bluuebunny/crossref_metadata_2025 huggingface dataset:
Vertically Aligned CNTs Embedded in Cr/TiO2 Membranes For Realization of Ion Sources
Authors: Abdi Yaser , Sadeghi Mehdi , Mohajerzadeh Shams , Koohsorkhi Javad , Hekmat-Shoar Bahman
Published: April 2011

PECVD-grown carbon nanotubes on (100) silicon membranes have been realized and exploited for electron and ion emission applications. The growth of CNT's is achieved by a mixture of hydrogen and acetylene gases in a CVD reactor and a 5-10nm thick nickel is used as the seed for the growth. The presence of a DC-plasma yields a vertical growth of carbon nanotubes. The as-grown nanotubes are encapsulated by means of an insulating TiO2 layer. The formation of a thin membrane is possible by means of a chemical anisotropic etching technique. The membrane is then removed from the back side to fully suspend the CNT-holding TiO2 layer. Upon exposure to a plasma ashing step the nanotubes are partially removed and a both-end opened hollow nanostructure is formed which can be used as a miniaturized ion source. The CNT-holding substrate can be exploited as a grid to extract the ions from an ionization chamber just underneath the membrane. Applying a proper accelerating electric field, positive ions made inside a DC discharge cavity can form a beam-shape emission of ions towards the opposite negative electrode. The beam is well suited for a source of ion lithography. In which, the emission has the ability of direct writing on a photo-resist coated substrates. Preliminary nano-scale dots have been created with sizes between 50 and 80nm. Scanning electron microscopy has been used to investigate the results.
TEM Observations of Bio-Conjugated Streptavidin-Gold Nanoparticles
Authors: Koh Ai Leen , Sinclair Robert
Published: April 2011

Simultaneous visualization of inorganic nanoparticles and their bio-functionalized coating under the TEM can be achieved with negative staining, where electron dense material is introduced onto the specimen to enhance contrast. Using this technique, streptavidin-functionalized gold nanoparticles were negatively stained using phosphotungstic acid (PTA) at pH 7.0 and then observed using the TEM. The proteins appear as light regions/halos surrounding the gold nanoparticles, with widths similar to those of streptavidin protein molecules reported in literature. Experiments were performed to bio-conjugate streptavidin-gold nanoparticles to biotinylated antibodies and biotinylated actin, and then negatively staining the samples with PTA for TEM analyses. In the first experiment, an increase in halo widths in more than 60% of the particles was observed. In the second experiment, the nanoparticles were found to localize around the long actin filaments. Negative staining is useful for studying bio-functionalized nanoparticles as it enables the proteins surrounding the nanoparticles to be imaged and studied using the TEM.
Non-invasive high-resolution acoustic microscopy technique using embedded nanostructures
Authors: Wulin Daniel , Ramanathan Shriram
Published: April 2011

An opto-acoustic system capable of operating at frequencies greater than 1 GHz with novel biological applications is proposed for the first time. Metallic spheres with radii on the order of hundreds of nanometers dispersed inside a bio-matrix can be used to generate in-situ ultra-high frequency acoustic waves whose normal mode frequencies can be calculated using Lamb's theory for acoustic oscillations of elastic spheres. The frequency and amplitude of the resulting acoustic waves can be related to the physical properties of the metallic spheres and the surrounding bio-matrix: the acoustic waves produced by the metallic spheres are well-suited to high resolution acoustic imaging. We anticipate that our approach will open up new nanoscale techniques to study cells non-invasively.
Magnetic Hyperthermia Study of Mn-Zn-Fe and Zn-Gd-Fe Nanoparticle Systems as Possible Low-Tc Agents for Magnetic Particle Hyperthermia
Authors: Hayek Saleh S. , Chen Ching-Jen , Flores Glen , Batich Christopher D. , Haik Yousef S.
Published: April 2011

Magnetic nanoparticles have found utility in many biological applications, including imaging, cancer therapy, drug delivery, sensing and hyperthermia for tumor therapy. Hyperthermia is raising the tissue temperature between 41.5 - 46 degrees Celsius to kill cancerous cells while preserving the normal cells. Due to the fact that many robust synthetic strategies exist for iron oxides which results in high quality, monodisperse and crystalline nanoparticles, hyperthermia applications have traditionally used magnetic oxide nanoparticles. On the other hand, new materials for hyperthermia that combine the advantages of stability with those of magnetic behavior are desirable. We report the synthesis of MnZnFe, CoGdZn and ZnGdFe nanoparticle systems which are ideal for biological applications over magnetic oxides due to their conjugation chemistry, and surface chemistry. We present an AC magnetic heating studies of these nanoparticle systems which exhibit magnetic field heating. The frequency dependence of the heating follows general trends predicted by power loss equations and is similar to traditional materials. The heating pattern of Zn-Gd-Fe (20mg/ml) using alcohol thermometer at 961 kHz and 433 KHz and the heating pattern of Mn-Zn-Fe [Zn = 0.5 conc.](20mg/ml) using alcohol thermometer at 961 kHz and finally the heating pattern of Co-Gd Zn [Zn = 0.2 conc. Gd (1-X)] (20mg/ml) using alcohol thermometer at 961 kHz are reported. X Ray Diffraction studies and SQUID magnetic measurements and TEM and EDX particle size and constituents measurements are also included for the nanoparticle systems. In conclusion, high quality heating nanoparticle composites were developed for hyperthermia treatment of cancer. The composites generate sufficient heat at room temperature and stops heating at the Curie temperature Tc of the respective nanoparticle system.
Enhancing the Biological Stability and Functionalities of Quantum Dots via Compact Multifunctional Ligands
Authors: Susumu Kimihiro , Pons Thomas , Medintz Igor L. , Mattoussi Hedi
Published: April 2011

