bluuebunny/crossref_metadata_2025 huggingface dataset:
Thickness and Strain Effects on RF/Microwave Properties of BST Thin Films on NdGaO3 Substrates
Authors: Simon William Kurt , Koray Akdogan E. , Bellotti Jeffery , Safari Ahmad
Published: April 2011

Ba0.60Sr0.40TiO3 thin films were deposited on <100> oriented NdGaO3 substrates by pulsed-laser deposition. Film thickness ranged from 20 nm to 800 nm. Microstructural features, as evaluated with AFM and FESEM, have exhibited high quality thickness dependent topography. X-ray analyses have shown consistently <110> textured films of high crystallinity. Permittivity, Q-factor, and tunability, were investigated using interdigitated capacitors in the 0.1–20 GHz range. Effect of film thickness on dielectric properties and tunability in polycrystalline <110> textured films exhibited strong thickness dependence in their elasto-dielectric properties. Tunability up to 45% was observed at moderate field levels (∼ 7 MV/m), while the Q-factors remained ≤40.
Growth of epitaxial tetragonal Pb(Zr,Ti)O3thin films with 100% polar-axis-orientation and their electrical properties
Authors: Morioka Hitoshi , Yokoyama Shintaro , Oikawa Takahiro , Saito Keisuke , Funakubo Hiroshi
Published: April 2011

Pb(ZrxTi1-x)O3(PZT) thin films with the various Zr/(Zr+Ti) ratios and the film thickness of 50 and 250 nm were epitaxiallly grown on (100)cSrRuO3//(100)SrTiO3substrates by metalorganic chemical vapor deposition at 540 °C. 50 nm-thick tetragonal PZT films consistd of 100%c-axis-orientation for the Zr/(Zr+Ti) ratio ranging from 0.13 to 0.56, while 250 nm-thick tetragonal ones consistd of about 70%c-axis-orientation for the range from 0.19 to 0.45. On the other hand, 50 and 250 nm-thick films composed rhombohedral single phase for the Zr/(Zr+Ti) ratio above 0.56 and 0.60, respectively. Mixture region of tetragonal and rhombohedral phases was observed from 0.45 to 0.60 for 250 nm-thick films, but was not for 50 nm-thick ones. Remanent polarization monotonously decreased with increasing the Zr/(Zr+Ti) ratio for 50 nm-thick films in tetragonal PZT films. These results show that Ti rich tetragonal PZT thin films have large spontaneous polarization with good square-shape hysteresis loops and are applicable for the high-density capacitor-type ferroelectric random access memories.
Enhancing Tunability and Decreasing Temperature Sensitivity
Authors: Tidrow S. C. , Tauber A. , Potrepka D. M. , Crowne F. , Rod B.
Published: April 2011

The employment of judicious substitution on B-sites in the perovskite oxide, BaTiO3, has yielded materials suitable for relatively temperature insensitive electric field tunable microwave devices. The properties, single-phase cubic perovskites with tunabilities as large as 30% at 1 V/μm and room temperature that possess low temperature coefficient of dielectric constant and tunability over the majority of the military specified temperature range, -55 to 125 °C, have been achieved in the charge compensated system Ba1-xSrxTi1–2yCyDyO3 where C is Ho, Er, Tm, Lu, Sc, Y, In and D is Ta, Sb with 0 ≤ X ≤ 0.2, and 0 < y ≤ 0.10.
Bi-Directional Motion Achieved with a Surface Micromachined Electrothermal MEMS Microengine
Authors: Kolesar Edward , Jayachandran Alfred , Odom William , Ruff Matthew , McAllister Justin , Ko Simon , Howard Jeffrey , Allen Peter , Wilks Richard , Wilken Josh , Boydston Noah , Bosch Jorge
Published: April 2011

This research is focused on the design and experimental characterization of an electrothermal microengine that is capable of bi-directional motion. The microengine has been operated to control the position a linear shuttle and rotate a set of gears.
Microstructure and Magnetostriction of Rapidly-solidified Fe-Ga System Alloy
Authors: Okazaki Teiko , Furuya Yasubumi , Saito Chihiro , Matsuzaki Takashi , Watanabe Tadao , Wuttig Manfred
Published: April 2011

Rapid-solidification method was applied to make Fe-15at%Ga and Fe-17at%Ga ribbons of 100 μm thickness. These ribbons have large magnetostriction of 270 ppm, where the coercive force exhibits a maximum value. The phenomenon is related to special metallic texture, that is, the ribbon has strongly [001]-oriented textured fine columnar microstructure with grain size of 2∼5 μm. The ribbon has little-hysteresis loop of magnetostriction and a good ductility (i.e., full bending is possible). Rapid-solidified Fe-Ga alloy has a promising possibility as a new magnetic-induced sensor/actuator material.
Accelerated Reliability Test Inputs in Analyzing the Device Response of MgZnO Based UV Detector
Authors: Hullavarad S.S. , Takeuchi I. , Berger J. , Dhar S. , Chang K.S. , Venkatesan T. , Loughran T.C. , Vispute R.D. , Yedave S.N.
Published: April 2011

In this paper we present the accelerated reliability testing of MgZnO based UV detectors. The UV detectors are fabricated on glass, quartz and sapphire substrates by Pulsed Laser Deposition (PLD) technique. The films are highly oriented and show sharp transmission at 350nm and 330nm for Mg composition of 10% and 20% in ZnO, respectively. The device response has been studied and life expectancy of the devices has been estimated from the accelerated tests.
A Large Grain Polycrystalline Silicon Film for Resistive Bolometers
Authors: Kim Tae-Sik , Lee Hee Chul
Published: April 2011

