bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystalline Structure and Composition of Tin Oxide Film Grown by Reactive Ion Assisted Deposition as a Function of Average Diradiating Energy
Authors: Choi W.K. , Song S.K. , Cho J.S. , Jung H.-J. , Koh S.K.
Published: April 2011

Tin oxide films with highly preferred orientation along <101 axis were grown on Si(100) substrate by using reactive ion assisted deposition method. The impinging average ion energy per depositing Sn atom was changed from 10 to 100 eV/atom. Oxygen content in the deposited tin oxide films increased as average impinging ion energy were raised. The maximum XRD peak intensity appeared when the average energy of about 50 eV/atom was applied. From quantitative Auger electron spectroscopy, characteristic transitional Auger peaks of Sn MNN were shifted to lower kinetic energies as much as 4 ∼ 6±1.0 eV as the Sn4+ component became dominant in the deposited tin oxide films. On the basis of a tin 3d core level spectra analysis by XPS, it was determined that a sizable chemical shift of 1.0±0.02 eV occurred between stannous tin(Sn2+:SnO) and stannic tin(Sn4+:SnO2). The optical transmittance was also measured in the wavelength range from 200 to 800 nm for tin oxide films deposited on BK7 glass substrate.
Carbon, Nitrogen, and Oxygen Ion Implantation of Stainless Steel
Authors: Rej D.J. , Gavrilov N.V. , Emlin D. , Henins I. , Kern K. , Kurennykh T. , Mizgulin V.N. , Munson C.P. , Nastasi M. , Scheuer J.T. , Vykhodets V. , Walter K. C.
Published: April 2011

Ion implantation experiments of C, N and O into stainless steel have been performed with beam-line and plasma source ion implantation methods. Acceleration voltages are varied between 27 and 50 kV, with pulsed ion current densities between 1 and 10 mA/cm2. Implanted doses range from 0.5 to 3×1018cm-2, while workpiece temperatures are maintained between 25 and 800°C. The implant concentration profiles, microstructure and surface mechanical properties of the implanted materials are reported.
Effect of Coherency Stresses on the Stability of Lamellar (α2+γ) Titanium Aluminides
Authors: Appel F. , Christoph U. , Lorenz U. , Wagner D R.
Published: April 2011

Two phase titanium aluminides with a lamellar microstructure of the intermetallic phases α2(Ti3Al) and γ (TiAl) are being developed for high temperature structural applications. Due to differences in lattice parameters and crystal structure, coherency stresses and mismatch structures occur at various types of semicoherent interfaces present in the material. The implications of these structural features on the stability of lamellar microstructures were studied by TEM in situ heating experiments. The investigations revealed that the lamellar interfaces serve as sources for perfect and twinning dislocations. The results will be discussed with respect to the observed degradation of the strength properties of the two phase alloys in the intended service temperature range of 900- 1000 K.
Effects of Strain on the Electronic and Vibrational Properties of Semiconductors and Semiconductor Microstructures
Authors: Pollak Fred H.
Published: April 2011

This paper will review the effects of strain on the electronic and vibrational properties of semiconductors and semiconductor microstructures. Topics to be discussed include deformation potential theory for electronic states () and vibrational modes () of bulk material, polarization effects, the influence of strain (internal and external) on quantum states (band alignments, light-and heavy-hole splittings, polarization effects), piezoelectric effect, strain relaxation, etc. Also various measurement techniques will be mentioned. Selected examples of various phenomenon will be given, including some new and novel device applications.
Influence Of Growth Parameters On Interface Broadening In Mbe-Grown Interfaces: A Non Destructive Study By Magneto-Optics
Authors: Grieshaber W. , Haury A. , Cibert J. , d'Aubigné Y. Merle , Wasiela A.
Published: April 2011

We present a detailed study of the influence of growth parameters on the broadening of CdTe-CdMnTe interfaces using a new magneto-optical technique [1,2] in MBE-grown quantum wells and superlattices. For growth temperatures up to about 300°C the Mn content decreases exponentially at the CdTe on CdMnTe interface and conversely the Cd one decreases exponentially at the CdMnTe on CdTe interface. At temperatures exceeding 300°C an additional broadening takes place which acts equally on both interfaces. Growth interruptions and modified flux stoechiometry do not exhibit significant influence on the broadening.
Fourier Transform Analysis of Franz-Keldysh Oscillations Observed in Electromodulation Spectra
Authors: Holm R. T. , Glembocki O. J. , Tuchman J. A.
Published: April 2011

Discrete Fourier transform (DFr) techniques have been applied to the analysis of the Franz-Keldysh oscillations used in determining electric fields. It is shown that the DFT can be applied to a wide range of EM line shapes and that it can yield accurate results for the electric fields in the case where one field is present in the sample. For cases where there are contributions to the EM spectrum from either two electric fields or two degenerate transitions, such as excitations originating from light- and heavy-hole valence bands, care must be applied in extracting the field from the lower intensity DF” peak. The window used to obtain the DFT influences the peak position of lower intensity DFT peak and thus can lead to spurious shifts of the line.
Experimental Study of the Liquid-Glass Transition in an Inorganic Polymer Li0.5Na0.5PO3
Authors: Rufflé B. , Beaufils S. , Délugeard Y. , Coddens G. , Etrillard J. , Toudic B. , Bertault M. , Even J. , Gallier J. , Écolivet C.
Published: April 2011

New experimental results obtained with various techniques on a less-studied glass-forming system are presented. At low frequency, a secondary βslow-process, decoupled from the viscous flow, is observed by 3 1P NMR. Raman scattering spectra and coherent neutron scattering spectra has been obtained in wide frequency and temperature ranges showing the same qualitative features for the Boson peak while the quasielastic contribution seems to differ markedly.
Formation of Colloidal Copper Hydroxides and Oxides Biopolymeric Interfaces
Authors: Hinze U. , Thies M. , Paradies H. H.
Published: April 2011

