bluuebunny/crossref_metadata_2025 huggingface dataset:
Back-To-Back Amorphous Silicon Diodes For Driving Lc Displays
Authors: Dresner Joseph
Published: March 2011

This paper describes the preparation and electrical characteristics of a-Si:H p-i-n-i-p and n-i-p-i-n thin film diodes suitable for driving monochrome liquid crystal displays with more than 500 lines. The symmetrical current-voltage curves in the reverse breakdown regime can ge described by i=i exp (E/Eo) where E ≃9×104 V/cm. In the range 20–125°C, the current is thermally activated with an energy of 0.25eV. The response time to applied voltage pulses is ≤ 10 us. The stability of the electrical characteristics is adequate for at least 104 hours of operation in an liquid crystal display.

Electrical characteristics indicate that the reverse breakdown current is a tunneling current injected into the i-layer and that electrons are likely to be dominant.
Optical Response of As2 S3: Melt Quenched Versus Spin Casted Materials
Authors: Hammam M. , Santiago J. J.
Published: March 2011

The transmittance spectra of amorphous As2S3 films prepared by two different techniques, namely spin coating and quenched from the melt were investigated. All measurements were done at room temperature in the energy range from 1.2 to 3.8 eV. The spin casted material was prepared by dissolving powdered stoichiometric arsenic trisulfide in amines and amides, the resulting solution spinned on an oxide glass substrate and baked to remove the volatiles. A typical resulting film was a few micrometers thick and microstructure free as characterized under an optical microscope. The quenched material was prepared by melting a stoichiometric mixture of the reactants in an evacuated and sealed ampoule and alloying at 1100°K for 15 hrs. The melt was subsequently quenched in air to obtain vitreous materials. The transmittance spectra of both types of samples was measured and from the spectra the refractive index dispersion, film thickness and absorption coefficient were obtained. A considerable difference between the optical constants of the spin casted samples and thermally evaporated ones was found. This was attributed to the incorporation of carbon and hydrogen in the amine salt alkyl group formed when dissolving the chalcogenide material.
Intrinsic Gettering of Iron in Silicon: A Quantitative Study
Authors: Colas Etienne G. , Weber E.R. , Hahn S.
Published: March 2011

Intrinsic gettering of iron in silicon has been studied with a novel approach that involved the combination of two complementary techniques. Electron Paramagnetic Resonance (EPR) was used to determine the concentration of interstitial iron atoms which are electrically active in the silicon matrix. A systematic comparison of the effect of various oxygen precipitates of well defined morphologies on the solubility of iron was performed. A surprising result was found for bulk samples containing oxygen precipitates obtained after low temperature heat treatments (700ºC): the solubility of iron was reduced byalmost two orders of magnitude from the values obtained in untreated Cz silicon samples or in samples containing oxygen precipitates obtained at high temperature (1150ºC). The practical importance of this new result was demonstrated by a series of iron concentration measurements after various gettering and high temperature re-heating treatments.

Transmission Electron Microscopy (TEM) was used in order to confirm the proposed mechanism of formation of a new phase, different from FeSi2 in the silicon matrix. This new phase is assumed to limit the possible electrically active metallic content by acting as a boundary phase in quasi-equilibrium with interstitial iron atoms. Evidence ofthe formation of Fe2SiO4 was found in wafers that had been oxygenimplanted and subsequently subjected to similar precipitation and diffusion treatments than those performed with the bulk samples.

These findings suggest the possibility of dramatic improvements in the efficiency and the stability of the gettering process.
Regrowth of Implanted–Amorphous Si
Authors: Ling P. , Wu N.R. , Washburn J.
Published: March 2011

A two dimensional model of nucleation and growth is described which is consistent with the following experimental phenomena observed in the regrowth of ion-implanted silicon: (1) Substrate orientation effect on regrowth kinetics. (2) Impurity effects on regrowth kinetics. (3) The activation energy dependence of regrowth rate. (4) Impurity redistribution and supersaturation effect.
Dopant Diffusion From Ion- Implanted Tasi2
Authors: Gierishch H. , Neppl F. , Frenzel E. , Eichinger P. , Hieber K.
Published: March 2011

A SIMS analysis of As-, B- and P- diffusion across the TaSi2/si interface into mono- Si was carried out together with an electrical characterization of the resulting structures. In the temperature range 900°C T 1000°C all three types of dopants readily diffused into Si without drastic segregation effects when appropriate interface cleaning was applied. This implies a variety of applications. In particular, very shallow diffusion regions were obtained in the mono Si underneath the implanted Tasi2 for As as well as for B and P, even at relatively long annealing times sometimes needed for subsequent process steps.
On the Mechanism of Intrinsic Gettering by Butterfly-Type Defects in Silicon
Authors: Ueda O. , Nauka K. , Lagowski J. , Gatos H.C.
Published: March 2011

We have recently found that a very effective intrinsic gettering of metal contaminants in silicon can be realized via interaction of native defects. This process makes it possible to extend intrinsic gettering of crystals with low or virtually zero oxygen concentration. Transmission electron microscopy and energy dispersive x-ray spectroscopy were used to identify the microscopic structure of the gettering centers in oxygen-free silicon. These centers exhibited butterfly-type shape and they consisted of the interstitial type extended dislocation loops of 0.1 to 0.7 μm diameter. Small precipitates (3-15 nm diameter) of metal (Cu, Ni, Fe) silicides were found inside the dislocation loops and/or on the dislocation lines. The origin of butterfly-type gettering centers will be discussed in terms of the intrinsic gettering model involving lattice supersaturation with silicon self-interstitials as a driving force for their complexing and subsequent formation of dislocation loops and precipitates which immobilize metal contaminants.
Schottky Barrier Heights of Refractory Metals on Silicon
Authors: Aboelfotoh M. O.
Published: March 2011