Large grain polycrystalline silicon films as a sensing material for infrared bolometers have been proposed and investigated. Using a seed selection through ion channeling technique, we have successfully increased the average grain size of polysilicon films up to 1670Å. The achieved TCR value at 20°C and grain boundary defect density of the film are found to be as high as -2.46%/K for a resistivity of 30Ωcm and to be about 1.752×1012/cm2, respectively. From the measurement of noise characteristics of the film, the value of k, 1/f noise parameter, is calculated to be 1.35×10-9. As a result, the estimated detectivity is found to be 5.6×108cmHz1/2/W.
Combinatorial Thin Film Synthesis of NiMnAl Magnetic Shape Memory Alloys Using MBE Technique
Authors: Hassdorf R. , Feydt J. , Thienhaus S. , Borowski R. , Boese M. , Walther T. , Moske M.
Published: April 2011

Composition spreads close to the Heusler alloy Ni2MnAl were grown onto 4-inch wafer substrates using molecular beam epitaxy. Compositional variations of up to 10 at.% relative to each constituent enable a direct comparison of the chemical-structural relationship with respect to martensitic transformation and to magnetic ordering as well as an efficient identification of the emerging phase stability regions. In this study, we set the primary focus on the structural aspects of the transformation behavior as observed by X-ray microdiffraction in combination with a specially designed heating stage. Notably, cross-sectional HRTEM imaging of the respective composition areas reveals a laminated two-phase martensitic structure inside the single grains, identified as a sequence of 2M and 14M variants. Stress relief upon transformation as observed by mechanical stress measurements reaches to 400 MPa depending on the composition. Magnetization measurements so far indicate field-induced ordering to occur at low temperatures, here, below 50 K which is assumed to be closely related to a high degree of structural disorder on the Mn-Al sublattice. Single-crystal thin films were realized by means of an epitaxial relationship to MgO (001).
Synthesis and characterization of Ca1-X SrxCu3Ti4O12 thin films for dielectric applications
Authors: Guzman R. , Tomar M.S. , Melgarejo R.E.
Published: April 2011

There is a great deal of interest in CaCu3Ti4O12 system for dielectric applications. We have studied Ca1-xSrxCu3Ti4O12 system for different compositions. The material is synthesized by sol-gel chemical solution route and thin films were deposited by spin coating. Thin films were investigated by x-ray diffraction and Raman spectroscopy for structural properties. These results indicate a solid solution for the compositions x = 0.00 to 0.80. The SEM micrographs shows the uniform films at 800° C, but the dielectric response of Ca1-xSrxCu3Ti4O12 (x = 0.00) shows the dielectric constant value below 200.
Modified BiFeO3-PbTiO3 Morphotropic Phase Boundary (MPB) Piezoelectric Ceramics for High Temperature and High Power Applications
Authors: Cheng JinRong , Eric Cross L.
Published: April 2011

BiFeO3-PbTiO3 (BF-PT) crystalline solutions have been modified by La3+, Ga3+ and Ba2+ substituent. The modified BF-PT had morphotropic phase boundary (MPB), at which the ferroelectric rhombohedral phase transferred to the tetragonal symmetry. The piezoelectric properties at the MPB were strongly depended on different substituents. The modified BF-PT system showed the insulation resistivity up to 1012 ω·cm at room temperature. Lanthanum played a critical role making BF-PT softer to be poled to the piezoelectric state. Ga provided BF-PT additional polarization and breakdown strength with La substituent. In the system with La3+, Ga3+ and Ba3+ simultaneously, addition of Ba enhanced dielectric and piezoelectric activity. It was flexible to tailor BF-PT by using different substituents. In the vicinity of MPB, the Curie temperature Tc was above 385°C of BF-PT for La <10 at%, whereas the d33 constant was as high as 295 pC/N for one with La of 20 at%. The modified BF-PT revealed comparable performances to conventional Pb(Zr,Ti)O3 (PZT) ceramics, but in significantly lead reduced forms.
Nanoscale Ferroelectric Properties of PZN-PT Single Crystals Studied by Scanning Force Microscopy
Authors: Bdikin I. K. , Shvartsman V. V. , Kholkin A. L.
Published: April 2011

High-resolution domain studies were performed in Pb(Zn1/3Nb2/3)O3-4.5%PbTiO3 (PZN-PT) single crystals via piezoresponse force microscopy (PFM). Irregular domain patterns with the typical sizes of 20–100 nm were observed on the (001)-oriented surfaces of unpoled samples. On the contrary, (111) crystal cuts exhibited normal micron-sized regular domains with the domain boundaries directed along allowed crystallographic planes. The existence of nanodomains in (100)-oriented crystals was tentatively attributed to the relaxor nature of PZN-PT where small polar clusters were predicted to exist upon zero-field cooling. These nanodomains were considered as the nuclei of the opposite polarization state that ease the switching process for this particular crystal cut. Local piezoelectric hysteresis was also performed by PFM on the nanometer scale. Similar switching behavior of (111)- and (100)-oriented PZN-PT crystals suggests that their superior piezoelectric properties can be related to the domain wall motion rather than to the perovskite lattice itself.
Sterilizing Properties of Carbon Nanotube Composites
Authors: Narayan Roger J.
Published: April 2011

