bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of Organic Light-emitting Devices by Controlling Deposition Temperature and Inclusion of Carbon Nanotubes
Authors: Wang Guangfeng , Tao XiaoMing , Chen Wei
Published: April 2011

Research was conducted to improve performance of organic light-emitting devices (OLEDs) on flexible polyethylene terephthalate (PET) substrates based on tris-(8-hydroxyquinoline)¨Caluminum (Alq3). Based on double layer structure, indium tin oxide(ITO)/N,N’Diphenyl-N-N’-di(m-tdyl) benzidine (TPD)/Alq3/Al, flexible OLEDs on polyethylene terephthalate (PET) substrates were fabricated by physical vapor deposition (PVD) method, with the Alq3 layer deposited at 90°C , 120°C and 150°C, respectively. It was found that the temperature had great effect on the surface morphology of Alq3 and the devices fabricated at high temperature (150°C) showed a higher external efficiency than those fabricated at low temperature (90°C , 120°C).

Multi wall carbon nanotubes (MWCNTs) doping poly(3,4-ethylene dioxythiophene) (PEDOT) : poly(styrene sulfonate) (PSS) was used as hole injection layer to improve performance of OLEDs based on Alq3. PEDOT:PSS, which was doped by 0.2 wt.%, 0.4 wt.%, 0.6 wt.%, 0.8 wt.% and 1 wt.% MWCNTs, was coated on clean PET substrate with ITO by spin- coating method. The light-emitting layer (Alq3) and cathode layer (Al) were deposited by PVD method. It was found that the electroluminescence (EL) intensity of the OLEDs were highly improved by adopting MWCNTs doping PEDOT:PSS as hole injection layer. The luminous intensity obtained from the device with a concentration of 0.4 wt.% MWCNTs in the PEDOT:PSS layer was three folds as those adopted from device without MWCNTS doping in the PEDOT:PSS layer.
Effect of HVPE GaN Substrate Condition on the Characteristics and Performance of 405 nm LEDs
Authors: Grandusky James R , Jamil Muhammad , Jindal Vibhu , Shahedipour-Sandvik Fatemeh , Lu Hai , Cao Xian-An , Kaminsky Edmund B
Published: April 2011

This article reports on the effects of HVPE GaN substrate condition on the performance of 405 nm LEDs grown by MOCVD. Three 1 cm2 HVPE GaN substrates were received from a commercially available source and characterized for the substrate condition. AFM and optical microscope were used to characterize the surface morphology and this was found to vary from a “moonscaped” morphology to a smooth surface. The presence of nanoscale pits and substrate bowing were also found. XRD measurements showed a variation in crystalline quality of the substrates with the FWHM of the (0002) rocking curve varying from 87 arcsec to 192 arcsec with some substrates showing multiple peaks in the rocking curve. Photoluminescence was used to measure the optical quality of the substrates and both band edge luminescence and yellow luminescence were found to vary greatly within one substrate as well as from substrate to substrate. After characterization of each individual substrate a 405 nm LED structure was grown using identical growth conditions on each substrate, in separate growth runs. A GaN template was included in each growth for consistency. The surface morphology and crystalline quality of the device structures were then measured. Following this devices were fabricated and tested for electroluminescence optical output power and current-voltage characteristics. The device characteristics and performance as related to starting substrate quality will be presented with respect to substrate surface morphology and crystalline structure.
The Development of Zero-temperature-gradient Zero-bias Thermally Stimulated Current (ZTGZBTSC) Spectroscopy Technique for the Detection of Defect States in Ultra-thin High-k Dielectric Films
Authors: Lau Wai Shing , Wong Kum Fai , Han Taejoon , Sandler N. P.
Published: April 2011

Previously, we have reported our application of the zero-bias thermally stimulated current (ZBTSC) spectroscopy technique to study defect states in high-dielectric constant insulator films like tantalum oxide (Ta2O5) with much less parasitic current which can be a serious limitation for the conventional thermally stimulated current (TSC) method. However, a parasitic current can still be observed for ZBTSC because of a small parasitic temperature gradient across the sample. The thermal design of the ZBTSC system can be improved, resulting in zero-temperature-gradient ZBTSC (ZTGZBTSC) which can be used to detect deeper traps than ZBTSC.
Interfacial layer bonding and Dielectric properties of Hf-O-N gate dielectric thin films
Authors: Ramani Karthik , Essary Chad Robert , Craciun Valentin , Singh Rajiv K
Published: April 2011

The electrical response and interfacial layer characterization of nitrogen doped HfO2 gate dielectric thin films are reported. The films were processed at relatively low temperature (~ 400 0C) by pulsed laser deposition and ultra-violet radiation assisted oxidation technique. Nitrogen incorporation in the hafnia films led to O-N and Hf-Si-O-N bonding in the bulk and at hafnia-Si interface respectively. The nitrogen doped hafnia films exhibited a leakage current density lower than 10E-5 A/sq cm at -1 V and a simulated equivalent oxide thickness of 9.4 Å.
Silicate Formation at the Interface of high-k dielectrics and Si(001) Surfaces
Authors: Schmeisser Dieter , Zheng F. , Himpsel F.J. , Engelmann H.J.
Published: April 2011

