bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Role of Impurities in Hydride Vapor Phase Epitaxially Grown Gallium Nitride
Authors: Molnar R. J. , Nichols K. B. , Maki P. , Brown E. R. , Melngailis I. 
Published: April 2011

AbstractGallium nitride (GaN) films grown by hydride vapor phase epitaxy on a variety of substrates have been investigated to study what role silicon and oxygen impurities play in determining the residual donor levels found in these films. Secondary ion mass spectroscopy analysis has been performed on these films and impurity levels have been normalized to ion implanted calibration standards. While oxygen appears to be a predominate impurity in all of the films, in many of them the sum of silicon and oxygen levels is insufficient to account for the donor concentration determined by Hall measurements. This suggests that either another impurity or a native defect is at least partly responsible for the autodoping of GaN. Additionally, the variation of impurity and carrier concentration with surface orientation and/or nucleation density suggests either a crystallographic or defect-related incorporation mechanism.
Study of Deep Levels by Admittance Spectroscopy in High Resistivity P-Type 6H-SiC Single Crystals
Authors: Evwaraye A. O. , Smith S. R. , Mitchel W. C. 
Published: April 2011

AbstractDeep levels in high resistivity p-type 6H-SiC has been studied using optical admittance spectroscopy ( OAS ). Besides the conductance peak due to the band to band transitions, there are three conductance peaks in the spectra of most of the samples. The conductance peak due to the vanadium donor (0/+) level at EV+ 1.55 eV is identified. The persistent photoconductance (PPC) at this defect was also studied. The decay kinetics of the PPC follow the stretched exponential form. The potential barrier against recapture of carriers was determined to be 220 meV for the vanadium donor level.
Applications of Scanning Defect Mapping System for Semiconductor Characterization
Authors: Carr Kavin F , Carlson N. , Weitzman P. , Sopori B. L. , Marshall C. , Allen L. 
Published: April 2011

AbstractA laser scanning system has been developed by the National Renewable Energy Laboratory for the rapid characterization of crystal defects in single- and poly-crystalline semiconductors. The scanning defect mapping system has been commercialized by Labsphere, Inc. as the PVScan 5000. In the unprocessed material, the system produces digital color maps of the spatial distributions of dislocations and grain boundaries simultaneously. After device fabrication, the PVScan 5000 is used to produce photoresponsivity maps of the light beam induced current (LBIC) on a photovoltaic device such as a solar cell or a photodetector. An additional feature is that it also measures the spatial distributions of optical reflectance, both specular and diffuse, which can be applied to the LBIC maps to determine the internal responsivity of the device. The internal responsivity is proportional to the minority carrier diffusion length of silicon devices. It may be possible, therefore, to determine the diffusion length for certain devices.
Influence of Electric Field and Temperature on Magnetic Field Induced Prolonged Changes of Electric Parameters of Silicon Systems
Authors: Maslovsky Vladimir M 
Published: April 2011

AbstractMagnetic field induced prolonged changes (MFIPC) of electric parameters of semiconductor systems is the phenomenon that has been recently established experimentally. In this work it is investigated for the first time the influence of electric field and temperature on duration of MFIPC of carrier generation lifetime in Si subsurface region and the influence of temperature on MFIPC of the MOS structure leakage voltage. The value of determined mobility of generated defects corresponds to the diffusion coefficient of vacancy -impurity complexes. These investigations of MFIPC of microstructure confirm that non-equilibrium defects reactions are limited by diffusion (in the absence of external electric field). It is shown that the corresponding diffusion coefficient is about 10−13 cm2s−1 and the magnitude of diffusion activation energy determined from these investigations is in the range 0.45–0.5 eV. This value is nearly the same as the diffusion coefficient of vacancy-impurity complex.
Influence of Dislocations on the I-V Characteristics of Silicon Solar Cells
Authors: Murphy Robert , Sopori Bhushan L. , Rose Doug 
Published: April 2011

AbstractThis paper presents a phenomenological approach for analysis of dislocations in a large-area device like a solar cell. A microscopic model of a dislocation is used to calculate the local effects of a dislocation on the dark and the illuminated characteristics of a p-n junction device. A statistical approach is then used to empirically arrive at the I-V characteristics of a small-area device with a uniform distribution of dislocations. Finally, these results are applied to develop a network model to determine the terminal characteristics of a large-area solar cell of a known spatial distribution of dislocations. We show that the performance of a solar cell is influenced not only by the density of dislocations but also by their spatial distribution; heavily dislocated regions exert a disproportionately large degradation effect on the device characteristics.
Defects and Impurities in Mercuric Iodide Processing
Authors: Van Scyoc J. M. , James R. B. , Schlesinger T. E. , Gilbert T. S. 
Published: April 2011

