bluuebunny/crossref_metadata_2025_split huggingface dataset:
Submicron, Noble Metal Particle Reference Standards: A Proposal
Authors: Hockett R. S. , Craig Angela Y. , Le Diem 
Published: April 2011

ABSTRACTThere is a need in the semiconductor industry to develop new techniques and instrumentation for the elemental and chemical analysis of submicron, particularly <0.2 μm, particles. The development of these techniques and instrumentation could be assisted by submicron particle reference standards. We propose that high number-density, noble metal (Cu, Ag, Au) particles on silicon, with controlled diameters in the range of 0.02 μm to 0.10 μm, be developed and used as particle reference standards.
Removal of Fluorine From a Si (100) Surface by a Remote RF Hydrogen Plasma
Authors: Barnak J. P. , King S. , Montgomery J. , Ku Ja-Hum , Nemanich R. J. 
Published: April 2011

ABSTRACTFluorine contamination was removed from a Si(100) surface by an atomic H flux. The surface was intentionally contaminated to approximate the residual fluorine concentration remaining after a concentrated HF last process. By dipping the wafers in concentrated HF the thin oxide was removed and replaced with a hydrogen and fluorine terminated surface. This surface was then either vacuum annealed or exposed to a 20 Watt rf excited H-plasma at 50 mTorr, in order to achieve an atomically clean surface. The substrate temperature during the Hplasma exposure and vacuum anneal was 450°C. The surface chemistry was characterized with x-ray photoemission spectroscopy (XPS), auger electron spectroscopy (AES), and angle-resolved UV photoemission spectroscopy (ARUPS). The surface symmetry was characterized with low energy electron diffraction (LEED). Before the H-plasma exposure, the XPS spectra indicated Si-F bonding, and a l×1 LEED diffraction pattern was observed. Immediately following the Hplasma exposure, the fluorine concentration was reduced below detection limits of XPS, and the surface showed a 2×1 reconstruction. A mechanism is proposed by which molecular HF results from atomic hydrogen interactions with fluorine on the surface.
Low Temperature Film Growth by Supersonic Jets of CBr4
Authors: Ohlberg Douglas A. A. , Rose Garry , Ren James , Stanley Williams R. 
Published: April 2011

AbstractPulsed, supersonic jets of CBr4 seeded in a hydrogen bath gas have been used to deposit films on silicon at low temperatures (c A. 100° C) in a high vacuum chamber. IN situ analysis of the films using x-ray photoelectron spectroscopy (XPS) and depth profiling indicate a surface composition of 34% Br and 66 % C and a bulk composition of 88% C and 12% Br. the deposition efficiency of CBr4 was found to drop dramatically when seeded in bath gases of deuterium, helium, and argon, suggesting that the film growth is an activated process, requiring precursor energies of at least 3.6 eV.
Luminescent Nanometer-Sized Si Crystals Formed in an amorphous Silicon Dioxide Matrk by Ion Implantation and Annealing
Authors: Iwayama T.S. , Terao Y. , Kamiya A. , Takeda M. , Nakao S. , Saitoh K. 
Published: April 2011

AbstractSi ion implantation followed by thermal annealing has been used to synthesize luminescent nanometer-sized Si crystals in an amorphous Si02 matrix. Transmission electron microscopy indicates the formation of Si nanocrystals by annealing at 1100 °C, and the growth in average size of Si nanocrystals with increasing annealing time. the shape of the emission spectrum of the photoluminescence is found to be independent of both excitation energy and annealing time, while the excitation spectrum of photoluminescence increases as the photon energy increases and its shape depends on annealing time. the results indicate that the photons are absorbed by Si nanocrystals, for which the band-gap energy is modified by the quantum confinement effects, and the emission of photons is not due to direct electron-hole recombination inside Si nanocrystals but is related to defects probably at the interface between Si nanocrystals and Si02.
Planar Laser-Induced Fluorescence Diagnostics of Pulsed Laser Ablation of Silicon
Authors: Goodwin D. G. , Capewell D. L. , Paul P. H. 
Published: April 2011

AbstractPlanar laser-induced fluorescence has been used to acquire time sequence images of ground-state, neutral Si and SiO during laser ablation of an Si target in vacuum and in the presence of a background gas at a fluence of 3-4 J/cm2. the SiO images, taken in air, strongly suggest that the observed SiO is created through reaction of silicon with oxygen at the contact front as the plume expands.
Effects of Laser Irradiation on Growth and Doping Characteristics of GaAs in Chemical Beam Epitaxy
Authors: Dong H. K. , Li N. Y. , Tu C. W. 
Published: April 2011