The composition and chemical bonding of the first atoms across the interface between Si(001) and the dielectric determine the quality of dielectric gate stacks. An analysis of that hidden interface is a challenge as it requires both, high sensitivity and elemental and chemical state information. We used SR based photoelectron spectroscopies and, in particular, X-ray absorption spectroscopy in total electron yield and total fluorescence yield at the Si2p and the O1s edges to address that issue. We report on results of Hf-oxide prepared by ALD and compare to Pr2O3 / Si(001), and compare the two to the SiO2 / Si(001) system as a reference. For both, Hf-oxide and Pr-oxide thin films we find evidence for the silicate formation at the interface as derived from the characteristic features at the Si2p and the O1s edges.
Interface Engineering During Epitaxial Growth of High-K Lanthanide Oxides on Silicon
Authors: Osten H. Joerg , Czernohorsky Malte , Bugiel Eberhard , Kuehne Dirk , Fissel Andreas
Published: April 2011

We investigated the influence of additional oxygen supply and temperature during the growth of thin Gd2O3 layers on Si(001) with molecular beam epitaxy. Additional oxygen supply during growth improves the dielectric properties significantly; however too high oxygen partial pressures lead to an increase in the lower permittivity interfacial layer thickness. The growth temperature mainly influences the dielectric gate stack properties due to changes of the Gd2O3/Si interface structure. Optimized conditions (600 °C, pO2 = 5·10-7 mbar) were found to achieve equivalent oxide thickness values below 1 nm accompanied by leakage current densities below 1 mA/cm2 at 1 V.
Surface Preparation Techniques for the Atomic Layer Deposition of Hafnium Oxide
Authors: Nyns Laura , Hall Lindsey , Conard Thierry , Delabie Annelies , Deweerd Wim , Heyns Marc , Van Elshocht Sven , Van Hoornick Nausikaa , Vinckier Chris , De Gendt Stefan
Published: April 2011

Atomic layer deposition (ALD) has been successfully used over the years for the deposition of conformal dielectric layers with precise thickness down to the nanometer scale. Therefore, optimization of the growth behaviour of the dielectric is mandatory. Since ALD is a surface sensitive growth technique, determined by the amount of available reaction sites at the starting surface, the impact of various wet chemical and thermal Si treatments on the HfO2 growth was evaluated. Thin SiO2 starting layers, based on wet chemical processing, were prepared by using a diluted peroxide mixture and an ozone/DI-water treatment. The thermally grown oxides were gradually etched by slowly immersing the oxidized Si substrate into a diluted HF solution, creating a thickness range on a single wafer. Our results demonstrate that the HfO2 deposition is more dependent on the thickness of the SiO2 layer than on the chemistry used to grow the oxide layer. For all studied oxides, two regions can clearly be distinguished. First, a linear relationship between the oxide thickness and the amount of deposited HfO2 is seen. Because chemical oxides tend to grow in islands, this trend can be explained by an increase in density of surface OH groups when the oxide grows thicker. When an ellipsometric thickness of ~0.8 nm is reached, saturation of the HfO2 growth is obtained. We believe that, from this thickness on, the starting surface is completely covered with hydroxyl groups, leaving the HfO2 growth only dependent on the ALD process itself. Since both the wet chemical as the thermal oxides are showing the same trend in HfO2 deposition, it can be stated that surface preparations can be selected solely based on their ease of processing. However, the electrical results show that there may be a difference between the ozone based wet chemical oxides and the etched thermal oxides, since the latter seems to possess slightly more leakage current. The electrical results will be discussed in more detail during the presentation.
Understanding Structural Changes in Phase Change Memory Alloys
Authors: Fons Paul James , Brewe Dale , Stern Ed , Kolobov A. V. , Tominaga Junji
Published: April 2011

In addition to their wide-spread application in the re-writable optical memory markets, phase-change memory alloys are also poised to take a prominent role in future non-volatile memory applications due to their potential for low-energy usage and indefinite cyclability compared with their silicon-based flash memory counterparts. In contrast with their widespread use, however, the details of the crystalline to amorphous switching process utilized for memory storage remain an active research topic with many details still lacking. Considering the conflicting requirements for high-speed switching, yet long term data storage integrity, a deeper understanding of these materials is essential for insightful application development. We have used x-ray absorption fine structure spectroscopy (XAFS), a technique equally suitable for amorphous and crystalline phases to elaborate details in structural changes in the phase-change process for a variety of phase-change alloys in static measurements. As the kinetics of the switching process are the linchpin for optimizing switching characteristics, we have recently initialted dynamic measurements of light -induced structural changes in Ge-Sb-Te (GST) alloys. These measurements have been carried out synchronously using both femtosecond and nanosecond laser pump pulses in conjunction with 100~ps x-ray pulses generated by an electron storage ring. By synchronously triggering the laser with a variable sub-nanosecond delay, we have been able to use XAFS to probe details of the dynamics of the switching process. Preliminary results learned from this approach applied to GST alloys are presented.
Modeling Considerations for Phase Change Electronic Memory Devices
Authors: Wicker Guy
Published: April 2011

This paper discusses the modeling of phase change, chalcogenide alloy, electrical memory devices. Optical disk modeling, which uses the same alloys has yielded a good understanding of how the material's structural change is related to temperature, time, nucleation of crystallites, and crystal growth. From this base, models of electrical memory behavior have been developed. Modeling the complex electronic nature of the amorphous phase is discussed and suggestions for improving device performance using these models are made.
Localized Light Focusing and Super Resolution Readout via Chalcogenide Thin Film
Authors: Tominaga Junji , Fons Paul , Shima Takayuki , Kurihara Kazuma , Nakano Takashi , Kolobov Alexander , Petit Stephane
Published: April 2011

