bluuebunny/crossref_metadata_2025 huggingface dataset:
PECVD of Amorphous Silicon Carbide from Trimethylsilane
Authors: Kelliher J. T. , Massuda M. , DiFonzo P. A. , Neal T. R.
Published: April 2011

Amorphous silicon carbide (SiC) was deposited by plasma enhanced chemical vapor deposition (PECVD) in an Applied Materials (AMT5000) tool from sources of trimethylsilane (3MS) and either argon or nitrogen. A deposition rate of ≈ 800 nm/min on a 150 mm silicon wafer was achieved at 350°C. Process conditions investigated were temperature (200–400°C), power (100–600W), pressure (2–8 torr), gas flow rates, and spacing. Various process condition regimes generated a high particle count that was eliminated by controlling parameters of pressure and spacing. Ellipsometry and n&k Analyzer techniques determined the index of refraction. The index of refraction was in agreement between both tools and range from 1.79–2.36 depending on the 3MS flow (25–100 seem) and carrier gas. A Prometrix FT500 with a fixed index of refraction measured 49 points of thickness determined the uniformity. The SiC films stoichiometric composition was measured by X-ray Photoelectron Spectroscopy (XPS). Small quantities of oxygen or nitrogen were found. Additional properties examined were crystallinity, stress, and pinhole density. Dielectric constant was measured by CV techniques.
Solution Processing of YBa2Cu3OT7-x Thin Films
Authors: Singhal A. , Paranthaman M. , Specht E. D. , Hunt R. D. , Beach D. B. , Martin P. M. , Lee D. F.
Published: April 2011

The aim of this work was to develop a non-vacuum chemical deposition technique for YBa2Cu3O7-x (YBCO) coated conductors on rolling-assisted biaxially textured substrates (RABiTS). We have chosen the metal-organic decomposition (MOD) and sol-gel precursor routes to grow textured YBCO films. In the MOD process, yttrium 2-ethylhexonate, barium neodecanoate, copper 2-ethylhexonate and toluene were used as the starting reagents. YBCO films processed by the MOD method on SrTiO3 (100) single crystal substrates were predominately epitaxial and consisted of c and a-axis oriented material. Films have a TC,onset of 89K and the best superconducting transition temperature of 63K. Films pyrolyzed at 525 °C and subsequently annealed at 780 °C in P(O2) of 3.5 × 10−4 atm contained YBCO phase predominately in a-axis orientation. In the sol-gel route, yttrium-isopropoxide, barium metal, copper methoxide and 2-methoxyethanol were used as the starting reagents. Sol-gel YBCO films on SrTiO3 substrates were epitaxial and c-axis oriented.
The Spray Deposition of Transition Metal Nitride thin Films Using Alcohol Based Precursor Solutions
Authors: Weil K. S. , Kumta P. N.
Published: April 2011

A new alcohol solution based approach has been developed for preparing transition metal nitride thin films and coatings. In this technique, the metal of interest is dissolved as a chloride in acetonitrile, then chelated with triethanolamine to form a highly viscous solution which settles out of the solvent phase. The acetonitrile is then evaporated off and the remaining thick liquid precursor is easily diluted with water or methanol, yielding a semi-viscous liquid which can be used directly to coat various substrates. When heat treated under the appropriate conditions in ammonia, the precursor coating transforms to yield the corresponding nitride. This approach is currently being considered for preparing nitride-based thin film electrical components and has been successfully used thus far to spray deposit TaN and NbN nitride films onto silicon substrates. Results of the preliminary study on these two nitride films are discussed in this paper.
Colossal Magnetoresisttve Tffin Films of (La1-x,Prx)0.7Ca0.3MnO3 Prepared by Aerosol MOCVD
Authors: Gorbenko O. Yu. , BOSAK A. A. , KAUL A. R. , BABUSHKINA N. A. , BELOVA L. M.
Published: April 2011

Thin epitaxial films of (La1-x,Prx)0.7Ca0.3MnO3 (x=0,0.25,0.5,0.75,l) were grown on LaA1O3, SrTiO3 and ZrO2(Y2O3) by aerosol MOCVD at 750°C Variation of x greatly influences the electrical properties of material by changing of the tolerance factor t. The tensile strain in the films on perovskite substrates produces the effect on the maximum resistivity temperature Tp comparable with the effect of chemical pressure nearby critical value of t ∼ 0.91. By variation of x the colossal magnetoresistance in very low magnetic fields was achieved in the thin films: an applied field of 0.3 T was enough for 32 times decrease of the resistivity of (La0.35,Pr0.35)Ca0.3MnO3 film on LaA1O3 at 155 K. The charge ordering starting in (La1-x,Prx)0.7Ca0.3MnO3 at 160–210 K leads to the switching from Arrhenius law (lggρ ∼ T1 ) to Mott law (lgρ ∼ T1/4) of resistivity. Large-angle boundaries dominating the structure of the films on ZrO2(Y2O3) increase the resistivity both above and below Tp.
Chemical and Sonochemical Approaches to the Formation of VO2 Films and VO2-Impregnated Materials
Authors: Keppens V. , Mandrus D. , Boatner L. A.
Published: April 2011