AbstractIn this paper, we report laser-assisted chemical beam epitaxy (CBE) of GaAs using triethylgallium (TEGa), tris-dimethylaminoarsenic (TDMAAs), and an ar ion laser operating at visible or ultraviolet (UV) wavelength. the laser-assisted growth with TDMAAs, compared to as4 or asH3, shows a wider range of growth enhancement at low substrate temperatures. Unlike CBE of GaAs without laser irradiation, laser-enhanced GaAs growth rate was found to be constant as the V/III incorporation ratio changes. by using diiodomethane (CI2H2) as a dopant gas, the GaAs films with laser irradiation show a much higher hole concentration than those grown simultaneously without laser irradiation at substrate temperatures from 460-530°C. Laser irradiation was also found to enhance silicon incorporation at low temperatures. Photothermal effects are responsible for laser-enhanced growth and silicon doping, but the wider temperature window in laser-enhanced growth and the laser-enhanced carbon incorporation are caused by additional photocatalytic or photochemical effects.
Spreading Kinetics of Molten 60Sn40Pb on Higher Melting Temperature Pb-Sn Alloy Substrates
Authors: Conrad H. , Guo Z. , Jung D. Y. 
Published: April 2011

ABSTRACTThe spreading of molten 60Sn40Pb drops on higher melting point Pb-Sn alloy substrates (3 to 10 wt.% Sn) was investigated for reflow temperatures of 205° to 300°C. Following melting the drop assumed the form of a slightly flared, spherical cap with some penetration into the substrate beneath the contact area. The effects of time and temperature on the contact angle θ and the depth of penetration h were of the formwhere the apparent activation energy Q was 4.2 kcal/mole for θ and 16 kcal/mole for h. The time exponent m (negative for θ and positive for h) decreased with temperature from ∼ 0.2–0.3 at 205°C to ∼0.05 at 260° and then increased again at higher temperatures. The magnitude of Q for θ is in accord with that for the viscosity of molten Pb-Sn alloys and that for h with a combined liquid-solid diffusion involved in the dissolution. Further work is however needed to identify unequivocally the mechanisms which govern the wetting in these duplex Pb-Sn alloy systems.
Stress Concentrations in Electronic Packaging
Authors: Mahajan Ravi , Madenci Erdogan , Ileri Levent , Thurston Mark 
Published: April 2011

ABSTRACTThe reliability of ceramic and plastic packages used in microelectronics is compromised by interface (delamination) and homogeneous (bulk) cracking that is initiated during processing and stress testing. These cracking failures have certain characteristics in that they begin at locations of geometric stress concentrations and propagate along typical failure paths. Characterization of these stress concentrations is therefore essential to a good design and for defining material response parameters such as bulk and interfacial fracture toughness. In this paper, applications of a general-purpose finite element technique for the characterization of stress concentrations are presented. The technique uses the full twodimensional elasticity solution for different materials that are bonded together. It is possible to use this technique to extract relevant material parameters, such as stress intensity factors, the J-integral, or energy release rate, and hence to eventually define the conditions necessary for crack initiation and propagation.
Waveguides Fabricated in Fused Silica by Germanium Ion Implantation at Varying Doses
Authors: Leech Patrick W. , Ridgway Mark C. 
Published: April 2011

AbstractThe implantation of MeV Ge3+ ions into fused silica has been used to fabricate single mode channel waveguides with a low propagation loss of 0.10–0.15 dB/cm. The loss coefficient, α, has been measured as a function of ion dose (8 × 1013 to 8 × 1016 ions/cm2) and annealing temperature (250 to 600 °C) at λ = 1300 nm. The value of cc for the as-implanted waveguides exhibited a minimum of -1.0 dB/cm at an intermediate range of dose from 8 × 1014 to 8 × 1015 ions/cm2. A progressive reduction in α occurred as the annealing temperature was increased from 300 to 500 °C. Annealing of the implanted waveguides at 500 °C for 1 h has produced an order of magnitude decrease in α to 0.1 dB/cm at 8 × 1014 ions/cm2. At doses which were outside of the intermediate range, the value of α was ≥ 10 dB/cm. This trend in α with ion dose has been attributed to the dominance of a residual nuclear component of damage after annealing.
Ion Synthesis of Colloidal Silver Nanoclusters in the Organic Substrate
Authors: Stepanov A. L. , Abdullin S. N. , Khaibullin R. I. , Valeev V. F. , Osin Yu. N. , Bazarov V. V. , Khaibullin I. B. 
Published: April 2011

