bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modification of Nanoporous Silica Structures by Fluorocarbon Plasma Treatment
Authors: Cho Woojin , Saxena Ravi , Rodriguez Oscar , Achanta Ravi , Ojha Manas , Plawsky Joel L. , Gill William. N. , Baklanov Mikhail R. 
Published: April 2011

AbstractPolymerization occurring during fluorocarbon plasma treatment as a potential method for pore sealing was investigated. CHF3 was used as a reactant gas to expedite the rate of polymerization due to the presence of hydrogen and the low C/F ratio. The reactor pressure was varied from 30mTorr to 90mTorr to change the number of neutrals that act as the polymerizing species. The films were exposed to the plasma for times of 1min, 3min, and 5 min to observe the penetration depth of neutrals and the thickness of modified layer as a function of time. Dielectric constants were measured before and after plasma treatment. The film morphology was investigated by scanning electron microscopy before and after plasma treatment and a featureless surface morphology was observed at 90mTorr on a 56% porosity film. After plasma treatment, the average pore neck size decreases which may help reduce metal precursor penetration during metallization.
Silver Metallization with Reactively Sputtered TiN Diffusion Barrier Films
Authors: Gao L. , Gstöttner J. , Emling R. , Linsmeier Ch. , Balden M. , Wiltner A. , Hansch W. , Schmitt-Landsiedel D. 
Published: April 2011

AbstractThe physical and electrical properties as well as thermal stability of reactively sputtered titanium nitride (TiN) film serving as a diffusion barrier was studied for silver (Ag) metallization. The thermal stability of Ag/TiN metallizations on Si with 12-nm-thick TiN barriers, as-deposited and after annealing at 300-650°C in N2/H2 for 30 min, was investigated with sheet resistance measurement, X-ray diffraction, focused ion beam-scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. According to electrical measurement no change of sheet resistance was found after annealing at 600°C, but an abrupt rise appeared at 650°C annealing. There are two causes by which the Ag/TiN/Si structure became degraded. One is agglomeration of the silver layer, and the other is oxidation and diffusion which are also associated problems during thermal annealing.
Fabrication and Photoelectrical Characteristics of Polymer-Organic-Blend Photodetectors
Authors: Qi Difei , Varahramyan Kody , Selmic Sandra 
Published: April 2011

AbstractPolymer optoelectronics and microelectronics have been recognized as next generation technologies. One of the widely investigated materials for photodiode, LED and solar cell applications is the insoluble conjugated polymer poly(p-phenylene vinylene) or PPV. In this paper we present experimental results of a blended polymer-organic compound photodiode. This diode is based on a soluble derivative of PPV, poly(2-methoxy-5- (2,9-ethyl-hexyloxy)-1,4- phenylene vinylene) or MEH-PPV, and the organic material ethyl viologen dibromide or EVD. In making the photodiodes, solutions of MEH-PPV and EVD were spin-coated on indium tin oxide coated glass substrates. The thicknesses of these polymer-organic thin films were approximately 190 nm. An aluminum cathode was deposited by thermal evaporation. These devices were illuminated under monochromatic light in UV and visible range wavelengths. These thin polymer-organic blend photodiodes have shown an eight-fold increase in responsivity and quantum efficiency compared to pure MEH-PPV photodiode devices. The increase in photoconductivity of blended MEH-PPV:EVD photodiodes may be due to charge transfer by EVD dication. The results from this work clearly demonstrate the application of the reported approach for the realization of polymer photodiodes with increased photoconductivity characteristics.
A-Si Amoled Display Backplanes on Flexible Substrates
Authors: Nathan A. , Striakhilev D. , Servati P. , Sakariya K. , Sazonov A. , Alexander S. , Tao S. , Lee C.-H. , Kumar A. , Sambandan S. , Jafarabadiashtiani S. , Vygranenko Y. , Chan I.W. 
Published: April 2011