Light sensitive colloidal particles of copper hydrous oxides were prepared at interfaces of exopolymeric materials. Dislike copper oxide or hydroxide nanoclusters were obtained which might be useful as p-type semiconductors. The colloidal Cu2O xH2O and Cu(OH)2 particles reveal fractal dimensions of D = 2.15 ±0.05 for Cu(OH)2 and D= 1.75 ±0.07 for Cu2O xH20.
Zirconia Solubility in Boroaluminosilicate Glass
Authors: Raman S. V. , Bopp R. , Batcheller T. A. , Yan Q.
Published: April 2011

In the Idaho Chemical Processing Plant (ICPP) waste streams, zirconia is often the waste load limiting species. It modifies the glass network, enhances durability, increases viscosity and induces crystallization. The limits of its dissolution in boroaluminosilicate glass, with magnesia and soda additions were experimentally determined. A ternary compositional surface is evolved to present the isothermal regimes of liquid, liquid+zircon, liquid+forsterite, and liquid phase sintered ceramic. The potential of partitioning the transuranics, transition elements and solutes in these regimes is discussed. The visible Raman spectroscopic results are presented to elucidate the dependence among glass composition, structure and chemical durability.
Electrochemical Treatment of Mixed and Hazardous Waste
Authors: Dziewinski J. , Marczak S. , Nuttall E. , Smith W.
Published: April 2011

Los Alamos National Laboratory (LANL) and The University of New Mexico are jointly developing an electrochemical process for treating hazardous and radioactive wastes. The wastes treatable by the process include toxic metal solutions, cyanide solutions, and various organic wastes that may contain chlorinated organic compounds. The main component of the process is a stack of electrolytic cells with peripheral equipment such as a rectifier, feed system, tanks with feed and treated solutions, and a gas-venting system. During the treatment, toxic metals are deposited on the cathode, cyanides are oxidized on the anode, and organic compounds are anodically oxidized by direct or mediated electrooxidation, depending on their type. Bench scale experimental studies have confirmed the feasibility of applying electrochemical systems to processing of a great variety of hazardous and mixed wastes. The operating parameters have been defined for different waste compositions using surrogate wastes. Mixed wastes are currently treated at bench scale as part of the treatability study.
Ultra-High-Tg Chromophoric Polyimides and Polyureas as High-Performance Nonlinear Optical Materials
Authors: Geng Lifeng , Wang Jiafu , Marks Tobin J. , Lin Weiping , Zhou Haitian , Lunquist Paul M. , Wong George K.
Published: April 2011

Three approaches to the construction of high-Tg polyimides and polyureas as second-order NLO materials are discussed. In the first approach, copolymerization of bismaleimides with o,o‚-diallylbisphenol-A followed by functionalization with high-β NLO chromophores using a Mitsunobu procedure yields, after poling and curing, a series of heavily crosslinked chromophoric polyimides with Tg values as high as 320°C and partially resonant χ(2) responses as high as 1.0×10-7 esu (42 pm/V at 1064 nm, 1.17 eV). In the second two approaches, copolymerization of the chromophore 4,5-bis(4‚-aminophenyl)-2-(4„- nitrophenyl)imidazole with bismaleimides or diisocyanates yields polyimides and polyureas with Tg values as high as 292°C and partially resonant χ(2)values as high as 0.62× 10-7 esu(25 pm/V at 1064 nm). It is found that careful attention to the details of curing and crosslinking during poling results in NLO- active matrices exhibiting negligible decay in ( on aging in air at 100°C for periods of 1,000-4,000 h. The imidazole based materials exhibit only about 10% χ(2) decay on aging for 100 h at 200°C under N2.
Optical Characterization of Binuclear Phthalocyanines
Authors: Sokoloff Jason P. , Yanagi Shuichi , McGinnis Brian P. , Tian Minquan , Wada Tatsuo , Sasabc Hiroyuki
Published: April 2011

We report the synthesis, and optical characterization of the planar binuclcar phthalocyanines metal free (-1)( H2Pc)2(t-bu)6 and (-l)(VOPc)2(t-bu)6. Several of their optical properties, including linear absorption, concentration dependence, electroabsorption, and transient optical response were measured.
Magnetic Properties Of Tdae-C60: Remanence and Relaxation
Authors: Tokumoto M. , Song Y. S. , Tanaka K. , Sato T. , Yamabe T.
Published: April 2011

Precise measurements of low-field magnetization of TDAE-C60 (TDAE; tetrakis(dimethylamino)ethylene) by SQUID magnetometer revealed a clear “remanence” or “irreversibility”, i.e. difference in the temperature dependence between zero-field cooled (ZFC) and field cooled (FC) conditions below the freezing temperature Tf around 10 K. Also, an extremely slow relaxation phenomena of magnetization was observed. These “glassy” characteristics are reminiscent of a “spin-glass” with Tf at about 10 K as the nature of the magnetic ground state of TDAE-C60.
Electrochromic and Redox Electroactive Polymers Based on Ethylenedioxythiophene Derivatives
Authors: Reynolds John R. , Sankaran Balasubramanian , sotzing Gregory A. , Irvin David J. , Irvin Jennifer A. , Reddinger Jerry L. , Sapp Shawn A.
Published: April 2011