A new chemical and chemical/ultrasonic approach to the preparation of VO2 films and VO2-impregnated bulk materials has been developed. In this approach, a V2O5 sol prepared by quenching is used to coat SiO2 substrates. The resulting gel-film is heat treated in a reducing atmosphere to form a film identified as VO2 from the results of X-ray diffraction and both optical and resistivity measurements, which reveal the phase transition characteristic of vanadium dioxide. The advantage of this approach to the formation of VO2 is that the V2O5 sol can be used to impregnate porous materials, which are then heat treated to form an optically active composite material. The switching properties of the VO2 films are investigated using optical and resistivity measurements, and the results are compared to those obtained for VO2-films prepared by more-conventional methods.
Chemical Vapor Deposition of Strontium Ruthenate Thin Films from Bis(2, 4-Dimethylpentadienyl) Ruthenium and Bis(Tetramethylheptanedionato) Strontium
Authors: Breitkopf Richard , Meda Lamartine J. , Haas Terry , Kirss Rein U.
Published: April 2011

Adherent, polycrystalline films containing mixtures of SrRuO3, Sr2gRuO4 and RuO2 were deposited on silicon and alumina substrates by hot wall chemical vapor deposition from bis(2, 4-dimethylpentadienyl) ruthenium and Sr(thd)2 between 650 and 700°C. The as-deposited mixed phase films, which contained polycrystalline phases of RuO2 and amorphous phases of the mixed oxide exhibited resistivities between 6.5 and 20 mΩcm. Rims were annealed at 1000°C under oxygen/argon ambient. The annealed films exhibited higher resistivities than their as-deposited counterparts and a substrate dependence of phases present was observed. The decrease in conductivity upon annealing for films on both substrates is attributed to the formation of volatile ruthenium oxides. The higher conductivity of post-annealed samples on alumina (compared to samples prepared and annealed on Si) is attributed to Sr uptake by the substrate and thus a suppression of Sr2RuO4 formation.
Macroporous Materials with Uniform Pores by Emulsion Templating
Authors: Imhof A. , Pine D. J.
Published: April 2011

A method was developed for the production of macroporous oxide materials by using the droplets of a nonaqueous emulsion as the templates around which material is deposited through a sol-gel process. Moreover, uniform pores arranged in regular arrays can be obtained by starting with an emulsion of uniform droplets. These droplets first self-assemble into a colloidal crystal after which gelation of the suspending sol-gel mixture captures the ordered structure. After drying and calcination pellets are obtained which contain ordered arrays of spherical pores left behind by the emulsion droplets. The method can be used to make uniform pores in the range from 0.05–5 micrometers in many different materials. We demonstrate the process for titania, silica, and zirconia.
Hybrid Catalysts: Internal or External Configuration for Better Catalytic Performance?
Authors: Le Van Mao R. , Saberi M. A. , Lavigne J. A. , Xiao S. , Denes G.
Published: April 2011

Hybrid catalysts with the external configuration for the cocatalyst showed enhanced product diffusion rates in the n-octane hydrocracking, only if the reaction was carried out at relatively high temperatures. In the n-heptane isomerization, direct incorporation of the Al species into the HY zeolite micropores produced sorption sites which positively affected the selectivity to liquid isomers. Such as internal hybrid configuration resulted in a more important increase in the liquid isomer selectivity than that given by the external hybrid configuration, both systems being designed for better product outward-diffusion.
Investigation of the Optical Properties of Diamond-Like Carbon Films
Authors: Kim B. K. , Grotjohn T. A.
Published: April 2011

Hydrogenated-amorphous carbon films are deposited in a microwave ECR plasma reactor with an rf biased substrate holder using methane-argon and acetylene-argon gas mixtures. The film's optical properties are characterized versus deposition conditions including pressure (1–5 mTorr), rf induced bias (-100 to 20 volts), and argon/hydrocarbon flow ratio. The acetylene-argon discharges show that ion species formed from acetylene are more important than the argon ions, conversely, the methane-argon discharges showed that argon ions are a major ionic species in the deposition. The influence of the thickness of insulating substrates is studied and the feasibility of depositing multilayer a-C:H films with different film properties in each layer is demonstrated.
Cesium-Enhanced R. F. Magnetron Deposition of Carbon Nitride and Diamond-Like Carbon Films
Authors: Murzin I. H. , Hussain M. A. , Tompa G. S.
Published: April 2011

We report the design, manufacturing, and testing of a new cesium enhanced negative carbon ion source that can be useful to synthesize hard and/or electron emitting carbon nitride and diamond-like carbon (DLC) thin films. The design of the source includes a conventional magnetron-sputtering gun, low voltage ion extraction lenses, and a cesium oven to provide cesium vapor for formation of a fractional mono layer of Cs on the carbon target. Cs reduces the surface work function of the carbon target and enhances the emission of negative carbon ions. Argon and argon-nitrogen gas mixtures were used to ignite and sustain the plasma in the chamber. We compare the properties of carbon nitride and DLC films deposited with and without cesium. Nitrogen composition in the Ar-N2 gas mixture was observed to be an important process parameter affecting mechanical properties of the film. The effect of the Cs oven temperature on deposition rate and current absorbed at the substrate was also investigated for RF powers from 0 to 150 W.
Effects of substrate bias on the properties of a-C:H films by DC saddle-field plasma enhanced CVD
Authors: Yoo Young-Zo , Kim HyoGun , Jang HongKyu , Jeong YoungGeun , Kima Geunsik
Published: April 2011