Hydrogen-free carbon nanotube composites have been created that possess unusual free radical generation properties. These films have the ability to nonspecifically kill bacterial cells and can be used to sterilize a surface. These composites have been formed by simultaneous pulsed laser ablation of carbon and bombardment of nitrogen ions generated by a Kaufman ion source at high temperatures (600- 700°C). The results suggest the creation of a new form of carbon that is predominantly trigonally-coordinated, with small fractions of carbon-nitrogen bonds. TEM studies allow us to conclude that the material consists of sp2-bonded ribbons wrapped approximately +/-15° normal to the surface. Plan-view high resolution TEM specimens demonstrate layers with curvature similar to that seen in multiwalled nanotube structures. In addition, the interlayer order extends to approximately 15–30 nm. These novel structures result from the use of energetic ions, which create nonequilibrium conditions that alter the growth mode of graphitic planes. In vitro testing revealed significant antimicrobial activity against Staphylococcus aureus bacteria. Possible applications include use on the functional surfaces of dialysis equipment, scalpels, and other sterile equipment.
Stability of Nitrogen and Hydrogen in High-k Dielectrics
Authors: Bastos K.P. , Pezzi R.P. , Miotti L. , Soares G.V. , Driemeier C. , Morais J. , Baumvol I.J.R.
Published: April 2011

We report here on atomic transport, thermal stability, and chemical evolution of HfSiO, HfSiN, and AlON films on Si(001), aiming at investigating the atomic scale behaviour of the involved chemical species, N and H in particular, when the films are submitted to usual thermal processing steps in inert and oxidizing atmospheres. The films were characterized by nuclear reaction analyses in resonant and non-resonant regions of the cross-section curves, X-ray photoelectron spectroscopy, and low energy ion scattering. The HfSiN/Si structure was shown to be more resistant to oxygen diffusion than HfSiO/Si, although the amounts of O incorporated in HfSiN/Si are larger than in HfSiO/Si. The main channel of oxygen incorporation is atomic exchange with nitrogen or oxygen atoms. HfSiN film on Si incorporate more hydrogen (or deuterium) and in more stable configurations than HfSiO/Si. Nitrogen incorporation into AlON films on Si renders this structure more stable against thermal annealing in vacuum and/or oxidizing atmospheres than Al2O3/Si.
Crystallinity and Wet Etch Behavior of HfO2 Films Grown by MOCVD
Authors: Saenger Katherine L. , Cabral Cyril , Jamison Paul C. , Preisler Edward , Kellock Andrew J.
Published: April 2011

The crystallinity and wet etching behaviors of ultrathin (<10 nm) HfO2 films grown by metal organic chemical vapor deposition (MOCVD) were examined as a function of deposition temperature, film thickness, and post-deposition annealing. Films 3 nm in thickness deposited at 400 or 500 °C were amorphous as-deposited and slowly etchable in aqueous HF; after annealing at 700 °C, the same films showed some nanocrystallinity and were impervious to HF. However, thicker films grown under the same conditions showed significant crystallinity and were impervious to HF even as-deposited. These observations, in combination with measurements on various samples etched back by an Ar+ ion damage/wet etch process, suggest a film structure comprising an initially amorphous near-interface region capped with a HF-resistant crystalline upper layer. It was found that the initially amorphous near-interface region (the bottom 1–3 nm) of films grown at 500 °C can be induced to at least partially crystallize as the upper part of the film starts becoming crystalline as-deposited, but that this near-interface region remains at least partially amorphous after annealing at 700°C.
Optical and Dielectric Properties of Eu- and Y-Polytantalate Thin Films
Authors: Vasilyev Vladimir , Drehman Alvin , Dauplaise Helen , Bouthillette Lionel , Volinsky Alex
Published: April 2011

Due to their highly efficient photo-luminescent (PL) characteristics, the physical properties of rare-earth polytantalates, RETa7O19(RE=Eu and Y) were further studied. AFM, SEM, HRTEM, x-ray reflectometry, spectroscopic ellipsometry and standard dielectric testing were used to determine film thickness, roughness, index of refraction, band-gap, dielectric constant, leakage current and breakdown field for as-deposited (amorphous) and post-annealed (crystalline) films. Structural and morphological properties of the Film/SiO2/Si interfaces were also examined.
Study of metal gate work function modulation using plasma and SiH4 treated TiN thin films
Authors: Fillot F. , Maîtrejean S. , Farjot T. , Guillaumot B. , Chenevier B. , Passemard G.
Published: April 2011

As gate oxide thickness decreases, the capacitance associated with the depleted layer in polysilicon gate becomes significant, making it necessary to consider alternative gate electrodes. Titanium nitride (TiN) films elaborated with TiCl4 precursor is widely studied as metal gate in semi-conductor technology. In this work, a study of TiN metal gate deposited by MOCVD using TDMAT (Tetrakisdimethylamino titanium) precursor is proposed. N2, H2 plasma application and SiH4 treatment after TiN thin film growth modify composition and microstructure. Consequently, they alter the physical properties of films. Such treatments may be a way to modulate work function and thus to control threshold voltage.

Metallic layers were deposited in a chamber using a commercial 8 inch wafer deposition tool. In this study, structural and compositional properties of TiN were correlated with work function measurements. Firstly, the composition evolution (carbon content) was studied by AES and SIMS as a function of plasma and SiH4 treatments; XRD gave details on the microstructure. Secondly, MOS structures were processed on uniformly p-type doped wafers. C-V curves of capacitors were used to estimate the flat band voltage (VFB) and gave access to the work function, the effect of oxide fixed charges and the density of interface states. It is shown that as-deposited amorphous films exhibit a work function of 4.4 eV. Exposure to SiH4 is shown to increase this work function of about 150 meV. Thin films properties are not impacted by anneal treatments. Work function stability was tested at 425 °C, 900 °C and 1050 °C. Thermodynamic compatibility with gate oxide was verified thanks to experimental results and calculations.
Structural Comparisons of SiOx and Si/SiOx Formed by Passivation of Single-Crystal Silicon by Atomic and Molecular Oxygen
Authors: Kisa Maja , Twesten Ray D. , Yang Judith C.
Published: April 2011