A family of electrically conductive polymers based on 3,4-ethylenedioxythiophene (EDOT) and its derivatives will be discussed as electrochromic and redox electroactive materials. Poly(alkylethylenedioxythiophenes), derivatized with octyl and tetradecyl pendant chains, exhibit significantly faster redox switching characteristics than the unsubstituted parent polymer. Bis(2-(3,4-ethylenedioxy)thienyl)arylene (BEDOT-Ar) and vinylene monomers electropolymerize at low potentials avoiding degradative side reactions. We outline the properties of EDOT polymers which exhibit low band gaps allowing for the formation of conductive complexes with a high degree of visible light transmission and show their electrochromic properties. The BEDOT-vinylene polymer, for example, has a band gap of 1.4 eV. A relatively high degree of electrochromic contrast is found at 600 nm as the polymers switch between insulating deep purple absorptive and conductive light blue states. Solid-state dual polymer electrochromic devices have been constructed using a combination of complementary anodically and cathodically coloring polymers based on the EDOT core.
Characterization of the Viscoelastic Behavior of Polyaniline Solutions for Fiber Spinning
Authors: Chacko A. P. , Hardaker S. S. , Huang B. , Gregory R. V.
Published: April 2011

Solutions of emeraldine base(EB) in DMPU have been successfully spun into fibers and characterized according to their morphology, mechanical and electrical properties. This study presents results for as-spun (undrawn) fibers. The viscoelastic behavior of EB spin solutions have been investigated with dynamic measurements of the complex moduli, first normal stress coefficient, and complex viscosity. A knowledge of the viscoelastic behavior of emeraldine base solutions is crucial for effective processing into fibers and films.
The Molecular Conformation of Non-Doped Polyaniline and its Effect on the Properties of Doped Polyaniline
Authors: Zheng W. , Min Y. , Lee S-J. , Macdiarmid A. G. , Angelopoulos M. , Liao Y-H. , Epstein A. J.
Published: April 2011

When thin films of polyaniline (emeraldine base, EB) are deposited on glass substrates from aqueous solutions of polymerizing aniline (“in-situ” EB-I film), they exhibit a Vis/UV spectrum in which the exciton peak has an absorption maximum at ∼600 nm; exposure to NMP vapor results in a shift of this peak to ∼650 nm (EB-II film). Doping of EBI film by aq. HCl gives the characteristic Vis/UV spectrum of “tight coil” doped polyaniline with a localized polaron peak at ∼820 nm. Treatment of EB-II film with HCl in a similar manner gives the characteristic spectrum of “expanded coil” doped polyaniline in which the ∼820 nm peak has disappeared and is replaced by a free carrier tail. It is concluded that EB-I and EB-II exist in “tight coil” and “expanded coil” molecular conformations respectively which do not change on doping in aqueous HCl.
White and Unsaturated Color Organic Light Emitting Diodes
Authors: Dodabalapur A. , Strukelj M. , Jordan R. H. , Rothberg L. J. , Miller T. M.
Published: April 2011

We describe the principles of operation and device characteristics of novel organic light emitting diodes in which the emission originates in a number of optically active layers. The effective emission color can be controlled by adjusting the thicknesses of the individual layers, and in this manner white and other unsaturated color LEDs with external quantum efficiency > 0.5% have been fabricated. The maximum luminance that has been achieved is ∼4,700 Cd/m2.
Effect of Photooxidation on the Transient Photoconductivity and Photoluminescence of Alq3
Authors: Sokolik I. , Walser A. D. , Priestley R. , Dorsinville R. , Tang C. W.
Published: April 2011

Photogeneration of charge carriers and radiative excited states in pristine and photooxidized tris-(8-hydroxyquinoline) aluminum (Alq3) were studied by simultaneously measuring the photoconductive response and the kinetics of photoluminescence with subnanosecond resolution. 25 ps laser pulses at 355 nm were used for the excitation of vacuum-evaporated films of Alq3 2–4 μm thick. At equal excitation intensities the time dependence of the photoconductive response was very similar to that of the photoluminescence, independent of whether the sample was pristine or partially oxidized. Photooxidation of Alq3 substantially decreases the magnitude and lifetime of the photoconductivity and the photoluminescence. The decrease is shown to be a result of quenching of singlet molecular excitations by product(s) of photooxidation of Alq3. Photogeneration of charge carriers is controlled by the mutual annihilation of singlet excitons.
Chemistry and the Electronic Properties of Diamond Surfaces
Authors: Pehrsson Pehr E.
Published: April 2011

The structure and chemistry of annealed and oxygen or hydrogen-terminated low-index (100, 110) diamond surfaces was determined with high resolution electron energy loss spectroscopy (HREELS), low energy electron diffraction (LEED) and other techniques. HREELS revealed carbonyl, hydroxyl and bridge-bonded oxygen groups on oxidized C(100) and C(110) surfaces. The surface chemistry was correlated with secondary electron emission spectra and other data. The oxidized and annealed (reconstructed) surfaces exhibited larger work functions and electron affinity than hydrogenated surfaces, which we attribute to both band-bending and dipole layer effects due to surface oxygen.
Observation of a new phase on the hydrogen terminated diamond (111)-surface by helium atom scattering
Authors: Lange† G. , Schaich Th. , Toennies† J. P. , Wöll Ch.
Published: April 2011

The structural phase diagram of the hydrogen terminated diamond-(111) surface, which is of considerable relevance with regard to the low-pressure synthesis of diamond, has been investigated by the highly surface sensitive technique of thermal energy helium atom scattering. A new phase with a (2 × 1) symmetry has been observed to occur upon heating above 940 K, significantly below the well known transition to the hydrogen-free (2 × 1) π-bonded chain structure at 1250 K. It is proposed that the new phase consists of a hydrogen (2 × 1) overlayer on an unreconstructed (1 × 1) diamond substrate. Structural models for this new phase will be presented.
Electrochemical Studies of Boron-doped Diamond Electrodes
Authors: Argoitia A. , Martin H. B. , Rozak E. J. , Landau U. , Angus J. C.
Published: April 2011