Measurements of Schottky-barrier heights in the temperature range 175-295 K for refractory metal-silicon and corresponding silicide-silicon interfaces are presented. Refractory metal silicide formation is shown to have only a small effect on the barrier height. The n-type and p-type barrier heights for both the metal and the reacted silicide phase are shown to decrease with increasing temperature with the stun equal, within the experimental accuracy, to the indirect energy gap of silicon at any measured temperature. These results indicate that the temperature dependence of the barrier heights is mainly due to that of the indirect energy gap in the silicon.
Comparison of Electromigration Induced Resistance Changes in Multilayer Al-Si/Ti and Al-Si/Ta Interconnects
Authors: Finetti M. , Suni I. , Desanti G. , Bacci L. , Caprile C.
Published: March 2011

We have applied a temperature-ramp resistance analysis to investigate electromigration effects in unpassivated Al-Si/Ta multilayer structures. The results are compared to the behaviour previously observed in Al-Si/Ti interconnects. For comparison, single layer Al-Si metallizations were also studied.
Comparison of Kinetics of TiSi2 Formation on Si(100) and Si(111)
Authors: Pico C. A. , Tran N. C. , Jacobs J. R. , Lagally M. G.
Published: March 2011

Refractory-metal silicides are currently receiving widespread attention because of their usefulness as interconnects in VLSI devices. Potentially the most important of these silicides is TiSi2. TiSi2 offers a sharp stable interface, a high process-compatible eutectic temperature, and the lowest resistivity of all refractory-metal silicides. Much of the previous work on TiSi2 [1-8] has been directed towards the understanding of the kinetics of silicide formation in order to optimize these electrical and interfacial properties. One parameter that may affect the silicide formation is substrate orientation [9]. We have compared the kinetics of formation of TiSi2 for Ti deposited onto p-type 10Ω-cm Si(100) and Si(111). All process parameters except substrate orientation were identical. 2800Å of Ti was electron-beam evaporated at a rate of 20Å/s and a background pressure of 9×10−8 torr onto chemically cleaned (HNO3, HF, rinse) Si substrates and subsequently annealed at temperatures between 470°C and 700°C in evacuated sealed quartz tubes. A turbopumped vacuum system was used to evacuate the quartz tube before sealing. A Ti getter was independently heated to remove remaining background contaminants prior to annealing.
The Effect of HCl on Silicon Point Defect Formation During Thermal Oxidatign of (100) Float Zone Silicon Wafers: A Theoretical Analysis
Authors: Oh Seajin , Tiller W.A. , Hahin Soo Kap
Published: March 2011

The effect of HCl in an oxidizing ambient on Si interstitial formation during oxidation has been studied by the buried marker diffusion technique. Adding HCl reduces the self-interstitial flux generated at the oxidation front but it does not completely eliminate it. A uniform blocking layer model predicts fairly well the Cl effect on self-interstitial generation during the thermal oxidation. By reducing the rigidity of the SiO2, Cl incorporation into the SiO2 is strongly proposed to alter the Si interstitial partition coefficient at the interface.
Modeling Dopant Redistribution During Rapid Thermal Annealing
Authors: Chan Archie Y.C.
Published: March 2011

The diffusion of ion-implanted dopants in silicon during rapid thermal annealing is modeled using the finite difference method.The change in impurity profile for an initial Pearson IV boron implant is negligible(less than 1 % change in junction depth) when the peak annealing temperature(TP ) is less than 1050 °C and its duration is shorter than 20 seconds. The dopant redistribution becomes significant(greater than 25 % change in junction depth) when Tp is greater than 1200 °C and its duration is longer than 40 seconds.The heatup and cooldown portions of the transient annealing cycle are found to have little effect on dopant redistribution provided that their rates are higher than 120 °C per second.
Laser Activated Glass Flow Modeling
Authors: Aronowit Sheldon , Delfino Michelangelo
Published: March 2011

Laser induced flow of phosphosilicate glass, where the glass is a member of a multi-layer structure, was modeled with a one-dimensional coupled set of heat conduction and generation equations; the conventional approach was modified for explicit inclusion of non-ideal interfacial regions. There were no restrictions on the number or nature of material layers. Modeled behavior for 0.7 μm or 1 μm thick glass covering Al, or Si02, or Si agreed with observation; aluminum fusion accompanied by minimal glass flow when the AZ layer was covered by 0.7 μm glass was predicted and observed for the experimental laser pulse, as an example. Analysis also exposed the characteristics for successful laser generated glass flow; a rectangular pulse shape will permit the greatest control over the laser induced flow as well as provide the largest window for producing the desired flow while minimizing the effect on other material regions. Finally, experimental results with CW laser induced flow support the conclusion that the modeling successfully bridges four orders of magnitude in the thermal flux regime.
Electrical Characteristics of High Pressure Nitrided Oxides
Authors: Ellul J.P. , Tay S.P. , Kalnitsky A.
Published: March 2011

In this paper, we present preliminary electrical characteristics of as-grown and NH3-nitrided thin gate and polysilicon oxides. Material characteristics are discussed in terms of ammonia concentration and nitridation temperature and pressure. Dielectric thicknesses obtained by ellipsometry, by Auger analysis and by capacitance-voltage measurements are compared. Electrical breakdown statistics for 10 atm and 1 atm pressure nitrided oxides are compared to as-grown thermal oxides.
High Quality 100 Å Thermal Oxide
Authors: Nguyen Thao N. , Quinlan Dawn L.
Published: March 2011