AbstractHigh-dose ion implantation was used to create silver metallic grains in the epoxy resins The structure and optical properties of Ag/organic systems were investigated by transmission electron microscopy and absorption UV-visible spectroscopy, It was established that silver implantation into the organic substrate produced colloidal nanoclusters in the near-surface region, whose average size and size distribution were function of dose value. The silver nanoclusters give rise to optical absorption at the plasmon wavelength. and maximum absorption was shown to be correlated with filling factors. The d.c. resistivities of irradiated samples were measured in temperature range from 5 to 300 K The observed exp(T0/T)n behaviour of resistivity indicated that synthesized metal particles are separated.
Enzymatically Degradable Synthetic Polymers
Authors: Shao Wen , Leong Kam W. 
Published: April 2011

AbstractComplex coacervation is an appealing method of microencapsulating delicate proteins for controlled drug delivery. Natural polyelectrolytes, such as collagen, gelatin, hyaluronic acid, and chondroitin sulfate, are popular choices for formulating the microspheres. For advantage of versatility, synthetic systems are attractive. Typical synthetic polyelectrolytes are composed of a carbon-carbon backbone that is nonbiodegradable. To design synthetic polyelectrolytes that are biodegradable, we synthesized diamines containing dipeptide or tripeptide sequences that are enzymatically degradable. The enzymatically degradable linkages comprised gly-phe, gly-phe-phe, or gly-gly-phe, and lysine and 2,3-diaminopropionic acid co-monomers served as the charged component. Using an interfacial polymerization technique, these monomers were condensed with diacyl chlorides, including succinyl, adipoyl, or terephthaloyl chloride to form polyamides. Results of gel permeation chromatography and ninhydrin assays showed that the polymers degraded in PBS containing α-chymotrypsin.
Growth and Properties of III-V Nitride Films, Quantum Well Structures and Integrated Heterostructure Devices
Authors: Schetzina J.F. 
Published: April 2011

ABSTRACTGrowth of lll-V nitrides by molecular beam epitaxy (MBE) is being studied at NCSU using an rf nitrogen plasma source. GaN/SiC substrates consisting of ∼3 μm thick GaN buffer layers grown on 6H-SiC wafers by MOVPE at Cree Research, Inc. are being used as substrates in the MBE film growth experiments. The MBE-grown GaN films exhibit excellent structural and optical properties — comparable to the best GaN films grown by MOVPE—as determined from photoluminescence, x-ray diffraction, and vertical-cross-section TEM micrographs. Mg and Si have been used as dopants for p-type and n-type layers, respectively. AlxGa1−xN films (x∼0.06-0.08) and AlxGa1−xN/GaN multi-quantum-well structures have been grown which display good optical properties. Light-emitting diodes (LEDs) based on double-heterostructures of AlxGa1−xN/GaN which emit violet light at ∼400 nm have also been demonstrated. Key issues that must be addressed before lll-V nitride laser diodes can be demonstrated and commercialized are discussed. New integrated heterostructures are proposed for the development of a variety of vertical-transport devices such as light-emitting diodes, laser diodes, photocathodes, electron emitters based on the negative-electron-affinity of AIN, and certain transistor structures.
AlGaInN Quaternary Alloys by MOCVD
Authors: Mcintosh F.G. , Piner E. , Boutros K. , Roberts J.C. , He Y. , Moussa M. , El-Masry N. , Bedair S.M. 
Published: April 2011

ABSTRACTAlGaInN quaternary alloy based devices can cover the emission wavelength from deep UV to red. This Quaternary alloy also offers lattice matched heterostructures for both optical and microwave devices. We will report on the MOCVD growth of AlxGa1−x-yInyN (0<x<0.12), (0<y<0.15) at 750 °C on sapphire substrates, using TMG, EDMIn, TMAl and NH3 precursors. Chemical composition, lattice constants and bandgaps of the grown films were determined by EDS, X-ray diffraction and room temperature PL. Data indicates that the lattice constants can also be deduced using Vegard's law, indicating a solid solution of this alloy. PL showed band edge emission, however emission from deep levels was also observed. Optimized growth conditions and heterostructures using this quaternary alloy will be presented.
Strain Effects in GaN on Sapphire: Towards a Quantitative Comprehension
Authors: Briot O. , Alexis J.P. , Gil B. , Aulombard R.L. 
Published: April 2011