We have designed and synthesized a series of modular ligands based on poly(ethylene glycol) (PEG) coupled with functional terminal groups to promote biocompatibility of water-soluble quantum dots (QDs). Each hydrophilic ligand is comprised of three modules: a PEG single chain to promote hydrophilicity, dihydrolipoic acid (DHLA) unit connected to one end of the PEG chain for strong anchoring on the QD surface, and potential biological functional groups (biotin, amino, and carboxyl groups) at the other end of the PEG. Water-soluble QDs capped with one type or mixtures of the functional ligands were prepared via cap exchange with the native hydrophobic caps. Homogeneous QD solutions that are stable over extended periods of time and over broad pH range were prepared. Surface binding assay showed that DHLA-PEG-biotin-functionalized QDs strongly interacted with NeutrAvidin-modified surfaces. The new functional surface ligands studied here provide not only stable and highly water-soluble QDs but also simple and easy access to various biological entities.
Swift Heavy Ion Beam-Based Nanopatterning Using Self-Assembled Masks
Authors: Jensen Jens , Sanz Ruy , Skupinski Marek , Hernandez-Vélez Manuel , Possnert Göran , Hjort Klas
Published: April 2011

Swift heavy ion beam-based lithography using masks of self-assembled materials has been applied for transferring well-ordered micro- and nanopatterns to rutile TiO2 single crystals. As the induced damage has a high etching selectivity the patterns can be developed in HF with very high contrast. Here we present resulting patterns when using a mask of self-ordered silica spheres. Since the obtained structures are replicas of the mass distribution of the applied mask, the shape and size of resulting structures depend on the geometric configuration of the silica sphere layers. In addition, the resulting pattern can be tuned by varying the applied ion energy and fluence. Direct modifications of the optical properties of TiO2 in a well-defined pattern are also presented.
Nano-film and Coating for Biomedical Application Prepared by Plasma-based Technologies
Authors: Liu Xuanyong , Chu Paul K
Published: April 2011

Nanosized materials have been widely applied in biomedical engineering due to their unique nano-effects. In this work, nano-TiO2 coatings and ZrO2 films were prepared using plasma technologies including plasma spraying and cathodic arc plasma deposition. The microstructure the coatings and films were assessed using TEM, SEM, and AFM. Their bioactivity and biocompatibility were evaluated using simulated body fluid soaking tests and cell culturing. Films and coatings with nanostructured surfaces can be obtained using plasma spraying and cathodic arc plasma deposition. The nanostructured surfaces can endow the films and coatings excellent bioactivity and biocompatibility. The UV-illuminated and hydrogen implanted nano-TiO2 coatings and ZrO2 films can induce bone-like apatite formation on their surfaces after immersion in a simulated body fluid for a certain period of time. The nano-TiO2 coating has better cytocompatibility than the micro-TiO2 coating, and the cytocompatibility can be improved by UV-illumination and hydrogen implantation. The bioactivity of the ZrO2 thin film deteriorates after thermal treated. The size of the particles on the surface of the film is thought to be one of the key factors responsible for the bioactivity.
Effects of MeV Si ion bombardments on the Properties of Nano-layers of SiO2/SiO2+Zn4Sb3
Authors: Budak S. , Guner S. , Muntele C. , Smith C. C. , Zimmerman R. L. , ILA D.
Published: April 2011

We prepared 8 periodic nano-layers of SiO2/SiO2+Zn4Sb3. The deposited multi-layer films have a periodic structure consisting of alternating layers where each layer is between 1-10 nm thick. The purpose of this research is to generate nanolayers of nanostructures of Zn4Sb3 with SiO2 as host and as buffer layer using a combination of co-deposition and MeV ion bombardment taking advantage of the electronics energy deposited in the MeV ion track due to ionization in order to nucleate nanostructures. The electrical and thermal properties of the layered structures were studied before and after bombardment by 5 MeV Si ions at various fluences to form nanostructures in layers of SiO2 containing Zn4Sb3. Rutherford Backscattering Spectrometry (RBS) was used to monitor the stoichiometry before and after MeV bombardments.
Capillary Kinetics of Thin Polymer Films in Permeable Microcavities
Authors: Suh Kahp-Yang
Published: April 2011

We present a Poiseuille model that can explain the rate of capillary rise of thin polymer films in permeable microcavities. In comparison to the traditional Poiseuille formulation, two unique features of the system were considered: the permeable nature of the enclosure and the effect of thin polymer films that are confined to the substrate. The model predicts that the rate is inversely proportional to the channel width, contrary to what the original Poiseuille model predicts, and it is proportional to the initial film thickness, which the original model cannot account for. The modified model is in satisfactory agreement with experimental data.
Characterization of Heat Propagation along Single Tin Dioxide Nanobelt Using the Thermoreflectance Method
Authors: Wang Xi , Ezzahri Younes , Christofferson James , Zhang Yi , Shakouri Ali , Shi Li , Yu Choongho , Wang Zhong Lin
Published: April 2011

In this paper, we studied heat transfer properties of a 230nm wide，450nm thick and 5.4 m long single tin dioxide nanobelt using non-contacted high resolution thermoreflectance imaging technique. Temperature difference across the nanobelt was created by attaching its both ends to a microfabricated thin film heater and sensor pair. High resolution thermal images of the nanobelt and thin film devices were obtained at variant pulsing current amplitudes and frequencies, which allowed us to study the inherent thermal conductance of the nanobelt. Thermal expansion induced thermoreflectance coefficient change is also discussed in this paper.
Thermal Conductivity Measurement of Cu Thin Films using Radiation Heat Exchange Method
Authors: Ryu Sang , Kim Youngman , Juhng Woonam
Published: April 2011

A measurement method of thermal conductivities of Cu thin films was devised from the temperature distributions of substrate surfaces. The substrate was prepared to have a prismatic bar shape, and was deposited with Cu thin films using sputtering. Two metal coated surfaces of specimens were brought into contact to maintain the insulated boundary condition. Specimens were heated with constant temperature at both ends. The temperature distributions were measured from the back surface of substrate using a radiation thermometry.

