOPO and hexadecylamine (HDA) as the surfactant. The TOPO/HDA nanocrystals exhibit a narrower size distribution and several orders of magnitude greater fluorescence compared to that of the TOPO only nanocrystals. Interestingly, the Z-STEM images show a striking difference in nanocrystal morphology as the result of the addition of HDA to the reaction mixture. This result suggests surface morphology can be tuned through judicious choice of surfactant. A second example of Z- STEM imaging involves the characterization of CdSe/ZnS core/shell nanocrystals. The mass contrast afforded by Z-STEM can easily distinguish between core and shell.
Reaction and diffusion dynamics in a microfluidic format
Authors: Kohlheyer Dietrich , Lammertink Rob G. H. , Schlautmann Stefan , Besselink Geert A. J. , Vulto Paul , Schasfoort Richard B. M.
Published: April 2011

A novel microfluidic structure based on the electroosmotic guiding of reagent streams is presented that can be used as a fully adjustable diffusion based microreactor. The position and the width of two aqueous reactant streams entering a laminar-flow chamber can be controlled individually by changing the flow ratio of three parallel guiding streams containing buffer only. To control the intensity of product formation, the overlapping area between the diffusion regions of the two different reagent streams can be adjusted. This article describes the fabrication and experimental characterization of the device.
Design and Fabrication of a Constant Shear Microfluidic Network for Tissue Engineering
Authors: Weinberg E.J. , Borenstein J.T. , Kaazempur-Mofrad M.R. , Orrick B. , Vacanti J.P.
Published: April 2011

Recent progress in microfabrication of biodegradable materials has resulted in the development of a three-dimensional construct suitable for use as a scaffold for engineering blood vessel networks. These networks are designed to replicate the critical fluid dynamic properties of physiological systems such as the microcirculation within a vital organ. Ultimately, these 3D microvascular constructs will serve as a framework for population with organ-specific cells for applications in organ assist and organ replacement. This approach for tissue engineering utilizes highly engineered designs and microfabrication technology to assemble cells in three-dimensional constructs which have physiological values for properties such as mechanical strength, oxygen, nutrient and waste transport, and fluidic parameters such as flow volume and pressure.

Three-dimensional networks with appropriate values for blood flow velocity, pressure drop and hematocrit distribution have been designed and fabricated using replica molding techniques, and populated with endothelial cells for long-term microfluidic cell culture. One critical aspect of the fluid dynamics of these systems is the shear stress exerted by blood flow at the walls of the vessel; a key parameter because of well-known mechanotransduction phenomena from mechanical shear forces which govern endothelial cell behavior. In this work, we report the design and construction of three-dimensional microfluidic constructs for tissue engineering which have uniform wall shear stress throughout the network. This type of control over the shear stress offers several advantages over earlier approaches, including more uniform seeding, more rapid achievement of confluent coatings, and better control over endothelial cell behavior for in vitro and in vivo studies.
Synthesis and Characterization of Ag Nanoparticle, Ag-TiO2 Nanoparticle and Ag-TiO2-Chitosan Complex and Their Application to Antibiosis and Deodorization
Authors: Kim Young Hwan , Kang Young Soo
Published: April 2011

Ag nanoparticles have been prepared by thermal decomposition of Ag-oleate complex using electric furnace at 300 °C for about 4 hrs. TEM images of the particles showed 2-dimensional assembly of particles with diameter of 8.0 ± 1.3 nm, demonstrating the uniformity of these nanoparticles. Ag-TiO2 nanoparticles were synthesized by sol-gel process and they had core-shell structure. Results showed the formation of the silver core and titanium oxide shell. In this study, we investigated the structure of Ag nanoparticle and Ag-TiO2 nanoparticle and Ag-TiO2-chitosan complex and their functions of antibiosis and deodorization.
Integrating Biomaterials into Microsystems: Formation and Characterization of Nanostructured Titania
Authors: Samah Zuruzi Abu , Butler Blaine C. , Parker Emily R. , Ahmed Ayesha , Evans Heather M. , Safinya Cyrus R. , MacDonald Noel C.
Published: April 2011