The growth of high quality 100 Å thermal oxide is investigated. Different growth conditions including oxidation temperature, oxidation rate, and gas ambient are explored and they all produce good oxides. However, it will be demonstrated that the best oxide with defect density as low as 0.2cm−2, breakdown field ≃ 12 MV/cm and good reproducibility is grown with low temperature (800°C) low rate oxidation in dry oxygen. The midgap interface trap density of this oxide is ∼ 2.0 × 1010eV−1cm−2 obtained from high-frequency and quasi-static C-V data. A model based on physical mechanisms controlling the kinetics of thin oxide growth is developed to understand how the quality of thin oxide is affected by growth conditions and to explain why the low temperature oxidation in dry oxygen yields the best film.
On the Question of Oxygen Diffusion During Oxygen Related Thermal Donor Formation In Silicon.
Authors: Oehrlein G. S. , Tan T. Y. , Kleinhenz R. L. , Lindstrom J. L.
Published: March 2011

In an attempt to decide the question whether enhanced oxygen diffusion is important for heat-treatments of silicon at ∼450ºC where thermal donors are formed we have conducted two types of experiments aimed at providing a measure of the “effective” oxygen diffusivity. First, we have extensively measured the temperature dependence of the thermal donor introduction rate for very short heat treatment times (20min). This measurement provides the thermal activation energy of TD formation. Since effects of long range diffusion and formation of large oxygen clusters are negligible for suchtimes and temperatures and, presumably, thermal donor formation at the lowest heat treatment temperatures is oxygen diffusion limited, it should be possible to interprete the obtained activation energy in terms of oxygen diffusivity. The change of the interstitialoxygen content is immeasureable for 20min heat treatment times. Therefore, the decay of the interstitial oxygen content was measured for longer heat treatments at 450ºC (up to 500hours). The two experiments are complementary in several ways: In one experiment the oxygen diffusion activation energy is extracted, while the other measurement provides the value of the diffusion coefficient at a given temperature. In one case thermal donors are monitored for short heat treatment times while in the other experiment the interstitial oxygen content is measured for long heat treatment times. The present measurements are different from other diffusion experiments in this temperature range where theatomic jump of isolated oxygen is monitored [1]. Here we attempt to extract an effective oxygen diffusivity under conditions of thermal donor formation since the thermal donor formation process itself might be the cause of an enhanced oxygen diffusivity.
Growth of Heteroepitaxial Lead Chalcogenide Infrared Detector Arrays on Fluoride Coveredsilicon Substrates
Authors: Zogg H. , Vogt W. , Melchior H.
Published: March 2011

Composition graded buffer layers of group Ila fluorides allow the heteroepitaxial growthof device quality narrow gap lead chalcogenides onto Si. Mechanical stresses in the layers are almost completely relaxed at room temperature despite large thermal expansion mismatches. Photovoltaic infrared sensors with up to about 9.5 um cut—off wavelengths and which operate at or near the 300K background noise limit have been fabricated in such PbTe and (Pb,Sn)Se on Si structures.

Furthermore, epitaxial graded fluoride buffers seem to be suited to connect other semiconductors with even large lattice mismatches. Initial heteroepitaxial growth of CdTe on fluoride/Si(lll) substrates (mismatch 20%) supports such more general applications.
Application of Sans to Ceramic Characterization
Authors: Frase K. G. , Hardman-Rhyne K. A. , Berk N. F.
Published: March 2011

Traditionally, small angle neutron scattering (SANS) has been used to study dilute concentrations of defects 1 -100 nm in size. Recent extensions of the scattering theory have allowed the expansion of the technique to include larger sizes through the use of multiple scattering. With multiple small angle neutron scattering, defects (pores, microcracks, precipitates) up to 10 μm in size can be studied. SANS is inherently a non-destructive, bulk probe of microstructure, with wide applications in the characterization of materials.

A number of studies of ceramic materials using multiple and traditional (single particle diffraction) small angle neutron scattering will be discussed. The emphasis will be on the strength of the technique in the characterization of materials. Particular examples will include: the assessment of pore size distributions in spinel compacts as a function of sintering and agglomeration, the characterization of primary and secondary particle sizes in precipitated aggregates, and the determination of microporosity in MDF cements.
Microstructural Studies of Transparent Silica Gels and Aerogels
Authors: Tewari Param H. , Hunt Arlon J. , Lofftus K. D. , Lieber J. G.
Published: March 2011

Transmission electron microscopy, spectroscopy, light scattering and surface area measurements have been used to characterize the microstructural details of transparent silica aerogels. Light scattering intensity measurements have also been used to differentiate acid and base catalyzed hydrolysis and condensation reaction kinetics of Si(OC2H5)4. A plot of logarithm of the light scattering intensity vs. logarithm of time diring gelation gives distinctly different slopes for acid and base catalyzed systems (6 for acid and 2 for base). These slopes for the two systems can be explained on the basis of the point of zero charge of silica and the resulting interactions of the uncharged and charged particles in the systems.
Fractal Aspects of Ceramic Synthesis
Authors: Schaefer Dale W. , Keefer Keith D.
Published: March 2011