The structural characteristics of a silica layer and Si/SiO2 interface formed on Si single-crystal by oxidation in hyperthermal atomic oxygen (AO) and molecular oxygen (MO) at 493K were compared by wide variety of experimental techniques. The hyperthermal AO with kinetic energy of 5.1eV was created by the pulsed laser detonation of oxygen gas. The oxide formed by AO and MO on Si single crystal is amorphous as observed by HRTEM and selected area electron diffraction (SAED). However, the oxide formed by AO has a less random distribution of silicon and oxygen atoms as compared to the oxide formed by MO, as evidenced by the SAED patterns and EELS spectra. In contrast to MO formed silica, initial EELS results across the Si/SiO2 interface revealed no region of suboxides exists near the interface in the AO formed silica. The Si/SiO2 interface formed by AO species was found to be very abrupt and the oxide homogeneous, as opposed to the broad interface and non-homogeneous oxide created by MO, as determined by HRTEM and EELS.
Theoretical Analysis of Oxygen Diffusion in monoclinic HfO2
Authors: Ikeda Minoru , Kresse Georg , Nabatame Toshihide , Toriumi Akira
Published: April 2011

In this report, we present the detailed analysis of the interstitial oxygen (O2+, O0, O2-) diffusion in monoclinic HfO2 (hafnia) using the first principles calculations. The interstitial oxygen atom kicks out the oxygen atom at the 3-fold-site and occupies the 3-fold-site. And then the newly kicked-out interstitial oxygen atom jumps to the nearest neighbor site and couples again with the atoms at the crystal sites. This kick-out- mechanism is valid for all charge states of the interstitial oxygen in monoclinic HfO2. In hafnia, the interstitial oxygen atom can take 3 charge states (+2, 0, -2) depending on the chemical potential (Ef), whereas the oxygen-vacancy in hafnia can get +2 or 0 charge state being dependent on Ef. In the lower range of Ef, O2+ and O0 might contribute. In the middle range of Ef, the O2- does not contribute to the diffusion process in hafnia because of the pair annihilation process between O2- and oxygen vacancy (V2+) defect pair. We can simulate such a pair annihilation process in hafnia. In the higher range, O2- might contribute the diffusion process.
Study of work function of CVD WSix thin film on high K dielectric.
Authors: Maîtrejean S. , Allégret S. , Fillot F. , Farjot T. , Guillaumot B. , Passemard G.
Published: April 2011

To meet requirements of CMOS circuits at sub 45nm scale, gate oxide thickness shall decrease. Thus high K materials are needed as dielectric gate. In this setting, due to gate depletion effect, metallic material should be used as an alternative to poly silicon gate. Moreover, specifications on threshold voltage require modulation of gate material work function with respect to nMOS or pMOS transistor. WSix work function is known to be sensitive to material stoichiometry. In this work, WSix thin films with x between 2.2 and 2.5 are evaluated as metal gate on HfO2 and SiO2 dielectric. Film chemical characteristics are correlated with work function measurements.

Thin films are deposited using WF6 and dichlorosilane on a 200mm wafer industrial chamber. Thermal treatments are applied to sample in order to recrystallise the film and confirm it stability. MOS Capacitors are processed. Electrical characterizations (capacitance vs voltage) are used to extract work function with respect to film composition.

Films are chemically and morphologically stable up to 800°C. A W/Si ratio gradient is observed between surface and dielectric/film interface. Whatever the nominal stoichiometry, Si/W ratio is constant at this interface. This result is correlated with identical work function measurement for different nominal stoichiometry. Moreover no differences are observed between Vfb vs equivalent oxide thickness curves for HfO2 and SiO2 dielectric. High EOT variations have been identified for SiO2 capacitors in contrast with SiO2/HfO2 capacitors. These results characterize WSix as a suitable metal gate for nMOS transistors.
Oxide Reduction in Advanced Metal Stacks for Microelectronic Applications
Authors: Qin Wentao , Volinsky Alex A. , Werho Dennis , David Theodore N.
Published: April 2011

Aluminum and copper are widely used for microelectronic interconnect applications. Interfacial oxides can cause device performance degradation and failure by significantly increasing electrical resistance. Interfacial oxide layers found in Al/Ta and Ta/Cu metal stacks were studied using Transmission Electron Microscopy (TEM) combined with Energy Dispersive Spectroscopy (EDS) and Parallel Electron Energy Loss Spectroscopy (PEELS). The analysis indicates that the observed interfacial oxide layers, Al2O3 and mainly Ta2O5, result from spontaneous reductions of Ta oxide and Cu oxide, respectively. Thermodynamics enables interpretation of the results.
Long Retention Performance of a MFIS Device Achieved by Introducing High-k Al2O3/Si3N4/Si Buffer Layer
Authors: Fujisaki Yoshihisa , Iseki Kunie , Ishiwara Hiroshi
Published: April 2011