AbstractIn view of its maturity and low-cost, the amorphous silicon (a-Si) technology is an attractive candidate for active matrix organic light emitting diode (AMOLED) display backplanes on flexible substrates. However, the a-Si material comes with significant intrinsic shortcomings related to speed (mobility) and stability of operation, requiring novel threshold-voltage-shift (ΔVT) compensated thin-film transistor (TFT) pixel circuits and architectures to enable stable OLED operation. But given the dramatic progress in efficiency of OLED materials over recent years, the drive current requirement has been significantly lowered, thus relaxing the constraints on a-Si TFTs. For compatibility to plastic substrates, the a-Si TFT process temperature must be reduced from the conventional 300°C to ∼150°C or below, which tends to compromise the integrity of thin- film materials and device performance. Hence, optimizing the TFT process for high device performance with limited thermal budget is a necessary step towards flexible AMOLEDs with a-Si backplanes. This paper reviews the design and process challenges, and specifically examines the performance of TFTs and ΔVT-compensated integrated pixel driver circuits on plastic substrates with respect to current driving ability and long term stability. More importantly, lifetime tests of circuit degradation behaviour over extended time periods demonstrate highly stable drive currents and its ability to meet commercial standards.
Stability of Organic Thin Film Transistors
Authors: Han Jeong In , Kim Yong Hoon , Park Sung Kyu , Moon Dae Gyu , Kim Won Keun 
Published: April 2011

AbstractThe stability of organic thin film transistors (OTFTs) has become one of the most vital issues in this area of research. In this report, we investigated the stability of rubber stamp printed OTFTs. The electrical properties such as saturation field effect mobility, threshold voltage and on/off current ratio change significantly in ambient air condition. In order to analyze the degradation of the device, transistors were measured in vacuum, dry N2 and air environment as a function of time. In vacuum and dry N2 atmosphere, saturation field effect mobility and threshold voltage variations are relatively small compared to those measured in ambient condition.To realize an air stable device, we applied a passivation layer which protects the device from oxygen or water molecules which is believed to be the source of the degradation. With the passivation layer, the threshold voltage shift was reduced suggesting that a proper passivation layer is a prerequisite in organic-based electronics.
Polycrystalline Germanium and Silicon-Germanium Alloys on Plastic for Realization of Thin-Film Transistors
Authors: Hekmatshoar B. , Shahrjerdi D. , Mohajerzadeh S. , Khakifirooz A. , Robertson M. , Asl E. 
Published: April 2011

AbstractDevice-quality polycrystalline Ge layers have been grown on flexible poly-ethylene terephthalate (PET) substrates by means of stress-assisted Cu-induced crystallization at temperatures as low as 130°C and employed for fabrication of depletion-mode poly-Ge thin-film transistors (TFTs). These TFTs show an ON/OFF ratio of 104and an effective hole mobility of 110 cm2/Vs. The stress-assisted crystallization technique has been extended to crystallize SiGe alloys at low temperatures for possible fabrication of poly-SiGe TFTs on plastic. As a result, poly-Ge seeded poly-crystalline SiGe layers with 40% Si content are grown at a low annealing temperature of 180°C in the presence of 0.05% equivalent compressive strain.
The Electronic Circuit Composition and Structure of String for a Novel Braid Electronics-Systems by Kumihimo Structure
Authors: Kuniyoshi Shigekazu , Tanaka Kuniaki 
Published: April 2011

AbstractThe new integrated circuit concept that forms electronic equipment by the textile structure using the flexible fiber that has equipped the field effect transistor, the light emitting diode, the wiring pattern, etc. was proposed [1,2]. In this report, the structure of the filamentous body as a basic structure of the kumihimo with various electronic functions was examined. There are many kinds of one in the kumihimo by the number and how to unite the plaited thread used. Although such a highly efficient kumihimo-structure electronic integrated circuit can be realized using kumihimo with much thread, it becomes that much complicated. In order to simplify an argument here, square-type kumihimo that uses eight plaited threads is employed, and a basic logical circuit composition and the element arrangement on plaited thread are examined. Eight plaited-threads are divided into two groups that have four threads respectively, and they exist in the plane that intersected perpendicularly mutually. However, kumihimo is a 1-dimensional system fundamentally, it can be extended in the length direction if necessary, and it is considered that a quite complicated function is also realizable for a circuit with few input and output. Here, plaited thread that belongs to one group for convenience will be called warp and the other group will be called woof. The circuit composition and a concrete structure of threads for kumihimo are discussed.
Excimer Laser Crystallization of Sputter Deposited a-Si Films on Flexible Substrates
Authors: Kim Yong Hoon , Park Sung Kyu , Moon Dae Gyu , Kim Won Keun , Han Jeong In 
Published: April 2011