The concept of fractal geometry is used to describe the structure of silica polymers, colloidal aggregates, and critical systems. We illustrate the interpretation of scattering curves (X-ray, neutron and light) for fractal systems, and review simple growth models which generate fractal structures. We describe the polymerization of silica under various conditions and demonstrate that, depending on chemical conditions, polymerization maps onto simple fractal growth processes. The key factors which control growth are monomer-cluster vs. cluster-cluster growth, and reaction-limited vs. diffusion-limited growth.
Particle Compaction with Alternating Electric Fields: The Effects of Electrode Geometry
Authors: Hurd Alan J.
Published: March 2011

A technique for inducing ordered, close-packed arrangements of various symmetries among colloidal particles is discussed. An external alternating electric field applied to the colloid induces dipole interactions of variable strength by polarizing either the dielectric material of the particles or their electrostatic double layers. Ordering in various symmetries can be obtained by switching the field rapidly between pairs of electrodes, thereby changing the orientation of the induced dipoles. A small dc bias serves to deposit and compact the aligned particles.
Fractal Pores or a Distribution of Pore sizes: Alternative Interpretations of Power-Law Small-Angle Scattering
Authors: Schmidt Paul W.
Published: March 2011

The intensity I(q) of the small-angle x-ray or neutron scattering has been calculated for a system of randomly oriented, independently scatter-ing pores with a number distribution of pore diameters which has the form of a power law. As has already been shown, [P. W. Schmidt, J. Appl. Cryst. 15, 567–569 (1982)], when the number distribution of the maximum diameters a of the pores is proportional to a−γ, I(q) is proportional to q−(7−γ), where q = 4πλ−1sin(θ/2), θ is the scattering angle, and λ is the wavelength. The coefficient of the power-law intensity has been expressed in terms of some of the constants which determine the diameter distribu-tion. Equations have been obtained for the scattered intensity I(q) at q values larger and smaller than those at which power-law scattering occurs. The intensity scattered by this system is compared with the intensity from a system of pores with fractal pore-boundary surfaces which have a fractal dimension D.
The Pyrolysis of a Tungsten Alkyne Complex as a Low Temperature Route to Tungsten Carbide
Authors: Laine Richard N. , Hirschon Albert S.
Published: March 2011

The synthesis of designed organometallic compounds and their selective activation and transformation into materials of high purity (for electronic applications), high strength and/or high temperature stability (for refrac-tory or structural applications), represents a potential area of extreme growth in organometallic chemistry. Research in this area could provide entirely new, inexpensive, fabrication methods for common and exotic materials.

In this paper, we develop design principles for the preparation of organometallic precursors, “premetallics” that can be selectively con-verted, in high yields, to a desired refractory metal. We also describe our preliminary efforts to prepare tungsten carbides (WCx) from a pre-metallic. Pyrolysis studies using Cp2W2(CO)4(DMAD) [DMAD = Dimethyl-acetylene dicarboxylate], 5, as the premetallic demonstrate that 5 will decompose at temperatures of ∼ 700°C to give good yields of W2C. 5 is soluble and decomposes fully in 10–20 minutes, without the need of another reactant.
Precursors of Titanium Carbonitride
Authors: Maya L.
Published: March 2011

A series of novel compounds was isolated in the course of exploratory work on the chemistry of titanium halides in liquid ammonia. This work was undertaken to study synthetic approaches to titanium-containing precursors of ceramic materials. Representative of these compounds is a mixed valence Ti(III)-Ti(IV) tetramer, [NH4+·NH3]2[Ti4Br4 (NH2)12]−2, which was produced by the reaction of potassium borohydride and titanium IV bromide in liquid ammonia at room temperature. Similar ammonium salts of either Ti(IV) or Ti(III) were also prepared. The reaction of the ammonium salts with sodium acetylide in liquid ammonia evolves acetylene in an amount equivalent to the ammonium ion present. This provided the charge of the complex and yielded novel titanium acetylide derivatives. The acetylides convert into titanium carbonitrides upon thermal treatment to 800°C.

The reaction of titanium halides of their ammonolytic products with sodium acetylide in liquid ammonia to yield halogen-free acetylide precur-sors having a relatively high titanium content appears to be a convenient synthetic approach. This is made possible by the fact that the alkali metal halide by-products are soluble and easily separated in that reaction medium. This approach appears to be a generalized route applicable to a number of transition metal elements of interest.
Conversion of Chemically-Derived Polymeric Precursors to High performance Ceramic Fibers
Authors: Haider M. Ishaq , Clark Terence J.
Published: March 2011

In recent years, there has been steadily increasing research activity directed towards preparation of ceramic materials via polymer pyrolysis. Among the most thermomechanically stable structural ceramics are SiC, Si3N4, and their solid solutions. These materials are widely used as ceramic fiber reinforcements in composites owing to their high mechanical strength, stiffness, and oxidative stability. Processes have now been developed to make these fibers by utilizing melt spinning. Fine diameter continuous filaments are formed, and further processing involves the steps of mild reactive cure and high-temperature pyrolysis. The approach in this review is to summarize the fiber making process with emphasis on improving fired properties by utilizing known mechanisms of fiber failure and process modification procedures. Fiber characteristics, applications of high performance fiber, and perceived trends will also be discussed.
A Theoretical Study of Silanol Polymerization
Authors: Burggraf Larry W. , Davis Larry P.
Published: March 2011