We introduced high-k Al2O3/Si3N4 buffer layer in MFIS (Metal-Ferroelectric-Insulator-Semiconductor) devices to reduce the leakage current though the buffer (I) layer. We prepared the buffer layer by nitridizing Si substrate by atomic nitrogen radicals and then deposited Al2O3 film using ALD (Atomic Layer Deposition) technique. The interface state density between the ALD-Al2O3/Radical-Si3N4 stacked insulator and a Si substrate is as low as 1011 cm−2eV−1. The current density less than 10−9 A/cm2 is realized under the 1V bias application using films with the capacitance density of 12fF/mm2. The c-axis oriented Bi3.45La0.75Ti3O12 (BLT) ferroelectric films were deposited to make MFIS structure. With this structure, we obtained the retention time as long as 1.5×106 sec (about 17 days). This excellent retention character is attributable to the high insulating property of the ALD-Al2O3/Radical-Si3N4 stacked insulator and also attributable to the perfect elimination of defects at the interfaces in the MFIS structure.
Separation of baculoviruses using molecularly imprinted polymer hydrogels
Authors: Bolisay Linden D.V. , March John F. , Bentley William E. , Kofinas Peter
Published: April 2011

The goal of this research is to develop molecular imprinted polymers (MIP) for biomimetic recognition of viruses. Our experimental results indicate that hydrogels can be produced, which can specifically and selectively bind recombinant baculoviruses. Although it is expected that imprinted cavities will be distorted due to the swelling of the hydrogel in water, our experiments show that even the swollen gels exhibit remarkable affinity toward recombinant baculovirus. The proposed methodologies for the synthesis and characterization of MIPs thus offer exciting avenues for the development of virus recognition techniques. The virus MIPs must function in aqueous environments. Our approach employs a more flexible non-covalent imprinting method, starting from a readily available polyamine polymer, and both MIP synthesis and testing are performed in aqueous solutions. The development of a virus imprinted MIP, which would apply to the identification, classification, and removal of viruses. This is currently a very difficult task, but the need is widespread in diverse sectors, including national security, human and animal health, crop protection, and biologics production. The development of general methods using MIPs capable of specific recognition of biological analytes would have an enormous value in medicine and bioanalytics.
Optical Transduction Schemes for Molecularly Imprinted Polymer Sensors
Authors: Murray George M. , Southard Glen E.
Published: April 2011

Molecular imprinting is a useful technique for making a chemically selective binding site. [1] The method involves building a synthetic polymeric scaffold of molecular compliments containing the target molecule with subsequent removal of the target to leave a cavity with a structural “memory” of the target. Molecularly imprinted polymers can be employed as selective adsorbents of specific molecules or molecular functional groups. Sensors for specific molecules can be made using optical transduction through chromophores residing in the imprinted site. The use of metal ions as chromophores can improve selectivity due to directional bonding. The combination of molecular imprinting and spectroscopic selectivity can result in sensors that are highly sensitive and nearly immune to interferences. [2]
Imprinting with Chemical Sensors - Challenges in Molecular Recognition and Universal Application
Authors: Dickert Franz L. , Lieberzeit Peter A. , Gazda-Miarecka Sylwia , Halikias Konstantin , Bindeus Roland
Published: April 2011

Molecular imprinting leads to functional polymers that are capable to incorporate the template used and thus lead to selective chemical sensor systems when combined with a suitable transducer. Benzene and xylene can e.g. be distinguished with a selectivity factor of nearly ten using mass-sensitive devices such as QCM and SAW, although they both contain an aromatic system and differ only by the methyl groups. Sensing materials are further tuned by using binary mixtures as templates. When analyzing polycyclic aromatic hydrocarbons (PAH) by fluorescence and QCM measurements, the sensitivity is substantially increased if a second template molecule is applied as a porogen. Capacitive sensor measurements on polymers imprinted with microorganisms, such as yeasts, show substantial sensor responses due to highly selective inclusion compared with a non-functionalised surface yielding only negligible effects.
Molecularly Imprinted Bile Acid Sequestrants: Synthesis and Biological Studies
Authors: Huval Chad C. , Chen Xi , Holmes-Farley S. Randall , Mandeville W. Harry , Polomoscanik Steven C. , Sacchiero Robert J. , Dhal Pradeep K.
Published: April 2011

Novel bile acid sequestrants based on a polyammonium backbone were synthesized using molecular imprinting technique. These imprinted polymer networks were prepared by crosslinking different polymeric amines with crosslinking agents in the presence of sodium cholate as the template. The template molecules were completely removed from the polymer matrices by repeated washings. The bile acid sequestration properties of these polymeric resins were evaluated under bothin vitroandin vivoconditions. Adsorption isotherms performed in physiologically relevant media revealed that molecular imprinting led to improvement in bile acid sequestration with about a twofold increase in the Ka(association constant). More importantly, hamsters fed with imprinted polymers in their diet excreted more bile acids than the non-imprinted control polymer. These results suggest that molecular imprinting may be potentially an interesting approach to prepare novel polymer therapeutics.
Engineering membranes for molecular recognition
Authors: Ciardelli Gianluca , Cioni Beatrice , Netri Riccardo , Porciani Francesco , Silvestri Davide , Cristallini Caterina , Barbani Niccoletta , Giusti Paolo
Published: April 2011

The technology of molecular imprinting permits recognition sites to be inserted into a polymeric material through the polymerisation of a monomer in the presence of a template, or through the dissolution of a preformed polymer in a solution containing the template and then crosslinking or phase inversion so as to obtain the matrix-template complex. This paper will focus on the application of both techniques in the realisation of polymeric membranes with molecular recognition properties in aqueous environments.
Multi-color Luminescence from Surface Oxidized Silicon
Authors: Sato Nanoparticles K. , Hirakuri K. , Iwase M. , Izumi T. , Morisaki H.
Published: April 2011