The evolution of hydrogen and oxygen from a 0.5 M H2SO4 solution on heavily borondoped diamond electrodes was studied. A very wide potential range without water decomposition, from approximately -1.5 to +2.75 V relative to the standard hydrogen electrode, was observed on high quality diamond. A much smaller range, from -0.7 to 1.7 V, and higher background currents were observed on diamond electrodes with significant sp2 content. The Ce(III)/Ce(IV) redox couple was observable on diamond electrodes, but was highly irreversible.
Development of Epitaxial, Tiling, and Cutting Processes for a Diamond Single Crystal Wafer Technology
Authors: Posthill J. B. , Malta D. P. , Humphreys T. P. , Hudson G. C. , Thomas R. E. , Rudder R. A. , Markunas R. J.
Published: April 2011

Development of a diamond homoepitaxial deposition process that utilizes water and-ethanol at a growth temperature of ∼600°C is described. Topographies are excellent, and etch-pit densities (EPD) are in the 106cm-2range when growth is done on type Ia C(100) substrates.-This process has been used to epitaxially join diamond single crystals that were bonded in close-proximity to each other. This process of “tiling” single crystal diamonds in close proximity in-order to manufacture a large-area diamond single crystal template is also described. Specially-prepared diamonds that have had their faces and edges oriented to { 100} were coated with-heteroepitaxial Ni, then pressed onto a Si wafer while being heated in an inert gas atmosphere.-The resulting bond is excellent; thereby permitting our 600°C diamond deposition process to-epitaxially join the diamonds. A diamond wafer cutting technology has been addressed using a-specific sequence consisting of: ion implantation, homoepitaxial diamond growth, annealing, and-contactless electrochemical etching. This “lift-off” method of cutting has thus far resulted in a 2mm×O.5mm×17.5μm transparent, synthetic, free-standing, single crystal diamond plate being-fabricated. Raman spectroscopy and EPD show the plate to be comparable to our best-homoepitaxial diamond.
Boron Diffusion Coefficient in Diamond
Authors: Sung T. , Popovici G. , Prelas M. A. , Wilson R. G.
Published: April 2011

A study of boron diffusion into diamond lattice was performed. Diffusion was made in hydrogen atmosphere at 30 torr. Two type IIa diamonds were heated at 1200 and 1400 °C for 20 hours and 5 minutes, respectively. Boron powder was used as a dopant source. The boron concentration profiles of both samples were measured by secondary ion mass spectrometry. Based on Fick's law, the diffusion coefficients were computed.
High-Temperature Oxygen Dissolution in Liquid Zirconium
Authors: Molodetsky I. E. , Dreizin E. L.
Published: April 2011

The enthalpy of oxygen dissolution in liquid zirconium occurring during the combustion of Zr particles is estimated. The analysis presented uses direct experimental measurements of the temperature, size, and composition histories of burning Zr particles. The dissolution enthalpy is limited by the range of 700–830 kJ/mol and is somewhat less than that of Zr oxidation. This enthalpy determines the rate of the heat release during Zr combustion until stoichiometric ZrO2 forms out of the supersaturated Zr/O solution. Stoichiometric ZrO2 is formed near the end of combustion and the additional energy released at that time causes a rapid temperature increase which can trigger a particle explosion.
Aminonitroheterocyclic N-Oxides – a New Class of Insensitive Energetic Materials
Authors: Hollins Richard A. , Merwin Lawrence H. , Nissan Robin A. , Wilson William S. , Gilardi Richard D.
Published: April 2011

The need continues for new powerful but insensitive explosive ingredients, which match the performance of RDX with the insensitivity of TATB. One approach has been to take the inherent stability of an aromatic heterocycle, combine this with the explosive insensitivity and thermal stability associated with alternating amino and nitro groups, and to supplement the performance of the molecule with an energy contribution from the N-oxide functionality. The synthesis, characterization and properties (both sensitivity and performance) of aminonitropyridine-l-oxides and aminonitropyrimidine-1,3-dioxides will be described.
From Intelligent Materials to Smart Sensors: a-Si:H Position Sensitive Detectors
Authors: Fortunato E. , Fernandes M. , Soares F. , Lavareda G. , Martins R.
Published: April 2011

This work presents the main static and dynamic performances showed by one dimensional thin film position sensitive detectors (ID TFPSD), based on a-Si:H technology, with a size of 80 mm × 5 mm. The results obtained show that the TFPSD is able to respond to light powers as low as 2μ W/cm2, presenting a detection accuracy, linearity and response frequency better than 10 gm, 2% and 2 KHz, respectively. These results are quite promising regarding the application of these sensors to a wide variety of optical inspection systems where continuous quality control is required.
Amorphous Silicon-Carbon alloys Deposited by Electron-Cyclotron Resonance PECVD
Authors: Chu V. , Conde J. P.
Published: April 2011

Hydrogenated amorphous silicon-carbon alloys are prepared using electron-cyclotron resonance (ECR) plasma-enhanced chemical-vapor deposition. Hydrogen is used as the excitation gas in the resonance chamber while silane and methane (or ethylene) are introduced in the main chamber. A minimum of 95% hydrogen dilution is used. The microwave power is kept constant at 150 W. The effect of the type of carbon source gas, silane to carbon source gas ratio, deposition pressure, substrate temperature and hydrogen dilution on the deposition rate, bandgap and Urbach energy are studied. The photoconductivity and the Urbach energy of the ECR-deposited films are compared to those prepared with glow discharge with the same bandgap.
Plasma Post-Hydrogenation of Hydrogenated Amorphous Silicon and Germanium
Authors: Beyer W. , Zastrow U.
Published: April 2011