We have applied state-of-the-art semi-empirical molecular orbital methods to a study of the anionic polymerization of silanols to form silica. In particular, we have considered nucleophilic attack on silanols and subsequent reactions of the products. Hydroxide addition proceeds without activation to form five-coordinate silicate anions. Five-coordinate structures can also be formed by oligomerization following the attack of hydroxide on neutral silanols to abstract a proton. These five-coordinate structures are predicted to play a key role as intermediates in the polymerization process. Water can be eliminated from these anions, but with a substantial activation barrier. The activation barrier appears to be lower for the larger, more complex systems. These predictions are consistent with a rapid pre-equilibrium to form dimer anions followed by the slower reaction to form higher oligomers.
Polymer Growth and Gelation in Borate-Based Systems
Authors: Brinker C. J. , Ward K. J. , Keefer K. D. , Holupka E. , Bray P. J.
Published: March 2011

In situ FTIR, NMR and SAXS were used to investigate the synthesis and molecular structure of xLi2O-(1−x)B2O3 gels derived from tri-n-butyl borate (TBB) and lithium methoxide. In solution the fraction of tetrahedrally coordinated borons (N4) increases linearly with x, and a critical value of N4 must be exceeded in order to form gels. The primary criterion affecting gel formation is the kinetic stability of borate bonds toward molecules which are able to undergo dissociative chemisorption.
Reactivity of Silicates 1. Kinetic Studies of the Hydrolysis of Linear and Cyclic Siloxanes as Models for Defect Structure in Silicates
Authors: Balfe Carol A. , Ward Kenneth J. , Tallant David R. , Martinez Sheryl L.
Published: March 2011

The kinetics of hydrolysis of hexamethylcyclotrisiloxane and di-t-butyldimesitylcyclodisiloxane in tetrahydrofuran solution have been determined and compared to hydrolysis rates of silica defects. In the presence of sufficient excess witer, the first-order rate constant of the cyclotrisiloxine, k= 3.8 × 10−3 min is similar to the rate constant, k = 5.2 × 10−1 min, of the disappearance of the D2 Raman silica defect band it has been proposed to model. Limited hydrolysis rate data for the cyclodisiloxane suggests that it hydrolyzes at least four times faster than does the cyclotrisiloxane. These data are consistent with rate data available for silica crack growth and support the assignment of highly strained siloxane bonds at the crack tip to cyclodisiloxanes. Infrared spectra determined for the cyclodisiloxanes lend further support to this model.
SOL-GEL AR Films for Solar Applications
Authors: Ashley Carol S. , Reed Scott T.
Published: March 2011

Sol-gel derived antireflective films have been prepared for a variety of solar applications. The optical properties of the films are optimized by microstructure tailoring in solution by aging and/or in the film by heating and etching. The resulting film provides a quarter-wave, single layer interference surface with a reflectance minimum of <1% at 600 nm. We have applied sol-gel derived AR films to glass and plastics for solar thermal and photovoltaic applications, e.g., parabolic trough collector envelopes, plastic Fresnel lenses, and glazing materials for flat plate collectors.
Nucleation and Growth of Uniform m-ZRO2
Authors: Bleier A. , Cannon R. M.
Published: March 2011

Hydrothermal treatment of zirconyl salt solutions produces uniform m-ZrO2 powder on the order of 80 nm. This powder is porous, has a 3-nm crystallite size, and exhibits an unusually high degree of crystallographic alignment within particles. The generation of this powder occurs via a complex process involving nucleation, growth, and controlled agglomeration of primary particles. Particle formation, crystallographic alignment and particulate uniformity are explained in terms of solution reactions and colloidal behavior.
Preparation of Gradient-Index Glass Rods by the Sol-Gel Process
Authors: Yamane Masayuki , Caldwell J. Brian , Moore Duncan T.
Published: March 2011

The fabrication of gradient-index material via the sol-gel technique is reported. The material is based on the PbO-B2O3-SiO2 system and a K2 O- PbO liquid phase interdiffusion is used to produce the necessary composition gradient.
Effect of in Situ Polymer Adsorption on the Synthesis of Monodisperse Tio2 Powders
Authors: Jean J. H. , Ring T. A.
Published: March 2011

Monodisperse and spherical titania powders were prepared by the hydrolysis of titanium tetraethoxide in ethanol with hydroxy-propyl cellulose(HPC) present during particle precipitation. The mean particle size decreased as the concentration of tLPC increased. The critical concentration of HPC for the in situ stabilization of titania powder suspensions was determined by a photographic method, and found to be independent of the molecular weight of HPC within the molecular range of 60,000 to 300,000. The amount of HPC adsorbed on the particle surface, determined by a colorimetric method using a UV-visible spectrophotometer, decreased with the increasing molecular weight of HPC. Suspension stability was confirmed by theoretical calculations based on experimental results.
Excimer Laser Induced Oxidation of Silicon: Characterization of the Oxide Stoichiometry in the Interface Region
Authors: Mantell D. A. , Orlowski T. E.
Published: March 2011

New results on the ultrafast laser-induced formation of high-quality patterned silicon dioxide (SiO2) layers on silicon substrates at room temperature are presented. Using a pulsed ArF excimer laser (λ = 193 nm) operating at pulse energies near the melting threshold of silicon, SiO2 layers can be grown at a rate of 3–4 Å/pulse with an oxygen pressure of 500 torr. This growth rate exceeds by a factor of 5 the rate found using a XeCI excimer laser (λ = 308 nm) indicating that oxygen atoms produced by the direct photodissociation of oxygen by the ArF excimer laser play a role in achieving this extremely fast oxidation rate. Careful analysis of the laser exposed regions following each laser shot was performed using angle-resolved XPS with 150 micron spatial resolution. After one laser shot, a nonstoichiometric SiOx interface layer (<5Å) is clearly visible. Subsequent laser shots show the oxide peak shifting to higher energy as the oxide thickness increases until the characteristic ∼4.5 eV chemical shift for SiO2 (relative to the bulk Si 2p peak) is realized at a thickness of ∼20Å. The nonstoichiometric SiOx layer is still present at this oxide thickness but is confined to the interface region (<10Å) as observed in thermally grown oxides. Oxide thicknesses obtained by angle-resolved XPS were confirmed using sputter depth-profiling. XPS measurements on samples irradiated at low oxygen pressure (5 torr) show evidence for oxidation of the silicon substrate outside the focused laser beam (2X). At this pressure the recombination time for oxygen atoms is long enough to allow diffusion and apparent reaction with the silicon substrate at reduced temperatures.
Influence of Environment on Excimer Laser Irradiation of Metals
Authors: Partridge Julian P. , Pellegrino Joseph , Murphy Craig , Strutt Peter R.
Published: March 2011