ABSTRACTWe present here a detailed investigation of the optical properties of GaN epilayers grown by low pressure MOVPE on sapphire substrates, using 2K photoluminescence as well as 2K reflectance spectroscopy. A large series of samples has been grown under eclectic conditions (V/III ratio, growth temperature, nitridation steps,...) which allows us to propose the first semi-quantitative investigation of the sample-dependent band gap energies. This dependence of the bandgap is analyzed in terms of i) residual stress, ii) exciton parameters and iii) deformation potential characteristics of the A, B, C excitons. the residual stress cannot be simply explained in terms of the differences between the thermal expansion coefficients of the various compounds, but are strongly correlated to the V/III growth ratio imposed during the growth, and subsequently to the influence of this parameter at the scale of electronic and structural characteristics of the deposited layers.
Monte Carlo Calculation of Hole Transport in Bulk Zincblende Phase of GaN including a Pseudopotential Calculated Band Structure
Authors: Oguzman I. H. , Kolnik J. , Brennan K.F. , Wang R. , Ruden P. P. 
Published: April 2011

ABSTRACTIn this paper, we present ensemble Monte Carlo based calculations of the steady state hole transport properties, i.e. average energy, drift velocity, and band occupancy of zincblende GaN. The Monte Carlo calculation includes the full details of the valence bands and a numerically determined scattering rate derived from an empirical pseudopotential calculation. Calculations are made for electric field strengths up to 1000 kV/cm. It is found that the average hole energies are much lower than the corresponding electron energies at comparable electric field strengths, and that some anisotropy in the drift velocity and average energy appears at the higher fields examined here.
Excitonic Recombination Processes in Undoped and Doped Wurtzite GaN Films Deposited on Sapphire Substrates
Authors: Freitas J.A. , Doverspike K. , Wickenden A.E. 
Published: April 2011

ABSTRACTExcitonic recombination processes in GaN films grown by low pressure metalorganic chemical vapor deposition technique have been studied in the temperature range between 6K to 320K by photoluminescence spectroscopy. Low temperature photoluminescence spectra of high resistivity films show well-resolved spectral features associated with the excitonic interband transitions. A detailed spectral analysis allowed us to estimate the exciton binding energy and the energy gap. Spectral studies of Si-doped GaN films demonstrate that the high energy recombination processes in these films are dominated by excitons bound to neutral Si donors. Comparison between the recombination channels in high resistivity and in Si-doped films indicated that Si has a larger exciton binding energy than the unknown pervasive donor in undoped materials. These results confirm the excellent electronic properties of the undoped and doped films.
Magnesium Doping of GaN by Metalorganic Chemical Vapor Deposition
Authors: Lu Hongqiang , Bhat Ishwara 
Published: April 2011

ABSTRACTP-type GaN films were grown on sapphire substrates in a horizontal metalorganic chemical vapor deposition system using (C5H5)2Mg (Cp2Mg) as the p-dopant source. It is found that the acceptor concentration in the post-growth annealed GaN samples increases with the Mg flow rate and reaches a peak value of 1×1019 cm−3 at Mg flow rate of 0.84 ĉmol/min. The films remain semi-insulating even after annealing when the Mg flow rate is higher than 1.08 ĉmol/min. The effects of annealing temperature and duration on the electrical properties of GaN are also investigated. The results confirm that a 800 °C, 30 minutes post-growth annealing in N2 ambient is sufficient to activate most of the Mg atoms. In addition, study of rapid thermal annealing of Mg-doped GaN was carried out and the results show that the p-type acceptor concentration obtained is comparable to the results obtained using furnace annealing process. Finally, GaN light emitting diodes (LEDs) are demonstrated using undoped layer as the n-type base layer in a p-on-n structure. The light emission spectra are dominated by the 430 nm peak, accompanied with two relatively weak peaks located at 380nm and 550nm.
Growth of GaN without Yellow Luminescence
Authors: Zhang X. , Kung P. , Walker D. , Saxler A. , Razeghi M. 
Published: April 2011

ABSTRACTWe report the growth and photoluminescence characterization of GaN grown on different substrates and under different growth conditions using metalorganic chemical vapor deposition. The deep-level yellow luminescence centered at around 2.2eV is attributed to native defect, most possibly the gallium vacancy. The yellow luminescence can be substantially reduced By growing GaN under Ga-rich condition or doping GaN with Ge or Mg.
Reactive Ion Etching of AlN, AlGaN, and GaN Using BCl3
Authors: Hughes W. C. , Rowland W. H. , Johnson M. A. L. , Cook J. W. , Schetzina J. F. 
Published: April 2011