Incorporation and kinetics of hydrogen during plasma post-hydrogenation and thermal treatment are discussed for a-Si:H and a-Ge:H films. For material of low hydrogen content, the hydrogen surface concentration reached by plasma treatment equals the hydrogen concentration obtained by deposition at the same temperature and under similar plasma conditions. Enhancements of the hydrogen diffusion coefficient and of hydrogen solubility observed for plasma treatment at temperatures ≤400°C and ≤300°C for a-Si:H and a-Ge:H, respectively, are attributed to a plasma induced rise of the surface hydrogen chemical potential.
Excitation and DE-Excitation of Yb3+ in Inp and Er3+ in Si: Photoluminescence and Impact Ionization Studies
Authors: Gregorkiewicz T. , Tsimperidis I. , Ammerlaan C. A. J. , Widdershoven F. P. , Sobolev N. A.
Published: April 2011

In the paper the existing information on the optical excitation of the erbium ion in crystalline silicon is critically reviewed. The proposed excitation mechanism is compared to the one which is believed to be responsible for the luminescence of ytterbium in indium phosphide. To this end the influence of constant and microwave electric field on the photoluminescence of both systems is inspected. It is shown that, although both systems show some similarities, their analogy is limited.

The particular role of excitons and electrons in both the excitation as well as the de-excitation mechanism is investigated for the Si:Er system. The results of photoluminescence decay studies (T=4.2 K) are presented. It is argued that a nonradiative energy transfer to conduction electrons is responsible for the limitation of the energy transfer to the Er core and for its nonradiative recombination. Also, a prominent role of excitons in the energy transfer mechanism is confirmed. Finally, the origin of the 873 meV photoluminescence band recently reported in Er-implanted Si is discussed in relation to a possible defect-mediated activation of Er.
Ohmic Contacts to n-Type 6H-SiC Without Post-Annealing
Authors: Teraji Tokuyuki , Hara Shiro , Okushi Hideyo , Kajimura Koji
Published: April 2011

We formed titanium Ohmic contacts to n-type 6H-SiC epitaxial layer byreducing the Schottky barrier heights. The barrier heights were reduced enough toform the Ohmic contacts by releasing the Fermi level from pinning through makingatomically-flat surfaces. The current transport by thermionic emission wasdominant at the Ti/SiC interface. Since the Ti contacts were formed without postannealing,surfaces of the Ti electrodes were flat and homogeneous maintaining asdepositedstructures. Contact resistivity was (6±1)×10−3 Ω-cm2, which is comparableto that of the annealed Ni contact formed on the SiC epitaxial layer with the samecarrier concentration.
Growth of High Quality (In,Ga,Al)N/GaN Heterostructure Materials and Devices by Atmospheric Pressure MOCVD
Authors: Denbaars S. P. , Keller S. , Keller B. P. , Wu Y. F. , Kapolnek D. , Mishra U. K.
Published: April 2011

Using atmospheric pressure MOCVD we have obtained high quality InGaN/GaN and AlGaN/GaN heterostructure materials and devices. For nominally undoped 4 μm thick GaN films, we obtained 300 K mobilities of 780 cm2/Vs and an unintentional background impurity level of n300K = 6*1016 cm−3. For InGaN/GaN heterostructures we have obtained direct band-edge transitions with FWHM as narrow as 7.9 nm (59 meV) for 50Å thick In0.16Ga0.84N quantum wells at 300K, which is the among the best reported values. The quantum wells display energy shifts towards shorter wavelength with decreasing well thickness, and the shift agrees with predicted quantum effects. These materials have been incorporated into InGaN single quantum well LEDs that emit at 450 nm. In addition AlGaN/GaN heterostructure materials have been incorporated into HFETs and MODFETs. Gate-drain breakdown voltage well exceeding 100 V, and extrinsic transconductance gm of up to 140 mS/mm were realized in the MODFET.
Kinetics Approach To The Growth Of Cubic Boron Nitride
Authors: Taylor C. A. , Clarke Roy
Published: April 2011

We have deposited cubic BN films on silicon (100) using a novel ion-assisted RF-sputtering process. Our efforts over the past several years have enabled us to significantly reduce the ionenergy needed to form the cubic phase, with values now substantially less than 100 eV. Through a better understanding of the growth process we have been able to make improvements in film crystallinity and orientation, with an associated reduction of the high film stress which has severely limited film thickness in the past. The combination of low-energy nitrogen ions and high temperature growth has enabled us to deposit cubic BN films as thick as 1.9 μm. A nucleation study, performed using scanning force microscopy, shows that the cubic BN is nucleating as triangular crystallites, indicative of (111) growth. More specifically, the cubic BN appears to be nucleating on the edges of perpendicularly oriented hexagonal planes such that the cubic BN [ 111] is normal to the hexagonal BN [0002] (c-axis). The results suggest a pathway to “compliant” oriented growth on a variety of substrates.
Lattice-Matched InAsN(X=0.38) on GaAs Grown by Molecular Beam Epitaxy
Authors: Kao Y. C. , Broekaert T. P. E. , Liu H. Y. , Tang S. , Ho I. H. , Stringfellow G. B.
Published: April 2011

In this paper, we report the MBE growth of high nitrogen content lattice-matched InAs1−xNx (x=0.38) single crystal epitaxial films on GaAs. The nitrogen incorporation is about an order higher than previously reported on other mixed group V nitride alloys. These data are consistent with a nitrogen solubility limit calculation in various III-V binary alloys, which predicts orders of magnitude higher nitrogen incorporation in InAs than any other alloys. InAsN growths were obtained using a modified ECR-MBE system with atomic-nitrogen generated by an ECR plasma source. Improved crystal quality was obtained using a “template” growth technique. An x-ray linewidth of 270 arc-s was achieved on a 0.4 μm thick InAs0.62N0.38/GaAs multi-layer structure. Hall effect data show these InAsN films are semi-metallic.
Tetrahedral Amorphous Carbon Thin Film Transistors
Authors: Clough F. J. , Kleinsorge B. , Milne W. I. , Robertson J.
Published: April 2011