AbstractIn this report, excimer laser annealed polycrystalline silicon (poly-Si) films on flexible polymer substrates are investigated. The amorphous silicon (a-Si) films were first deposited on polycarbonate (PC) and polyethersulfone (PES) substrates by radio-frequency (RF) magnetron sputter and sequentially annealed by XeCl excimer laser annealing system (λ = 308 nm). The argon concentration of a-Si films which was estimated by Rutherford Backscattering Spectrometry (RBS) was found to be dependent on the dynamic pressure during the deposition process and the sputtering gas. Typically, the argon concentration of a-Si film was 1 ∼ 2% when the film was deposited using argon gas at 6 mTorr. After the annealing process, the average grain size of the poly-Si film annealed with laser energy density of 289 mJ/cm2was 400 nm estimated from transmission electron microscope (TEM) investigations.
Failure Modes and Grain-Boundary Effects in Polycrystalline Materials
Authors: Zikry M. A. , Ashmawi W. M. 
Published: April 2011

AbstractDislocation-density based multiple-slip constitutive formulations and specialized computational schemes are introduced to account for large-strain ductile failure modes in polycrystalline aggregates. Furthermore, new kinematically based interfacial grain-boundary regions and formulations are introduced to account for dislocation-density transmission, absorption, and pile-ups that may occur due to grain-boundary misorientations and void interactions.
Oxygen-Induced Dynamic Embrittlement in Nickel-Base Superalloys
Authors: McMahon C. J. , Kane W. M. 
Published: April 2011

AbstractThe phenomenon of dynamic embrittlement involves the stress-induced diffusion of a surface- adsorbed embrittling element into grain boundaries, leading to time-dependent decohesion along these boundaries. Here, the state of our understanding of this generic type of brittle fracture is reviewed, with the focus on cracking of nickel-base superalloys caused by oxygen, including recent and new results on cracking in bicrystals, thermo-mechanical processing to reduce the susceptibility to dynamic embrittlement, and quench cracking.
Distribution of Grain Boundary Planes at Coincident Site Lattice Misorientations
Authors: Rohrer Gregory S. , El-Dasher Bassem S. , Miller Herbert M. , Rollett Anthony D. , Saylor David M. 
Published: April 2011

AbstractThe grain boundary plane distributions in MgO, SrTiO3, MgAl2O4, and Al are compared at lattice misorientations with a coincident site density of greater than or equal to 1/9. In most situations, the most frequently adopted grain boundary orientation is a habit plane of low index and low surface energy that depends on the particular material. Cases where the most common boundary orientation is a plane of high planar coincident site density instead of a characteristic habit plane are rare. In fact, in most cases, the distributions of grain boundary planes at misorientations with high lattice coincidence are not substantially different from the distributions at other, more general misorientations. The results indicate that a model for grain boundary energy and structure based on grain surface relationships is more appropriate than the widely accepted models based on lattice orientation relationships.
Thermal Stability of InGaAs Quantum Dots Under Large Temperature Transients
Authors: Rangarajan R. , Elarde V. C. , Coleman J. J. 
Published: April 2011

ABSTRACTWe report here studies of the thermal stability of InGaAs quantum dots that have been subjected to various thermal treatments. Atomic force microscopy and photoluminescence spectroscopy are used to analyze the effects of the thermal treatments. In this paper we present data that demonstrates a remarkable improvement in the thermal stability of quantum dots that were rapidly cooled down to room temperature following the growth of a GaAs capping layer. The observed thermal behavior is attributed to metastable states formed during post growth thermal cycle.
Spectroscopic analysis of external stresses in semiconductor quantum-well materials
Authors: Tomm Jens W. , Biermann Mark L. , Passmore B. S. , Manasreh M. O. , Gerhardt A. , Tien Tran Q. 
Published: April 2011

ABSTRACTWe present an approach for spectroscopic strain analysis in semiconductor quantum-well devices. This approach is applicable to all types of semiconductor materials, and to spectroscopic techniques which employ the electronic band-structure of the material, such as photoluminescence, photoreflection, photocurrent, and transmittance. The approach is based on two components, namely the theoretical calculation of the strain-sensitivity of the spectral positions of the relevant quantum-confined optical transitions within a particular quantum-well, and the spatially resolved measurement of a substantial part of the optical transition sequence within the quantum-well. The primary experimental technique applied in our approach is photocurrent spectroscopy. InAlGaAs/GaAlAs/GaAs, high-power lasers serve as the model species.
ZnO Spintronics and Nanowire Devices
Authors: Norton David P. , Heo Young-Woo , Tien L C , Ivill M P , Li Y , Kang B S , Ren Fan , Kelly J , Hebard A F , Pearton Stephen 
Published: April 2011