The thermal conductivities of Cu thin films were found to be much lower than those of bulk materials. Wiedemann-Franz law could be applied to thin films produced in this study. Thermal conductivity was also estimated from the resistivity of thin film and Lorenz number of bulk material.
Creating Dense, Constrained Ce0.9Gd0.1O1.95Films at Low Temperature for SOFC Applications
Authors: Nicholas Jason D. , De Jonghe Lutgard C.
Published: April 2011

We have investigated the effect of various dopants on the sintering characteristics of Ce0.9Gd0.1O1.95(CGO) and found that 99% dense electrolyte pellets can be produced at the record low temperature of 800°C (as opposed to the 1400°C typically needed) by sintering Ce0.9Gd0.1O1.95with as little 3mol% lithium. Our studies indicate that doping the CGO surface with lithium nitrate, as opposed to using alternative lithium salts, produces the largest decrease in sintering temperature. Unlike other dopants that lower the sintering temperature by altering the near grain boundary vacancy concentration, lithium lowers the sintering temperature through the formation of an intergranular liquid phase. This liquid phase allows fully dense, completely constrained CGO films to be produced on inert substrates at temperatures as low as 950°C.
Anodization of Sputtered Titanium Films
Authors: Dhawan Deepak , Bhargava Suresh K. , Wlodarski Wojtek , Kalantar-zadeh Kourosh
Published: April 2011

Nanoporous Ti (and TiOx) has been formed by anodization of RF sputtered titanium thin films. A solution of 1M (NH4)2SO4 (ammonium sulphate) electrolytes containing 0.5wt% (NH4)F (ammonium fluoride) was used in the anodization process. Different nano and micro structures were obtained. Voltage in a rage of 2 to 10V was employed in the process. It was observed that the magnitude of applied voltage have a significant impact in the formation of different surface morphologies with various nano/micro structures. The anodized titanium thin films were characterised using scanning electron microscopy and X-ray diffraction techniques.
Combinatorial Searching for Noble Metal-based Thin Film Amorphous Alloys for Glass Lens Mold
Authors: Sakurai Junpei , Hata Seiichi , Yamauchi Ryusuke , Tachikawa Hiroyuki , Shimokohbe Akira
Published: April 2011

This paper presents the properties of Pt-based thin film amorphous alloys developed for a glass lens mold. To search for the amorphous alloys, Pt-Zr-Ni and Pt-Hf-Ni thin film libraries were fabricated using combinatorial arc plasma deposition (CAPD). The composition ranges of the amorphous region in each library were 50 to 60 at.% Pt, 0 to 20 at.% Ni, and balance being Zr or Hf. To evaluate the thermal and mechanical properties of these amorphous alloys, Pt51Zr39Ni10 and Pt52Hf36Ni12 samples, as typical amorphous samples, were prepared by sputtering. The Pt51Zr39Ni10 sample showed a crystallization temperature, Tx, of 939 K and a fracture stress, σf, of 1.44 GPa. The Pt52Hf36Ni12 sample showed a Tx of 978 K and a σf of 0.3 GPa. The Pt51Zr39Ni10 and Pt52Hf36Ni12 samples did not achieve the target Tx (973K) and σf (1.0 GPa). In order to achieve the target properties, Zr was displaced with Hf to increase the Tx of Pt-Zr-Ni and four Pt51HfxZr37-xNi12 samples were prepared. The Pt51Hf20Zr17Ni12 sample had a Tx of 992 K and a σf of 0.87 GPa, and almost achieved the target properties. The machinability of the Pt51Hf20Zr17Ni12 sample was also evaluated. Though this sample could be cut using a diamond tool, it did not show sufficient machinability. In order to improve the accuracy of the glass mold shape, the machinability of the Pt-based thin film amorphous alloys require further modification.
An Autonomous and Intelligent System Using Mobile-Agent Software to Model the Calculation Processes of Film Deposition Simulators
Authors: Takahashi Takahiro , Fukui Noriyuki , Arakawa Masamoto , Funatsu Kimito , Ema Yoshinori
Published: April 2011

We developed an autonomous modeling system for the calculation processes of the simulator for film deposition processes in order to decrease the calculation cost for reproducing experimental results. Replacing the simulator with the mathematical models proposed by the modeling system decreased huge calculation cost of the simulator. The system consists of onemobile agentand three platforms for the agent. The agent autonomously moved in the computer-networks and operated the process simulator in the platform in order to make training data needed for modeling and then operated the generalized modeling software in the platform using the training data and finally the agent created the models. The models showed both good reproducibility and predictability with the calculated results of the simulator.
Stress distribution in polycrystalline silicon thin film solar cells on glass measured by micro-Raman spectroscopy
Authors: Sarau George , Becker Michael , Berger Andreas , Schneider Jens , Christiansen Silke
Published: April 2011