AbstractIn the fabrication of mercuric iodide (HgI2) room temperature radiation detectors, as in any semiconductor process, the quality of the final device is very sensitive to the impurities and defects present. Each process step can change the effects of existing defects, reduce the number of defects, or introduce new defects. In HgI2 detectors these defects act as trapping and recombination centers, thereby degrading immediate performance and leading to unstable devices. In this work we characterized some of the defects believed to strongly affect detector operation. Specifically, we studied impurities that are known to be present in typical HgI2 materials. Leakage current measurements were used to study the introduction and characteristics of these impurities, as such experiments reveal the mobile nature of these defects. In particular, we found that copper, which acts as a hole trap, introduces a positively charged center that diffuses and drifts readily in typical device environments. These measurements suggest that Cu, and related impurities like silver, may be one of the leading causes of HgI2 detector failures.
Study of Oxygen Diffusion and Clustering in Silicon Using an Empirical Interatomic Potential
Authors: Jiang Z. , Brown R. A. 
Published: April 2011

AbstractThe diffusion path and diffusivity of oxygen in crystalline silicon are computed using an empirical interatomic potential which was recently developed [1] for modelling the interactions between oxygen and silicon atoms. The diffusion path is determined by constrained energy minimization, and the diffusivity is computed using jump rate theory. The calculated diffusivity D=0.025 exp(-2.43eV/kBT) cm2/sec is in excellent agreement with experimental data. The same interatomic potential also is used to study the formation of small clusters of oxygen atoms in silicon. The structures of these clusters are found by NPT molecular dynamics simulations, and their free energies are calculated by thermodynamic integration. These free energies are used to predict the temperature dependence of the equilibrium partitioning of oxygen atoms into clusters of different sizes. The calculations show that, for given total oxygen concentration, most oxygen atoms are in clusters at temperature below 1300K, and that the average cluster size increases with decreasing temperature. These results are in qualitative agreement with the effects of thermal annealing on oxygen precipitation in silicon crystals.
Recombination at Oxidation Induced Stacking Faults in Silicon
Authors: Davidson J. A. , Evans J. H. , Vandini M. , Peaker A. R. 
Published: April 2011

AbstractWe have characterised the recombination at Oxidation Induced Stacking Faults (OISF) by employing a combination of DLTS and Minority Carrier Transient Spectroscopy (MCTS). The recombination rate at traps associated with the OISF has been compared with recombination at a conventional point defect also present in the silicon. We find that the effect of small amounts of decoration by copper is to increase hole capture rates at electron filled traps. Infra Red Beam Induced Current measurements are consistent with this in that they also indicate that decoration causes enhanced recombination at the extended defects.
Two Dimensional Magnetic Properties of PdFe Layers
Authors: Petroff F. , Cros V. , Fert A. , Lamolle S. , Wiedmann M. , Schuhl A. 
Published: April 2011

ABSTRACTWe have studied the magnetic properties of very thin PdFe films grown by molecular beam epitaxy. The behavior expected for a 2D Heisenberg system - that is a variation of the susceptibility as exp(B/T) and a logarithmic dependence of the magnetization on the applied field - is observed in a certain range of temperature and field. This is in agreement with recent results of Webb et al [1].
Direct Experimental Study of Domain Structure In Magnetic Multilayers
Authors: Nikitenko V.I. , Gornakov V.S. , Dedukh L.M. , Bennett L.H. , McMichael R.D. , Swartzendruber L.J. , Hua S. , Lashmore D.L. , Shapiro A.J. 
Published: April 2011