ABSTRACTZnO is a very promising material for spintronics applications, with many groups reporting room temperature ferromagnetism in films doped with transition metals during growth or by ion implantation. In films doped with Mn during PLD, we find an inverse correlation between magnetization and electron density as controlled by Sn doping. The saturation magnetization and coercivity of the implanted single-phase films were both strong functions of the initial anneal temperature, suggesting that carrier concentration alone cannot account for the magnetic properties of ZnO:Mn and factors such as crystalline quality and residual defects play a role. Plausible mechanisms for the ferromagnetism include the bound magnetic polaron model or exchange is mediated by carriers in a spin-split impurity band derived from extended donor orbitals. We will also review progress in ZnO nanowires. The large surface area of nanorods makes them attractive for gas and chemical sensing, and the ability to control their nucleation sites makes them candidates for micro-lasers or memory arrays. Single ZnO nanowire depletion-mode metal-oxide semiconductor field effect transistors exhibit good saturation behavior, threshold voltage of ∼-3V and a maximum transconductance of 0.3 mS/mm. Under UV illumination, the drain-source current increased by approximately a factor of 5 and the maximum transconductance was ∼ 5 mS/mm. The channel mobility is estimated to be ∼3 cm2 /V.s, comparable to that for thin film ZnO enhancement mode MOSFETs and the on/off ratio was ∼25 in the dark and ∼125 under UV illumination. Pt Schottky diodes exhibit excellent ideality factors of 1.1 at 25 °C, very low reverse currents and a strong photoresponse, with only a minor component with long decay times thought to originate from surface states. In the temperature range from 25–150 °C, the resistivity of nanorods treated in H2 at 400 °C prior to measurement showed an activation energy of 0.089 eV and was insensitive to the ambient used. By contrast, the conductivity of nanorods not treated in H2 was sensitive to trace concentrations of gases in the measurement ambient even at room temperature, demonstrating their potential as gas sensors. We have also made sensitive pH sensors using single ZnO nanowires.
Electrical and Optical Properties of n-type and p-type ZnO
Authors: Look D. C. , Claflin B. 
Published: April 2011

ABSTRACTIn recent years, ZnO has been proposed for new electronic and optoelectronic devices, such as transparent transistors and UV light-emitting diodes (LEDs). The LED application will require both n-type and p-type ZnO, but the latter is difficult to produce, and progress in this area will require a detailed knowledge of the various impurities and defects that affect the electrical and optical properties. The dominant donors in as-grown ZnO are usually thought to be interstitial H and substitutional AlZn, with activation energies of about 40 and 65 meV, respectively. However, interstitial Zn and its associated complexes may also contribute free electrons. The dominant acceptor, at least in vapor-phase-grown material, is the Zn vacancy; however, substitutional NO is also present, although sometimes passivated by H. To produce p-type ZnO, it is necessary to dope with acceptor-type impurities, and some success has been achieved with N, P, As, and Sb. However, only N has been proven to have simple substitutional character (NO), and more complicated acceptor structures, such as AsZn-2VZn, have been proposed for some of the other group V elements. Both homostructural and heterostructural UV LEDs have been fabricated, although not of high luminescent power so far. The main objective of this paper is to review the Hall-effect and photoluminescence results on n-type and p-type ZnO.
Transport Properties of Polycrystalline SiGe Thin Films Grown on SiO2
Authors: Mitsui Minoru , Arimoto Keisuke , Yamanaka Junji , Nakagawa Kiyokazu , Sawano Kentarou , Shiraki Yasuhiro 
Published: April 2011

ABSTRACTTransport properties of polycrystalline Si1−xGex (x = 0, 30, 50 and 70) thin films on SiO2 were studied by Hall measurements and transport properties of the TFTs fabricated on the films were characterized. Si1−xGex films were p-type in spite of non-doping. Room temperature hole densities of Si1−xGex films increased from 5 × 1013 to 5 × 1016 cm−3 as Ge concentration increased from 30 % to 70 %. The acceptor levels in Si1−xGex were located at 0.43, 0.40 and 0.34 eV for x=0.3, 0.5 and 0.7 from valence band, respectively. The high leakage current of SiGe-TFTs was observed and drain current could not be turned off even when the high gate voltage was applied. The acceptor density increased with increasing annealing temperature from 700 °C to 800 °C. The leakage currents were independent of the annealing temperature and is thought to originate from Ge-related defects in grain boundaries.
Structural Defects related issues of GaN-based Laser Diodes
Authors: Tomiya Shigetaka , Takeya Motonobu , Goto Shu , Ikeda Masao 
Published: April 2011