Irradiation of metals in gaseous and liquid nitrogen by KrF excimer laser pulses shows the way in which vapor or plasma pressure fields determine the nature of the rapidly solidified surface topography. Wave patterns formed on aluminum by irradiation in N2 gas arise from recoil pressure differences produced by highly localised differential surface evaporation. The solidification time, calculated from the observed ripple wavelength, is in good agreement with that deduced from a heat flow calculation. For irradiation in liquid N2, the homogeneous pressure within the center of the dense plasma zone results in a smooth surface. Beyond this region the progressively diminishing pressure induces surface ripples, fragmentation and droplet formation. Intriguingly, immersion of Ni, Ti, Zn, and Al in liquid N2 (to a depth of 2 to 4 mm) considerably increases the area and depth of irradiation-modified regions.
Excimer Laser Processing of Crystalline Iron-Boron Alloys
Authors: McCamy J. W. , Pedraza A. J. , Lowndes D. H.
Published: March 2011

Crystalline Fe-B alloys in the concentration range of 5–25 at. pct. boron were processed by slightly (∼5%) overlapping single pulse XeCl excimer laser. The influence of the initial microstructure and phases upon the structure that results after laser processing (LP) were studied. The specimens were made by a rapid solidification procedure that permits readily glass-forming alloys to be obtained with structures ranging from fully amorphous to fully crystalline. The technique is briefly described. Two crystalline specimens of Fe-20 pct. boron, one in the as-cast condition and the other annealed, were laser treated. While the melted layer of the former was amorphous, the latter remained crystalline, exhibiting a similar phase content as before irradiation. Observations of both samples by scanning electron microscopy (SEM) prior to LP revealed a difference in particle size of one order of magnitude. A mathematical model of diffusion is developed for studying the homogenization process. It is concluded that the time for diffusion in the liquid state in the sample containing the larger particles is insufficient for homogenization to occur. Similar results regarding the influence of particle size were obtained with all the other samples.
Metastable Phase Formation in Laser Processed Al-Ge Thin Films
Authors: Catalina F. , Afonso C. N. , Ortiz C.
Published: March 2011

This paper presents a comparative study of the microstructures formed in Al.59Ge.41and Al.70Ge.30 (eutectic composition) free standing films under laser irradiation. An hexagonal metastable phase located between Allamella, can be formed depending on the film composition and the laser pulse length.
Plugging of Al Films Into Submicron Diameter Via Holes by Excimer Laser Irradiation
Authors: Mukai R. , Sasaki N. , Nakano M.
Published: March 2011

Via-hole filling technique by momentarily melting an aluminum film has been developed, whereby planarization of aluminum films for multilevel interconnects on integrated circuits can be achieved. The melting is performed with an optical pulse irradiation from an ArF excimer laser without the problem of junction spiking. This technique is applicable to filling submicron-diameter vias having a diameter of 0.6μm with 0.7μm depth(aspect ratio:∼1.2). Very high aspect ratio(2.0) via-hole filling is achieved by heating the sample. During the laser irradiation, the sample substrate was kept at 300°C.
Write-Erase Mechanism of Indium-Antimony Optical Disk Medium
Authors: Goto Y. , Utsumi K. , Ushioda A. , Tsugawa I. , Koshino N.
Published: March 2011

Written and erased bits of the In-Sb phase change type optical disk medium were studied using transmission electron microscopy (TEN) and electron probe microanalysis (EPMA). Both the bits were separated into inner and outer areas and were composed of only rhombohedral Sb crystals and zinc blende In50Sb50 crystals. The difference between the two bits were in crystal size and atomic distribution of the inner area. Models of the writing and erasing processes were derived from these observations and the In-Sb phase diagram. With these models, the thicknesses, grain sizes and optical contrasts of the both bits were consistently explained.
Beam-Solid Interactions of Pyrolytic Graphite as a Function of Angle of Cut Surface
Authors: Yip Pearl W. , Jaklitsch Donald J. , Perkins Janet S.
Published: March 2011

A study to examine beam-solid interaction as a function of the cut surfaces of pyrolytic graphite samples (0, 30, 60, and 90 degrees relative to the basal plane) was made using a high intensity, carbon dioxide laser beam operating at a wavelength of 10.6 μm.