ABSTRACTThe III-V nitrides are promising materials for use in UV-blue-green optoelectronics, high-temperature electronics, and negative-electron-affinity (NEA) electron emitter applications. In order to realize this potential, it is important to develop an etching technology for device fabrication. The stability of the III-V nitrides to harsh chemical environments makes most wet etching extremely difficult, so that dry etching alternatives are desirable. Recent experiments have shown that BCI3-based chemistries are effective for reactive ion etching of GaN and that KOH-based solutions may preferentially etch AIN from GaN. This paper reports on the use of BCI3 for etching AIN and AlGaN in addition to GaN and the creation of structures such as mesas and lines. It also examines the potential use of potassium Hydroxide (KOH) as a wet etchant of the nitrides. AIN, AlGaN, and GaN films grown by either metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) were patterned with Ni in 250 μm × 250 μm squares and 5 μm wide lines to create mesas and lines for typical light emitting diode (LED) or laser diode applications. Reactive ion etching was performed in a commercial reactor using BCI3 pressures ranging from 5 to 30 mTorr. Gas flow rates of 5 to 50 seem and RF powers of 50 to 150 W were employed. High nitride etch rates of up to 730 Å/min. were observed but lower etch rates were needed to avoid etching of the Ni mask. Smooth mesa surfaces and sidewalls were observed in scanning electron micrographs of the etched nitride structures. Mesas as small as 5 μm × 5 μm were patterned and made in this way. Lines were also made in a similar manner as narrow as 5 μm on GaN/AIN epilayers. Subsequent wet etching of these lines showed that KOH-based solutions such as AZ400K developer attack not only AIN but also GaN depending upon the quality of the film. Possibilities for using this wet etch as a defect etchant or selective etch of nitrides on SiC are discussed.
Calculations of the Specific Resistance of Contacts to III-V Nitride Compounds
Authors: Barnes P.A. , Zhang X-J , Lovejoy M.L. , Drummond T.J. , Hjalmarson H.P. , Crawford M. , Shul R.J. , Zolper J.C 
Published: April 2011

ABSTRACTWe present calculations of the specific contact resistance for metals to GaN. Our calculations include a correct determination of the Fermi level taking into account the effect of the degenerate doping levels, required in creating tunneling ohmic contacts. Using a recently reported improved WKB approximation suitable in representing the depletion width at the metal-semiconductor interface, and a two band k-p model for the effective masses, specific contact resistance was determined as a function of doping concentration. The specific contact resistance was calculated using the best data available for barrier heights, effective masses and dielectric coefficients for GaN. Because the barrier height at the metal-semiconductor interface has a very large effect on the contact resistance and the available data is sketchy or uncertain, the effect of varying the barrier height on the calculated specific contact resistance was investigated. Further, since the III-V nitrides are being considered for high temperature device applications, the specific contact resistance was also determined as a function of temperature.
C-Axis Oriented Ferroelectric thin Films of PbtiO3 on Silicon Substrate by Pulsed Laser Ablation
Authors: Palkar V. R. , Purandare S. C. , Pai S. P. , Chattopadhyay S. , Apte P. R. , Pinto R. , Multani M. S. 
Published: April 2011

ABSTRACTWe are reporting the successful deposition of single phase c-axis oriented ferroelectric thin films of PbTiO3 on Si (100) by pulsed laser deposition. It is shown that the formation of non ferroelectric Pb2Ti2O6 phase at the interface could be avoided by raising the substrate temperature sufficiently high. The film deposition conditions are optimized so as to achieve better ferroelectric properties.
Modeling of Film Growth in Pulsed Laser Deposition
Authors: Tyunin M. 
Published: April 2011

ABSTRACTFilm growth in pulsed laser deposition (PLD) is described as a process of sorption of ablated species on the substrate surface. Film growth rate and composition are qualitatively analyzed as a function of laser fluence and ambient gas pressure. As an example, analysis of the film composition is carried out for BiSrCaCuO and PbZrTiO pulsed laser deposited films.
Tantalum Oxide and Niobium Oxide thin Films Grown by Pulsed Laser Deposition
Authors: FernÁndez FÉlix E. , Marrero Pablo J. 
Published: April 2011

ABSTRACTAmorphous tantalum pentoxide (Ta2O5) and niobium pentoxide (Nb2O5) thin films were grown from both metal and oxide target by reactive pulsed laser deposition. Film structure and composition were studied as a function of substrate temperature and oxygen pressure. Good quality transparent films were obtained for substrate temperatures greater than 140° C, and O2 pressures of 200 mTorr. Lower temperatures and pressures produced opaque films, associated with lower oxides.