Micro-Raman spectroscopy is used to measure stress distributions in 1.5 µm thick polycrystalline silicon thin film solar cells on glass. These measurements are combined with transmission electron microscopy and atomic force microscopy to assign the measured local stresses to the sample's microstructure. Expansion and contraction of the silicon lattice in the layer and the borosilicate glass substrate during the thermal processing of the solar cell as well as quartz beads of µm size that reside on the glass substrate for light-trapping purposes induce internal stresses that locally vary with structural features. While the thermal processing induces an average tensile stress in the silicon layer originating from the thermal mismatch between glass and silicon, the latter results in lateral stress gradients up to 208 ± 12 MPa in the mapped area.
Oxidation Kinetics of Cu-Ni Alloy Observed by in situ UHV-TEM
Authors: Sun Li , Pearson John E. , Yang Judith C.
Published: April 2011

The nucleation and growth of Cu2O and NiO islands due to oxidation of Cu-24%Ni(001) films were monitored at various temperatures by in situ ultra-high vacuum (UHV) transmission electron microscopy (TEM). In remarkable contrast to our previous observations of Cu and Cu-Au oxidation, irregular-shaped polycrystalline oxide islands were observed to form with respect to the Cu-Ni alloy film, and an unusual second oxide nucleation stage was noted. Similar to Cu oxidation, the cross-sectional area growth rate of the oxide island is linear indicating oxygen surface diffusion is the primary mechanism of oxide growth.
EMCD: Magnetic Chiral Dichroism in the Electron Microscope
Authors: Rubino Stefano , Schattschneider Peter , Stöger-Pollach Michael , Hébert Cécile , Rusz Ján , Calmels Lionel , Warot-Fonrose Benedicte , Houdellier Florent , Serin Virginie , Novàk Pavel
Published: April 2011

A new technique called Energy-loss Magnetic Chiral Dichroism (EMCD) has recently been developed [1] to measure Magnetic Circular Dichroism (MCD) in the Transmission Electron Microscope (TEM) with a spatial resolution of 10 nm. This novel technique is the TEM counterpart of X-ray Magnetic Circular Dichroism (XMCD), which is widely used for the characterization of magnetic materials with synchrotron radiation.

In this paper we describe several experimental methods which can be used to measure the EMCD signal [1-5] and give a review of the recent improvements of this new investigation tool. The dependence of the EMCD on several experimental conditions (such as thickness, relative orientation of beam and sample, collection and convergence angle) is investigated in the transition metals Iron, Cobalt and Nickel. Different scattering geometries are illustrated; their advantages and disadvantages are detailed, together with current limitations. The next realistic perspectives of this technique will consist in measuring atomic specific magnetic moments, using suitable spin and orbital sum rules [4,6], with a resolution down to 2-3 nm.
Imaging Oxide-Covered Doped Silicon Structures Using Low-Energy Electron Microscopy
Authors: Anderson Meredith , Nakakura C.Y. , Saiz K.F. , Kellogg G.L.
Published: April 2011

Low energy electron microscopy (LEEM) operated at incident electron energies just above the “mirror” mode is used to image Si-based test devices. Significant p- vs. n- doping contrast is observed, even when the structures are covered with a ∼3.5 nm thermal oxide. The contrast arises from a difference in surface potential between the two regions and is related to both p-n work function differences and electron-beam-induced charging of the oxide. The results show that the LEEM is capable of characterizing pn junctions without complicated sample preparation and that it is a promising technique for rapid, non-destructive imaging of microelectronic devices.
Nanoparticle suspensions studied by x-ray photon correlation spectroscopy
Authors: Lu Xinhui , Mochrie Simon G. J. , Narayanan S. , Sandy Alec R. , Sprung Michael
Published: April 2011

Multispeckle x-ray photon correlation spectroscopy measurements, carried out at beamline 8-ID at the Advanced Photon Source at Argonne National Laboratory, of opaque suspensions of silica nanoparticles in water and lutidine-water binary mixtures are presented.
Nano-engineering by MeV Ion Beams
Authors: Mishra Yogendra Kumar , Avasthi Devesh Kumar , Singh Fouran , Pivin Jean Claude , Pippel Eckhard
Published: April 2011

Thin silica films embedded with Au nanoparticles (NPs) were prepared by atom beam co-sputtering and RF-magnetron sputtering. The growth kinetics of Au NPs in atom beam co-sputtered film, under 90 MeV Ni ion irradiation, was studied by in-situ X ray diffraction experiment in the materials science beam line at IUAC, New Delhi. The growth of NPs from 4 nm (for pristine) to 9 nm at a fluence of 1 × 1014 ions/cm2 was observed with rapid growth upto the size track diameter, however slowed beyond it. 120 MeV Au ion irradiation of RF magnetron sputtered films resulted in the elongation of Au NPs along ion beam direction. The aspect ratio of elongated NPs (Au nanorods) is found to be ∼3.5, which mainly depends on the electronic energy deposited within the system. Hence the present work reports that the ion irradiation is an effective tool for tailoring the size, shape and size distribution of NPs. The results are discussed in the framework of thermal spike model.
Competitive Adsorption of Lung Surfactant and Serum Proteins at the Air-Liquid Interface: A Grazing Incidence X-Ray Diffraction Study
Authors: Stenger Patrick C , Wu Guohui H , Chi Eva Y , Frey Shelli L , Lee Ka Yee C , Majewski Jaroslaw , Kjaer Kristian , Zasadzinski Joseph A
Published: April 2011