Hydrogenated amorphous carbon (a-C:H) films were deposited on p-type Si(100) at room temperature by DC saddle-field plasma enhanced CVD using pure methane gas and diluted methane gas by inert gas. The effect of substrate bias (Vs) from 0 V to 400 V on deposition rate, hydrogen content, chemical bonding of the films have been investigated. FT-IR spectrum shows that a-C:H films consist of sp2 and sp3 bondings and the relative intensity ratio of sp2 and sp3,I(sp2)/I(sp3), decreases from 0.28 to 0.19 as the substrate bias changes from 0 V to 400 V. Deposition rates of the films rapidly decrease with increasing Vs up to 200 V, and then slightly decrease over Vs = 200 V. The hydrogen content of the films increase as Vs goes higher and the number of C-H bonds of a-C:H shows the same trend. Only in the range of Vs=0 V and Vs=100 V the Raman band of graphite and disorder is observed. The emission of white photoluminescence (PL) light from the films is observed with the naked eye even at room temperature. The intensity of PL has a maximum at Vs=200 V, then decreases as the Vs changes from 200 V to 400 V. The PL peak shifts to higher energy from 2.15 eV at 100V to 2.45 eV at Vs=400 V. The PL at Vs = 400 V was two times stronger without a peak shift by using an inert gas dilution into methane source compared with that of a film deposited using pure methane.
Assembling Small Fullerenes: A Molecular Dynamics Study
Authors: Gallic Giulia , Canning Andrew , Kim Jeongnim
Published: April 2011

Using tight-binding molecular dynamics, we have performed two series of computer experiments assembling small fullerenes: first, we have simulated the deposition of C28 clusters on a semiconducting surface, and then we have performed calculations mimicking the gas phase growth of a small fullerene solid. The results of the two computations are discussed and compared to those obtained for ordered forms of C28 solids.
Electron Emission Through Tetrahedral Amorphous Carbon Coatings on Mo and Si Emitters
Authors: Choi W. B. , Myers A. F. , Ding M. Q. , Sharma A. K. , Narayan J. , Hren J. J. , Cuomo J. J.
Published: April 2011

The field emission properties of molybdenum and silicon emitter coated with tetrahedral amorphous carbon (or amorphous diamond) were studied. The tetrahedral amorphous carbon was deposited by laser ablation and showed a uniformly coated columnar structure over the entire emitter. In general, current conditioning improved stability and increased the current density. Coatings of ta-C on Mo emitters with and without nitrogen incorporated both yielded significantly higher emissivity than uncoated emitters. Nitrogen incorporation reduced the effective workfunction and the sp3/sp2 ratio. However similar depositions on Si emitters reduced the emissivity, and may be attributable to the residual oxide at the ta-C/Si interface. Annealing in a hydrogen atmosphere enhanced emissivity from both ta-C/Mo and ta-C/Si emitters. In general, thick coatings lowered the emissivity and the slope of the I-V curves. A temperature dependence of emission was observed only in the low field regions.
On the Effects of the Thermal Treatment on the Structural, Mechanical and Tribological Properties of Amorphous Carbon-Nitrogen Films Deposited by Magnetron Sputtering
Authors: Lacerda M. M. , Freire F. L.
Published: April 2011

Amorphous carbon-nitrogen films, a-CNx, deposited by rf-magnetron sputtering in N2 atmosphere were annealed in vacuum at temperatures between 300 and 700 °C. The annealing time was 30 minutes. The modifications on the film microstructure were monitored by infrared spectroscopy (IR), while the composition and the atomic density were determined by Rutherford backscattering spectrometry (RBS), elastic recoil detection analysis (ERDA) and nuclear reaction analysis (NRA). The internal stress was determined by measuring the film-induced bending of the substrate and the hardness was measured by nanoindentation. Atomic force microscopy (AFM) provided the friction coefficient and the surface roughness. The ratio between nitrogen and carbon atomic concentration decreases for temperatures higher than 500 °C, whereas the film density increases with the annealing temperature: 40 % in the temperature range here studied. The behavior of the D and G Raman bands, IR active due to the nitrogen incorporation in the carbon network, suggests a progressive increase of the size of the graphite-like domains. The hardness of the as-deposited a-CNx film is around 2 GPa. However, both hardness and internal stress increase by a factor of three in samples annealed at 700 °C, while the surface roughness and the friction coefficient decrease by a factor of about two.
Studies of the Growth and Local Atomic Bonding of a-CxNyHz Films
Authors: Efstathiadis H. , Akkerman Z. , Smith F. W.
Published: April 2011

A systematic study of the growth and local atomic bonding (LAB) of a series of a-CxNyHz alloy films prepared via plasma enhanced chemical vapor deposition (PECVD) from mixtures of NH3/C2H2 and N2/C2H2 is presented. The effects of the reactants and their ratio on the film composition and bonding of hydrogen, the optical constants, and the optical energy gap have been determined. It is found that the presence of nitrogen and hydrogen in the plasma decreases the net film deposition rate due to enhanced etching and that incorporation of nitrogen into the film is limited to N/C ≈0.1. For the films deposited from N2/C2H2 as the concentration of N in the film increases, the concentration of C also increases while that of H decreases. No evidence for the type of bonding expected in the theoretically-predicted C3N4 compound has been found. It is observed that hydrogen is preferentially bonded to nitrogen and there is evidence for N-H…N hydrogen bonding in the films. The predictions of the free energy model (FEM) previously developed for the bonding in a-CxNyHz alloys are compared with these experimental results. The importance of entropy in determining the most stable state of these alloys is demonstrated. The FEM successfully predicts and explains some of the experimentally-observed properties of the alloys.
Structure, Optical and Electrical Properties of Pulsed Laser Deposited and Ion Beam Deposited CNx Films
Authors: Chan K. F. , Zhao X.-A. , Ong C. W.
Published: April 2011