We fabricated the multi-color electroluminescent (EL) device using hydrofluoric (HF) acid solution treated and oxidized silicon (Si) nanoparticles. Strong red luminescence was obtained from the HF treated Si nanoparticles based EL device under a low forward bias of 4.0 V. On the other hand, green and blue luminescence, which could be seen with naked eye under room illumination, was observed for the oxidized Si nanoparitcles based EL device at the forward bias below 9.5 V, because of reduction of size due to oxidation onto the Si nanoparticle surface. Furthermore, the red/green/blue lights showed good stability for aging of a long period of time in air by the formation of oxidized layer on the surface. These results indicate that the EL devices developed in this study can realize as application to future flat panel display.
Platinum nanoparticles growth by means of pulsed laser ablation
Authors: Dolbec R. , Irissou E. , Rosei F. , Guay D. , Chaker M. , El Khakani M. A.
Published: April 2011

Platinum nanoparticles were deposited onto Highly Oriented Pyrolitic Graphite (HOPG) substrate by laser ablating a Pt target at room temperature into a vacuum chamber. By varying the helium background pressure (from 10-5 to 0.5 Torr) and the target-to-substrate distance (from 3 to 6 cm), we were able to explore a large range of kinetic energies (i.e., from ∼4 to ∼130 eV/atom) of the Pt ablated neutrals species impinging on the HOPG substrates. Thus, the effect of the kinetic energy on the size and the surface density of Pt nanoparticles has been investigated ex-situ by means of scanning tunneling microscopy (STM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The pulsed laser deposition technique is shown to produce Pt nanoparticles (of which diameter in the 1 – 4 nm range) with a relatively narrow size distribution. While the size of the PLD Pt nanoparticles is shown to be mainly influenced by the number of laser pulses, their shape is found to be more sensitive to kinetic energy of the Pt ablated species.
Integration of fullerenes and carbon nanotubes with aggressively scaled CMOS gate stacks
Authors: Ganguly Udayan , Lee Chungho , Kan Edwin C.
Published: April 2011

Here we report the first study towards the integration of fullerenes and carbon nanotubes (CNT) in the gate stack of CMOS technology, which is a promising hybrid approach of top-down and bottom-up fabrication process. Prospective processes for C60 and CNT deposition over an aggressively scaled 2 nm gate oxide in the MOS capacitor structure have been monitored. CV measurements show minimal silicon contamination and interface states. Step charging at a specific voltage that corresponds to a fixed number density of C60 is used to establish the structural integrity and size-mono-dispersion of C60. The CV method can be further used to probe the charge injection into C60 and its anions to establish fundamental understanding of their molecular orbital (MO) structure.
Quantum Dots from Carbon Nanotube Junctions
Authors: Cleri Fabrizio , Keblinski Pawel , Jang Inkook , Sinnott Susan B.
Published: April 2011

A tight-binding hamiltonian is used to study the electronic properties of covalently-bonded, crossed (5,5) metallic nanotubes with increasing degree of disorder in the junction region. At one extreme, ideal junctions between coplanar nanotubes with a minimal number of topological defects show a good ohmic behavior. Upon increasing disorder, ohmic conduction is suppressed in favor of hopping conductivity. At the opposite extreme, strongly disordered junctions as could be obtained after electron-beam irradiation of overlayed nanotubes, display weak localization and energy quantization, indicating the formation of a quantum dot contacted to metallic nanowires by tunnel barriers.
Si-N nanowire formation from Silicon nano and microparticles.
Authors: Rath Chandana , Pinyol A. , Farjas J. , Roura P. , Bertran E.
Published: April 2011

We report silicon nitride whisker formation from hydrogenated amorphous silicon (a-Si:H) nanoparticles grown by PECVD for the first time. We compared the results with the kinetics of whisker formation from ball milled crystalline silicon (c-Si) microparticles. Whisker formation is analyzed at different temperatures (900–1440 °C) and oxygen partial pressures. At temperatures equal or above 1350 C and at low oxygen partial pressure we observe monocrystalline α-Si3N4 whiskers having 30–100 nm diameter and several microns length. By increasing the oxygen partial pressure, the structure of whiskers is completely changed, as shown by electron microscopy. In this case we observe α-Si3N4 whiskers covered by an amorphous silica layer at 1350 C. Finally, when the precursor material is silicon microparticles, thicker (170–330 nm) and longer whiskers are formed.
Tunable Optical Absorption of Composites of Nanocrystalline Copper Prepared by in situ Chemical Reduction within a Cu2+-Polymer Complex
Authors: Huang Cheng , Huang Gang , Yang C. Z.
Published: April 2011

Research on nanocrystalline materials and the physics behind their properties have attracted considerable attention. A number of physical and chemical techniques have been used to synthesize different nanomaterials and nanocomposites. Optical absorption characteristics of composites containing nanosized metals or semiconductors have been investigated for potential applications in nonlinear optics and photonic crystals and also to understand the effect of particle size on the band gap of the material concerned. These materials show a large third-order nonlinear susceptibility. A polymer-matrix nanocomposite containing copper particles has been prepared by in situ chemical reduction within a polymer-metal complex solid film. The copper particle size in the order of 10 nm is controlled by the initial content of the metal ions in the complex. Their fractal pattern and the value of the fractal dimension indicate that there exists a cluster-cluster aggregation (CCA) process in the present system. Optical absorption spectra of copper-polymer nanocomposites show distinct plasma absorption bands and quantum size effect in the samples. More studies on optical properties of composites containing nanosized metals are within the Drudeframe on the basis of Mie theory, but the electrons behave in a wavelike rather than a particlelike way as the particle size decreases to below 10 nm, and the classical Drude model should be modified considering the quantum confinement effect. In this paper, the calculated blueshift of the resonance peak based on a quantum-sphere model (QSM) proposed by Huang and Lue, gives remarkable agreement with the experimental data as the size of copper particles embedded in the polymer becomes smaller.
New Zinc and Cadmium Chalcogenide Structured Nanoparticles
Authors: Daniels S. M. , O'Brien P. , Pickett N. L. , Smith J. M.
Published: April 2011