We have demonstrated that certain chalcogenide layers within a spinning super-RENS optical disc allow to squeeze the 650 nm laser beam to a spot size as fine as 50 nm using a 15-nm chalcogenide film. The near-field light was focused at a depth of just over 30 nm after passing through a chalcogenide film. Finite-difference time-domain (FDTD) simulations also reproduced these results. We suggest that a conductive ring aperture generated in the chalcogenide layers plays an important role in the localized light focusing.
Ag-Sb-S Thin Films Prepared by RF Magnetron Sputtering and Their Properties
Authors: Gutwirth Jan , Wagner Tomas , Vlcek Milan , Drasar Cestmir , Benes Ludvik , Hrdlicka Martin , Frumar Miloslav , Schwarz Jiri , Ticha Helena
Published: April 2011

One of the recent applications of thin chalcogenide films is rewritable optical data recording. This technology is based on reversible phase transition between crystalline and amorphous state and vice versa. Dominant materials for rewritable optical recording are Ge Sb Te and Ag In Sb Te alloys. Material research still continues due to need of increasing storage capacity and data rates. Thin Ag Sb S films were prepared by RF magnetron sputtering as potential candidates for rewritable optical data storage films.

There were prepared polycrystalline bulks of AgSbS2. Composition and homogeneity of these bulks were checked by scanning electron microscopy with energy dispersive analysis (SEM EDX) structure and bonding relations were studied by Raman spectroscopy and × ray diffraction (XRD).

Targets for RF magnetron sputtering were prepared from pulverized bulks by hot pressing technique. Targets were characterized the same way as bulks.

Composition and homogeneity of prepared thin films were characterized by SEM EDX, character (amorphous/crystalline) was studied by XRD. Optical properties (spectral dependence of refractive index) were evaluated on basis of UV Vis NIR spectroscopy and variable angle spectral ellipsometry (VASE).

Crystallization abilities were traced by thermal dependence of optical transmission of prepared thin films.
A DoD Perspective on Left Handed Negative Index Materials and Potential Applications
Authors: Browning Valerie , Tanielian Minas H , Ziolkowski Richard W. , Engheta Nader , Smith David R.
Published: April 2011

In the quest for ever smaller, lighter weight, and conformal components and devices for radar and communication applications, researchers in the RF community have increasingly turned to artificially engineered, composite structures (or “metamaterials”) in order to exploit the extraordinary electromagnetic response these materials offer. One particularly promising class of metamaterials that has recently received a great deal of attention are “left-handed” or negative index materials. Because these metamaterials exhibit the unique ability to bend and focus light in ways no other conventional materials can, they hold great potential for enabling a number of innovative lens and antenna structures for a broad range of commercial and DoD relevant applications. Exploring the possible implementation of negative index materials for such applications will require significant enhancements in the properties of existing Negative Index Materials (NIM) (bandwidth, loss, operational frequency, etc.), as well as improved understanding of the physics of their electromagnetic transport properties. For this reason the Defense Advanced Research Project Agency (DARPA) has initiated a program that seeks to further develop and demonstrate NIM for future DoD missions including, but not limited to, the following: 1) lightweight, compact lenses with improved optics; 2) sub wavelength/high resolution imaging across the electromagnetic spectrum; 3) novel approaches to beam steering for radar, RF, and/or optical communications; and 4) novel approaches for integrating optics with semiconductor electronics. A brief overview of the salient properties of NIM will be presented as well as a general discussion of a few of their potential applications.
Novel Passive and Active Transmission Line Metamaterial Devices
Authors: Caloz Christophe
Published: April 2011

This paper presents a number of metamaterial (MTM) structures and devices, with emphasis on the so-called transmission line (TL) MTMs, which have lead to most practical applications so far. Both results obtained from 2002 to mid-2005 [1] and recent advances over the past few months are described.
Novel Continuous Poly(vinylidene fluoride) Nanofibers
Authors: Ren Xi , Dzenis Yuris
Published: April 2011

Poly(vinylidene fluoride) (PVDF) is well known for its ferroelectric and piezoelectric properties. Currently, this polymer is used in applications in the form of films. PVDF fibers are expected to open up exciting new opportunities such as design and use of active textiles and composites. It is well-known that synthetic fiber properties improve substantially with the decrease of their diameter. However, conventional mechanical fiber spinning processes usually produce fibers with diameters in the range from tens to hundreds of microns. In this work, ultrafine, submicron-diameter continuous PVDF nanofibers were fabricated by electrospinning method. The method consists of spinning polymer solutions in high electric fields. Effects of process parameters on nanofiber diameter and morphology were studied. XRD and FTIR analyses of PVDF nanofibers were performed. The latter indicated that the initial á phase of the raw material was converted to â phase PVDF during electrospinning. As â phase is primarily responsible for the piezo- and ferroelectric properties of PVDF, the latter result is very encouraging. The demonstrated novel continuous PVDF nanofibers can be used in nanostructured active textiles and composites and can lead to unusual new designs for actuators and sensors.
Electrical Percolation in Carbon Nanotube Dispersions: A Mesoscale Modeling and Experimental Study
Authors: Rahatekar Sameer Sharad , Shaffer Milo S P , Elliott James A
Published: April 2011