The competitive adsorption of lung surfactant (LS) and albumin at the air-liquid interface and the ability of polyethylene glycol (PEG) to mediate LS adsorption are analyzed using pressure area isotherms and grazing incidence x-ray diffraction (GIXD). The addition of albumin drastically reduces the amount of LS on the interface and slightly increases the LS lattice spacing. The addition of PEG restores the characteristic LS peaks, yielding a slightly more compact lattice. The scattering results are consistent with recent work which proposed that albumin creates a physical barrier which eliminates LS adsorption and that PEG enhances LS adsorption but does not significantly change LS surface ordering.
ALL-ORGANIC FLEXIBLE AND TRANSARENT AMBIPOLAR FETs WITH ORGANIC BULK HETEROJUNCTIONS
Authors: Cosseddu Piero , Bonfiglio Annalisa , Salzmann Ingo , Rabe Jurge P. , Koch Norbert
Published: April 2011

We report on the realization of flexible and transparent all-organic Ambipolar Field Effect Transistors. The devices were assembled on a flexible plastic foil, i.e. Mylar®, and the contacts were realized with poly(ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and patterned by means of Soft Lithography, MicroContact Printing (μCP). As semiconductor layer we used organic bulk heterojunctions of pentacene/C60 realized either by co-deposition of the two different molecules or by a double layer structure in which pentacene was used as buffer layer at the interface with the gate dielectric. Interestingly, all devices (co-deposited and double layer), measured in air, worked in accumulation mode as ambipolar OFETs, however some interesting differences between the two structures can be pointed out. Supported by Atomic Force Microscopy, we demonstrated that growing C60 on a pre-deposited pentacene buffer layer leads to a clear improvement in the morphology and crystallinity of the deposited film allowing to improve n-type conduction by two orders of magnitude. This work is particularly interesting because on one hand it confirms the importance of the substrate properties for the ordered growth of organic semiconductors, which determines the transport properties of organic materials; moreover, it demonstrates, also for n-type and ambipolar transistors, the possibility of avoiding problems normally associated to metal contacts: the lack of mechanical robustness, flexibility, and the unfeasibility of realizing contacts with low cost techniques like printing or soft lithography. The flexibility and transparency of the final OFET structure and the simple low cost fabrication technique employed pave the way for an economic mass production of large area transparent “Plastic Electronics”.
Metal Suppression of Pentacene Grain Growth
Authors: Lo Hsi-wen , Tai Yu-Chong
Published: April 2011

Pentacene thin-film transistors use either bottom-contact or top-contact electrodes. Transistors with bottom-contact electrodes are fabricated in such a way that metal is deposited and patterned before pentacene deposition while those with top-contact electrodes are fabricated in reverse order. Hole mobility is closely related to pentacene grain sizes and grain sizes of pentacene depend heavily on the surface roughness. When the surfaces are flat and smooth enough, the grains of pentacene are still small if metal is deposited before pentacene, i.e., bottom-contact configuration. Pentacene inside the channels formed by source and drain electrodes has much smaller grains than those far away from metal electrodes.

To further understand this phenomenon, we first studied pentacene grain growth on different substrates (oxide, Poly-4-vinylphenol or PVP, and SU8-2.) but with same metal electrodes (500 Ö Au). Next, we studied pentacene grain growth on the same substrate (oxide) but with different metal electrodes (500 Ö Au, 500 Ö Al, and 500 ÖCr). To avoid contaminating and damaging substrate surfaces, we used shadow masks for metal deposition.

For substrate studies, the fabrication process of testing samples began by oxidation of silicon wafers. PVP and SU8-2 were spin-coated on oxide wafers and cured. 500 Ö Au was thermally evaporated through shadow masks onto wafers to form source and drain. Pentacene was then thermally evaporated onto the wafers.

Likewise, the fabrication process of the second study began by oxidation of silicon wafers. Different metals were thermally evaporated through shadow masks onto oxide wafers. Finally, pentacene was thermally evaporated onto the wafers.

To further study the relation between pentacene grain sizes and distance from metal electrodes, we also made metal ring structures. The substrates were kept at room temperature during pentacene deposition for all samples.

Grain diameters were calculated from scanning probe microscopic or atomic force microscopic images. Images taken with Veeco Digital Instrument Dimension 3100 AFM were analyzed with Scion Image program. After counting particle numbers, average grain diameters were calculated assuming grains are circular.

Our data show that pentacene has drastically smaller grains inside the channels electrodes than that far away electrodes for all 3 kinds of substrates: oxide, PVP and SU8-2. EDS spectrum confirms that there is no Au inside the channels. Not only Au, but also Al and Cr show the same phenomenon. Across the 400-um metal rings, pentacene grain diameters increase first and then decrease, confirming that pentacene grain growth is somehow suppressed by the presence of metal.

This phenomenon adds another reason supporting that pentacene thin-film transistors with bottom-contact electrodes have worse performances due to smaller grains. Currently, we are working on modeling this phenomenon and finding theoretical explanations.
Planarization Materials for Active Matrix Thin Film Transistor Arrays
Authors: Krishnamoorthy Ahila , Spear Richard , Gebrebrhan Amanuel , Stifanos Mehari , Bien Hai , Lowe Marie , yellowaga Deborah , Smith Peter
Published: April 2011

Traditional plasma based dielectric films are conformal and cost-prohibitive for large displays. Solution based dielectrics are planarizing in nature and provide a flat surface for indium tin oxide (ITO) layer with the resultant uniform liquid crystal response throughout the pixel. In this paper, we present the display-related material properties and integration results obtained by using a solution-based organosilsesquioxane material. The material exhibits extremely high transmittance and planarization, low outgassing, high resistance to moisture absorption and diffusion, good adhesion to other layers integrated with it and ease of integration.
Electro-Fragmentation Analysis of Dielectric Thin Films on Flexible Polymer Substrates
Authors: Pinyol Albert , Meylan Bastian , Gilliéron Damien , Mottet Aurélie , Mewani Vinodh , Leterrier Yves , Månson Jan-Anders E
Published: April 2011