CNx films were deposited using pulsed laser deposition (PLD) and ion beam deposition (IBD). The PLD films deposited at substrate temperature Ts = 25°C and high N2 partial pressure have the highest N content (fN) and polymerlike structure, accompanied by large band gap (Eg) and low electrical conductivity (σroom). The rise in Ts lowers fN and induces graphitization of the film structure, so Eg reduces and σroom increases. IBD (with and without N2+ assist) films are graphitic. Higher Ts further enhances the graphitization of the film structure, such that the conduction and valence bands overlap, and σroom approaches to that of graphite. No evidence was found to show successful formation of the hypothetical β-C3N4 phase in the films.
X-Ray Structural Study of Li3N at High Pressure
Authors: Ho Allen C. , Granger Maurice K. , Ruoff Arthur L.
Published: April 2011

The equation of state (EOS) of Li3N has been determined by energy-dispersive x-ray diffraction (EDXD) using synchrotron radiation up to 35 GPa at ambient temperature. Both the hexagonal D6h4(P63/mmc) and the hexagonal D6h1(P6/mmm) phases were present at ambient pressure. The D6h1 -structure completely transforms into the D6h4 -structure at modest pressure. The change in Gibb's free energy as a function of pressure for Li3N was calculated using the experimental EOS.
High-Pressure Properties of Na3ClO Anti-perovskite from First Principles: an exploratory study
Authors: Chizmeshya A. V. G. , Sankey O. F. , McMillan P. F.
Published: April 2011

We present the results of an exploratory theoretical study of Na3ClO in the anti-perovskite structure. The FLAPW method is used to calculate the static lattice properties, pressure equation of state, and the ferroic Flu phonon frequencies in the cubic PmSm phase. We also compute the compression behavior of NaCl and Na2O and find that the lattice energy of Na3ClO at ambient pressure (static lattice) is only marginally larger than of products, in agreement with experiment. However, detailed calculations reveal M- and R-point phonon instabilities in the ideal cubic phase and suggest the existence of lower symmetry structure involving slight rotations of ONa6 octahedra.
Magnetic Collapse and the Behavior of Transition Metal Oxides: FeO at High Pressures
Authors: Cohen R. E. , Fei Y. , Downs R. , Mazin I. I. , Isaak D. G.
Published: April 2011

Linearized augmented plane wave (LAPW) results are presented for FeO at high pressures using the Generalized Gradient Approximation (GGA) to study the high-spin low-spin transition previously predicted by LAPW with the Local Density Approximation (LDA) and Linear Muffin Tin Orbital (LMTO-ASA) methods within the GGA. We find a first-order transition at a pressure of about 105 GPa for the cubic lattice, consistent with earlier LAPW results, but much lower than obtained with the LMTO. The results are generally consistent with recent Mössbauer experiments that show a transition at about 100 GPa. We also discuss the origin of the transition, and show that it is not due to electrostatic crystal-field effects, but is rather due to hybridization and band widening with pressure. Examination of experimental data and computations suggest that the high pressure hexagonal phase of FeO is likely a polytype between the B8 NiAs and anti-B8 AsNi structures. The former is predicted to be an antiferromagnetic metal, and the latter an antiferromagnetic insulator. Implications for geophysics are discussed.
Ruby's Optical Transitions: Effects of Pressure-Induced Phase Transformation
Authors: Duan Wenhui , Paiva G. , Wentzcovitch Renata M. , Fazzio A.
Published: April 2011

Here we summarize our investigation of the effect of a recently observed phase transformation on ruby's optical transitions. This study involved a first principles calculation of the electronic and structural properties of a chromium impurity in alumina host lattices and a subsequent calculation of the multiple structure using eigenvalues and eigenvectors derived from the first principles calculation. This investigation is relevant to clarify the behavior of the fluorescent optical transitions which are used as pressure sensor in diamond anvil experiments across the structural transformation.
Diffusivity and Nuclear Spin Relaxation Measurements at High Pressure in Methanol
Authors: Marzke R. F. , Raffaelle D. P. , Wolf G. H. , Yarger J. L.
Published: April 2011

Diffusivity D and nuclear spin relaxation times T1 and T2 have been measured by NMR to 4.0 GPa in methanol, using a diamond anvil cell probe. In pure MeOH, D−1 and T2 show essentially identical activation volumes. However, these are ∼18% larger than the activation volume of viscosity. By relating these observations to an average molecular correlation time a pressure-dependent infinite-frequency shear modulus G∞ can be inferred, using two independent approaches. The relation between diffusivity and viscosity shows increasing departure from Stokes-Einstein behavior with increasing pressure, if a constant hydrodynamic radius is assumed. This departure is attributed to the pressure dependence of G∞, and can be described empirically by a simple modification of the Stokes-Einstein relation.
Laser Peening of Metals - Enabling Laser Technology
Authors: Brent Dane C. , Hackel Lloyd A.
Published: April 2011

Laser shot peening, a surface treatment for metals, is shown to induce compressive residual stresses of over 0.040 inch to provide improved resistance to vairous forms of failure. A solid state laser technology employing Nd:glass slabs and phase conjugation enables this process to move into high throughput production processing. Details of the technology are discussed.
High Pressure Carbon Behavior Induced from Carbide Hugoniots
Authors: Sekine T. , Takazawa E. , Kobayashi T.
Published: April 2011