This paper describes our current work on electrical percolation in carbon nanotubes filled thermoplastic polymer fibers. The objective of this work is to develop an understanding of how the electrical properties of the nanotube/polymer composites are affected by processing conditions, orientation of nanotubes, and their loading fraction. In the first part of the work, mesoscale modelling of nanotubes was carried out using a dissipative particle dynamics method. The percolation threshold required to achieve an electrically conductive network of nanotubes within in a polymer fibre was predicted as a function of orientation and aspect ratio of nanotubes using a Monte Carlo method to measure the network impedance. In the second part of this work, X-ray diffraction analyses were carried out to find the degree of alignment of nanotubes in polyamide 12 fibers.
Eu-Doped Silica Nanotubes: Synthesis and Optical Properties
Authors: Murphy Catherine , Hunyadi Simona E.
Published: April 2011

Silver nanowires were coated with a silica shell through an indirect approach. Incorporation of the fluorescent ion Eu(III) into the silica shell in situ was achieved. Subsequent chemical dissolution of the inner metal core resulted in fluorescent silica nanotubes. Transmission electron microscopy (TEM), electron dispersive X-ray microanalysis (EDAX), fluorescence spectroscopy, and zeta potential measurements were used to characterize the materials.
Supramolecular Nanotube Hosts for Encapsulation of 10-nm-Scale Objects
Authors: Shimizu Toshimi
Published: April 2011

Supramolecular nanotube hosts with precisely controlled inner or outer diameters have been synthesized by self-assembly of cardanol-based glycolipids, glucopyranosylamide lipids, or glucose-based unsymmetrical bolaamphiphiles. Time-resolved fluorescent measurement using 8-anilinonaphtahalene-1-sulfonate (ANS) as a probe revealed that the water confined in a cardanol-based glycolipid nanotube has relatively lower solvent polarity than bulk water, which corresponds to that of 1-propanol. Extensively developed hydrogen bond networks also characterize the confined water in comparison to the case in bulk water. Encapsulation ability of the glucopyranosylamide lipid nanotube, which depends on capillary action, has been examined by filling the lyophilized lipid nanotubes with aqueous dispersions of gold or silver nanocrystals, ferritin, or magnetic crystals. We have also succeeded in filling the unsymmetrical bolaamphiphile nanotube, which possesses positively charged inner surfaces, with negatively charged polymer beads or ferritin without depending on capillary action.
“Scratching” Carbon Nanotubes onto Si Substrates
Authors: Yu Jun , Chen Ying
Published: April 2011

Large-scale, high-density, and patterned carbon nanotubes (CNTs) on both pure Si and quartz (SiO2) substrates have been produced using different approaches. The CNTs were synthesized by pyrolysis of the ball-milled iron phthalocyanine (FePc) in a tube furnace under a Ar-5% H2 gas flow. Because patterned CNTs are difficult to grow directly on smooth and perfect single-crystalline Si wafer surface, mechanical scratches were created to help the selective deposition and growth of CNTs on the scratched areas. This simple process does not require pre-deposition of any metal catalysts. For SiO2 substrates, which can be readily covered by a CNT film, patterned CNTs are produced using a TEM grid as mask to cover the areas where CNTs are not needed. The growth temperature and vapor density have strong influence on the patterned CNT formation. The scratch areas with a special structure and a higher surface energy help the selective nucleation of CNTs.
In-situ Study on Effects of Annealing Temperature and Mo Interlayer on Stress Relaxation Behaviors of Pure Al Films on Glass Substrates
Authors: Park Young-Bae , Hwang Soo-Jung , Lee Yong-Duk , Jung Ja-Young , Joo Young-Chang
Published: April 2011

The in-situ SEM observation of real-time hillock evolution in pure Al thin films on glass substrate during isothermal annealing at 194°C was analyzed quantitatively to understand the compressive stress relaxation mechanism by focusing on the effect of Mo interlayer between Al film and glass substrate. There is a good correlation between the hillock-induced stress relaxation and the measured stress relaxation by wafer curvature method. It is also clearly shown that the existence of Mo interlayer plays an important role in hillock formation probably due to the large difference in interfacial diffusivity of Al films.
Fabrication and Characterization of Flexible, Microfabricated Neural Electrode Arrays Made from Liquid Crystal Polymer and Polynorbornene
Authors: Keesara Varun Vardhan , Durand Dominique M. , Zorman Christian A.
Published: April 2011

This paper reports the development of flexible, neural electrode arrays made from liquid crystal polymer (LCP) and a polynorbornene (PNB) known by its trade name AvatrelTM. Each array consists of a single flexible, polymeric structure composed of an 8 mm-wide pad supporting eight Pt contacts connected to an ASIC mounting pad by a 5 cm-long, 2 mm-wide shaft carrying eight, 50 μm-wide Pt interconnect lines. The Pt conductors sit atop a 50 μm-thick base layer and are isolated from the environment except at the contacts by a capping layer of the same material as the base. In both cases, the devices were fabricated using conventional microfabrication techniques adapted for the particular polymeric material. In the case of LCP, the base structure was fabricated on 50 μm-thick sheets that were laminated and etched into the final structure. In contrast to LCP, PNB is spin castable and photodefinable, which enabled conventional photolithographic patterning techniques to be employed in a straightforward manner. The PNB-based devices could readily be fabricated, however issues related to LCP etching necessitated the development of a multi-step etch process to form the vias that expose the contacts. Electrodes made from both polymers could support electrical loads typical of stimulation applications without failing. A simple cell culture test suggests that Avatrel™ may be biocompatible, at least for short term applications.
Structural and Hydriding/Dehydriding Properties of HoMn2Hx with Cubic and Hexagonal Laves Phase Structure
Authors: Makihara Yoshikazu , Iwata Youichi , Umeda Kazumi , Miyairi Yoshio , Fujii Hironobu
Published: April 2011