ABSTRACTStructural defects affecting the lifetime of GaN-based laser diodes (LDs) on epitaxial lateral overgrown (ELO) GaN layers have been investigated. Almost all of the threading dislocations that appeared in the wing regions have edge character, whereas the dislocations at the coalescence boundaries have both edge character and mixed character. The origins of the threading dislocations in the wing regions are the lateral extension of dislocations from the seed regions that contingently bend upwards to the epi-surface. Thus, edge dislocations are most considerable threading dislocations in GaN-based LDs on ELO GaN layers, since the laser stripes are fabricated in the wing regions. In the degraded LDs, neither dislocation multiplication from the threading dislocations nor any structural changes of the threading dislocations were observed. This indicates that degradation is not caused by dislocation multiplication at the active layers, which is usually observed in LDs featuring zincblende-based structures. Although the threading dislocations in the LD stripes do not multiply during device operation, our degradation experiments revealed that the lifetime of the GaN-based LDs depends on the dislocation density. The degradation rate was almost proportional to the square root of the aging time. Our results indicate that degradation is governed by a diffusion process, and a detailed degradation mechanism is proposed.
A Nucleation Study of GaN Multifunctional Nanostructures
Authors: Shalini Gupta , Hun Kang , Martin Strassburg , Ali Asghar , Jayantha Senawiratne , Nikolaus Dietz , Ian T. Ferguson 
Published: April 2011

ABSTRACTThis paper reports the Metal Organic Chemical Vapor Deposition (MOCVD) growth of GaN nanostructures. The use of MOCVD allows the direct integration of these nanostructures into pre-existing device technology. The formation of GaN nanostructures grown on AlN epitaxial layers were studied as a function of growth temperature, growth rate, V-III ratio and the amount of deposited material. A wide range of temperatures from 800 °C to 1100 °C and V-III ratios from 30 to 3500 were applied to determine the optimal growth conditions for nucleation studies in a modified production reactor. Small GaN nanostructures with lateral dimensions below 50 nm and low aspect ratios were obtained using relatively low temperatures of 815 °C and extreme metal-rich growth conditions. Island densities up to 1010cm−2were achieved using silane as an anti-surfactant to increase the available nucleation sites. Manganese has been incorporated into these nanostructures to enhance the multifunctional ferromagnetic properties of GaMnN.
GaN Quantum Dots Grown at High Temperatures by Molecular Beam Epitaxy
Authors: Xu Tao , Williams Adrian , Thomidis Christos , Moustakas Theodore D. , Zhou Lin , Smith David J. 
Published: April 2011

ABSTRACTIn this paper we report the growth by MBE of GaN quantum dot superlattices (QDSLs) with AlN barriers on (0001) sapphire substrates at relatively high temperatures (770 °C) by the modified Stranski-Krastanov method. TEM studies indicate that the GaN QDs are truncated pyramids. We find that the height distribution of the dots depends strongly on the number of GaN monolayer coverage on the top of AlN. Specifically, we find that the height distribution consists of two Gaussian distributions (bimodal) for coverage of 3 and 4 MLs, and becomes single Gaussian distribution for 5 and 6 MLs of coverage. Furthermore, we find that the density of quantum dots increases with the degree of coverage and saturates at 2×1011 dots/cm2. The number of stacks in the superlattice structure was also found to lead to bimodal height distribution of the QDs. Ordering of the quantum dots was accomplished by thermal annealing of the sapphire substrates at 1400 °C prior to the growth of GaN QDs. The annealing process reveals the vicinal steps due to the miscut of the substrates and the GaN QDs were found to line up along those steps. Photoluminescence studies show a broad luminescence spectrum centered at 3 eV which is red shifted with respect to that of bulk GaN and is consistent with internal fields due to polarization (Quantum Confined Stark Effect). Furthermore, we find that the luminescence intensity increases with the number of stacks in the superlattice structure due to higher spatial density of QDs.