A novel electro-fragmentation method was developed as a fast alternative to the time consuming fragmentation test carried out in situ in a microscope, to investigate the failure of dielectric coatings on polymer substrates using an ultrathin conductive layer. Focus was put on SiNx coatings on polyimide substrates. A careful selection of the conductive layer was carried out to avoid artifacts resulting for instance from a change of the residual stress state of the investigated coating. Au layers were found to be too ductile and Al-Ti layers altered the stress state of the nitride, which invalidated their use to probe the failure of the nitride coatings. In contrast, a 20 nm thick graphite layer was found to accurately reproduce the failure of the nitride, which was analyzed in terms of residual strain and cohesive properties of the graphite layer. An electro-fatigue device was built and preliminary results suggest that damage already develops in ultrathin coatings at relatively low strain levels under long-term fatigue loading.
Fabrication of Conductive Polymeric Arrays using Direct Laser Interference micro/nano Patterning
Authors: Lasagni Andrés Fabian , Acevedo Diego , Barbero Cesar , Muecklich Frank
Published: April 2011

Thin films of polyaniline (PANI) deposited onto different substrates were nano-structured using direct laser interference patterning (DLIP) at room temperature and pressure in air atmosphere. Regular line-like arrays with thicknesses up to 600 nm were fabricated by means of this technique in only one single step. The activity of the remained polyaniline was determined by monitoring its doping level using Energy Dispersive X-Ray Analysis (EDX), while its chemical structure was confirmed by Fourier Transform Infrared Spectroscopy using Attenuated Transmission Reflectance (FTIR-ATR). The structuring mechanisms of PANI supported in both polycarbonate (PC) and polyimide (PI) films were demonstrated using cross-sectional analyses performed with a dual-beam workstation (FIB/SEM Tomography). Moreover, by varying the fluence of the laser beam, it is possible to control the width of the PANI arrays, and large areas (mm2 - cm2) could be patterned. Additionally, electrical resistance measurements of the individual PANI strips demonstrated that electrical properties of unmodified regions remain unchanged.
Two-step Defect Reduction of GaAs/Si Epitaxy by Selective Aspect Ratio Trapping
Authors: Li Jizhong , Bai J. , Major C. , Carroll M. , Lochtefeld A. , Shellenbarger Z.
Published: April 2011

We report on the MOCVD growth of GaAs on patterned Si utilizing the Aspect Ratio Trapping (ART) method to reduce threading dislocations resulting from lattice mismatch. Defect-free GaAs was obtained from growth in sub-micron trenches formed in SiO2 on Si (001) substrates. Material quality has been characterized by cross-sectional and plan-view TEM and XRD. It was found that when growing GaAs above the trenched region, coalescence-induced threading dislocations (TDs) and planar defects were introduced at the coalescence junction interfaces. These defects were found to be unrelated to the misfit defects (MDs) on GaAs/Si interface that originated during initial epitaxial growth. Causes of coalescence defect formation were experimentally investigated by employing a two-step defect reduction scheme. It is concluded that by further optimizing growth conditions during coalesce layer growth, low defect-density GaAs material can be obtained on Si substrate.
Advances in the Research of the Intermediate Band (IB) Solar Cell
Authors: Luque Antonio , Martí Antonio
Published: April 2011

We describe the present state of the intermediate band (IB) solar cell research, a cell concept with very high efficiency potential. A comprehensive presentation of the theory is included followed of a description of its implementation using quantum dots and of the experiments performed to prove their principles. Present solar cells do not give today very high efficiencies; the steps to be given towards the real achievement of higher efficiencies is described and the use of alloys, instead of nanostructured materials, to fabricate IB cells is also discussed.
Evidence of Sequential Carrier Escape in III-V p-i-n Multi-Quantum Well Solar Cells
Authors: Alemu Andenet , Coaquira Jose A. H. , Freundlich Alex
Published: April 2011

Several InAsP/InP p-i-n Multi-Quantum Well (MQW) solar cells, only differing by their MQW region composition and geometry, were investigated. For each sample, the Arrhenius plot of the temperature related variation of the photoluminescence intensity was used to deduce the radiative recombination activation energy. The electron and holes confinement energy levels in the quantum wells and the associated effective potential barriers seen by each carrier were theoretically calculated. Carrier escape times were also estimated for each carrier. The fastest escaping carrier is found to display an effective potential energy barrier equal to the experimentally determined photoluminescence activation energy. This not only shows that the temperature related radiative recombination extinction process is driven by the carrier escape mechanism but also that the carriers escape process is sequential. Moreover, a discrepancy in device performance is directly correlated to the nature of the fastest escaping carrier.
Fabrication of Discrete Track Media with Patterned Servo-areas and Tracks on Disk Substrate
Authors: Tsuchiya Yuko , Ito Kenichi , Haginoya Chiseki , Hirayama Yoshiyuki
Published: April 2011

Discrete track media (DTM) with patterned servo-areas and recording tracks were fabricated on disk substrates in a two-step RIE process, creating a fine pattern transfer from an imprinted resist mask to a substrate surface without variations in groove depth. The fabricated DTM with perpendicular magnetic recording layers flew stably during read out signal detection.
Compositional Evolution of FePt Nanoparticles Prepared by Different Organometallic Synthesis Routes
Authors: Srivastava Chandan , Thompson Gregory B
Published: April 2011