Both the cubic C15-type and the hexagonal C14-type Laves phase compounds HoMn2 were successfully prepared. We found that they absorbed hydrogen up to 3.4 atoms per formula unit at room temperature and discharged it at around 490 K, reversibly. Structural and hydriding/dehydriding properties of the host HoMn2 and their hydrides HoMn2Hx have been investigated by powder X-ray diffraction (XRD) and thermogravimetry/differential thermal analysis (TG/DTA). With increasing the hydrogen content, the host C15-type HoMn2 is distorted into a rhombohedral phase at above x = 2.9, while the host C14-type one keeps the hexagonal structure up to x = 3.4. The experimental results obtained from TG/DTA measurement suggest that two possible interstitial sites with different activation energies for hydrogen desorption exist in the C14 HoMn2, while one site in the C15 HoMn2.
H Adsorption On Rh (110) Surface
Authors: Chen Shao-Ping
Published: April 2011

We have used the density functional theory to study the H adsorption phenomena on Rh (110) surface with H coverage from 0.33 to 2.00 mono-layers. We found H atom favors the three-fold coordinated site as observed experimentally. We confirmed the existence of 1x3-H (0.33 H coverage), 1x2-H (0.5 H coverage), 1x3-2H (0.66 H coverage), 1x1-2H (2.0 H coverage) ordered structures. We also found that the proposed 1x3-2H structure for H coverage of 0.66 is not the lowest energy configuration. We have proposed a new 1x3-2H structure which needs to be tested by future experiments. This is a preliminary report and a more detailed description of the work will be published later.
Self-selective Epitaxial Growth of BST Films: toward Nano-composite Structure for Microwave Tunable Devices
Authors: Yamada Tomoaki , Sherman Vladimir O. , Noeth Andreas , Muralt Paul , Tagantsev Alexander K. , Setter Nava
Published: April 2011

Ba0.3Sr0.7TiO3 (BST) thin film composite structures were fabricated by means of a selective epitaxial growth process. The epitaxial growth of BST on SrRuO3 electrode surface was selectively achieved at 450∼485°C using a prepatterned ultra-thin amorphous BST layer that locally prevented crystallization. This self build-up mechanism resulted in a columnar composite structure, where epitaxial and amorphous BST columns are electrically connected in parallel. The epitaxial BST showed a high permittivity and a high tunability, whereas the amorphous BST showed a significantly lower permittivity and a very weak tunable behavior. The effective permittivity of the composite capacitors decreased linearly upon increasing the amorphous BST concentration q, while the tunability stayed fairly unchanged until q reached 70%, which agrees with the theoretical ferroelectric/dielectric parallel composite model. The results also give indirect evidence of a good separation between both BST phases.
Characterization of Glancing Angle Deposition Thin Film Optical Filters with Engineered Index Profiles
Authors: Gospodyn James , Taschuk Michael T. , Hrudey Peter C. P. , Tsui Ying Y. , Fedosejevs Robert , Brett Michael J. , Sit Jeremy C.
Published: April 2011

Periodic high-/low-index film stacks of Y2O3:Eu were grown with varying periodicities us-ing the glancing angle deposition (GLAD) technique onto silicon and fused silica substrates. Post-deposition annealing at temperatures from 600 to 1000°C for 1 hour in atmosphere was per-formed to enhance the photoluminescent output of the films. The films were optically character-ized using transmission measurements and Mueller matrix ellipsometry. The luminescence was measured using a spectrometer calibrated for absolute intensity measurements using a frequency-quadrupled Nd:YAG pulsed laser as an excitation source. Absolute conversion efficiencies were measured for the films by characterizing the angular emission profile. The angular emission pro-file of the films was found to follow a non-Lambertian emission profile, with peak emission in-tensities at 50° to 60° with respect to the substrate normal.
Spectroscopic Study of Titanium Oxide Thin Films at Low Temperatures by X-ray Diffraction, Raman Scattering, Fourier Transform Infrared Spectroscopy and Photoluminescence
Authors: Zhao Zhiwei , Tay Beng Kang
Published: April 2011

Titanium oxide thin films were prepared by filtered cathodic vacuum arc (FCVA) at low temperatures ranged from room temperature to 330°C. Spectroscopic study of the deposited films were carried out by X-ray diffraction, Raman Scattering, Fourier transform infrared spectroscopy (FTIR) and photoluminescence (PL), respectively. The films remained amorphous up to the substrate temperature of 230°C. Nanocrystalline titanium oxide thin films occurred at 330°C with the strongest peak intensity from anatase (101) plane. The average grain size was around 20 nm and no rutile phase could be found. Various allowed vibrational frequencies (e.g. 152, 199, 399, 640 cm−1) in Raman spectra and Ti-O-Ti transverse mode at 436 cm−1 in the FTIR spectrum evidently verified the presence of anatase phase in the films at 330°C. Moreover, at room temperature only crystalline film exhibited a PL peak with the center at 379 nm in PL spectrum and the origin was discussed.
Effect of Polyvinylpyrrolidone Molecular Weight on the Critical Thickness, Crystallization, Densification and Properties of PLZT Films
Authors: Du Zehui , Ma J.
Published: April 2011