We demonstrate the facile fabrication of crack-free nanostructured crystalline titania into microsystems. Titania layers were formed by reacting Ti thin films, deposited by evaporation and sputtering, with aqueous H202. Cracks were observed in titania layers formed on blanket Ti films but absent on arrays of patterned Ti pads below a threshold dimension. Nanostructured titania formed from sputtered and evaporated Ti films consists of aligned fibrous and sponge-like nanoporous morphologies, respectively. Rat fibroblasts L-cells cultured on these titania fibers remain viable up to 3 days. These observations demonstrate the feasibility of this technique to integrate nanostructured titania into Nano|Micro-Electromechanical systems (N|MEMS) devices.
Microfluidics and Beyond – Devices for Applications in Biotechnology -
Authors: Daub Martina , Kaack Rolf M. , Gutmann Oliver , Steinert Chris P. , Niekrawietz Remigius , Koltay Peter , Heij Bas de , Zengerle Roland
Published: April 2011

For the performance of certain analytical and diagnostic tasks in modern Life Science applications high throughput screening (HTS) methods are essential. Miniaturization, parallelization and automation allow to decrease consumption of expensive materials and lead to faster analyzing times. The miniaturization of total assay volumes by the use of microtiter plates as well as the microarray technology have revolutionized the field of biotechnology and Life Sciences. Neither printing of microarrays with droplet volumes of several picoliters, nor handling of precious enzymes in the upper nanoliter range can be accomplished with traditional liquid handling devices like air displacement pipettes. The development of novel low volume liquid handling devices, which are subject to current research, addresses the diverse requirements shifting steadily to lower volumes. Various novel non-contact dispensing methods in the nanoliter and picoliter range are presented and classified according to their working principles like air displacement and direct displacement methods (TopSpot®, NanoJetTM, Dispensing Well PlateTM). Properties of the various methods are compared in terms of flexibility, integration density, speed of operation, precision, addressable volume range and amenability to multi-parallel operation.
Three-Dimensional Representation of Curved Nanostructures
Authors: Huang Z. , Dikin D.A. , Ding W. , Qiao Y. , Fridman Y. , Ruoff R.S.
Published: April 2011

Nanostructures, such as nanowires, nanotubes, and nanocoils, can be described in many cases as quasi one-dimensional (1D) curved objects projecting in three-dimensional (3D) space. A parallax method to reconstruct the correct three-dimensional geometry of such 1D nanostructures is presented. A series of images were acquired at different view angles, and from those image pairs, 3D representations were constructed using a MATLAB program. Error analysis as a function of view-angle between the two images is discussed. As an example application, we demonstrate the importance of knowing the true 3D shape of Boron nanowires. Without precise knowledge of the nanowire's dimensions, diameter and length, mechanical resonance data cannot be properly fit to obtain an accurate estimate of the Young's modulus.
Determination of Ion Irradiation Influence on π-plasmon Properties of Carbon Nanotubes
Authors: Brzhezinskaya Mariya M. , Baitinger Eugen M. , Shnitov Vladimir V. , Smirnov Aleksey
Published: April 2011

In this paper, the results of experiments on irradiation of the singlewall (SWNT) and multiwall carbon nanotube (MWNT) samples by argon ions are presented. They were obtained by reflection electron energy loss spectroscopy and Auger electron spectroscopy.

Results indicate the π-plasmon energy Eπ and the full width at half maximum (FWHM) of the plasma peak were sensitive to the dose of ion irradiation. In particular, the π-plasmon energy Eπ decreases and the plasma peak broadens with the increase of the dose of Ar+irradiation.

The π-plasmon peak broadening is associated with damage of carbon nanotubes under ion irradiation. Possible causes of the carbon nanotubes deformation and influence of deformation on π-band structure of carbon nanotubes are discussed.
Fabrication and Characteristics of Zirconia-Alumina Composites with Bilayer Structure
Authors: Je Sung-Jae , Lee Myung-Won , Lee Jae-Ean , Jung Yeon-Gil , Park Dong-Soo , Paik Ungyu
Published: April 2011