Investigations of Hugoniots the diamond-type carbides(various SiC) and NaCl-type carbides such as TiC give some insights into the high-pressure carbon behaviors. The experimental results of phase transitions of a-SiC and β-SiC, together with those of diamond-structure Si, imply that the candidate as post-diamond phase has sixfold coordination and that a possible transition pressure is about 1–2 TPa. The NaCl-type carbide Hugoniots indicate that sixfold coordinated C is very stable at high pressures. The partial molar volume of carbon in the NaCl-type carbides ranges between 1.4 to 2.6 cnvVg-atom C at 1 atm and reaches about 2.8 cm3/g-atom C at 100 GPa. Taking into account structural variations of the corresponding metals, the volume of the sixfold coordinated C is estimated to be 1.7 cm3/g-atom C, about half of that of diamond, and the post-diamond phase appears to be extremely hard.
Influence of surface silanol structure and hydration forces on alkoxide-derived silica gel structure
Authors: Kamiya H. , Yoshida M. , Mitsui M.
Published: April 2011

The effects of the surface silanol structure and interaction force between solid surfaces in water on the gel structure using acid catalyzed hydrolysis alkoxide-derived silica gels with various preparation conditions. The present study focused on the amount of catalysts and H2O/TEOS mole ratios. Surface silanol structure, interaction between solid surfaces and the structure in dried-gels were determined by a FT-nIR, FT-IR, Atomic Force Microscope (AFM) and a mercury porosimetry, respectively. As results, when a relatively low H2O/TEOS mole ratio ( from 4 to 40) was used, surface silanol was almost hydrogen bonded silanol, and isolated silanol disappeared. Since this hydrogen-bonded silanol formed a hydrogen bonded water layer on silica surface, short-range additional hydration force (less than 2 nm) appeared between solid surface and the tip of AFM. When H2O/TEOS mole ratio increase in the range from 20 to 40, the surface density of isolated silanol increased and that of residual Si-OC2H5 decreased. Relatively long-range additional repulsive force on these silica gels reached 20 nm from solid surface. The pore diameter in each dried gel almost corresponded to the surface distance, which acted the additional repulsive force.
Nanocrystalline Materials as Potential Gas Sensing Elements
Authors: Coles G. S. V. , Williams G.
Published: April 2011

Sensors and Transducers, and in the specific context of this paper gas sensors, are currently amongst the largest growth areas in the modem electronics industry and this seems likely to continue for the foreseeable future. Nanocrystalline materials posses many properties that could make them ideal as potential gas sensing elements with many advantages over their microcrystalline counterparts. Most importantly these include increased surface area coupled with reduced sintering temperatures and times. However, it should also be noted that there are several disadvantages including the comparatively high cost of materials and increased electrical resistance.

This paper reviews the operating mechanisms of semiconductor gas sensors and the possible advantages of using nano sized powders to produce gas sensitive devices. Results are presented which have been obtained from several materials produced by laser evaporation including alumina (Al2O3), zirconia (ZrO2), and tin dioxide (SnO2) in contaminated atmospheres incorporating carbon monoxide, hydrogen and methane.
Orientation and Electrical Resistivity of Aluminum Oxide Films Prepared by Ion Beam Assisted Plasma Cvd
Authors: Nakai H. , Harasaki O. , Shinohara J.
Published: April 2011

Aluminum oxide (A12O3) films were prepared on a nickel based superalloy (Inconel 718) by ion beam assisted plasma CVD at the multiple incident angles of the ion beams to a substrate. Crystal structure of these films was analyzed by X-ray diffraction (XRD). Electrical resistance of the films was measured at temperatures ranging from room temperature to 850°C. The incident angle of the ion beams influenced the orientation of A12O3 crystals. The net integrated intensity was calculated in order to compare the intensity among the different thickness samples whose thickness is thinner than X-ray penetration depth. The electrical resistivity depends on the relative X-ray intensity of (110) and (300) of α-A12O3.
Defect production during ion-assisted deposition of molybdenum films studied by molecular dynamics
Authors: Klaver Peter , Thijsse Barend
Published: April 2011

Low energy argon-ion assisted growth of thin molybdenum films (∼ 60 Å) has been studied by molecular dynamics simulations. The effects of a single ion impact are discussed, but more particularly we consider film growth from a manufacturing viewpoint and examine the properties of the completed films. Results for ion-beam assisted deposition are compared with those for unassisted growth (i.e. physical vapor deposition). Surface morphology, defect generation, argon incorporation, and the various responsible atomic mechanisms are discussed.
Charge State of Copper-Silicide Precipitates in Silicon and its Application to the Understanding of Copper Precipitation Kinetics
Authors: Istratov A.A. , Vyvenko O.F. , Flink C. , Heiser T. , Hieslmair H. , Weber E.R.
Published: April 2011

Deep level spectra obtained on n-type silicon samples after copper diffusion and rapid quench give evidence of a positive charge state of the precipitates in p-type silicon. Non-exponential precipitation behavior of interstitial Cu is demonstrated and explained. The possibility of Coulomb interaction between copper ions and copper precipitates is suggested and its influence on Cu precipitation kinetics is disCussed.
Behavior of Deep Defects After Hydrogen Passivation in Znte Studied by Photoluminescence and Photoconductivity
Authors: Bhunia S. , Bose D.N.
Published: April 2011