PLZT 9.5/65/35 ceramic films were prepared from the sol-gel solutions containing the stress-relaxing agent of polyvinylpyrrolidone(PVP) with the molecular weight of 40000, 360000 and 630000 (abbreviated as PVP40, PVP360 and PVP630) respectively. It is found that PVP40 can increase the critical thickness of the PLZT films to 0.22μm(compared with the critical thickness of 0.077μm in case of without PVP) and PVP360 and PVP630 can increase the critical thickness up to 0.49μm and 0.93μm individually. With the molecular weight of PVP increasing, the perovskite formation in the PLZT films was improved but the morphology of the films tended to be nano-porous. The films modified by PVP360 can be densified by optimizing the heat treatment conditions. When pyrolyzed at 600°C and then annealed at 700°C, the one-coating films with the thickness of 0.5μm were dense and exhibited a very slim hysteresis loop with the remnant polarization of 5.96×10−4μC/cm2 and coercive field of 21.51kV/cm, and a transmittance of around 90% and above in the wavelength of 450nm∼900nm.
Annealing and Persistent Photoconductivity Effects in Amorphous and Crystalline Vanadium Oxide Films
Authors: Kekas Jason , Dhawan Anuj , Gollakota Praveen , Muth John
Published: April 2011

Vanadium dioxide films have long attracted attention because of the phase transition between the semiconducting state and the metallic state at 68 degrees centigrade. Vanadium oxide films have been prepared by a variety of methods, including the annealing and oxidation of evaporated vanadium under controlled conditions. In this study we explore a different route by producing amorphous and crystalline VOx films by pulsed laser deposition and annealing under a variety of conditions. We found that that in amorphous films grown at lower temperatures and then annealed, persistent photoconductivity effects can be observed, while in epitaxial crystalline films grown at high temperature, persistent effects were not observed. Furthermore, it was found that for some crystalline films persistent optical effects were observed and that optical hysteresis was dependent on the amount of time after the film anneal.
Magnetic Resonance Imaging (MRI) of Water Diffusion in 2-Hydroxyethyl Methacrylate (HEMA) Gels
Authors: Raguin Guy , Falkenberg Cibele V. , Prakash Shaurya , FitzHenry Heather R. , Mensing Glennys , Ciobanu Luisa , Georgiadis John G. , Shannon Mark A.
Published: April 2011

A fundamental study focusing on correlating the local water self-diffusion coefficient to the local free water content in 2-hydroxyethyl methacrylate (HEMA) gels was conducted. HEMA gels were synthesized with different nominal water content (50% to 90%). MRI measurements of local diffusion coefficient distribution and local water content profiles are conducted on a 600 MHz scanner. The local water content is measured via two spin-echo images with sufficiently long repetition time (TR) to eliminate T1-weighting and two values for the echo time (TE) in order to account for T2-weighting. The local diffusion coefficient is determined using a standard pulsed-field gradient spin-echo sequence. The measured local water content and diffusion coefficient data are compared with several single-parameter diffusion models for interstitial diffusion in the hydrogel (Makie-Meares, Stokes-Einstein, Brownian motion around overlapping spheres).
Infusion of Nanotechnology in Chemistry Courses Through Laboratory Redesign and Vertical Threads
Authors: Nivens Delana A. , Lynch Will E. , Helmly Brian C. , Nguyen Nguyen T. , Dingra Nin , Chow Joyce , Svendsen Amanda , Harris Beverly D , Meeks April , Dyal Cassandra , Hadden Jodi , Tibah Denis M
Published: April 2011

Chemistry occupies a unique place in the university curriculum and is required by a wide variety of other disciplines because of its general utility. Unfortunately, the laboratory portion of the course does not always reflect the diversity and excitement of new research in and interesting applications of chemistry since the laboratory experience is designed to help the student master fundamental concepts. At Armstrong Atlantic State University (AASU) we are attacking this problem with the implementation of two series of nanotechnology based “vertical threads” throughout our chemistry curriculum. The vertical threads begin in the freshman year and provide continuity throughout the rest of the curriculum. Experiments direct the student's attention towards modern applications of chemical technology while providing chemical fundamentals expected in traditional laboratory exercises. By seeing these recurring threads at ever increasing levels of complexity, students build upon knowledge gained about nanotechnology with each additional laboratory course.

The approach used at AASU created two experimental “vertical threads” which are woven into the educational experience from the bottom-up in both the curriculum and the chemical methodology. Experiments performed in the freshman chemistry lab reappear in expanded forms in subsequent years as part of new experiments that mimic the biological, industrial and medical applications of nanotechnology.

We have concentrated our efforts in two areas: magnetite nanoparticles thread, and the chalcogenide nanoparticles thread. Magnetite nanoparticles are prepared by freshmen students while more advanced students modify these nanoparticles for real-world applications. Chalcogenide nanoparticles are synthesized by junior and senior level students and their spectroscopic properties are studied. Senior and undergraduate research students are involved in green synthesis of silver and gold nanoparticles as well as the use of ZnS, CdS and ceria nanoparticles for photocatalysis applications. The upper division students learn numerous instrumental techniques (i.e. UV-VIS, Fluorescence, FT-IR) within the context of nanotechnology. All students are presented with pre-laboratory and background materials that address the needs for new materials, new techniques for biomedical analysis and drug delivery as well as the environmental impacts of nanotechnology.
Nanotechnology Education: The Pennsylvania Approach
Authors: Fonash Stephen , Fenwick Douglas , Hallacher Paul , Kuzma Terry , Brunner Amy , Mahoney William , Ehrmann Robert
Published: April 2011