Self-assembled FePt nanoparticle arrays are candidate structures for ultrahigh density magnetic storage media. One of the factors limiting their application to this technology is particle-to-particle compositional variation. In the present study, an analysis is provided for the formation mechanism of FePt nanoparticles synthesized from the thermal decomposition of Fe(CO)5 and the reduction of FeCl2 by superhydride. In both processes, Pt rich seeds initially form from the reduction of Pt acetylacetonate. The particle formation mechanism has been studied by extracting particles at different stages of the synthesis and individually determining particle-to-particle composition by STEM-XEDS. In the case Fe(CO)5, the Fe is gradually incorporated into the Pt seeds and produces a wide variation in compositional distribution about the mean value. In contrast, the FeCl2 has a nearly instantaneous shift in composition to the average value with the introduction of the superhydride reducing agent. The discrepancies in compositional uniformity between the two processes will be discussed in terms of the intrinsic differences between the different precursors.
The Effect of Fe Substitutions on the Microstructure of Gd5Si2Ge2
Authors: Podmiljsak Benjamin , McGuiness Paul , Kobe Spomenka , Skulj Irena
Published: April 2011

Gd5Si2Ge2 exhibits the so-called giant magnetocaloric effect, making it a potential material for next-generation near-room-temperature permanent-magnet-based refrigeration devices. In the as-cast form this material is relatively complicated in terms of its structure and its metallurgy.

Recent reports have suggested that small additions of iron can substantially improve the problems associated with hysteresis losses, so enhancing the material's potential for real-world applications. We have looked at iron substitutions in the range X=0 to X=1 for Gd5Si2-XGe2 to investigate the macrostructures and microstructures of cast and homogenized materials, with particular emphasis on the amount of iron substituting for silicon in the Gd5(SiGe)4 phase and the effect of the substituting iron on the Ge/Si ratio. The larger iron substitutions were found to eliminate the unusual macrostructures, and conventional ingots with smooth surfaces were the result. The iron was also found to dissolve at levels of 1-3% in the Gd5(SiGe)4 phase and encourage the formation of the Gd5(SiGe)3 phase at the expense of the magnetocaloric Gd5(SiGe)4 phase. A substitution of X=1 was found to be sufficient to produce as-cast microstructures consisting almost entirely of the Gd5(SiGe)3 phase.

With a scanning electron microscope (Jeol 840A) and an analytical transmission electron microscope (Jeol 2010 F with a field-emission gun) and an EDXS system from Oxford Instruments (Link Isis 300) we performed a detailed microstructural investigation of the processed materials. Special emphasis was placed on the intergrain regions and an assessment of the amount of Fe substituting in the main magnetocaloric phase.
Epitaxial Growth of Fe3Si Thin Films on (100) Magnesia Substrates
Authors: Akiyama Kensuke , Kaneko Satoru , Kadowaki Teiko , Hirabayashi Yasuo , Kyoduka Azusa , Sawada Yutaka , Kobayashi Yoshihiko , Asai Kichizo , Funakubo Hiroshi
Published: April 2011

A high-quality (100)-oriented epitaxial Fe3Si films were grown on (100) MgO substrates by RF-magnetron sputtering. The full width at half maximum of the Fe3Si 400 rocking curve was 0.18°, when the film was grown at 750°C. The epitaxial films of 100 nm thicknesses had a smooth continuous surface. The coercive field (Hc) was approximately 10 Oe, and the saturation magnetization (Ms) was 900 emu/cm3, which are almost the same as those of bulk Fe3Si. The anisotropy constant (K1) of magnetization indicated that the epitaxial Fe3Si films grown at 750°C mainly consisted of long range ordering phase (DO3 phase) and that the epitaxial films post-annealed at 900°C was constituted with ordering phase.
Large Magnetoresistance Variation of Pseudo Spin Valves with Different Nano Oxide Layer Position
Authors: Suh Jeong Dae , Ross C.A.
Published: April 2011

We have investigated the influence of the nano-oxide layer positions on giant magnetoresistance(GMR) of the NiFe(9nm)/Cu(4nm)/Co(5nm) pseudo spin valves. Nano-oxide layer positions had a several effects on the multilayer structure that changes its magnetotransport behavior. GMR ratio varied between 2.8% and 0.15% depending on the nano-oxide layer positions within the stack. The increase of the GMR ratio was accompanied by increase in resistance change, decrease in sheet resistance, and decrease in surface roughness. These significant variations of GMR ratio was explained by the changes on the spin dependent scattering or current shunting effect. Our results showed that appropriate placement of a nano-oxide layer was essential fo optimize magnetoresistance and properties of spin valves.
Magnetoresistance in Spin Valves Based on Organic Semiconductors with Ferromagnetic Electrodes
Authors: Tada Hirokazu , Kakita Motoyasu , Ikegami Tomonori , Nagano Tomohiro , Kawayama Iwao , Tonouchi Masayoshi
Published: April 2011

We have prepared layered sandwich structures composed of Co / organic materials / La0.67Sr0.33MnO3 and measured the magnetic field effect on electrical resistance. We inserted various OMs including pentacene, C60, 8-hydroxy-quinoline aluminum and titanyl-phthalocyanine with a thickness in the range from 200 nm to 1,000 nm. All devises prepared showed clear spin-valve characteristics with magneto-resistance (MR) ratios of approximately a few to 10% at low temperature. It was found that spins were transported in rather thick organic films, and the polarity of MR depended upon materials inserted and their film thickness.
Characterization of Epitaxial Bi-Layer-Structured Bi5Ti3FeO15 (m = 4) and Bi4Ti3O12-Bi5Ti3FeO15 (m = 3-4) Natural-Superlattice-Structured Multiferroic Thin Films Prepared by Pulsed Laser deposition
Authors: Nakashima Seiji , Nakamura Yoshitaka , Okuyama Masanori
Published: April 2011