This paper describes the design and fabrication of a carbon based thin film transistor (TFT). The active layer is formed from a novel form of amorphous carbon (a-C) known as tetrahedrally bonded amorphous carbon (ta-C) which can be deposited at room temperature using a filtered cathodic vacuum arc (FCVA) technique. In its ‘as grown’ condition, ta-C is p-type and the devices described here, produced using undoped material, exhibit p-channel operation.
Influence of the Growth Atmosphere on the Properties of AIN Grown by Plasma - Assisted Pulsed Laser Deposition
Authors: Ogawa T. , Okamoto M. , Mori Y. , Sasaki T.
Published: April 2011

We have grown highly oriented aluminum nitride (AIN) thin films on Si (100) substrates by using pulsed laser deposition from sintering AIN targets. Three different growth environments, vacuum, nitrogen gas, and nitrogen plasma, have been used in order to investigate the effect of the ambient on the film quality. Rutherford backscattering spectrometry suggests that the N/Al ratio increases when the AIN film is grown in a nitrogen-contained ambient. Cathodoluminescence study implies the decrease of oxygen content in the film grown in a nitrogen plasma ambient.
Atomic Force Microscopy Study of GaN-Buffer Layers on SiC(0001) By MOCVD
Authors: Lim Dongsup , Byun Dongjin , Kim Gyeungho , Nam Ok-Hyun , Choi In-Hoon , Park Dalkeun , Kum Dong-Wha
Published: April 2011

Buffer layers promote lateral growth of films due to a decrease in interfacial free energy between the film and substrate, and large 2-dimensional nucleation. Smooth surfaces of thebuffer layers are desired. Optimum conditions for GaN-buffer growth on the vicinal surface of 6H-SiC(0001) were determined by atomic force microscope (AFM). AFM analysis of the GaN nucleation layers led to an optimum growth conditions of the GaN-buffer layer which was confirmed by cross-sectional transmission electron microscopy, Hall measurements and photoluminescence spectra. Optimum growth conditions for GaN-buffer layer on SiC(0001) was determined to be 1 minute growing at 550°C.
Electron Paramagnetic Resonance Studies of Hf-CVD Diamond Films
Authors: Ramakrishnan B. , Keeble D. J. , Rodrigo H. , Kulkarni A.
Published: April 2011

Diamond thin films have been deposited on silicon substrates by hot-filament chemical vapor deposition (HF-CVD). Substrate temperature and methane concentration have been varied and the resulting structural properties of the deposited films studied. Raman spectroscopy, scanning electron microscopy and electron paramagnetic resonance (EPR) measurements were performed. The EPR measurements showed a single spectrum at g = 2.0027(2). The bulk concentration of the paramagnetic species, as determined from the total EPR absorption were found to vary in the range 1017 to 1019 cm−3. Low paramagnetic defect concentrations were found for samples exhibiting a low non-diamond carbon contribution to the Raman spectrum. These samples were those grown with a methane concentration of I % or less.
CVD Diamond Wires as X-Ray Detectors
Authors: Manfredotti C. , Fizzotti F. , Galetto M. , Giudice A. Lo , Margherita D. , Ongaro C. , Polesello P. , Vittone E.
Published: April 2011

Miniature metal-diamond wire detectors have been fabricated by Hot Filament Chemical Vapor Deposition (HFCVD) method and characterized as x-ray dosimeters in the energy range 50 keV–250 keV. Linearity of the response and the sensitivity as a function of energy have been accurately determined in a range routinely used for x-ray radiotherapy. With a Mo wire substrate, a 10 μm thick CVD diamond film can reach sensitivities of the order of 4×10−8 A/Gy/min, more than one order of magnitude larger than for a 6 cm3 standard ionization chamber.
Material Properties of Sipos Films Prepared by XeCl Excimer Laser Annealing of a-Si:Nx Films
Authors: Choi Hong-Seok , Jun Jae-Hong , Jang Keun-Ho , Han Min-Koo
Published: April 2011

The material properties of laser-annealed a-Si:Nx films were investigated. The a-Si:Nx films for laser-annealing were deposited by rf plasma enhanced chemical vapor deposition (PECVD) with NH3 and SiH4 gas mixtures. At the 0.35 of NH3/SiH4 ratio, the optical band-gap was abruptly increased to 2.82 eV from 2.05 eV by laser-annealing which indicates that Si-N bonding comes to be notable at that ratio. The electrical conductivity showed the maximum value of 4× 10-6 S/cm at the 0.11 of NH3/SiH4 ratio where the grain growth and the increase of Si-N bonding are optimized for the enhancement of electrical conductivity. The σP/σD ratio which is related to the defects states for photo generation centers was decreased with increasing NH 3/SiH 4 ratio. Our experimental data showed that the optical band gap and electrical conductivity of laserannealed a-Si:Nx films were dominantly affected by the NH3/SiH4 ratio at the 250 mJ/cm2 of laser-annealing energy density.
Approaches to modifying solid phase crystallization kinetics for a-Si films
Authors: Kingi Reece , Wang Yaozu , Fonash Stephen , Awadelkarim Osama , Li Yuan-Mn
Published: April 2011

Three approaches to modifying the solid phase crystallization kinetics of amorphous silicon thin films are examined with the goal of reducing the thermal budget and improving the poly-Si quality for thin film transistor applications. The three approaches consist of (1) variations in the PECVD a-Si deposition parameters; (2) the application of pre-fumace-anneal surface treatments; and (3) using both rapid thermal annealing and furnace annealing at different temperatures. We also examine the synergism among these approaches.