The effects of hydrogen passivation in undoped p-ZnTe single crystals were studied by photoluminescence (PL) and photoconductivity (PC) measurements. Samples were exposed to r.f hydrogen plasma at 250 °C for different durations. Before passivation PL peaks were observed at 2.06 eV, 1.47 eV, 1.33 eV and 1.06 eV. After 60 minutes exposure, samples showed strong band edge green luminescence at 2.37 eV due to an exciton bound to a Cu acceptor. Further exposure to plasma resulted in disappearance of 2.37eV and 2.34 eV peaks due to damage. In PC studies the dark current was found to decrease by a factor of 70 on 60 minutes passivation. From the temperature dependence of PC gain, the minority carrier lifetime τn, was found to go through a maximum of 4.5 × 10−7 sec at 220 K before passivation. After 60 minutes exposure, τn, remained constant at 4.5 × 10−7 sec for T > 220 K and decreased for T < 220 K. The activation energies of τn, were determined and show marked changes on passivation for T > 220 K. Comparison between PL and PC studies showed that the deep acceptor level OTe responsible for emission at 2.06 eV is passivated giving rise to strong band edge emission at 2.37 eV while emission due to the midgap impurity levels at 1.47, 1.33 and 1.05 eV remained unaffected. The thermal activation energies of the PL peaks have also been determined and allow the construction of a defect energy level diagram for ZnTe.
Defect Engineering In Ion-Implanted Diamond
Authors: Gippius A.A. , Khmelnitski R.A. , Dravin V.A. , Tkachenko S.D.
Published: April 2011

Optical interference studies of graphitized layers formed in diamond by ion implantation and annealing provided the data on the depth and the thickness of the layers as well as their optical parzmeters. The latter were found to be close to those of dispersed graphite. Cathodoluminescince analysis of implanted diamond samples gave evidence of vacancy migration over macroscopic distances (∼1001μ).
Advanced Knowledge for Impurity Motion of Oxygen in Silicon and its Application to Defect-State Analysis
Authors: Yamada-Kaneta H.
Published: April 2011

We review our two models for the impurity excitation of the oxygen in silicon. The first model aims to explain the energies and intensities of the infrared absorption lines. The coupled excitation is formulated for the first time under the D3d symmetry. Taking into account the lowenergy excitation of the oxygen, the A2u local mode, and the anharmonic coupling between them, we quantitatively describe the absorption lines in the 30-, 1100-, and 1200-cm−1 bands, including those of the 18O isotope. We next take into account the A1g local mode, the Eu resonant mode, and the couplings between the excitation elements. This enables us to qualitatively explain the origin and characteristic aspects of other absorptions, e.g., the 500- and 1700-cm−1 bands. The second model is a simplification of the first one with the coupling to the band (extended) phonons included. The model describes the strong temperature dependence of the line widths observed for both of the phonon-resonant 30-cm−1 band and the phonon-off-resonant 1100-cm−1 band. The life-time limiting process causing the finite line-widths is shown to be the one-phonon transitions in the energy-level ladders of the low-energy excitation each belonging to the ground and the first excited states of the A2u local mode. The vibrational excitations of the similar impurity systems in Si, Ge, Ge xSi1−x crystals are analyzed.
Characterization of Deep Impurities in Semiconductors by Terahertz Tunnel Ionization
Authors: Ziemann E. , Ganichev S.D. , Yassievich I.N. , Schmalzv K. , Prettl W.
Published: April 2011

The ionization of deep impurity centers by high intensity far-infrared radiation, with photon energies tens of times lower than the impurity binding energy, has been investigated. It is shown that the ionization is caused by phonon-assisted tunneling in the electric field of radiation, in which carrier emission is accompanied by electron tunneling and defect tunneling in the configuration space. The field and temperature dependencies of the ionization probability allow to obtain defect parameters like tunneling times and the Huang-Rhys factor as well as the basic structure of the defect adiabatic potentials. In very strong fields, the ionization changes to direct tunneling without assistance of phonons. It is shown that for the case of charged impurities and in a relatively low electric field strength the Poole-Frenkel effect plays a dominant role in ionization, which allows to identify the charge state of the center. Within a broad range of intensities, wavelengths and temperature, the terahertz electric field of the radiation acts as a static field. An enhancement of tunneling with increase of frequency has been observed for very high frequencies or low temperatures.
Thermo-Mechanical Stresses in Laminated Polymer Films on Silicon Substrates
Authors: Kim Jin S. , Paik Kyung W. , Oh Seung H. , Seo Hyun S.
Published: April 2011

Thermo-mechanical stresses in MCM-D substrate are important reliability and fabrication issues. The differences in coefficient of thermal expansion (CTE) between substrate, polymer, and metal leads to complicated stress fields in multilevel interconnect structures. While the majority of reports in the literature have focused on spin-coated polyimides, this paper mainly focuses on laminated polymer dielectrics. This study uses material sets representing typical MCM-D structures to monitor the stress level in the polymer films. The substrate deflection caused by composite stresses during fabrication and thermal cycling test is determined by a curvature measurement technique. A simple analytical model which predicts a stress contribution from each individual layer during MCM-D substrate fabrication is proposed and developed by computer simulation as well. The composite stress or bowing in multilayer structures is due to the summation of each individual layer contribution. From a thermo-mechanical stress viewpoint, Ultem® thermoplastic and the epoxy thermoset adhesive exhibit quite different behaviors. In case of the epoxy thermoset adhesive, the amount of bowing increases as number of layers increases and its behavior can be predicted by an elastic model. However, in the case of the Ultem® thermoplastic adhesive, bow values become stabilized as number of layers increases because of the stress relaxation effect of the thermoplastic adhesive during lamination process above Tg of the Ultem® thermoplastic.
Intergranular Coupling and Grain Isolation of Thin Co Films
Authors: Gong Heng , Yang Wei , Lambeth David N. , Laughlin David E.
Published: April 2011