ABSTRACTWe have applied a polarized light optical microscope in reflective mode with a Bi-substituted yttrium-iron-garnet indicator film with in-plane anisotropy for visualization of the magnetostatic fields produced by nanostructured magnetic CoNiCu/Cu electrodeposited multilayers. By analysis of the magneto-optical stray field image, detailed information is obtained not only on the as-grown multilayer magnetic structure but on its change during the magnetization reversal processes. The influences of crystal lattice defects and nonuniformity of the nonmagnetic spacers thicknesses on the domain wall nucleation and motion are studied. Peculiarities of the re-magnetization of antiferromagnetically exchange coupled multilayers are discussed, including real-time observations of domain wall creep in a constant applied field.
Unified Semi-Classical Theory of Parallel and Perpendicular Giant Magnetoresistance in Superlattices
Authors: Ustinov V.V. , Kravtsov E.A. 
Published: April 2011

ABSTRACTThe giant magnetoresistance in magnetic superlattices for the current perpendicular to and in the layer planes is studied within a unified semi-classical approach that is based on the Boltzman equation with exact boundary conditions for the spin-dependent distribution functions of conduction electrons. We show that the main differences between the in-plane and perpendicular-to-plane magnetoresistance result from the fact that they originate from different interface processes responsible for spin-dependent scattering. A correlation between the giant magnetoresistance and the superlattice magnetization is also discussed and it is shown that its study has much potential for yielding information about properties of spin-dependent scattering in magnetic superlattices.
Second Order Magneto-Optic Effects in Epitaxial FE(110)/MO(110) Bilayers
Authors: Osgood R.M. , White R.L. , Clemens B.M. 
Published: April 2011

ABSTRACTThe signal measured during a Magneto-Optic Kerr Effect (MOKE) experiment is usually assumed to be linear in the magnetization (or the magnitude of the magneto-optic coupling vector Q that is proportional to the magnetization) so that a plot of the magnetization versus applied field can be obtained. We have observed an appreciable contribution from the Q2 term in the magneto-optic response of epitaxial Fe(110)/Mo(110) bilayers. The Q2 term in the magneto-optic response is much larger than that predicted by existing theory. We re-derive and modify the existing theory to fit the Q2 term.
Surface Enhanced Magneto-Optics in Noble Metal / Ferromagnetic Metal Multilayers
Authors: Safarov V. I. , Kosobukin V. A. , Hermann C. , Lampel G. , Peretti J. , MarliÉre C. 
Published: April 2011

ABSTRACTWe present an electromagnetic enhancement mechanism for the magneto-optical response of noble metal / ferromagnetic metal multilayer thin films. When such a structure is illuminated in total reflection condition, the resonant coupling of light with the noble metal surface plasmons gives rise to an amplification of the magneto-optically induced component of the light electric field. The experimental results obtained on a 30nm-thick Au / Co / Au model system show that this resonant feature observed in the Kerr rotation and ellipticity corresponds to a strong enhancement of the magneto-optical figure of merit and signal-to-noise ratio.
Towards the Synthesis of Atomic Scale Wires
Authors: Anderson P. A. , Woodall L. J. , Porch A. , Armstrong A. R. , Hussain I. , Edwards P. P. 
Published: April 2011

ABSTRACTRecent work1 has highlighted the possibility that through the introduction of metals into the one-dimensional channels of zeolite L, it may be feasible to engineer charge transport along the channels to produce a unique compound comprising a precise, assembled array of ultrafine, atomic-scale conducting wires embedded within the aluminosilicate framework. Using electron spin resonance (ESR), and microwave cavity perturbation measurements, we examine the properties of these remarkable materials as a function of composition as they approach the insulator to metal transition.
Plasma Polymerized Primers for Rubber to Metal Bonding: Characterization of the Interphase
Authors: Tsai Y. M. , Boerio F. J. , Kim Dong K. 
Published: April 2011

ABSTRACTPlasma polymerized acetylene films contained mono- and di-substituted acetylene groups, aromatic groups, and carbonyl groups which resulted from reaction of residual free radicals with oxygen when the films were exposed to the atmosphere. There was some evidence for formation of acetylides in the interphase between the films and the substrates. Reactions occurring in the interphase between the plasma polymerized films and natural rubber were simulated using a model rubber compound consisting of a mixture of squalene, zinc oxide, carbon black, sulfur, stearic acid, diaryl-p-diphenyleneamine, and N,N-dicyclohexylbenzothiazole sulfenamide (DCBS). Zinc oxide and cobalt naphthenate reacted with stearic acid to form zinc and cobalt stearates. The stearates reacted with the benzothiazole sulfonamide moiety of DCBS and with sulfur to form zinc and cobalt accelerator complexes and perthiomercaptides. The complexes and perthiomercaptides reacted with squalene and the plasma polymer to form pendant groups which eventually disproportionated to form crosslinks between squalene and the primer. Migration of double bonds during reaction of the model rubber compound with the films resulted in formation of conjugated double bonds in squalene.
Sticking Probability and Step Coverage Studies of SiO2 and Polymerized Siloxane Thin Films Deposited by Plasma Enhanced Chemical Vapor Deposition
Authors: Theil Jeremy A. 
Published: April 2011