Results reveal that (1) film deposition dilution and dilution/temperature changes do not strongly affect crystallization time, but do affect grain size; (2) pre-anneal surface treatments can dramatically reduce the solid phase crystallization thermal budget for diluted films and act synergistically with deposition dilution or dilution/temperature effects; and (3) rapid thermal annealing leads to different crystallization kinetics from that seen for furnace annealing.
Investigation of Electron Emission From Si and Hot Filament CVD Diamond
Authors: Shim J. Y. , Chi E. J. , Rho S. J. , Baik H. K.
Published: April 2011

The field emission characteristics of the Si emitters and the diamond coated Si emitters are investigated. The Fowler-Nordheim plots of the two types of Si emitters show linear slopes. It means that the I-V characteristics follow the Fowler-Nordheim relation. Field emission for the two types of diamond coated Si emitters exhibits significant enhancement both in turn-on voltage and total emission current. The Raman spectrum shows that the high intensity graphite peak is observed with diamond peak and thereby large amounts of graphite may be included in the diamond grain boundary. It seems to be thought that the graphite participates in the low field emission. However, further investigations are needed to understand whether the graphite may enhance the emission characteristics of diamond or not.
Electroluminescent Diodes Using Cyclohexane-Based Glass Forming Liquid Crystals and Their Analogues
Authors: Lin C. P. , Tsutsui T. , Saito S. , Chen S. H. , Mastrangelo J. C. , Shi H.
Published: April 2011

Organic electroluminescent(EL) diodes using spin-coat films of cyclohexane-based glass-forming liquid crystal (LC) materials were fabricated. The cyclohexane-based LC materials were found to be useful for EL diodes. Blending the LC materials with charge transport molecules was found to be a promising method for improving device performance. Conventional hole transport and electron transport molecules were found to show a tendency to form exciplexes with cyclohexanebased LC materials. This difficulty was overcome by the introduction of cyclohexane-based charge transport molecules. The EL quantum efficiency of 0.06% was attained in the single-layer devices with two-component blends.
Synthesis and Mesomorphic Properties of Chiral Biphenylol Benzoates
Authors: Lu Wan-Fang , Zhang Zhi-Yong , Shang Yong-Jia
Published: April 2011

Ten new chiral liquid crystalline compounds I1–10 of 4′ -acyl-4-biphenylol (S) -4- (2-methyl-l-butoxy) benzoates were synthesized and their mesomorphic properties were tested. They are all smectic liquid crystals with wide temperature ranges and except for compounds I1, all exhibit a Sc*phase. The influence of molecular structure on phase behavior is discussed.
Improvement of the ITO-p Interface In a-SI:H Solar Cells Using a Thin SiO Intermediate Layer
Authors: Carvalho C. Nunes De , Nijs J. M. M. De , Ferreira I. , Fortunato E. , Martins R.
Published: April 2011

The use of ITO thin films on glass/ITO/p-i-n/metal amorphous silicon solar cells is reviewed. It is suggested a new application for silicon monoxide thin films on the ITO-p interface, as an intermediate layer, to minimize the fTO thin film deterioration process, during the early stage of exposure to a silane plasma rich in hydrogen. The thickness of the silicon monoxide thin films is chosen not to worsen the optical and electrical properties of the ITO thin films. The TO-p interface is optimized (due to impurities diffusion decrease), leading to an overall improvement of the device performance.
Study of ZnTe:Cu Back Contacts on CdTe/CdS Thin Film Solar Cells
Authors: Tang J. , Feng L. , Mao D. , Song W. , Zhu Y. , Trefny J. U.
Published: April 2011

Vacuum-evaporated Cu-doped ZnTe films have been studied as the intermediate layer between CdTe and metal contacts in CdTe/CdS thin-film solar cells for the formation of low resistance back contacts. Different metals (Au, Ni, Co) have been investigated as the contact material to the ZnTe layer. The effects of Cu concentration, ZnTe:Cu layer thickness, and ZnTe post-deposition annealing temperature on the cell performances have been investigated. We found that different metal contacts on the ZnTe layer lead to different doping densities in the CdTe layer and different open-circuit photovoltages of the solar cells. The possible formation of a back contact diode at the CdTe/ZnTe interface was explored, based on capacitance-voltage analysis. The series resistance of the CdTe/CdS cells was reduced significantly by the introduction of the ZnTe layer. Fill factors greater than 0.76 and an energy conversion efficiency of 12.9% have been achieved using ZnTe back contacts on electrodeposited CdTe.
Duty Cycle and Frequency Effects of Pulsed-DC Currents on Electromigration-Induced Stress in Al Interconnects
Authors: Frankovic Richard , Bernstein Gary H.
Published: April 2011

The effects of the duty cycle and frequency of a pulsed-current stress on the critical length-current density product, (jlc) were measured using edge-displacement techniques. In our study, Al edge-displacement segments were stressed at a temperature of 200 °C and at peak pulsed-dc current densities below 6×105 A/cm2 in a nitrogen ambient. jlc was measured for duty cycles of 25%, 50%, 75% and 100% at 100 kHz, and for 50% duty cycle at lower frequencies. jlc was observed to increase with decreasing duty cycle and increasing frequency. We measured a 2.6-fold increase in jlc for the 25% duty cycle at 100 kHz as compared to dc. We have used the vacancy supersaturation model to predict the jlc enhancement for lower duty cycle operation.
Grain-Boundary Slit Propagation in an Electric Field
Authors: Klinger L. M. , Chuj X. , Bauer C. L. , Mullin W. W.
Published: April 2011