A workforce educated at the two-year degree and four-year degree level in nanotechnology, nanofabrication, and nano-scale characterization is required to grow and sustain nanotechnology manufacturing, and R&D. Pennsylvania has addressed this need with the creation of the Nanofabrication Manufacturing Technology (NMT) Partnership, a state-wide collaborative involving Penn State University, Pennsylvania College of Technology, all of the community colleges in PA, the 14 universities of the state-system, PA state government, the National Science Foundation, and PA industry. This partnership is based on sharing the expertise and facilities at Penn State's University Park campus with partner colleges and universities across the state. With this state-wide approach, the NMT Partner educational institutions can offer two-year degrees in nanotechnology and four-year degrees in biology, physics, and chemistry, with a concentration in nanotechnology, across PA. With the Partnership approach, participating institutions are also able to offer three-day Nanotech Camps for secondary school students, three-day nanotechnology workshops for secondary school teachers, and a variety of tools and materials for introducing nanotechnology into the secondary school classroom.
Advanced Inter-/Multi-Disciplinary Graduate-Level Programs for Education, Research, and Training in Nanoscience and Nanotechnology Offered at Osaka University
Authors: Itoh Tadashi , Akai Hisazumi , Ogawa Hisahito , Diño Wilson Agerico , Ichikawa Satoshi , Matsui Hiroaki , Ara Masato , Yoshiki Keisuke
Published: April 2011

Nanoscience: an area that promises new understanding of nature with the aid of rapid progress of nanotechnology. Nanotechnology: the use of nanoscience to build new technologies that will change the world. Nanoscience and Nanotechnology have captured the attention of the public, government, and corporations. How they will influence our lives depend on how we prepare ourselves, and our successors. Here we present a brief outline of the efforts being taken at Osaka University since 2004, in order to prepare our future scientists, engineers, and leaders in the rapidly flourishing trans-/multi-disciplinary field of Nanoscience and Nanotechnology.
Modeling Misfit Dislocation Arrays for the Growth of Low-Defect Density AlSb on Si
Authors: Jallipalli Anitha , Balakrishnan G. , Huang S.H. , Khoshakhlagh A. , Dawson L.R. , Huffaker D.L.
Published: April 2011

We present analytical models and experimental results to describe low-defect density growth (∼ 6 × 105/cm2) of highly mismatched antimonides on Si and GaAs substrates, with strain relief achieved at the growth interface through periodic, 90° interfacial misfit dislocations (IMF). We use molecular mechanics (MM) based modeling techniques to understand, at the atomic level, the spontaneous formation and energetics of these IMF. We have modeled, grown and characterized two systems extensively, these are - AlSb on Si with ∼ 13% mismatch and GaSb on GaAs with 7.83% lattice mismatch. Growth of these materials by molecular beam epitaxy (MBE) and subsequent High-Resolution Transmission Electron Microscopy (HR-TEM) has indicated that there is no tetragonal distortion in these two systems despite the high lattice mismatch. Instead, the mismatched epi-layers spontaneously form periodic IMF arrays that run along both [110] and [1-10] directions and relieve almost 100% of the strain in a few monolayers of deposition. To model this form of strain relief, we use existing theories of strain relief adapted for very high strain conditions and we also use bond energetics to model the strain-relieving interface. The IMFs in these systems are periodic and so is the deviation in bond lengths and bond angles, which restricts our calculation space to a finite number of elements. We shall also demonstrate extensive growth and characterization results of the materials grown with a particular emphasis on the strain-relieving interface to show excellent agreement of the experimental data with the proposed models. The high quality and low-defect density in AlSb grown on Si, has helped us demonstrate optically pumped IR VCSELs and edge emitters monolithically on Si (001) and this data will also be presented.
Spatially Resolved Characterization of Microstructure, Defects and Tilts in GaN Layers Grown on Si(111) Substrates by Maskless Cantilever Epitaxy
Authors: Barabash Rozaliya , Roder C. , Ice G. E. , Einfeldt S. , Budai J. D. , Liu W. , Barabash O. M. , Figge S. , Hommel D.
Published: April 2011

The spatially resolved distribution of strain, misfit and threading dislocations, and crystallographic orientation in uncoalesced GaN layers grown on Si(111) substrates by maskless cantilever epitaxy was studied by white-beam Laue x-ray microdiffraction, scanning electron microscopy, and orientation imaging microscopy. Tilt boundaries formed at the column/wing interface with the misorientation strongly depending on the growth conditions. A depth-dependent deviatoric strain gradient is found in the GaN. Types and density of misfit dislocations as well as their arrangement within different dislocation arrays was quantified. The results are discussed with respect to the miscut of the Si(111) surface and misfit dislocations formed at the interface.
High Sensitivity Sensor Based on Porous Silicon Waveguide
Authors: Rong Guoguang , Saarinen Jarkko J. , Sipe John E. , Weiss Sharon M.
Published: April 2011