Crystal growth of redeposited carbon and impurities in the burn area as well as a melt on the burn edge were observed and examined using Scanning Electron (SEM) and Scanning Auger Microscopy (SAM). Similarities and differences relating to the structure of the material were further investigated using X-ray diffraction. Thermal transport properties as a function of angle were also examined.
Synthesis Induced by Laser Irradiation at Liquid/Solid Interfaces
Authors: Chan Siu-Wai , Dijkkamp D. , Wu X. D. , Venkatesan T. , Chang C. C.
Published: March 2011

Synthesis of transition metal nitrides induced by excimer laser irradiation of metal foils immersed in liquid nitrogen was studied. Nitrogen incorporation was found by sputtering Auger Electron Spectroscopy in all six investigated metals (Ti, Zr, Hf, V, Nb and Ta). X-ray diffraction was used to determine the compounds formed. The morphologies of the irradiated surfaces often indicated that the surfaces had gone through a molten state. Micronthick mononitrides were grown on Ti, Zr and Hf, whereas Ta and Nb formed Ta2N and Nb2N respectively. The nitrides on V were not satisfactorily identified. The extent of nitridation correlates with the thermodynamic driving force, i.e. the Gibbs free energy for nitride formation.
Recrystallisation of Cadmium Sulphide Powder Films with a CO2 Laser
Authors: Barden P. E. , Cumberbatch T. J.
Published: March 2011

Thin films (1–2μm) of cadmium sulphide, deposited by electrophoresis, consist of a close packed layer of randomly oriented cubic-phase microcrystalline particles with an average diameter of 30nm. A CW CO2 laser, operating at 10.6μm has been used to convert this into a polycrystalline structure with columnar crystals, of hexagonal phase, which extend through the thickness of the film and whose c-axis is perpendicular to the substrate. The recrystallised regions comprise aligned grains up to 300nm in diameter whose cathodoluminescence spectrum exhibits a narrow peak centred at 2.42eV with a half width identical to that for evaporated CdS (0.1eV).
Combined Hrem and Eels Studies of the Electron Beam Induced Reduction of Maximal-Valence Transition-Metal Oxides.
Authors: Long Neil J. , Petford-Long Amanda K.
Published: March 2011

High resolution electron microscopy has been used in conjunction with electron energy loss spectroscopy to follow the beam-induced reduction of WO3, V2O5and CuO, all of which are maximal valence oxides. All three oxides underwent reduction, although there are differences in the reduction pathway: WO3is reduced directly to the metal by loss of oxygen from the surface layers; CuO is reduced to the metal via at least two intermediate oxides (Cu4O3and Cu2O); and V205forms a reduced oxide (possibly V6O13) and then remains stable. It was possible to drill holes in V2O5with an intense, small electron probe (using a field-emission electron gun) provided the sample had previously only been exposed to an electron dose below a critical value (<108e/nm2). Preliminary doses higher than this critical value rendered the oxide immune to hole drilling (but not to a subsequent reduction to the stable oxide mentioned above), suggesting that holes can only be drilled while the material retains the original V2O5structure.
Ion Beam Enhanced Grain Growth in Thin Films
Authors: Atwater Harry A. , Tiiompson Carl V. , Smith Henry I.
Published: March 2011

Ion beam enhanced grain growth has been investigated in thin films of Ge. Grain boundary mobilities are greatly enhanced over their thermal equilibrium values and exhibit a very weak temperature dependence. We propose that defects which are generated by the ion beam at or near the grain boundary are responsible for the boundary mobility enhancement. Films of Ge deposited under different conditions, either unsupported or on thermally oxidized Si, exhibit similar normal grain growth enhancement when implanted with 50 keV Ge+. Beam-enhanced grain growth in Ge was also demonstrated using Xe+, Kr+, and Ar+ ions. The variation in growth enhancement with projectile ion mass is in good agreement with the enhanced Frenkel defect population calculated using a modified Kinchin-Pease formula and Monte Carlo simulation of ion transport in thin films. Calculations based on experiments suggest that there is approximately one atomic jump across the grain boundary per defect generated. Also, the grain growth rate for a given beam-generated defect concentration near the boundary is approximately equal to the expected growth rate for the same defect concentration if thermally generated.
Characteristic Comparison Between Ge-on-Insulator (GOI) and SI-on-Insulator (SOI) Beam-Induced Crystallization Mechanism
Authors: Lee El-Hang , Awal M. Abdul
Published: March 2011

Characteristics of beam-recrystallized Si-on-insulator (SOT) and Ge-on-insulator (GOI) material systems are compared for the first time to gain complementary understanding of the crystallization mechanism that would benefit both systems. In general, GOI has been found to behave quite differently from SOI. In SOI, Si yields sub-boundaries; in GOI, Ge generates twinned or faceted crystals. In GOI, too, sub-boundary-like features were observed, but only occasionally in the midst of twinned crystals. Also observed in GOI was the phenomenon of seeded crystallization breakdown, where defect-free crystals from the seed abruptly turn into defect-laced crystals at a certain distance from the seed. This phenomenon is highly characteristic in SOI, but has never been reported for GOI. These findings are compared and discussed in light of the traditional understanding of crystal growth.
The Role of Low-Energy Ion/Surface Interactions During Crystal Growth From the Vapor Phase
Authors: Greene J. E. , Rockett A. , Sundgren J.-E.
Published: March 2011

Low-energy (often < 100 eV) ion bombardment during thin film deposition is commonly used in such diverse application areas as microelectronics, optical coatings. magnetic recording layers. and hard wear resistant coatings to modify the microstructure and microchemistry of films deposited by a variety of techniques (e.g. sputtering, primary ion deposition, plasma-assisted CVD, and accelerated-beam MBE). Ion irradiation has been shown to affect every phase of deposition including nucleation and growth kinetics, crystal structure and phase stability, the average grain size and degree of preferred orientation of polycrystalline films, the epitaxial temperature of single-crystal films, defect concentrations, elemental incorporation probabilities, surface segregation, and, hence, film properties. As discussed in this brief review, a detailed understanding of many of these processes is beginning to emerge. Effects such as trapping, preferential sputtering, enhanced diffusion, and collisional mixing have been used to interpret and, in some cases, model experimental results. Nevertheless, there are still large gaps in our knowledge of the role of ion bombardment on fundamental processes such as nucleation kinetics.
Studies of the Effect of Rapid Thermal Annealing on the Structural and Electrical Properties of Heteroepitaxial CaF2 /CoSi2 /Si(111) Structures
Authors: Phillips Julia M. , Hensel J. C. , Joy D. C. , Augustyniak W. M.
Published: March 2011