The effects of rapid oxidation and overcoat diffusion processes on the intergranular coupling and grain isolation in thin Co films were studied. The oxidation process was found to be strongly temperature dependent. The optimal coercivities can only be achieved within a narrow range of temperatures, while further increasing the temperature incurs significant thermal instability. CrMn underlayers were confirmed to be more effective in enhancing the grain isolation by the grain boundary diffusion during the oxidation process. The oxidation process does not change the Co anisotropy, and hence the coercivity increase is appears to be a result of better grain isolation. The in-situ diffusion of Ag and Cr overcoats were also found to have siginificant effects on the grain isolation in Co and CoCr films.
Disturbed Array Formation of Electrochemically Grown Self-Organised Nanostructures
Authors: Dierickx D.D. , Celis J.P. , Moshchalkov V.V.
Published: April 2011

The formation of electrochemically etched, self-organised nanostructures on aluminium enables the production of large area regular arrays in a fast and cost-effective way. These microstructures could form the basis to develop masks for subsequent materials deposition without the need for time consuming patterning techniques.

The desired regular arrays result from a steady state interaction between the electrolyte and samples' surface under the influence of a cell potential. The type of array formed depends on this cell potential and shows an evolution from lines to dots.

Although a gradual progress towards a regular lattice spanning large areas is expected, the presence of initial disturbances of the samples' surface or bulk distorts the final lattice considerably. In this work the modulation depth and type of the resultant nanostructures produced at different cell potentials are assessed in view of practical applications.
Corrosion Protection of Cu, Fe, Mn and Co Surfaces
Authors: Baglin J.E.E. , Kellock A.J. , Bardin T.T. , Karis T. , Keck D.
Published: April 2011

The mechanisms and effectiveness of corrosion protection provided by thin ion-beam carbon coatings on Cu, Fe, Mn and Co are discussed. A thin (# 10 Å) layer of protective carbon is produced on metal surfaces by ion-beam dissociation of adventitious or intentional hydrocarbon adsorbates. Below 200°C, oxidation is strongly inhibited, as is corrosion in a humid, sulphurous ambient. Above 200°C, the carbon layer may itself be destroyed by oxidation, due to catalytic action of the metal surface. Thicker PVD carbon (up to 60 Å) was not an effective corrosion barrier, even after ion irradiation. A technique for producing high integrity ion-beam carbon layers of high stability and durability is discussed.
High Density Recording on Conventionally Structured Magneto-Optical Disk by Magnetic Field Modulation
Authors: Kaneko M. , Fukumoto A.
Published: April 2011

Two recent topics on high density recording are reviewed in this paper on conventionally structured MO disk by magnetic field modulation. One topic is the MO disk with a capacity of 650 MB/ φ 64 mm. Using a light wavelength of 650 nm and an numerical aperture of an objective lens of 0.52, a track pitch of 0.95 μm and a bit length of 0.34 μm for (1,7) RLL coding has been applied to achieve 650 MB within a size of a Mini Disc(MD). Groove conditions such as the depth and groove duty in a 1.2-mm thick polycarbonate substrate are optimized to reduce the cross-talk from adjacent tracks. As a result, the recording power margin of ± 20% is obtained. The disk tilt margin is ± 0.82 deg and ± 0.63 deg in the radial and tangential direction, respectively.

The other topics is land/groove recording using an optical phase shifter. A maximum carrier level and a minimum cross-talk are achieved simultaneously when an optical phase shifter is inserted into the optical path before an analyzer. The optimum phase shift is 40 deg for recording on land and -40 deg for recording in groove. Recording on 0.5 μm land/0.5 μm groove with 1.2-mm thick substrate is investigated with a bit length of 0.35 μm for (1,7) RLL code using a light wavelength of 693 nm and a numerical aperture of 0.55. MO recording using an optical phase shifter is promising for an areal density of 3.7 Gb/in2. Furthermore, when an optical phase shifter is applied to recording on 0.36 jim land/0.36 μm groove with a bit length of 0.258 μm, light wavelength of 642 nm, and NA of 0.7, a capability of 7.0 Gb/in2 using conventionally structured MO disk is shown.
Interaction of Ultrafine Titanium Oxide Particles with Layered Vanadium Oxide Hydrate
Authors: Kittaka S. , Matsuno K. , Takahara S.
Published: April 2011

Vanadium pentoxide hydrate was pillared with ultrafine titanium dioxide particles to form expanded layered structure (∼20 A) and thereby forming microporous substance (diameter =∼10 A). Porous structure formation and adsorption of some toxic gases (CO and NO) were discussed.
Conducting Membranes and Coatings made from Redispersable Nanoscaled Crystalline SnO2:Sb Particles
Authors: Goebbert C. , Aegerter M. A. , Burgard D. , Nass R. , Schmidt H.
Published: April 2011

Inorganic membranes prepared by the sol gel method are promising candidates for use as filters in separation processes. Conducting supported membranes and coatings have been produced from redispersable nanoscaled crystalline Sb-doped SnO2powders with a Sb content up to 5 mole % (with respect to Sn). The crystalline particles are monosized (≅4 nm) and fully redispersable in aqueous solution at pH ≥ 8 with a solid content up to 70 wt. %. By thermal treatment at different temperatures and times, the pore size diameter of the material can be adjusted from 4 to 20 nm with a very narrow pore size distribution (∼ ±1 nm) and a total porosity of 63 %, practically independent of the sintering parameters. Uniaxial pressed substrates present similar characteristics with however larger pore size distribution (±5 nm) and 80 % total porosity. Their resistance decreases with sintering temperature and time down to 4 Ω (800 °C 8 h). Fully dispersed aqueous solutions of the powder (25 wt. %) were used to prepare transparent conducting coatings on glass or ceramics by spin-coating. After thermal treatment (1 hour at 550 °C) single layers 200 nm thick exhibited a typical specific electrical resistance ρ = 2.5·10−2ωcm with transmission in the visible range measured against air of 90%.
Model Reaction Systems to Produce Monodisperse Colloids
Authors: Lee Kangtaek , McCormick Alon
Published: April 2011