ABSTRACTThis paper describes a method for estimating the effective sticking probability for plasma enhanced chemical vapor deposition (PECVD) of hexamethyldisiloxane (HMDSO) using SiO2 and polymerized siloxanes deposited on specially prepared trench structures. Comparison of the data with direct Monte-Carlo simulation curves provides information about the incorporation probability relative to film growth. It is shown that besides variation in gas chemistry, the choice of trench and film dimensions influences the step coverage. The sticking probability is shown to increase with oxygen flow rate by about 30%, from 0:1 to 10:1 02:HMDSO flow ratio. This flow rate dependence is found to be consistent with work performed on tetraethoxysilane.
Iron Deposition From SC-1 on Silicon Wafer Surfaces
Authors: Dhanda S. , Helms C. R. , Gupta P. , Triplett B. B. , Tran M. 
Published: April 2011

ABSTRACTThis work examines the extent of the deposition of iron on the wafer from (iron) contaminated SC-1 solutions on silicon wafer surfaces, models this effect, and also predicts the chemical state of the iron thus deposited on the wafer surface. The deposition of iron from SC-1 on three different wafer surface terminations was studied. The surfaces were characterized by: (i) the presence of ∼10 Å of native oxide, (ii) by relatively little native oxide and (iii) by a thick thermal oxide. Experiments were performed at room temperature using a 1:1:5 SC-1 (NH4 OH-H2O2-H2O) solution, and also at 80°C with a more dilute composition (0.25:0.5:5). We found that irrespective of the initial surface termination, the amount of iron deposited on the silicon surface from SC-1 exhibited remarkably little deviation over a wide range of spiking levels, leading to the conclusion that in all cases an initial rapid oxidation of the silicon took place, followed by the preferential oxidation of the iron and its inclusion as the oxide into the oxide film. Finally, the model developed predicts that lower temperatures and more concentrated chemistries are more effective in keeping the iron in solution.
Interfacial Defects Induced by Silicidation and Effects of H-Termination at Metal/Silicon Contacts
Authors: Zaima Shigeaki , Yasuda Yukio 
Published: April 2011

ABSTRACTWe have investigated crystallographic structures and electrical properties at the interfaces of transition metals such as Ti, Zr, Hf and V and Si(100), from the viewpoint of an application to ohmic contacts in future ULSI's with low contact resistivity and high reliability. We have achieved very low contact resistivities of 3−5×10−8 Ωcm2 for Zr/ and Hf/n+-Si(100) contacts and 1−2×10-7 Ωcm2 for p+-Si at 400–600°C. It is found that the silicidation reaction in this temperature range brings about the formation of deep levels associated with vacancies in Hf/Si and with metal atoms in V/Si. This difference is considered to be related to that in the silicide formation process between these systems. Furthermore, an anomalous electrical characteristics observed for Hf/p-Si contacts has been found to be markedly improved by using a H-termination treatment of Si surfaces.
IR and MW Absorption Techniques for Bulk and Surface Recombination Control in High-Quaiity Silicon
Authors: Kaniava A. , Menczigar U. , Vanhellemont J. , Poortmans J. , Rotondaro A. L. P. , Gaubas E. , Vaitkus J. , KÖster L. , Graf D. 
Published: April 2011

ABSTRACTThe carrier recombination rate in high-quality FZ and Cz silicon substrates is studied by contactless infrared and microwave absorption techniques. Different surface treatments covering a wide range of surface recombination velocity have been used for the separation of bulk and surface recombination components and evaluating of the efficiency of passivation. Limitations of effective lifetime approach are analyzed specific for low and high injection level. Sensitivity limits of the techniques for iron contamination are discussed
Investigation of Pre-Tungsten Silicide Deposition Wet Chemical Processing
Authors: Philipossian A. , Moinpour M. , Wilkinson R. , Watt V. H. C. 
Published: April 2011