We have used electron channeling and scanning electron microscopy to study the crystallinity and morphology of epitaxial CaF2 layers on CoSi2 /Si(111) substrates before and after a rapid thermal anneal. The channeling patterns from the layers after a rapid thermal anneal are nearly indistinguishable from patterns from bulk crystals, indicating high crystalline quality. The annealing procedure also improves the film morphology substantially. We have studied the effect of the rapid thermal anneal on the electrical resistivity of the underlying CoSi2 layer. The room temperature resistivity is unaffected by the anneal, but the low temperature behavior of the resistivity indicates a high degree of diffuse surface scattering, in contrast to as-grown films.
Epitaxial Growth of Near Noble Silicides on (111)Si by Rapid Thermal Annealing
Authors: Cheng H. C. , Wu I. C. , Chen L. J.
Published: March 2011

The epitaxial growth of near noble silicides, including CoSi2, NiSi2, FeSi2, Pd2 Si, and PtSi on (111)Si, by rapid thermal annealing was studied by transmission electron microscopy. Single-crystalline CoSi2 was formed on (111)Si in the solid phase epitaxy regime by a non-ultra-high vacuum method. The effect on gas ambient was found to be of critical importance on the growth of single-crystal CoSi2 on (111)Si. The best NiSi2, FeSi2, Pd2 Si, and PtSi epitaxy grown on (111)Si by rapid thermal annealing were found to be of comparable quality to those grown by conventional furnace annealing.
Titanium-Silicon Interactions During Ion Beam Irradiation
Authors: Tracy Bryan M. , Shukla Rama K. , Davies Paul W.
Published: March 2011

As* ion beam irradiation of thin titanium (∼300Å) films deposited on silicon substrates at sufficiently high dose and energy has been shown to induce an athermal thin film reaction (as evidenced by insenstivity of the reaction to irradiation current) leading to the formation of a homogeneous titanium subsilicide phase with an extremely smooth interface to the underlying silicon. RBS indicates a stoichiometry of Ti3Si4 for this silicide phase. Subsequent rapid thermal annealing (RTA) of this silicide results in the incorporation of additional silicon leading ultimately to the formation of the stable C-54 TiSi2 phase. Silicided junctions fabricated using a ion beam irradiation show improved sheet resistance uniformity and leakage characteristics when compared with those fabricated using the conventional RTA salicide process.
Comparative Studies of Thin-Film Ti-Si and Ti-SiO2 Rapid Thermal Reactions Using the RIP/TEM Technique
Authors: Natan Menachem
Published: March 2011

One requirement of self-aligned microelectronics metallization processes is selectivity of reactions, e.g., a deposited, thin metal film must react with Si to form a silicide, yet avoid reaction with SiO2 Rapid thermal processing (RTP) techniques may enhance selectivity by utiliz-ing differences in competing reaction kinetics. In this paper, we apply the RTP/transmission electron microscopy (RTP/TEM) technique to determine processing temperature (T)/time (t) “win-dows” for selective sulicide formation in Ti-Si vs Ti-SiO2 reactions. Free-lying Si/Ti/Si and SiO2/Ti/SiO2 films deposited on electron microscope grids were RTP'd in pairs and immediately examined by TEM. The products of the interfacial reactions, their sequence of appearance, and the T/t conditions for silicide nucleation and growth in each system are described.
Rapid Thermal Annealing of Sputtered Ti-Ni-Si Films
Authors: Setton M. , Horache E. H. , Spiegel J. Van Der , Santiago J. J. , Fischer J. E. , Siegal M.
Published: March 2011

A ternary compound results from the fast radiative processing of Ni/Ti bilayers on Si<100> substrates. In the Ti-Ni-Si system, Ni is the dominant moving specie at low temperatures while Si starts to diffuse at 575°C. For bilayers with Ti in excess, the final product,above 750°C, is a mixture of ternary compound and TiSi2 whereas excess Ni leads to a layer of NiSi between the substrate and the ternary layer, at tempera-tures below 700° C.
Ultra-Thin p+ Layers in GaAs
Authors: Short K. T. , Chakrabarti U. K. , Pearton S. J.
Published: March 2011

The formation of shallow (0.05–0.2 μm) p+ layers in GaAs by pulse diffusion of Zn from a doped oxide source, thermal diffusion of Cd by vapor transport, or by low energy implantation of Cd, Mg, Be, Zn or Hg ions was investigated by electrochemical capacitance-voltage profiling, Secondary Ion Mass Spectrometry, Rutherford backscattering and Hall measurements. Hole densities in excess of 1019 cm−3 are obtainable by either Zn diffusion or acceptor implantation, though the high temperature cycle must be kept to ≤3 sec at (≤1000°C to prevent excessive redistribution of the acceptor dopants. Pulse diffusion at temperature °C leads to shallow regions with atomic concentrations above 1019 cm−3, but electrically active concentrations orders of magnitude less. These results are explained in terms of the unavailability of a sufficient density of vacancies at low temperatures.