Monodispersely-sized spherical metal oxide particles have recently attracted growing attention for many industrial applications. In particulate coating applications, controlling the size and distribution of the starting colloid plays a crucial role in the final coating properties (1,2). In chromatography, both porous and nonporous monodispersely sized colloidal particles have been used as a column-packing material (3,4). Monodisperse particles can also be used as a startingn material in a ceramic processing to make ceramic materials with uniform properties for mechanical, refractory, and catalysis applications.

Even though various monodisperse metal oxide colloids are already widely used in industry, predicting and controlling the particle size distribution is frequently more dependent on experience and ingenuity rather than on modeling. There is nothing wrong with empiricism, but models can help to achieve process control, optimization, and flexibility. We have sought to assess what combination of processes in solution (both reactive and aggregative) need to be modeled, and in doing so we have found a number of very useful references that give insight into 1) the mechanism of the particle formation and growth, and 2) the effect of reaction parameters on the final size distribution by using both experimental and numerical techniques. Understanding these should allow us to intelligently design a new process in order to make particles with the desired size and distribution. In this short contribution we hope that it will be of service to provide a brief overview of some key work that may yield itself to modeling. This review is not intended to be comprehensive; instead, we have selected work that shows features that one hopes should be captured by meaningful models.
The Effect of Parent Metal Properties on the Performance of Lattice Block MaterialTM
Authors: Renauld M. L. , Giamei A. F. , Thompson M. S. , Priluck J.
Published: April 2011

Lattice Block MaterialTM, or LBMTM is a unique lightweight structure consisting of repeated cells with an internal node connected to, in the most common configuration, 14 ligaments. In its metallic version, this product is available in a variety of castable metals including aluminum alloys, copper alloys, nickel alloys and steels. The relationship between LBMTM structural performance (strength and stiffness) and parent metal properties is investigated using compression tests in three primary orientations and 3-pt. bend tests. Analytical assessment of the LBMTM via finite element analysis shows reasonable agreement with experimental findings and provides predictions for LBMTM capabilities with different materials, unit cell sizes and ligament geometries.
Reduction In Young's Modulus Of Aluminum Foams Due To Cell Wall Curvature And Corrugation
Authors: Sanders W. , Gibson L. J.
Published: April 2011

Measurements of the Young's modulus and compressive strength of several closedcell aluminum foams indicate that they are lower than expected from models for foam behaviour. Microstructural characterization has revealed that there are a number of defects in the cell structure which may contribute to the reduction in mechanical properties. These include: cell wall curvature, cell wall corrugations, density variations and non-equiaxed cell shape. Finite element analysis of a closed-cell tetrakaidecahedral unit cell with idealized curved or corrugated cell walls indicates that these two types of defects can reduce the Young's modulus and compressive strength by up to 70%. In this paper we report the results of measurements of the curvature of the cell walls and of the amplitude and frequency of corrugations in the cell walls and use simple bounds to estimate the reduction in modulus that they are responsible for.
A Comparison of Mos Devices with In-Situ Boron Doped Polysilicon and Poly Sige Gates Deposited in an Rtcvd System Using S12H6 and B2H6 Gas Mixture
Authors: Mirabedini M. R. , Li V. Z-Q , Acker A. R. , Kuehn R. T. , Venables D. , Öztürk M. C. , Wortman J. J.
Published: April 2011

In this work, in-situ doped polysilicon and poly-SiGe films have been used as the gate material for the fabrication of MOS devices to evaluate their respective performances. These films were deposited in an RTCVD system using a Si2H6 and GeH4 gas mixture. MOS capacitors with 45 Å thick gate oxides and polysilicon/poly-SiGe gates were subjected to different anneals to study boron penetration. SIMS analysis and flat band voltage measurements showed much lower boron penetration for devices with poly-SiGe gates than for devices with polysilicon gates. In addition, C-V measurements showed no poly depletion effects for poly-SiGe gates while polysilicon gates had a depletion effect of about 8%. A comparison of resistivities of these films showed a low resistivity of 1 mΩ-cm for poly-SiGe films versus 3 mΩ-cm for polysilicon films after an anneal at 950 °C for 30 seconds.
The Effect Of Chamber Components On Wafer Temperature Response In An Rtp System
Authors: Acharya N. , Timans P. J.
Published: April 2011

In recent years, simulation techniques have emerged as useful tools for the design of semiconductor equipment. However, the need for rapid assessment of potential designs stretches the capability of even the most advanced tools currently available to the limit. In this paper, a simplified model of a rapid thermal processing (RTP) system that significantly reduces the execution time is presented. The model is based on a coupling of semi-analytical expressions for radiation fluxes with a one-dimensional finite element heat transfer model for wafer and slip-free ring temperatures. Results showing the effects of plate reflectivity and slip-free ring emissivity on wafer temperature are presented. It is shown that the simplified model yields results that are in agreement with detailed two-dimensional simulations of the same geometry.