Bi-layer-structured mutiferroic Bi5Ti3FeO15 (BTFO15) (m = 4) and natural-superlattice-structured Bi4Ti3O12- Bi5Ti3FeO15 (BIT-BTFO15) (m = 3-4) thin films have been prepared on (001) and (110) oriented SrTiO3 (STO) single crystal substrates by using pulsed laser deposition. X-ray diffraction patterns of these thin films on (00l) STO single crystals shows the obtained thin films were (00l)-oriented layer-perovskite single phase, and BIT-BTFO15 (m = 3-4) natural-superlattice-structure has also obtained. On (110) STO single crystal, layer perovskite (11l) oriented thin films have been also obtained. For characterizing ferroelectric properties, these thin films have been prepared on (001) and (110) oriented La-doped (3.73 wt%) STO single crystal substrates. From ferroelectric D-E hysteresis loops measurements, BTFO15 (m = 4) and BIT-BTFO (m = 3-4) thin films on (110) La-doped STO single crystals shows good ferroelectric hysteresis loops and their double remanent polarizations (2Pr) were 47 μC/cm2 and 44 μC/cm2, respectively. However, these thin films on (001) La-doped STO single crystals do not show ferroelectric characteristics.
Multiferroic Bi2NiMnO6 with a Double-Perovskite Structure: High-Pressure Synthesized Bulk and Epitaxially Grown Thin Films
Authors: Shimakawa Yuichi
Published: April 2011

A new multiferroic compound Bi2NiMnO6 was synthesized in both bulk and thin-film forms. Bulk samples were prepared under a high pressure condition at 6 GPa, and thin-film samples were epitaxially grown on single-crystal SrTiO3 substrates by a pulsed-laser deposition method. The crystal structure of the material is a double perovskite, in which Ni2+ and Mn4+ ions are ordered in a rock-salt configuration. Bi3+ ions at the A-site cause a noncentrosymmetric (C2) structural distortion which allows a spontaneous ferroelectric polarization at room temperature. Ni2+–O–Mn4+ magnetic paths lead to ferromagnetism through the superexchange interaction according to the Kanamori-Goodenough rule. A coupling between the ferromagnetic and ferroelectric interactions appears to exist, but it is quite small.
Dynamical Nonlinearities in Piezoelectric Materials
Authors: Seppälä Eira , Korpelainen Virpi , Ojasalo Kari , Sarjala Matti , Alava Mikko , Lassila Antti , Manninen Antti
Published: April 2011

Dynamical nonlinearities in piezoelectric materials have been investigated over different time and frequency scales using four different methods; measurements of displacement and electric polarization of bulk material, measurements of nanometer scale surface structure of the material by an atomic force microscope (AFM), and numerical modelling of ferroelectric materials with quenched randomness. Laser vibrometer measurements of the deformations of piezoelectric materials, d31 type PZT and PMN-PT sheets, have been done under sinusoidal voltage loading with different frequencies. This yields information about the dynamical hysteresis behavior, such as the area of the hysteresis loops as a function of the applied frequency f and voltage amplitude. Similarly the hysteresis loops have been measured for the electric polarization of the same samples. Relaxation behaviors of the same materials have been measured by an AFM. Topography of the piezo sheets was measured after applied DC voltage, indicating slow collective changes in the polarization close and at the sample surface. To investigate the time-dependent hysteresis, we have studied numerically a Ginzburg-Landau-Devonshire (GLD) model for ferroelectric materials including dilution type quenched randomness. Quantities studied include the area of the hysteresis loop, of the polarization in the material, and the coercive electric field Ec as a function of the frequency f, both as a function of the disorder strength.
Effect of Strain on the Tunability of Highly (100) Oriented Mn-doped Barium Strontium Stannate Titanate Thin Films
Authors: Lu Shengbo , Li Ngai Wing , Xu Zhengkui
Published: April 2011

Highly (100)-oriented Mn-doped barium strontium stannate titanate thin films of a nominal composition (Ba0.7Sr0.3)(Sn0.2Ti0.8-xMnx)O3(Mn-BSSnT) (x=0%, 0.2%, 0.4%, 0.6% and 1%), were fabricated by pulsed laser deposition on (La0.7Sr0.3)O3/LaAlO3substrates. Both elastic strain and inhomogeneous strain were measured by x-ray diffraction techniques. Relationship between the strain and the dielectric properties of the Mn-BSSnT thin films were systematically investigated as a function of the Mn content. Our results show that the tunability is dependent upon not only the elastic strain induced by thermal expansion coefficient and lattice mismatch between the thin film and the substrate but also inhomogeneous strain induced by Mn doping. The tunability decreases with increasing inhomogeneous strain and can be easily manipulated by changing Mn doping content, which is beneficial to real tunable device applications.
The Effect of Bi-excess Surface Layers on BiFeO3 Thin Films Prepared by Chemical Solution Deposition
Authors: Nakamura Yoshitaka , Nakashima Seiji , Ricinschi Dan , Okuyama Masanori
Published: April 2011

We have investigated the effect of Bi-excess surface layers of stoichiometric BiFeO3 thin films prepared by chemical solution deposition. A stoichiometric BiFeO3 thin film with both the Bi-excess top and bottom surface layers shows improved crystallinity with the remanent polarization of 65 μC/cm2 at 80 K, which is larger than BiFeO3 film prepared by the same process using stoichiometric solution. These results are attributed to the reduction of the imperfect crystal at the interface between BiFeO3 film and electrode. Stoichiometric BiFeO3 thin film with Bi-excess top and bottom surface layers also reserves the magnetic property of stoichiometric film. Stoichiometric BiFeO3 thin films with Bi-excess surface layers are an effective way to obtain good multiferroic properties.