ABSTRACTRemoving the native oxide from the poly-Si surface prior to WSix deposition is essential for achieving high quality silicides as well as sufficient film adhesion, particularly after high temperature anneal or oxidation. Contact angle studies have been used to determine initial and time-dependent surface characteristics of several types of silicon surfaces following immersions in HF-based etchants for varying amounts of time. The morphological characteristics of the surfaces before and after exposure to etchants, as well as the relative etch rates and wetting capabilities of the etchants have been used to explain the following results: With respect to initial contact angle studies, the implanted & annealed polycrystalline silicon surface has the lowest contact angle followed by polycrystalline and monocrystalline surfaces. Longer immersion times yield lower initial contact angles. The 0.1% lightly-buffered HF solution results in the highest contact angle followed by the 1% buffered HF solution with surfactant, and the 1% HF solution. With respect to contact angle changes during ambient air exposure time, the asdeposited polycrystalline silicon surface is most stable followed by monocrystalline, and implanted & annealed polycrystalline silicon surfaces. Longer immersion times improve surface stability while the 0.1% lightly-buffered HF solution results in the most stable surface followed by the 1% buffered HF solution with surfactant, and the 1% HF solution.
Rapid Growth of Diamond-Like-Carbon Films by Copper Vapor Laser ablation
Authors: Mclean W. , Warner B. E. , Havstad M. A. , Balooch M. 
Published: April 2011

AbstractVisible light from a copper vapor laser (CVL) operating with 510 and 578 nm radiation (intensity ratio approximately 2:1), an average power of 100 W, a pulse duration of 50 ns, and a repetition frequency of 4.4 kHz has been shown to produce high quality diamond-like-carbon (DLC) films at fluences between 2xl08 and 5xl010 W/cm2. Maximum deposition rates of 2000 μm.cm2/h were obtained at 5xl08 W/cm2. DLC films with hardness values of approximately 60 GPa were characterized by a variety of techniques to confirm DLC character, hydrogen content, and surface morphology. the presence of C2 in the vapor plume was confirmed by the presence of the C2 Swan bands in emission spectra obtained during the process. Economic implications of process scale-up to industrially meaningful component sizes are presented.
Role of Ions in Bias Enhanced Nucleation of Diamond
Authors: Lannon J.M. , Gold J.S. , Stinespring Cd. 
Published: April 2011

AbstractIon-surface interactions are thought to play a role in bias enhanced nucleation of diamond. To explore this hypothesis and understand the mechanisms, surface studies of hydrogen and hydrocarbon ion interactions with silicon and silicon carbide have been performed. the experiments were carried out at room temperature and used in-situ auger analyses to monitor the surface composition of thin films produced or modified by the ions. Ion energies ranged from 10 to 2000 eV. Hydrogen ions were found to modify silicon carbide thin films by removing silicon and converting the resulting carbon-rich layers to a mixture of sp2- and sp3-C. the interaction of hydrocarbon ions with silicon was shown to produce a thin film containing SiC-, sp2-, and sp3-C species. IN general, the relative amount of each species formed was dependent upon ion energy, fluence, and mass. the results of these studies, interpreted in terms of chemical and energy transfer processes, provide key insights into the mechanisms of bias enhanced nucleation.
Conductivity of the Granular Metal Films Obtained by High Dose Ion Implantation into Pmma
Authors: Bazarov V.V. , Petukhov V.Yu. , Zhikharev V.A. , Khaibullin I.B. 
Published: April 2011

AbstractThin granular metal films in polymethylmethacrylate(PMMA) have been synthesized by 40 keV Fe+, ag+ or Pb+ ions implantation with fluencies up to 6*1017 ion/cm2. the resistivity of synthesized films was measured in the temperature range from 300K. to 5K. the temperature dependence of the resistivity of PMMA implanted with ag+, Pb+ and small fluence Fe+ obeys the well known law lnR~(l/T)1/2. the samples implanted by high fluence Fe+ reveal rather a different behaviour. at low temperature (T<100K) the curves R(T) fit the formulae inR~lnT. the two mechanisms of conductivity of a granular film are considered: direct tunneling and thermally activated hopping. Combined with the morphology features of films, obtained by high fluence Fe+ implantation, the above mentioned consideration offers a satisfactory explanation of the observed temperature dependence R(T).