Bilayer structures consisting of ZrO2-3mol% Y2O3(TZ-3Y) and zirconia-alumina composites as inner (substrate) and outer (coating) layers, respectively, are fabricated using gel-casting for the inner layer and dip-coating for the outer layer in aqueous system. The relatively tough TZ-3Y is used as the inner layer for damage absorption due to its mechanical properties. The mixture ratio of alumina/zirconia slips for dip-coating is 1:9, 2:8, and 3:7 as mole ratio. The processing additives for gel casting, such as dispersant, monomer, dimer, and initiator, are adjusted and optimized by measuring viscosity. From which the solid loading of starting material (TZ-3Y) is determined. The optimum amount of dispersant (D-3019; anionic dispersant agent) for TZ-3Y is 0.7 wt%. The slip pH affects the electric double layer in sols, which causes the different rheological behaviors and solid loadings. The castable solid loading of TZ-3Y is 37 vol%, showing a pseudoplastic rheological behavior. The effect of slip type (different mixture ratio) on sintered body is investigated through hardness (Vickers indentation), microstructure (SEM), and strength (4-point bending tests). Strength of sintered bodies after dip-coating into the slips is higher than that before dip-coating, but hardness is not much different among cases. The effects of thickness in the outer layer on damage resistance and mechanical properties of the bilayer structures are discussed extensively.
Instability Induced by Near-substrate Electric Field
Authors: Salac David , Lu Wei
Published: April 2011

This paper reports experimental work using an electric field close to a substrate to induce morphological patterns in a thin polymer film. The film was spin-coated onto a glass wafer, and subsequently heated to above its glass transition temperature to allow viscous flow. An electric field was applied by two parallel electrodes spacing 10 mm apart. The initially flat polymer/air interface lost stability and formed islands. The self-assembled islands exhibited a narrow size distribution and demonstrated spatial ordering. We attribute the pattern formation to the minimization of combined interface energy and electrostatic energy.
Nanocrystalline fcc metals: bridging experiments with simulations
Authors: Swygenhoven H. Van , Derlet P. M. , Frøseth A. G. , Petegem S. Van , Budrovic Z. , Hasnaoui A.
Published: April 2011

Atomistic simulations have provided unprecedented insight into the structural and mechanical properties of nanocrystalline materials, highlighting the role of the non-equilibrium grain boundary structure in both inter- and intra-grains deformation processes. One of the most important results is the capability of the nanosized grain boundary to act as a source and sink for dislocations. However the extrapolation of this knowledge to the experimental regime requires a clear understanding of the temporal and spatial scales of the modelling technique and a detailed structural characterisation of the simulated samples. In this contribution some of the synergies that can be developed between atomistic simulations and experiments for this research field are briefly discussed by means of some typical examples.
Slip Transfer across Hetero-Interfaces in two-phase Titanium Aluminum Intermetallics
Authors: Wiezorek Jörg M.K. , Zhang Xiao-Dong , Fraser Hamish. L.
Published: April 2011

The role of slip transfer processes across the heterophase interfaces in two-phase TiAl intermetallics has been studied. Polysynthetically twinned crystals of TiAl (PST-TiAl) have been used as model systems for individual grains in technologically relevant polycrystalline lamellar TiAl alloys. Compressive plastic loads have been applied for orientations of the lamellar interfaces parallel and perpendicular to the loading directions to produce hard mode slip activity. Transmission electron microscopy has been used to determine the active deformation modes in the constituent phases and to study the slip transfer across heterophase interfaces. The results are discussed with respect to the mechanical behavior of PST-TiAl and lamellar TiAl alloys, which is of relevance to in-service performance and metallurgical processing operations.
Atomistic Simulations of Dislocation-Interface Interactions in Thin Films
Authors: Leger R. W. , Shen Y.-L.
Published: April 2011

Atomistic simulations are carried out to study the effect of atomic sliding capability at the interface between a plastically deforming film and a stiff substrate. Molecular statics modeling is utilized to corroborate the overall film response and the nano-scale defect mechanisms. A free-sliding interface is shown to be able to cause “reflection” of oncoming dislocations and enhance film plasticity. A rigidly bonded interface, on the other hand, is seen to resist approaching dislocations. Partial sliding results in a transitional behavior between the two extremes, as revealed in our parametric analysis. The sliding capability of interface atoms is also seen to dictate the overall film response.