Propagation (advancement) of a fine slit along a planar grain boundary in an electric field E0, applied parallel to the slit, is investigated by considering electromigration along both the grain boundary and the slit surface. Steady-state solutions of the transport equations are classified according to the value of a parameter β, which, under reasonable assumptions, depends on material constants only: for 5π/4 ≥ β > β2, unique steady-state solutions exist, for β2 > β > β1, multiple steady-state solutions exist, and for β1 ≥ β ≥ π/4, no steady-state solutions exist. For all steadystate solutions, slit width and tip velocity v scale as and , respectively. Generally, v can approach 1 nm/s (3.6 μm/h), thereby representing a likely failure mechanism in fine-line (near bamboo structure) interconnects.
Microscopic Estimates for Electromigration Velocities of Intragranular Voids in Thin Aluminum Lines
Authors: Wickham L. K. , Sethna J. P.
Published: April 2011

We explore the effect of faceting on possible mechanisms for mass transport around electromigration voids in aluminum interconnects. Motivated by linear response estimates which suggest that particle flux would be much higher along steps than across terraces on a clean aluminum surface, we study step nucleation in the presence of a small driving force along a surface. We find that step nucleation, even on a nearly defect-free void surface, would be slow if the step energy is equal to that calculated for a clean aluminum surface. In the presence of a uniform electromigration force, the creation of new steps between existing ones should not occur unless the free energy cost of a step is much less than thermal energies. We conclude that voids cannot move intragranularly at μm/hr rates without help from other factors such as local heating and impurities.
Copper Migration and Precipitate Dissolution in Aluminum/Copper Lines During Electromigration Testing
Authors: Shaw T. M. , Hu C -K. , Lee K. Y. , Rosenberg R.
Published: April 2011

We have used transmission electron microscopy to examine in detail how microstructural changes take place in aluminum/copper lines adjacent to tungsten contacts. A structure that could be powered in a probe station was deposited directly on an electron transparent silicon nitride window to allow direct observation of the structure of the line after different intervals of electromigration testing. Observations made on aluminum-4% copper lines show that significant changes in the grain structure surrounding precipitates occur during testing even under conditions where no normal grain growth is observed in the lines. Elecromigration testing at 260°C resulted in grain coarsening and the formation of new diffusion blocking structures in the lines. By making measurements of the volume of individual precipitates as a function of time, the flux of copper through specific segments of the microstructure of the line could be measured. The results indicate that the presence of a single grain boundary can increase the electromigration flux of copper along the line by an order of magnitude. In line segments where a bamboo grain occurred copper diffusion appears to be controlled by diffusion along the Al/oxide interface at the surface of the lines. It is also shown that, in polycrystalline lines, the rate of copper depletion frorr the cathode is largely determined by the rate of dissolution of the precipitates. In mixed structure lines the migration of copper can become quite complex as changes in diffusion paths can occur as precipitates dissolve or grow.
Oxidation Resistance of Copper Alloy Thin Films Formed by Chemical Vapor Deposition
Authors: Atanasova P. , Bhaskaran V. , Kodas T. , Hampden-Smith M.
Published: April 2011

Co-deposition of copper-palladium alloy films was demonstrated using low-pressure CVD from individual precursors - (hexafluoroacetylacetonato)copper(I)(vinyltrimethylsilane) [(hfac)Cu(I)vtms] and palladium(II)bis(hexafluoroacetylacetonate) [Pd(hfac)2], for Cu and Pd respectively. High-purity alloy films with controlled composition, microstructure and morphology were prepared and their oxidation behavior was examined at different temperatures and compared with that of pure copper CVD films with similar morphology. As-deposited copper-palladium alloy films showed improved resistance to oxidation up to 300°C in air. Enhanced oxidation resistance compared to Cu CVD films was observed at concentrations of palladium as low as 0.5 at. %.
Building in Reliability Through a 100x Reduction in Mobile Ions in a 0.8 μm BiCMOS Process
Authors: Anderson Larry , Parikh Suketu , Nagalingam Samuel
Published: April 2011

The reduction of mobile ions--mainly Na+, but also K+, H+ and Li+, is very critical as our gate oxide thickness and Leff decreases. Hot electron induced hydrogen compensation of boron doped silicon changes the PMOS Leff and NPN BVebo. This paper shows how to reduce Na+ by 100X, through the use of Triangular Voltage Sweep (TVS). This paper is designed to give scientists and engineers a case history where we reduced these levels from 1012 to 1010 mobile ions/cm2 in our 0.8μm BiCMOS process. This was accomplished by adding Ammonium Fluoride mixture dips at appropriate steps. For fast feedback, we can non-destructively measure Na, K, and H within 10 minutes of completing phororesist removal at any of the metallization steps using TVS. In addition to BiCMOS, TVS measure is a power tool in Nonvolatile Memories for predicting in-line data retention, when data retention is associated with charge gain.
Void-Free Metallization By Controlling Sputtering Conditions Of Tin Barrier Metal Films
Authors: Yamaoka T. , Yamauchi T.
Published: April 2011

Production Engineering R‘‘void-free’ metallization is proposed. It is shown that void formation is suppressed when the TiAl3 intermediate layer is formed at the interface between the Al alloy and reactively sputtered TiN barrier metal films. We have investigated the relationship between void formation and coverage of the intermediate layer. It is found that a coverage of more than 60 % TiAl3 perfectly suppresses void formation. The interfacial reaction is achieved by using ‘soft TiN', which arises from the short migration length of the sputtered particles impinging on the substrate surface when dc power is decreased. The soft TiN film includes many vacancies and crystallographically disordered regions which easily cause rearrangement of the TiN films by movement of Ti atoms during annealing. It is thought that these Ti atoms compensate vacancies in the Al-Si-Cu film and suppress the formation of Al voids.