Porous silicon (PSi) waveguides are fabricated as a new platform for high sensitivity biosensors. Biomolecules infiltrated into the PSi waveguide increase the effective refractive index of the waveguide and change the angle at which incident light couples into a waveguide mode. Due to the high surface area to volume ratio of PSi and the confinement of optical energy in the region where the biomolecules reside, the waveguide resonance is very sensitive to small concentrations of infiltrated molecular species. A resonance width below 0.1° has been obtained, which is sufficient to detect one monolayer of DNA covering the pore walls. In this work, a prism is used for the waveguide coupling in an arrangement that is similar to traditional surface plasmon resonance (SPR) sensing. Theoretical analysis suggests that an optimized PSi waveguide resonant sensor will show a 60-fold improvement in sensitivity when compared to a conventional SPR sensor due to the enhanced interaction between the electromagnetic field and biological material.
Effect of Silver Nanoparticles in the Hole Injection Layer on the Performance of Organic Light Emitting Diodes
Authors: Kim Jin heon , Lee Joon Ho , Kim Tae-Heon , Seoul Chang
Published: April 2011

The configuration of the OLED device is like this : ITO/PEDOT:PSS(Ag nanoparticle) /NPB/Alq3/Al

The effect of Ag nanoparticles in the hole injection layer on the performance of Organic Light Emitting Diodes(OLED) was investigated.

The hole mobility in the hole injection layer seems to be increased by Ag nanoparticles.

The increased current in the hole injection layer increased the emission efficiency of the OLED.

Initially, we try to incorporate silver nanoparticles(diameter:30nm) directly into the hole injection layer. However the Ag nanoparticles are aggregated into big particles, ( size 1∼2 μm). We can confirm this behavior by the optical microscope. Thus, PEDOT:PSS/Ag nanoparticles solutions were filtered before spin-coating and big particles were eliminated by this process.

The several silver nanoparticles concentration were selected (0.05, 0.1, 0.25 wt % of the silver nanoparticles was mixed with PEDOT;PSS solutions). Theses solutions were spin-coated on the ITO layer with 3000 rpm for 60 secs. The spin coated Ag, PEDOT:PSS solutions were heat treated at 100 °C in 30 min. The big Ag agglomerate was not observed in the optical microscope. Then the thermal evaporation of the NPB and Alq3 layer was conducted.

The current-voltage relation was measured for the device and compared with the OLED device without Ag particle. The lumninance of the devices are also measured. The Ag nanoparticle increases the deriving current and thus increases the quantum efficiency of the OLED.
Electrochromic Properties of Polycrystalline Nb2O5 Thin Films with Mg2+ Ions
Authors: Agarwal Gargi , Reddy G. B.
Published: April 2011

Sol-gel derived Nb2O5 thin films crystallize to a stable hexagonal phase on annealing at 600°C in air. These films have been intercalated with Mg2+ ions for the first time and the structural and the optical changes on intercalation have been reported. Films were intercalated and deintercalated with Mg2+ ions in galvanostatic mode. Mg intercalated films show about 35% transmittance variations in the entire spectral range. The FTIR studies show the formation of Mg-O-Nb bonds along with the formation of Nb-OH and Mg-O bonds. Small quantities of water is adsorbed during intercalation resulting in the formation of Mg(OH)2. The coloration is completely reversible on deintercalation. Formation of MgNb2O6 phase is seen on intercalation with 1M concentration of the electrolyte, which is found to be 'x' dependent, where ‘x’ is the ratio of the intercalated ions to the Nb atoms. 0.1 M electrolyte does not show the formation of this phase.
A Novel Sigma-Conjugated Hyperbranched Polysilane Polymethylphenylsilane-co-methylsilane (PMPS-co-MS)
Authors: Yu Jiang , Xu Weijian , Zhang Zhenghua , Ni Yu , Lu Yanbing , Xiong Yuanqin
Published: April 2011

A novel σ-conjugated hyperbranched polysilane is presented, and it has good solubility in common organic solvents. The photoluminescence (PL) emission spectrum of it exhibits an emission maximum at 425nm, which indicates that the polymer emits blue light. The resulting polymer also has good thermal stability and high glass transition temperature. Therefore, it demonstrates a promising application in blue light emitting diodes.
Hall Effect in Organic Single-crystal Field-effect Transistors
Authors: Takeya Jun , Yamada Koichi , Tsukagoshi Kazuhito , Aoyagi Yoshinobu , Takenobu Taishi , Iwasa Yoshihiro
Published: April 2011

We report Hall effect of charge carriers accumulated in organic field-effect transistors. Rubrene (C42H28) single crystals are shaped in to the Hall-bar congiguration in the devices so that the Hall signal is appropriately detected in external magnetic fields. It turned out that inverse Hall coefficient, having a positive sign, is close to the amount of electric-field induced charge upon the hole accumulation. The observation of the normal Hall effect means that the electromagnetic character of the surface charge is not of hopping carriers but resembles that of a two-dimensional hole-gas system. The direct access to the density of mobile charge carriers provides a tool to understand nontrivial features of organic field-effect transistors such as gate electric field dependent mobility.
Hopping Transport and Voltage Induced Metal-Insulator Transition in Polythiophene Field Effect Transistors
Authors: Dhoot Anoop Singh , Wang Guangming , Moses Daniel , Heeger Alan J.
Published: April 2011

We have studied the carrier transport in regio-regular polythiophene field effect transistors (FETs) by four-probe measurements of the steady-state channel conductance from room temperature to 4.2 K. At high gate voltage (constant total carrier density, n = 5×1012 cm−2) and at low temperatures, we demonstrate that the gate voltage and source-drain voltage combine to induce the insulator-to-metal transition. In the insulating regime, the carrier transport is well described by phonon assisted hopping in a disordered Fermi Glass (with Coulomb interactions between the hopping charge carrier and the charge left behind). At the highest gate voltages and at sufficiently high source-drain voltages, the data imply a zero-temperature transition from disordered insulator to metal.