The growth of 2D quantum dot quantum well (QDQW) nanocrystals in which a shell of CdSe is grown onto cores of ZnS and capped with a further shell of ZnS is reported. The red shift in the interband absorption and photoluminescence spectrum of the quantum dots (QDs) indicates relocalization of carriers from confinement in the ZnS core to the CdSe shell. The change in interband absorption energy utilizing the effective mass approximation with spherical symmetry was modeled, enabling an estimate of the CdSe thicknesses grown. 1.8nm and 2.5nm ZnS cores were selected as the base on which to grow the CdSe shells. Despite the 12% lattice mismatch between ZnS and CdSe, our results indicate that we have successfully grown CdSe shells approximately three monolayers thick onto 2.5nm ZnS core. Anything beyond a single monolayer of CdSe could not be grown onto the 1.8nm core, although some success was observed by incorporating a CdS graded layer in-between the ZnS core and CdSe shell. The effect of ZnS shell thickness on photoluminescence efficiency has also been studied with optimum shell thicknesses showing quantum yields as high as 52%. Growth of these nanocrystals represents a significant step in the development of strained nanocrystalline heterostructures.
Synthesis and Characterization of Cd1−xCuxSe Quantum Dots
Authors: Hanif Khalid M. , Strouse Geoffrey F.
Published: April 2011

Cu:CdSe nanoparticle alloys were synthesized using inorganic cluster precursor via a lyothermal method. The dots synthesized were approximately 4 nm in size and exhibited doping levels as high as 20% for Cu(I). Cu(I) cations are randomly doped on the Cd-Td site based on a Vegard's law analysis, suggesting that doping arises from a random ion substitution mechanism. The resulting dots exhibited essentially no band edge photoluminescence due to a high level of trap site inclusions in these materials resulting from Se vacancy formation in order to compensate for the Cu+ replacing a Cd2+ ion. Se vacancy formation is evident in the XPS analysis of the Cd:Cu:Se ratios for these materials.
Towards the Design and Implementation of Surface Tethered Quantum Dot-Based Nanosensors
Authors: Medintz Igor L. , Sapsford Kim E. , Golden Joel P. , Clapp Aaron R. , Goldman Ellen R. , Mattoussi Hedi
Published: April 2011

Considerable progress has been made towards creating quantum dot (QD) based nanosensors. The most promising developments have utilized QDs as energy donor in fluorescence resonance energy transfer (FRET) processes. Hybrid QD-protein-dye complexes have been assembled to study FRET, to prototype analyte sensing and even to control or modulate QD photoluminescence. In order to transition the benefits of this technology into the field, QD-based nanosensors will have to be integrated into microtiter wells, flow cells, portable arrays and other portable devices. This proceeding describes two examples of QD-protein-dye assemblies. The first investigates the concepts of FRET applied to QD energy donors and the second describes a prototype biosensor employing QDs. We also introduce the first steps towards implementing surface-tethered QD-bioconjugates, which could potentially serve in the design of solid-state QD-based sensing assemblies.
Polarization Spectroscopy of Charged Single Self-Assembled Quantum Dots
Authors: Ware Morgan E. , Bracker Allan , Gammon Daniel , Gershoni David
Published: April 2011

We have demonstrated single dot spectroscopy of InAs/GaAs self-assembled quantum dots embedded in a bias controlled Schottky diode. The photoluminescence spectra exhibit discrete lines depending on bias, which we attribute to the recombination of positively charged, neutral, and negatively charged confined excitons. With excitation directly into the dot, large circular polarization memory is exhibited by the two charged exciton (trion) lines. This indicates long spin lifetimes for both the electron and the heavy hole in the quantum dots.
Low Thermal Conductivity and Related Thermoelectric Properties of Zn4Sb3 and CoSb3 Thin Films
Authors: Ito Kazuhiro , Zhang Lanting , Adachi Katsuyuki , Yamaguchi Masaharu
Published: April 2011

Thermal conductivity and other thermoelectric properties were investigated on β-Zn4Sb3 and CoSb3 thin films. They are prepared by co-deposition of the specific sets of Zn, Sb and Co targets by RF magnetron sputtering. Thermal conductivity measurement was performed based on an AC calorimetry method using LaserPIT. The Zn4Sb3 thin films investigated are Zn-rich with respect to the stoichiometric composition. Their thermal conductivity decrement is proportional to the reciprocal film thickness. A nano-scale grain size in a ∼350 nm-thick film specimen gives arise to an almost 50% reduction in its thermal conductivity (∼0.5W/mK) at room temperature. Low electrical resistivity and high Seebeck coefficient can be achieved simultaneously in the film specimen with properly controlled thickness and microstructure. A ZT of 1.2 at ∼460K has been obtained for the ∼350nm thick Zn4Sb3 film specimen. The minimum thermal conductivity of about 1.1 W/mK was obtained in a ∼325 nm-thick CoSb3 film specimen at room temperature.
A Variational Solution of the Thermoelectric Transport Properties of Two-Component Nanocomposite Systems
Authors: Garrity Patrick L. , Stokes Kevin L.
Published: April 2011

The successful fabrication of a nanocomposite in bulk form consisting of a randomly oriented assembly of nanoscale sized core-shell particles has required an increased understanding of the theoretical aspects of the thermoelectric transport properties. Our particular nanocomposite consists of a nanorod core in 1D quantum confinement coated with an outer conducting polymer shell. Upon fabrication of the bulk composite, these nanorods are embedded within a three-dimensional conducting polymer matrix. We address the nanorod thermoelectric components by assuming a single parabolic band within the one-dimension density of states. Both elastic and inelastic scattering of electrons or holes is accommodated by solving the variational form of the Boltzmann transport equation. An altered lattice thermal conductivity for the confined nanorods is calculated separately to account for boundary scattering that is important in low dimension structures. Exact expressions for the bulk effective electrical and thermal conductivities, Seebeck coefficient and figure of merit are then obtained through the field decoupling transformation, which is a special case of two-component composites. Our method is easily generalized to any two component composite of spherical or cylindrical microstructure and is independent of the materials bulk geometry. The results similarly apply to one, two or three dimensional transport regimes with or without quantum confinement merely by solving the appropriate fundamental transport equations for each constituent material. Comparison to experimental data is then presented which helps validate the nanocomposite theory.
Thermoelectric Properties of the cubic AgPb10SbTe12
Authors: Hsu Kuei-Fang , Loo Sim , Chen Wei , Uher Ctirad , Hogan Tim , Kanatzidis Mercouri G
Published: April 2011

AgPb10SbTe12 is one member of the cubic family of materials AgPbmSbTem+2, which adopts NaCl structure where Ag, Pb and Sb atoms occupy the Na site and Te atoms occupy the Cl site. Ingots of this compound were prepared by a solid state reaction for thermoelectric measurements. AgPb10SbTe12 is a narrow band gap semiconductor with Eg∼0.26 eV. In order to optimize the ZT of this member, compositions with deficiency of Ag and Bi-substitution were examined and found to exhibit enhanced power factor at 300 K. The Bi-substituted ingot had ZT∼0.39 at 300 K and ZT∼0.68 at 400 K. Carrier concentration and the mobility measurements are reported.
Thermal Conductivity Reduction of SiGe Nanocomposites
Authors: Harris T. , Lee H. , Wang D. Z. , Huang J. Y. , Ren Z. F. , Klotz B. , Dowding R. , Dresselhaus M. S. , Chen G.
Published: April 2011

High figure of merit has been reported in superlattice structures in recent years mainly due to a large reduction in thermal conductivity, while maintaining or even enhancing the power factor. These findings suggest the possibility of using nanocomposites to reduce a material's thermal conductivity and thereby increasing the thermoelectric figure of merit. The current work reports on the thermal conductivity of various Si-Ge nanocomposites synthesized in a simple and straightforward process that allows one to exploit nanoscale physics while rapidly producing macroscale devices. Composite synthesis consisted of combining Si nanoparticles approximately 70 nm in diameter with micron-sized Ge particles in various atomic ratios via hotpressing to form macroscale samples. Room-temperature thermal conductivity was measured for each of the nanocomposite samples and compared with the values of SiGe bulk alloys. In this preliminary work, we observed a significant reduction in bulk thermal conductivity in such materials.
Development of Experimental Techniques for Thermoelectric Properties Characterization of Low-Dimensional Structures
Authors: Hapenciuc Claudiu L. , Khan Fazeel J. , Borca-Tasciuc Theodorian , Wang Gwo-Ching
Published: April 2011

This work reports current efforts in developing experimental techniques applicable for thermoelectric properties characterization at micro and nanoscale. A one-dimensional transport model was used to asses the effects of heat leakage, non-symmetric boundary conditions, and electrical contact resistance, on thermoelectric properties measurements performed by transient Harman method. If the above effects are important, the thermoelectric figure of merit cannot be extracted directly from the ratio between the Seebeck voltage and the resistive voltage drop across the sample. On the other hand, measurements of both thermal conductivity and Seebeck coefficient can be performed if the temperature drop across the sample is acquired simultaneously with the voltage drop. The theoretical model and the experimental technique are validated by measurements performed on bulk calibration samples. Furthermore, this work shows that the spatial resolution of thermoelectric properties characterization methods can be enhanced by using scanning probe based techniques. Preliminary results are presented for Seebeck coefficient measurements of p-type or n-type calibration samples performed using an AFM probe instrumented with a temperature sensor.
Discussion on plasma shock waves generated by high-power pulsed laser
Authors: Li ZhiHua , Zhang DuanMing , Guan Li
Published: April 2011

Sedov-Taylor theory is modified to describe plasma shock waves generated in a pulsed laser ablating process. Under the reasonable asymptotic behavior and boundary conditions, the propagating rules in the global free space (including close areas and mid-far areas) of pulsed-laser-induced shock waves are established for the first time. In particular, the temporal behavior of energy causing the difference of the propagation characteristics between the practical plasma shock wave and the ideal shock wave in point explosion model is discussed in detail.
Thermoelectric Properties of Hot-Pressed GaN and InN
Authors: Yamamoto A. , Yamaguchi S.
Published: April 2011

An attempt was made to obtain bulk III-nitride semiconductors such as InN, GaN and InxGa1−xN alloy using hot-press method in order to test their high temperature thermoelectric properties. The Seebeck coefficient and the resistivity were –10μV/K and 1.8×10−6Ωm for InN, and –50μV/K and 1.9×10−4Ωm for GaN at 300K, respectively. Thermal conductivity determined by laser flash method with porosity correction was 17W/mK for InN and 2.6W/mK for GaN. For InN the Seebeck coefficient and the resistivity increased monotonously with increasing temperature, which indicates that InN is a metal or a degenerately doped semiconductor. The power factor and the figure of merit were 2.1 × 10−4W/mK2and 1.5×10−5K−1for InN and 6.9 × 10−5W/mK2and 2.6×10−5K−1for GaN at 650K, respectively.